dear friends an d participants of the 2009 mr angio club...

MR-Angioclub East Lansing 2009 1

Dear friends and participants of the 2009 MR Angio Club Meeting It is with great pleasure that we welcome everyone back to Michigan State University for the 21st International Conference in MR Angiography. Since being founded by a team lead by Dr. Jim Potchen in 1989, Michigan State University has been proud to host the annual meeting on three previous occasions, the last in 1994. The MR Angio Club annual meeting has spanned the globe from Asia, to Europe, to the USA and Canada as well as the Far East. This wide diversity in locality has been matched with an ever-growing diversity and ingenuity to produce ever-improving clinical and research applications of MR Angiography. The Local Organizing Team is excited about the excellent quality of the greater than 115 abstracts submitted to the 21st MR Angiography meeting. Both the oral presentations and the expanded poster section should provide very stimulating discussions typical of the MRA Club meetings. We are also proud to announce a Student Poster Award as part of this year’s meeting. MSU Kellogg Center will be an excellent facility for our scientific program with a large, comfortable stadium seating auditorium and hotel rooms to accommodate many of the presenters in one building. The Local Organizing Team has also arranged an exciting social evening program to highlight the Michigan State University campus and the history of Michigan that we hope you will enjoy.

We are grateful for the ongoing support of our corporate sponsors who continue to support such stimulating meetings. The sponsors are listed elsewhere in this program an on the meeting homepage. We are also indebted to the London, Ontario Team including Janette Wallace, Johanne Guillemette, and Kellie Griffin. We hope you enjoy the 21st International Conference on MR Angiography and welcome back to Michigan State University. Local Organizing Team Jim Siebert – Scientific Committee Chairman Arlene Sierra – MRA Club International Secretary Stella Cash – MSU Alumni Interim Executive Director Tom Cooper – Vice Chairman MSU Radiology Colleen Hammond – Chief MSU MR Technologist Kevin DeMarco – President MRA Club 2009


Conference Organization

President President Elect Local Organizing Committee

J. Kevin DeMarco Martin Prince Stella Cash Tom Cooper Colleen Hammond Kevin Henley Cheryl Hunley Arlene Sierra

Past Presidents Executive Board James Potchen

Georg Bongartz

James E. Siebert

Paolo Pavone

Dennis L. Parker

Jorg F. Debatin

John Huston

E. Kent Yucel

Frank R. Korosec

David Saloner

James F. M. Meaney

Brian K. Rutt

Debiao Li

Stephen J. Riederer

Georg Bongartz

Kevin DeMarco

Phillipe Douek

Charles Dumoulin

Christoph Herborn

John Huston

Frank R. Korosec

Gerhard Laub

Debiao Li

James F.M. Meaney

Hitoshi Miki

Charles Mistretta

Dennis L. Parker

James Potchen

Martin Prince

Stephen J. Riederer

Brian Rutt

Kazuhiko (Kaz)Sadamoto

David Saloner

Klaus Scheffler

Stefan Schoenberg

James E. Siebert

Graham Wright

Program Committee Congress Organizing Team

Congress Office @ Robarts Research Institute

James Siebert

James Siebert Johanne Guillemette Janette Wallace

Conference Coordinator Executive Board Secretariat

Conference Manager Secretariat

Kellie Griffin Johanne Guillemette Carolyn Pakula Terri Schneider

Arlene Sierra Janette Wallace

Registration Service Accommodation www.registrationassistant.com www.hfs.msu.edu/kellogg

http://www.hfs.msu.edu/kellogg


The 2009 MR Angio Conference Timetable Tuesday, September 29, 2009

07:30 – 9:00

09:00 – 9:30

09:30 – 10:30

10:30 – 11:00

11:00 – 12:00

12:00 – 01:00

01:00 – 02:45

02:45 – 03:15

03:15 – 05:00

Registration

Opening Ceremony

Selected Non- and Low-Gd Contrast Methods and Applications

Coffee Break

Compressed Sensing and HYPR

Lunch

Plaque Characterization and Vessel Wall Imaging

Coffee Break

Peripheral MRA

Wednesday, September 30, 2009 08:00 – 09:45

09:45 – 10:15

10:15 – 12:00

12:00 – 01:00

01:00 – 02:45

02:45 – 03:15

03:15 – 05:00

Contrast Agents Performance and Safety

Coffee Break

Hemodynamics and Perfusion

Lunch

Head and Neck MRA

Coffee Break

Thoracic MRA

Thursday, October 1, 2009 08:30 – 09:45

09:45 – 10:15

10:15 – 12:00

12:00 – 01:00

01:00 – 02:45

02:45 – 03:15

03:15 – 05:00

Cardiac Imaging / Coronary MRA

Coffee Break

Abdominal MRA

Lunch

Venous Imaging and Beyond

Coffee Break

New Horizons and Challenges in MRA


MR Angio 2009 Club appreciates the generous support of the following sponsors:

PLATINUM SPONSORS

GOLD SPONSORS

SILVER SPONSORS


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Floor Plan for Exhibitors and Posters - Big 10 Room B (see pages 23-24)


General Information

Venue Kellogg Hotel and Conference Center Michigan State University East Lansing, Michigan Registration Foyer of Kellogg Hotel and Conference Center, Lobby Level, across from Auditorium. Message Board There will be a message board near the registration desk. Coffee Breaks & Lunches Snacks and drinks will be provided on the Lobby Level of the Kellogg Hotel and Conference Center in the Big Ten Room C. Internet Access Wireless Internet is available throughout the conference center. Speakers Speakers are requested to contact the speaker ready room (101, lobby level, right beside the Auditorium) and to hand in their Power Point presentation (on CD-ROM or data stick) at least 90 minutes before the start of the session of their presentation. Trained staff will be available to assist you with equipment. You can retrieve your CD-ROM or USB stick once your presentation has been uploaded. Your presentation will be deleted from the server after your talk and thus not made accessible to third parties. Posters Posters have to be mounted at the assigned stands in the poster Exhibition Area (Big Ten Room B) the morning of Tuesday September 29. Please dismount the poster Thursday October 1 by 5 pm. Remaining posters will be discarded.


Spousal Program Tuesday, September 29, 2009

09:00 – 03:30 pm Bus leaves Kellogg Center at 09:00 am Tour of the Gerald R. Ford Presidential Museum Lunch at Amway Grand Meijer Sculpture Gardens Bus leaves at 03:30 pm from Meijer Gardens back to the Kellogg Center

Wednesday, September 30, 2009

08:30 – 03:30 pm Bus leaves the Kellogg Center at 08:30 am Trip to Frankenmuth Lunch at “Zehnders” Restaurant Bus leaves at 03:00 pm from Zehnders back to the Kellogg Center

Thursday, October 1, 2009

Tour of Michigan State University Campus Lunch is provided


Social Events Monday, September 28, 2009

07:00 – 09:30 pm

Welcome Reception Radiology Department of Michigan State University

Tuesday, September 29, 2009

07:00 – 10:00 pm

Dinner at the University Club of Michigan State University

Wednesday, September 30, 2009

07:00 – 10:00 pm

Evening reception at the State Capital Michigan Historical Museum Dinner catered by Morton’s

Thursday, October 1, 2009

07:00 – 10:00 pm

Casual dining in a lakeside setting with Motown music.


Tuesday, September 29, 2009

9:00 am – 9:30 am Opening Ceremony

9:00 – 9:05

J. Kevin DeMarco

MR Angio Club President

9:05 – 9:15 Lou Anna K. Simon President, Michigan State University

9:15 – 9:20 J. Ian Gray Vice President for Research and Graduate

Studies

9:20 – 9:25 James Randolph Hillard Associate Provost for Human Health Affairs

9:25 – 9:30 James E. Siebert Program Director

9:30 am – 10:30 am Session 1 Selected Non - and Low- Gd Contrast Methods and Applications

Session Chairs: Stephen J. Riederer, Manuela Aschauer

9:30 Liesbeth Geerts 1.1 Non-CE Imaging of the Pulmonary Arteries

9:42 Kevin Johnson 1.2 Accelerated Time Resolved Inflow with 3D Radial bSSFP

9:54 Gerhard Laub 1.3 Low - Dose 4D MR Angiography

10:06 Samuel Fielden 1.4 Balanced-gradient TSE for Non-contrast Peripheral MRA

10:18 Jing Liu 1.5 Self-gated Free Breathing 3D Cardiac Cine Imaging with Data Acquisition During Slice Encoding

10:30 am – 11:00 am Coffee Break


11:00 am – 12:00 pm Session 2 Compressed Sensing and HYPR

Session Chairs: Mark A Griswold, Dennis L. Parker

11:00 Mark Griswold 2.1 A Simple View of Compressed Sensing and How it Could Change Everything We Do in MRI and MRA

11:12 Julia Velikina 2.2 Design of Compressed Sensing Reconstruction for Highly Accelerated Time-Resolved MR Angiography

11:24 Yijing Wu 2.3 Low Dose HYPR FLOW

11:36 Lan Ge 2.4 Myocardial Perfusion MRI in Canines with Improved Spatial Coverage, Resolution and SNR

11:48 Nicole Seiberlich 2.5 Reconstruction of MR Angiography Images Using Gradient Descent with Sparsification

12:00 pm – 1:00 pm Lunch


1:00 pm – 2:45 pm Session 3 Plaque Characterization and Vessel Wall Imaging

Session Chairs: J. Kevin DeMarco, Brian K. Rutt

1:00 Chun Yuan 3.1 Carotid Plaque Imaging and Clinical Risk Assessment

1:12 Hideki Ota 3.2 Carotid Intraplaque Hemorrhage Is Associated with Enlargement of Lipid-rich Necrotic Core and Plaque Volume Over Time: In Vivo 3T MRI Prospective Study

1:24 David Zhu 3.3 The 3D SHINE Sequence Optimizes the Quantification of Carotid Intraplaque Hemorrhage

1:36 Jinnan Wang 3.4 Improve Intraplaque Hemmorhage Detections by a Phase Sensitive IRTFE (SPI) Sequence

1:48 William Kerwin 3.5 Fibrous Cap Thickness Assessment: Fact or Fiction?

2:00 Rui Li 3.6 Gradient Echo Based Sequence Provides More Information from Ex Vivo Carotid Plaque Specimens

2:12 Seong-Eun Kim 3.7 Improved Black Blood Multi-Contrast Protocol for In-vivo Atherosclerotic Imaging

2:24 Yi Wang 3.8 3D peripheral vessel wall MRI with flow-insensitive blood suppression and isotropic resolution at 3 Tesla

2:36 Rock Hadley 3.9 A 16 Channel Anterior Neck RF Coil for Cervical Carotid MRA

2:45 pm – 3:15 pm Coffee Break


3:15 pm – 5:00 pm Session 4 Peripheral MRA

Session Chairs: Jeffrey Maki, Tim Leiner

3:15 Tim Leiner 4.1 Gadobenate dimeglumine vs. gadopentetate dimeglumine for peripheral MR angiography: comparison with DSA

3:27 Jeffrey Maki 4.2 Dose Comparison between Conventional and High Relaxivity Contrast Agents in Peripheral MRA

3:39 Matthias Voth - NOT ATTENDING 4.3 Periipheral MRA with Continuous Table (CTM) Movement in Combination with High Temporal and Spatial Resolution TWIST – MRA with 0.1 mmol/kg Gadobutrol at 3.0T

3:51 John Sheehan 4.4 Flow and Motion-Insensitive Unenhanced MR Angiography of the Peripheral Vascular System – A pilot study in the lower extremity

4:03 Clifton Haider 4.5 A Comparison of Time-Resolved 3D CE-MRA with Peripheral Run-off CTA in the Calves

4:15 Kang Wang 4.6 3D Time- Resolved MR Angiography of Lower Extremities using Cartesian Interleaved Variable Density Sampling and HYPR Reconstruction

4:27 Zhaoyang Fan 4.7 3D Noncontrast MRA Using FSD – Prepared Balanced SSFP

4:39 James Carr 4.8 Non Contrast MRA of the Hand in Patients with Raynauds disease using Flow Sensitized Dephasing Prepared SSFP

4:51 Casey Johnson 4.9 Two-Station Time-Resolved CE-MRA of the Lower Legs


Wednesday, September 30th, 2009 8:00 am – 9:45 am Session 5 Contrast Agents Performance and Safety

Session Chairs: Thomas M. Grist, Martin R. Prince

8:00 Mark Hibberd 5.1 An Update on the Clinical Experience with Gadofosveset

8:12 Edward Parsons 5.2 A Re-analysis of MS-325 (gadofoveset trisodium) Clinical Trial Data in Support of US-FDA Approval

8:24 Manuela Aschauer 5.3 Gadofoveset Excretion into Human Breast Milk

8:36 Thomas Grist 5.4 Overview of Gd-BOPTA Phase III Trail for CEMRA: What are the results, and how do we move forward?

8:48 Guenther Schneider 5.5 Safety of Gadobenate dimeglumine (Gd-BOPTA) in Cardiovascular Imaging of Pediatric Patients

9:00 Giles Roditi 5.6 Retrospective 7 year Study of the Incidence of Nephrogenic System Fibrosis in Patients Investigated with Gadolinium Contrast-Enhanced Renal Magnetic Resonance Angiography

9:12 Martin Prince 5.7 Risk Factors for NSF: a Meta-analysis

9:24 James Varani 5.8 Extracellular matrix metabolism in organ-cultured skin from patients with end-stage renal disease: Response to gadolinium based MRI contrast agents

9:36 Zheng-Rong Lu - NOT ATTENDING5.9 Manganese Based Biodegradable Macromolecular MRI Contrast Agents for Cardiovascular Imaging



10:15 am – 12:00 pm Session 6 Hemodynamics and Perfusion

Session Chairs: Scott B. Reeder, E. Mark Haacke

10:15 Thorsten Bley 6.1 Non-invasive Trans-Stenotic Pressure Measurements with 3D Phase Contrast MRA: Validation against Endovascular Pressure Measurements in Swine

10:27 Alex Frydrychowicz 6.2 Analysis of aortic hemodynamics after treatments for coarctation using flow-sensitive 4D MRA at 3T

10:39 Christopher Francois 6.3 Flow assessment of arterial dissections using 3D radial phase contrast MR angiography

10:51 Scott Reeder 6.4 High Temporal and High Spatial Resolution Perfusion Imaging of Hepatocellular Carcinoma in the Liver

11:03 Steven Kecskemeti 6.5 Stack of Stars 4D Phase Contrast Velocimetry of the Circle of Willis

11:15 Mark Haacke 6.6 High Resolution Perfusion Weighted Imaging

11:27 Luca Marinelli 6.7 Accelerated velocity imaging using compressed sensing

11:39 Michael Markl 6.8 Wall Shear Stress in Normal and Atherosclerotic Carotid Arteries

11:51 Scott McNally 6.9 MR imaging and significance of flow reversal and carotid atherosclerosis: Initial results

12:00 pm – 1:00 pm Lunch


1:00 pm – 2:45 pm Session 7 Head and Neck MRA

Session Chairs: John Huston, David Saloner

1:00 Winfried Willinek 7.1 4D-MRA in combination with arterial spin labeling for selective and functional information in patients with AVMs

1:12 Marco Essig 7.2 Intraindividual comparison between multislice CT and 4D TWIST MRA in the assessment of residual cerebral arteriovenous malformations – a prospective study protocol

1:24 Keiji Igase 7.3 Our Strategy for the Surgical Planning with 3T MRA in Detecting Unruptured Cerebral Aneurysms

1:36 Faiza Admiraal-Behloul 7.4 Hybrid of Opposite Contrast MR Angiography of the Brain

1:48 Ek Tsoon Tan 7.5 High Resolution Fast Inversion Recovery MRA (FIR-MRA)

2:00 Nick Zwart 7.6 3D Dual VENC PCMRA using Spiral Projection Imaging

2:12 Samuel Barnes 7.7 High Resolution Simultaneous Angiography and Venography (MRAV) with a Single Echo

2:24 Bum-soo Kim 7.8 Low Dose 3D Time-Resolved MR Angiography of the Supraaortic Artery: Correlation to High Spatial Resolution 3D Contrast-Enhanced MRA

2:36 7.9 Tae-Sub Chung Obstruction of IJV by Asymmetry of Lateral Mass of Atlas on Head and Neck CEMRA and Contrast CT



3:15 pm – 5:00 pm Session 8 Thoracic MRA

Session Chairs: Winfried A. Willinek, Charles L. Dumoulin

3:15 Dipan Shah 8.1 Evaluation of Gd-DOTA (DOTAREM) enhanced MRA compared to time-of-flight MRA in the diagnosis of clinically significant non-coronary arterial disease at 1.5 and 3.0 Tesla

3:27 Mark Schiebler 8.2 Pulmonary MRA in 75 patients with dyspnea

3:39 Mark Schiebler 8.3 Origin and Frequency of artifacts in Contrast Enhanced Pulmonary MRA in 80 patients with dyspnea

3:51 Paul Stein 8.4 Gadolinium Enhanced Magnetic Resonance Angiography for Pulmonary Embolism: Results of PIOPED III

4:03 Loic Boussel 8.5 4D time-resolved MR angiography for non-invasive pulmonary post-embolization AVM patency assessment

4:15 Timothy Carroll 8.6 Radial Sliding Window MRA in Pulmonary Hypertension

4:27 Peng Hu 8.7 Non-Contrast Enhanced Pulmonary Vein MRI with a Spatially Selective Slab Inversion Preparation Sequence

4:39 Grace Choi 8.8 MRA with the “No Phase Wrap”

4:51 Hitoshi Miki 8.9 Unruptured Intracranial Aneurysms; Detection and Follow-up on 3.0T MRA


Thursday, October 1st, 2009

8:00 am – 9:45 am Session 9 Cardiac Imaging / Coronary MRA

Session Chairs: Debiao Li, Harald H. Quick

8:00 Oliver Wieben 9.1 Comprehensive PC MR Imaging in Congenital Heart Disease

8:12 Gary Liu 9.2 Ultrasound guided cardiac gating for coronary MRA

8:24 Himanshu Bhat 9.3 Contrast-Enhanced Whole-Heart Coronary MRA at 3T Using Gradient Echo Interleaved EPI (GRE-EPI)

8:36 Jingsi Xie 9.4 Feasibility of Whole-Heart Coronary MRA on 3 Tesla Using Ultrashort-TR SSFP VIPR

8:48 James Goldfarb 9.5 Cardiac Imaging: Methods for the Detection of Intramyocardial Fat

9:00 Dana Peters 9.6 3D spiral high-resolution late gadolinium enhancement

9:12 Ben Grabow 9.7 Temporal Filtering for Sliding Window Time-resolved Angiography; Beyond Density Compensation Solutions



10:15 am – 12:00 pm Session 10 Abdominal MRA

Session Chairs: Franz Ebner, Walter F. Block

10:15 Kevin Johnson 10.1 Angiographic and Hemodynamic Assessment of the Hepatic Vasculature in Portal Venous Hypertension using High Resolution PC VIPR

10:27 Guenther Schneider 10.2 Renal MR angiography: multicenter intraindividual comparison of gadobenate dimeglumine and gadofosveset trisodium

10:39 Manojkumar Saranathan 10.3 FINESS (Flow Inversion-prepared Non-contrast Enhancement in the Steady State): A novel technique for non-contrast renal MRA

10:51 Tiffany Newman 10.4 Magnetic Resonance Angiography of the skin for perforator-based autologous breast reconstruction

11:03 Isabelle Parienty 10.5 Time-SLIP versus DSA in Patients with Renal Artery Stenosis

11:15 Katherine Wright 10.6 Simultaneous Renal Angiography and Perfusion Measurement Using Time-Resolved MRA

11:27 Nathan Artz 10.7 Assessing Kidney Perfusion using Arterial Spin Labeling and Radial Acquisition for Rapid Characterization of Inflow Dynamics

11:39 Walter Block 10.8 Imaging Capabilities for Real-time Guidance and Verification of Transcatheter Arterial Chemoembolization (TACE) Procedures

12:00 pm – 1:00 pm Lunch


1:00 pm – 2:45 pm Session 11 Venous Imaging and Beyond

Session Chairs: Frank R. Korosec, Yi Wang

1:00 M Louis Lauzon 11.1 Non-Contrast-Enhanced MR identification of DVT

1:12 Mark Haacke 11.2 Susceptibility mapping as a means to image veins

1:24 Petrice Mostardi 11.3 Modified CAPR MRA: Improved Imaging of the Arterial and Venous Phases

1:36 Hyun Jeong 11.4 CAMERA: Contrast-enhanced Angiography with Multi-Echo and Radial k-space

1:48 Philip Robson 11.5 Time-Resolved, Vessel-Selective, Cerebral Angiography Using Arterial Spin Labelling

2:00 David Steinman 11.6 Quantifying Lumen Geometry from Routine Carotid CEMRA

2:12 Yi Wang 11.7 Magnetic Source MRI for Quantitative Brain Iron Mapping

2:24 Kheireddine El-Boubbou 11.8 Targeted Glyco-Magnetic Fe304 Nanoprobes for Detections and Molecular Imaging of Atherosclerosis



3:15 pm – 5:00 pm Session 12 New Horizons and Challenges in MRA 3:15

Session Chairs: E. James Potchen, Charles A. Mistretta James E. Siebert Presentation of the Best Student Posters Awards

3:20 Charles Mistretta 12.1 4D DSA and Fluoroscopy: A New Challenge for MRA?

3:32 Bas Versluis 12.2 MR Angiography of muscular and collateral arteries in peripheral arterial disease: reproducibility of morphological and functional vascular status

3:44 Matt Bernstein 12.3 Multicenter Studies: Lessons Learned from ADNI

3:56 David Saloner 12.4 Imaging Considerations in Serial Studies of Vascular Disease

4:08 Mark Ladd 12.5 Towards Abdominal MRA at 7 Tesla

4:20 Harald Quick - NOT ATTENDING: Mark Ladd to present 12.6 7 Tesla Cardiac MRA in Humans

4:32 George Abela 12.7 The Role of Cholesterol Crystals in Acute Cardiovascular Events: Identifying the Cause for Gender Differences in Clinical Presentation

4:44 4:56

James E. Potchen Perspective on MRA and the MR Angio club (no abstract) Kevin DeMarco Presentation of the new President of the MRA Club Announcement of the new President Elect Announcement of the 22nd International MRA Conference 2010 in Seoul, South Korea


Posters

MRA Methods P1 Manuela Aschauer

CE-MRA with tailored 3D random sampling patterns and nonlinear parallel imaging reconstruction

P2 Jason Mendes Handling Motion in Sparse MRA with Whiskers

P3 Jordan Hulet Improved Carotid Imaging with HASTE using a reduced FOV and increased gradient performance

P4 Randall Stafford Towards Continuously Moving Table NCE Peripheral MRA

P5 Matthew Latourette R2* Calibration Phantoms for Cardiovascular Studies

P6 Giles Roditi Pictorial Review of Supra-Aortic Artery Pathologies as Visualised with MRA using Blood Pool Contrast Agent

P7 Kristine Blackham Robust Clinical Application of Time-Resolved MRA

P8 Jonathan Suever Reproducibility of Aortic Pulse Wave Velocity Measurements Obtained with Phase Contrast Magnetic Resonance (PCMR) and Applanation Tonometry

P9 Gregory Wilson Motion-compensated, flow-independent, non-contrast-enhanced renal MR angiography

MRA Applications P10 Chang-Ki Kang

Vascular response during visual stimulation at 3T MRI: functional phase contrast angiography (fPCA) study

P11 Jongmin Lee Optimization of Phase-contrast MR-based Flow Velocimetry and Shear Stress Measurement

P12 John Oshinski Blood Flow Patterns in the Abdominal Aorta of Mice: Implications for AAA localization


Posters Plaque Characterization and Vessel Wall Imaging P13 Niranjan Balu

3D Vessel Wall imaging of multiple vascular beds

P14 Keigo Kawaji Feasibility Study of Combining 3D SSFP with T2prep inversion Recovery (T2IR) for Black Blood Vessel Wall Imaging

P15 Zhaoyang Fan Identification of Optimal First-Order Gradient Moment for Flow-Sensitive Dephasing (FSD) Preparation

P16 Rahul Sarkar Combined Segmentation of Lumen and Intraplaque Hemorrhage in Black-blood T1-Weighted Carotid Imaging

P17 Rahul Sarkar Automatic Registration of Multiparametic T1 Weighted Images Using FOV-Selective Mutual Information

CFD Modeling and MR-Guided Endovascular

Interventions P18 Haruo Isoda

MR fluid dynamics using 4D-Flow for intracranial aneurysms with growing blebs and a ruptured intracranial aneurysm

P19 Charles Dumoulin Phase-Field Dithering for Active Catheter Tracking

P20 Ethan Brodsky Interventional Device Tracking and Imaging Using an Extensible Real-Time System

P21 Mahdi Salmani Rahimi Simplified Catheter-based Multimode Coil for Active MR Tracking and Intravascular Imaging

P22 Krishna Kurpad Transmit Power Optimization for Tracking, Wireless Marker and Imaging applications of a Multi-mode Endovascular coil


1.1 Non-CE imaging of the pulmonary arteries Liesbeth Geerts, Marco van Essen, Gregory Wilson, Tomoyuki Okuaki

Philips Healthcare, Best, The Netherlands

Purpose Bright blood ASL in a single acquisition – without subtraction of tag-on and tag-

off acquistions – can be used to depict vascular structures [1].The contrast mechanism

relies on inflow of fresh spins into the imaging region. Therefore, optimal imaging

parameters, such as the time allowed for inflow, may be patient dependant.

The purpose of this study was to 1) evaluate the use of a bright blood ASL approach in a

single acquisition for depiction of the pulmonary vasculature and to 2) evaluate the effect

of different TI times.

Methods A combination of a spatially non-selective and a selective inversion pulse was

implemented on a 1.5T Achieva scanner to obtain a bright blood ASL in a single

acquisition. A respiratory triggered 3D-TSE was used for readout. 12 Healthy volunteers

(mean 54.2 years, range 37 to 71) were scanned, using TI’s of 500, 800 and 1100 ms. In

two volunteers, additional measurements at TI 300, 700 and 900 ms were performed.

Image quality was qualitatively rated.

Results A TI of 800 ms gave the best depiction of a pure arterial filling. At longer TI (1100

ms) filling of the distal segments has progressed, however, also the venous signal

becomes more apparent.

TI 500 ms TI 800 ms TI 1100 ms

Conclusion Bright blood ASL in a single acquisition is suitable to depict the pulmonary vasculature. A TI of 800 ms was found to give good depiction of the pulmonary arteries. [1] Miyazaki. Radiology 248(1);20-43 (2008)


1.2 Accelerated Time Resolved Inflow with 3D Radial bSSFP Kevin M. Johnson, Oliver Wieben, Patrick Turski, Charles Mistretta

Departments of Medical Physics and Radiology, University of Wisconsin, Madison, WI, USA

Purpose: Recently the combination of blood tagging schemes [1] and bSSFP acquisitions

has allowed for sub second resolution of vascular filling dynamics [2]. However, bSSFP

can be sensitive to artifacts from off-resonance banding and flow artifacts. In this work we

investigate the use of 3D radial trajectories for highly accelerated non-contrast enhanced

angiography with reduced flow and banding related artifacts.

Methods: All imaging was performed on a clinical 1.5T scanner. An ecg-triggered,

inversion-recovery prepared, cardiac interleaved, bSSFP, 3D sequence was implemented

with both dual-half echo (non-flow compensated) and 4-half radial trajectories (flow

compensated) [3]. Angiographic images are acquired by subtracting of a pass with non-

selective inversion pulse from a pass with a selective inversion just covering the imaging

volume. Typical imaging parameters for 4-half echo (2-half echo) are TR=4.0ms (3.0ms),

readout bandwidth=+/-125kHz, FOV=24x24x14cm, resolution= 0.94x0.94x0.94mm, flip

angle = 45º, RR interval = 2, total scan time =~6min for 45,000 (60,000) total unique

projections.

Results: Representative images from the 4-half echo sequence are shown in Figure 1.

Images show filling of the major vessels without substantial blurring. Signal diminishes as

the signal recovers from inversion and as blood distant from the volume fills the vessels.

Results indicate improved performance of the 4-half echo trajectory, due to flow

compensation and improved sampling efficiency.

Conclusion: The proposed

3D radial sequence

provides significantly

shorter TRs for a given

resolution than their

Cartesian counterparts.

Considerable acceleration

can be achieved allowing

for higher-resolution

imaging or reduced scan time.

References: 1. Kim SG. MRM 34:293-301 (‘95) 2. Bi et al. Proc MRA Club 08 pg.31 3. Lu et al. MRM 53:692-699 (05’)


1.3 Dose 4D MR Angiography

Gerhard Laub, Ph.D. Siemens Healthcare, USA

Time resolved contrast-enhanced MR angiography has been increasingly used to

evaluate the hemodynamic status of normal versus abnormal vasculatures. Fast imaging

sequences, parallel imaging, and view-sharing techniques have been applied to provide

the needed temporal and spatial resolution. The Gadolinium-based contrast agent is

sometimes injected in double dose to enhance the image quality. In light of NSF and the

desire to lower the amount of Gadolinium-based contrast agent to the patient, we have

investigated the use of time resolved TWIST imaging (Time-resolved Imaging with

Stochastic Trajectories) in combination with a small dose of diluted contrast agent for 4D

imaging of the extracranial vasculature.

In this study, we tested the feasibility of using a very low dose of contrast for time-

resolved MRA in patients referred to get a clinical MRA examination. For low dose

dynamic MRA, 1-2 ml of Gd-DTPA, diluted with saline at a rate of 1 part Gd and 3 parts of

saline, was injected at a rate of 2 ml/sec. This was compared to routine contrast-enhanced

MRA using a single dose (0.1 mmol/kg) of contrast agent. All imaging was performed at

3T using a combination of a 12-channel head array, 4-channel neck array, and 6-channel

thorax array to extend the FOV and cover the entire aortic arch, the carotid arteries, and

the intracranial arteries all dynamically. Parallel imaging was used in two phase encode

directions with an acceleration factor of up to 9. An additional acceleration factor of 3.8

was achieved using the TWIST dynamic mode. 3D imaging, with 100 slices (slice

resolution = 2.5 mm), was acquired with an in-plane resolution of 1.3 mm x 2.2 mm and

interpolated to isotropic voxels of 1.3 mm.

Using only 2 ml of contrast agent, or less, all time-resolved results were clinically

useful to provide functional information in addition to the anatomical information provided

by the high-resolution, single-phase contrast-enhanced MRA. In this preliminary study,

there was good agreement between the low dose, time-resolved MRA and the routine,

high-resolution contrast-enhanced MRA. By using a combination of parallel imaging and

the TWIST dynamic mode, the temporal update rate was under 2 sec for each 3D

volumetric data set, depending on spatial resolution and vessel coverage.

Time-resolved, three-dimensional MRA with near isotropic resolution and large

coverage is feasible using a small amount of a Gadolinium-based contrast agents. Further

studies involving larger number of patients are needed to determine whether very low

dose time-resolved MRA would lead to any difference in clinical diagnosis.


1.4 Balanced-gradient TSE for Non-contrast Peripheral MRA SW Fielden1, JP Mugler III1,2, KD Hagspiel2,3, CM Kramer2,3, and CH Meyer1,2

1Biomedical Engineering, University of Virginia, Charlottesville, Virginia, United States, 2Department of Radiology, University of Virginia, Charlottesville, Virginia, United States, 3Department of Medicine,

University of Virginia, Charlottesville, Virginia, United States

Purpose: To develop a 3D balanced-gradient TSE sequence for generating non-contrast,

non-subtractive, peripheral angiograms.

Methods: A 3D dataset was acquired on

each of 9 healthy volunteers on a Siemens 3-

T Trio scanner (Siemens Medical Solutions)

with a TSE sequence modified with (1) a

frequency-encoding gradient which is

rewound between each set of refocusing

pulses and (2) excitation and refocusing RF

pulses applied along the same axis with a

180° phase alternation along the echo train,

analogous to common implementations of

balanced SSFP. Sequence parameters were

as follows: TR/TE/Echo Spacing =

3000/230/3.1 ms, resolution = 1.4 x 1.4 x 1.5

mm3, acquisition time = 5.38 ± 0.50 min.

Image quality was assessed based on SNR,

CNR, and vessel sharpness.

Results and Conclusion: The incorporation of balanced gradients and RF-pulse phase

alternation in a TSE sequence resulted in T2-weighted images with reduced flow-related

signal loss and blurring, yielding good contrast between arteries and veins without

subtraction1. As seen in the coronal MIP figure to the right, blood-muscle contrast is

similar to that obtained with flow-independent angiography2 and to that obtained with

traditional TSE sequences. The residual fat and edematous signal may be mitigated in

the future via chemically selective pulses and an inversion preparation.

References: 1Miyazaki M, et al. Radiology, 227(3):890-6, 2Brittain J, et al. Magn Reson

Med, 38(3):343-454


Fig. 3. Short axis images of five presentative slices at end diastole (top row) and end systole (bottom row).

Fig. 1. Samples acquired during sequential slice encodes (10 slices for example).

1.5 Self-Gated Free Breathing 3D Cardiac Cine Imaging With Data Acquisition During Slice Encoding

Jing Liu1, Martin R. Prince1, Yi Wang1 1Weill Medical College of Cornell University, New York, NY

Email: [email protected]

Self-gated free-breathing 3D cardiac cine imaging is becoming a promising

technique for heart visualization and functional measurements. The common techniques

for self-gating requires additional scan time for acquiring extra gating data. The purpose of

this study was to develop a cardiac and respiratory self-gated free-breathing 3D pulse

sequence that avoids extra scan time and provides robust self-gating information.

The multi-echo 3D hybrid radial pulse sequence was modified by adding

readout during the slice encoding pulse.

The acquired data during slice encoding

pulse are phase encoded k-space

centers along kz (Fig. 1). Different slice

encoding gives different kz coverage,

while the combination of sequential slice

encodes gives full kz coverage. The 1D

Fourier transform of this combined data

provides the z intensity profile, which

contains both cardiac and respiratory

motion information for cardiac and respiratory self gating. Typical imaging parameters

were: TR/TE/FA/BW/FOV=4.5ms/1.3ms/40°/±125kHz/34cm, 256x256 matrix, 10 slices of

slice thickness 10mm. A 1.5 T GE EXCITE 14M4 scanner was used.

Fig. 3 shows short axis heart images acquired within a scan time of 3.4 minutes.

The respiratory gating efficient was 50%.

A self-gating technique

with extra data acquisition

during slice encoding was

demonstrated with 3D hybrid

radial imaging. It can be applied

to other 3D pulse sequences,

such as 3D Cartesian and spiral

pulse sequences. Further

validation experiments of the

proposed self-gating method are underway.


2.1 A Simple View of Compressed Sensing and How it Could Change Everything We Do in MRI and MRA.

Mark A Griswold1, Nicole Seiberlich1 1Dept. of Radiology, Case Western Reserve University, Cleveland, OH

MRA provides exquisite depiction of vascular abnormalities without the ionizing radiation

found in conventional DSA or CTA. However, significant drawbacks still exist. This is

primarily due to the limited speed and SNR of MRI, and most important, the fact that they

are linked to each other. Traditionally, any increase in imaging speed has required a loss

in SNR and vice versa. In order to realize any truly dramatic increases in either SNR or

imaging time, some way to break this relationship must be found. The class of newly

described Compressed Sensing (CS) methods promises to revolutionize MRI by breaking

this link and could potentially allow the development of a set of completely new imaging

strategies with dramatic increases in SNR and imaging speed. Unfortunately much of the

field of CS is described in highly mathematical terms, limiting the ability of the average

listener to fully grasp the concepts involved. In this talk, we will review some of these basic

concepts of CS in a non-mathematical, intuitive way. In general, we will demonstrate how

CS will change the focus of an MR acquisition from simply collecting images to directly

collecting information. In particular, we will focus on how somewhat older methods, such

as UNFOLD, BLAST, PARSE, and other related methods can be seen in the framework of

CS, and will also show how methods such as HYPR meet this goal of directly collecting

the important information. Finally, we will highlight several examples where these new

methods have dramatically improved both the SNR and temporal resolution beyond all

previously established limits to provide clinically useful exams in dramatically reduced time

with increased SNR.


2.2 Design of Compressed Sensing Reconstruction for Highly Accelerated Time-Resolved MR Angiography

Julia Velikina, Alexey Samsonov Departments of Medical Physics and Radiology, University of Wisconsin – Madison

Introduction: Many angiographic tasks require high temporal resolution, which results in

data undersampling. A number of constrained reconstruction methods including

compressed sensing (CS) have been proposed to mitigate problems of conventional

reconstruction (aliasing and low SNR)1,2. However, even natural sparsity of angiographic

images cannot support acceleration factors higher than 4-8 without loss of spatial

resolution and artifacts. In time-resolved imaging, the efficiency of CS can be extended by

promoting joint sparsity in both spatial and temporal dimensions3,4. In this work, we

evaluate the performance of two CS approaches: k-t FOCUSS5 (sparsity in x-f domain)

and temporal constraining (sparsity of finite differences in x-t domain) in contrast-

enhanced (CE) and phase contrast (PC) imaging.

Theory and Methods: We adapted spatial/temporal regularization4 into CS framework.

The time series f is estimated as follows:

Φ+−= )(minarg

2

2fLmfEf

fλ [1], with the encoding matrix E , data

vector m , regularization parameter λ. L is a 1st or 2nd temporal derivative. We chose

Φ to be a hybrid 21 / norm6 to provide both SNR optimization (via 2 ) and CS

acceleration (via 1 norm).

Results and Conclusions: All approaches were tested on CE and PC data acquired in

healthy volunteers. For Cartesian trajectories acceleration of 8-10 were achieved, while

radials allowed acceleration up to 40 without loss of temporal and spatial resolution. The

developed temporal regularization was found to outperform kt FOCUSS in preservation of

temporal waveforms for high acceleration factors. Additionally, it was found more forgiving

to patient motion than kt FOCUSS. CS methods based on sparsity in x-t domain (Eq. [1])

are promising to accelerate time-resolved angiography.

References: [1] Çukur T, et al MRM, 2009;61:1122. [2] Mistretta CA, et al. MRM

2006;55:30. [3] Portniaguine, et al. ISMRM 2003,481. [4] Samsonov, ISMRM 2005, 2311.

[5] Tsao J, et al. MRM 2003;50:1031. [6] Bube KP, et al. Geophysics,1997:62:1183.


2.3 Low Dose HYPR FLOW Yijing Wu, Steven Kecskemeti, Kevin Johnson, Charles Mistretta, Patrick Turski

Departments of Medical Physics and Radiology, University of Wisconsin, Madison, WI

INTRODUCTION: Time resolved contrast-enhanced magnetic resonance angiography

has been widely used to evaluate the hemodynamics of the vascular structure. Due to

the recent concern of NSF disease, eliminating or reducing the Gadolinium-based

contrast agent is more desirable than ever. Phase Contrast (PC) HYPR FLOW is able to

decouple the high spatial resolution and SNR, which require relative long scan time,

from high temporal resolution, which demands for fast data acquisitions, and used

HYPR constrained reconstruction to obtain a time series of images with both high

temporal resolution, isotropic high spatial resolution, high SNR and quantitative flow

dynamics from the PC images. Our hypothesis is that the SNR of the HYPR FLOW

images depends on the post contrast PC composite, which requires minimum amount of

contrast agent. High temporal and spatial resolution time resolved contrast-enhanced

MRA can be obtained by using low dose HYPR FLOW method with reduced contrast

agent.

METHODS AND RESULTS: Low dose HYPR FLOW has been tested in three normal

volunteers and one brain AVM patient. Contrast agent was reduced to one half or one

quarter of a single dose (0.1 mmol/kg). Following contrast injection, a CE-MRA

examination of the head is performed using time resolved milt-echo VIPR.

Subsequently, a 5 minute PC VIPR acquisition was acquired and then used as a

composite image for HYPR LR reconstruction. The figure on the right shows a time

series of HYPR FLOW

images of the AVM patient

with half dose contrast

agent (~ 6 cc). Numbers on

the images are relative time

frames after contrast

arrival. Frame rate was 2/s,

with 0.7 mm isotropic spatial resolution. Our preliminary results show that low dose

HYPR FLOW is able to provide high temporal and spatial resolution with adequate SNR

and potential shorter bolus dispersion for intracranial MRA.

1 2 4 6

8 15 25 35

1 2 4 6

8 15 25 35


Figure 1. Comparison of conventional method and SW-CG-HYPR

2.4 Myocardial Perfusion MRI in Canines with Improved Spatial Coverage, Resolution and SNR

Lan Ge1, Aya Kino1, Daniel Lee1, Rohan Dharmakumar1, Mark Griswold2, Charles Mistretta3, James Carr1, Debiao Li1

1Northwestern University, Chicago, IL, USA, 2 Case Western Reserve University, Ohio, USA, 3University of Wisconsin-Madison, Madison, WI, USA

Purpose: First-pass perfusion MRI is a promising technique for detecting ischemic heart

disease. A combination of sliding window and CG-HYPR (1, 2) methods (SW-CG-HYPR)

have been proposed to increase spatial coverage, resolution, and SNR(3). In this work,

using a controlled animal model, we compare this new method with conventional clinical

protocols and test whether the flow deficits can be detected accurately. Methods: Five dogs with LCX occlusion were scanned using a 1.5T system during the

first-pass of the contrast agent in stress condition. An ECG-triggered, turbo-FLASH

sequence with radial k-space sampling and saturation recovery (SR) preparation was

used in this study. CG-HYPR method was used to reconstruct the time-resolved images.

The signals from the left ventricle, healthy myocardium, and flow deficits for all of the three

methods were measured and compared. Results: The SNR of the left ventricle at peak enhancement with SW-CG-HYPR

(32.1±2.32) is significantly higher than turbo-FLASH (20.6±2.62) and EPI (12.9±1.95).

Figure 1 shows examples of the comparison. The defects caused by LCX occlusion can

be clearly delineated in SW-CG-HYPR images. The signal intensity changes of the healthy

myocardium are highly correlated with a correlation coefficient of 0.956. Conclusions: In conclusion,

SW-CG-HYPR is a

promising method to

improve the

myocardial perfusion MR

imaging with reduced

acquisition window

increased spatial coverage,

improved spatial resolution and SNR.

References: 1. Mistretta CA, et. al. MRM, 55: 30-40, 2006. 2. Griswold MA, et. al. Proc

ISMRM, Berlin, 2007: 834. 3. Ge L, et al. Proc ISMRM, Toronto, 2008: 43

SW-CG- HYPR images

Reference images

turbo-FLASH vs. SW-CG-HYPR

Deficits

EPI vs. SW-CG-HYPR

Deficits


Figure 1: Gradient Descent with Sparsificationreconstruction depicting flow of contrast into the AVM.Figure 1: Gradient Descent with Sparsificationreconstruction depicting flow of contrast into the AVM.

2.5 Reconstruction of MR Angiography Images using Gradient Descent with Sparsification Nicole Seiberlich and Mark A. Griswold

Department of Radiology, Case Western Reserve University, Cleveland OH

Purpose: Recently, a new method for generating sparse images from highly

undersampled data, Gradient Descent with Sparsification, has been introduced [1]. This

method iteratively determines x, the sparse image to be reconstructed using the following

formulation: ))(( xyxHx T Φ−Φ⋅+← γ where y is the k-space data,Φis the

resampling/degridding operation, H is a thresholding operation, andγcontrols the rate of

convergence. This simple reconstruction algorithm was tested for the reconstruction of

images from highly undersampled MR Angiography data.

Methods: CE-MRA data were acquired on a patient with an arterial-venous malformation

(AVM) with the following parameters: radial GRE acquisition, TR=3ms, TE=1.5ms, total

projections=1344, 75% asymmetric echo, Matrix=192x192, FOV=220x220 FA=20°,

Partitions=15, slice thickness=4mm. Images were reconstructed using Gradient Descent

with Sparsification with 32 projections per frame, with the thresholding value H determined

using the center of k-space andγ

fixed as suggested in [1].

Results: Time frames showing the

arrival of contrast into the AVM

reconstructed using Gradient

Descent with Sparsification are

shown in Figure 1. The streaking

commonly evident in such highly undersampled images has been removed, and the

vessels feeding the AVM are clearly depicted without venous contamination.

Conclusion: Gradient Descent with Sparsification is a simple and fast method to

reconstruct highly undersampled sparse images, including MRA data. Unlike other

reconstruction methods, no composite image is required, reducing reconstruction errors.

Further improvements to the method such as the inclusion of coil sensitivity maps or

constraint on the thresholding images will be considered in the future.

References: [1] Garg R and Khandekar R. Proc. 26th International Conference on

Machine Learning, Montreal, Canada, 2009.


3.1 Carotid Plaque Imaging and Clinical Risk Assessment Chun Yuan, PhD, Hunter Underhill, MD, Thomas Hatsukami, MD

Vascular Imaging Laboratory, School of Medicine, University of Washington, Seattle, WA Carotid MRI has been proven to be able to measure plaque size and characterize tissue

composition. This information provides unique opportunities to study the ‘vulnerable

plaque’ in vivo. This talk aims to summarize the current understanding of vulnerable

plaque features based on longitudinal studies of carotid atherosclerosis, as well as the

relationship between carotid atherosclerosis and neurological symptoms. This talk will also

discuss the current technical and clinical needs of atherosclerosis imaging.


3.2 Carotid Intraplaque Hemorrhage Is Associated with Enlargement of Lipid-rich Necrotic Core and Plaque Volume Over

Time: In Vivo 3T MRI Prospective Study H Ota1, D. Zhu1M, JK DeMarco1

1Michigan State University, East Lansing, MI, USA

Purpose: To test the hypothesis that intraplaque hemorrhage identified by 3D Inversion

recovery fast SPGR (IR-FSPGR) images contributes to plaque progression over time as

measured by multi-contrast carotid MR imaging at 3.0T.

Methods: Twenty-six consecutive subjects with known 50-99% carotid stenosis

underwent serial carotid 3T MRI scans with a multicontrast weighted protocol (pre- and

post-contrast T1W, T2W, 3D TOF and 3D IRFSPGR) with intervals of 0.5-2.2 years. Two

reviewers blinded to subject’s clinical information and scan date interpreted images. In

order to insure a similar coverage of the carotid artery for quantitative measurements, only

image locations that could be matched across 2 time points were reviewed. The volumes

of vessel wall, lumen, lipid-rich necrotic core, hemorrhage and calcification were

documented for each study. The changes in each metric adjusted for the period (mean ±

standard deviation/year) were evaluated in the groups with and without intraplaque

hemorrhage at the baseline scans using one sample t-test.

Results: Eight subjects (31%) had intraplaque hemorrhage at baseline. Mean lipid-rich

necrotic core volume at baseline was significantly larger for patients with hemorrhage

(p=0.001) than those without hemorrhage. The mean volumes of lumen, wall and

calcification at baseline were not significantly different. In the eight subjects with

intraplaque hemorrhage at baseline, significant increases of the volumes were found for

wall (23.7± 26.3mm3/year, p=0.038), lipid-rich necrotic core (44.0±30.6 mm3/year,

p=0.005), and intraplaque hemorrhage (24.1±23.4 mm3/year, p= 0.022). The changes in

the volumes of lumen and calcification were not significant. In the remaining 18 subjects

without intraplaque hemorrhage at baseline, the changes in the volumes of wall, lipid-rich

necrotic core were not significant over time.

Conclusion: Intraplaque hemorrhage noted on baseline carotid wall 3T MR imaging is

associated with larger lipid rich necrotic core at baseline as well as significant progression

of overall plaque volume, the size of the lipid-rich necrotic core and intraplaque

hemorrhage over time.


3.3 The 3D SHINE Sequence Optimizes the Quantification of Carotid Intraplaque Hemorrhage

David C. Zhu1, Hideki Ota1, Marina S. Ferguson2, Anthony T. Vu3, J. Kevin DeMarco1 1Michigan State University, 2University of Washington, 3GE Healthcare

Introduction: Carotid intraplaque hemorrhage (IH) has been shown to promote plaque

progression. A novel optimized 3D SHINE sequence was developed to detect IH based on

high T1 contrast and to characterize hemorrhage into type I (early) and type II (recent)

based on T2* maps (1). With these advantages, algorithms were developed to estimate the

size and composition of intraplaque hemorrhage.

Methods: 3D SHINE images (1) were collected from nine patients with carotid IH at 3T.

At the first TE, the signal intensity ratios of IH versus lumen, wall and surrounding muscle

were 7.94 ± 3.4, 3.20 ± 1.21 and 3.82 ± 0.92. These high contrasts allowed for reliable

computerized segmentation. A target ROI contained IH and a background ROI contained

the surrounding muscle. At each slice, each voxel was normalized by the mean signal

intensity of the background ROI at this slice. Normalization reduced the signal intensity

variation due to the surface coil, and allowed a uniform cutoff of 1.5 on each slice to

identify the probable IH voxels. These voxels were further labeled as “IH” if they were

within a minimal “IH” size of 0.68 mm3 (14 voxels). The IH region was further divided into

type I and type II based a T2* cutoff value of 14 ms (1). The sizes of the segmented

intraplaque hemorrhage and its sub-regions were then calculated.

Results and Discussion: The segmented intraplaque hemorrhage (middle figure,

red/yellow: type I, blue: type II) shows a close match with the original data (left figure) and

a reasonable correspondence with matched histology data (right figure). A semi-

automated quantification of intraplaque hemorrhage would allow the monitoring of plaque

progression and could be used as an objective tool in multi-site clinical trials. Reference:1. Zhu DC, Ota H, Vu AT, DeMarco JK. ISMRM 2009, Honolulu, Hawaii.


3.4 Improved Intraplaque Hemorrhage Detection by a Phase Sensitive IRTFE (SPI) Sequence

Jinnan Wang 1, Marina Ferguson 2, Chun Yuan 2, Peter Börnert 3 Affiliations: 1. Philips Research North America, 2. University of Washington, 3. Philips Research Europe

Purpose: Hemorrhage in atherosclerosis plaque has been linked to an increased risk of

plaque progression and rupture [1]. However, only a small portion of the dynamic range

have been utilized [2, 3] by current T1 based hemorrhage detection sequences. This can

lead to inaccurate identification and segmentation of plaque components. In this study, a

Slab-selective Phase-sensitive IRTFE (SPI) sequence is proposed to improve image

contrast of intraplaque hemorrhage.

Methods: The SPI sequence is adapted from a regular IR-TFE sequence by making the

inversion pulse slab selective and phase sensitive. Simulations are used to evaluate the

signal contrast increase by using this novel SPI sequence.

9 carotid endarterectomy (CEA) specimens were scanned with both SPI and regular

IRTFE sequences. The hemorrhage to lumen contrast for each specimen was calculated

and compared between SPI and IRTFE images. Three of the nine CEA specimens were

processed for histology with 1 specimen confirmed to contain intraplaque hemorrhage. Results: Simulations

indicate that contrast

between hemorrhage

and normal vessel wall

can be increased by

over 50%. The hyper

intense regions on

both images

correspond very well

to the region of hemorrhage on matching histology. An approximate 30% improved tissue

contrast was obtained on the SPI image.

Conclusion: Simulation and ex-vivo experiments confirm that the novel SPI technique

can improve hemorrhage contrast on MR images by utilizing phase information. This

improved tissue contrast can potentially improve the identification and quantification of

intraplaque hemorrhage by carotid plaque MRI.

References: 1. Takaya N, et al. Stroke. 2006; 37:818-23. 2. Moody AR, et al. Circulation

2003;107;3047-3052. 3. Zhu DC, et al. 2008;26:1360-6.

Fig.1 Ex vivo MR images using routine IRTFE (left) and SPI (middle). Matching histology (right) confirms the presence of intraplaque hemorrhage. Note the improved contrast of hemorrhage on the SPI sequence (arrows).


3.5 Fibrous Cap Thickness Assessment: Fact or Fiction? William S. Kerwin, Huijun Chen

University of Washington, Department of Radiology, Seattle, WA, USA Purpose – Determining fibrous cap thickness in carotid atherosclerotic disease is the holy

grail of plaque imaging as cap thickness may be the most important factor in distinguishing

between vulnerable and stable lesions. While histological studies have indicated that the

key break point for vulnerable cap thickness is on the order of 200 microns [1], MRI

resolution in carotid studies is typically >500 microns. Nevertheless, claims of identifying

thin caps (<250 microns) [2] and actual measurement of cap thickness [3] have been

made. The purpose of this study is to assess the extent to which cap thickness can be

assessed at the fringes of MRI resolution.

Methods – A series of physical and computational phantoms that mimicked fibrous cap

geometry were used to probe the relationship between cap thickness, image resolution,

and appearance under MR imaging conditions. Based on these phantoms, a linear Fisher

classifier was constructed that produced a mathematical model for classifying fibrous cap

thickness derived from 11 intensity-related parameters. This classifier was then applied to

26 contrast-enhanced plaque images from 7 individuals with histologically measured cap

thickness.

Results – The experiments indicated that the fibrous cap could not be visualized when its

thickness was less than about half the fundamental resolution, which coincides well with

observations using the absence of a band separating the core from the lumen to define

“thin” caps [2]. Above this threshold, differences in cap appearance that correlated with

cap thickness could be ascertained even below the fundamental resolution; however,

measured thicknesses were heavily biased and sensitive to SNR and physical MR

parameters when the thickness was <1.5 times the fundamental resolution. The

determinant from the linear Fisher classifier was significantly correlated (p<0.05) with

measured cap thickness for in vivo imaging.

Conclusion – MRI is able to differentiate caps of different thicknesses even below the

fundamental resolution, using intensity criteria. Measurements of cap thickness will be

unreliable, however, unless resolutions of 100-300 microns can be attained in vivo.

[1] Redgrave Stroke 2008; [2] Hatsukami, Circ 2000; [3] Sadat, Atheroscl 2009


Information Plaque LRNC H(T1, T2, PD, GE) 13.37 11.31 H(T1 | T2, PD, GE) 0.65 0.29 H(T2 | T1, PD, GE) 0.80 0.30 H(PD | T1, T2, GE) 1.10 0.49 H(GE | T1, T2, PD) 0.92 0.47

Table 1. Joint and conditional entropy

Figure 1. Cross-sectional image and histogram of different ROI

3.6 Gradient Echo Based Sequence Provides More Information from Ex Vivo Carotid Plaque Specimens

Rui Li 1, Chun Yuan 1

Affiliation: 1. Radiology Department, University of Washington Purpose: Spin echo (SE) based MRI sequences are generally used for high resolution

plaque imaging. Criterion for vulnerable plaque also uses SE based T1, T2 and PD

weighted images to access the components in the plaque[1]. However gradient echo (GE)

based sequences has rarely been explored for plaque evaluation. This study aimed to find

out whether we can get more information from GE by carotid specimen examination.

Methods: Conventional GE imaging was performed on a 3T MRI system (Philips Achieva)

with the carotid specimens fixed in 70% formalin solution. The main parameters were TR:

721ms, TE: 9.2ms, FA: 60o, SLC: 32, TH: 1mm, FOV: 24*24mm2, and Res: 0.16*0.16mm2.

Four carotid endarterectomy specimens were inspected. Histogram, joint entropy and

conditional entropy[2]

were used to evaluate

the information for the

whole plaque and the

lipid rich necrotic core

(LRNC). Results: Ex vivo

images and their

histograms are shown in

figure 1. The intensity distribution of

GE and PD is scattered. Information

measured by joint entropy and conditional

entropy is shown in table 1. PD and GE images contributed more information to joint

entropy. We think this extra information comes from T2* weighting in GE based sequence.

Conclusion: Gradient echo based sequences can provide additional information to

existing plaque imaging protocols.

Reference: [1] C. Yuan, W.S. Kerwin, JMRI, 2004, 19, 710-719. [2] R.G. Gallager,

Information Theory and Reliable Communication, Wiley, 1968.


3.7 Improved Black Blood Multi-Contrast Protocol for In-vivo Atherosclerotic Imaging

Seong-Eun Kim1,3, John Roberts, Gerald S. Treiman2,4, Dennis L. Parker1,3 1Utah Center for Advanced Imaging Research, 2VA Salt Lake City Health Care System, 3Radiology,

4Surgery, University of Utah Purpose: Atherosclerotic plaque characterization by MRI is generally based on the signal

intensities and morphology of plaque in T1, PD and T2 weighted images, but intraplaque

thrombus cannot be detected by conventional contrast imaging. Our multi-contrast

protocol including DWI and 3D MPRAGE may help detect plaque hemorrhage and assist

in the identification of plaque components in the cervical carotid artery. Methods: DW images (1.0x1.0x2.0 mm3) were acquired using 2D ss-IMIV DWEPI with b

=10 and 300 s/mm2 to create the ADC maps. 2D T1w, T2w and PD images of the same

locations were acquired (0.5x0.5x2.0 mm3) with 2D TSE. (The T1w with our modified

version of the double inversion preparation). 3D MPRAGE images were acquired

(0.5x0.5x1.0 mm3) with non-selective inversion preparation and fat saturation. Total scan

time including 2D and 3D TOF was less than one hour. Results: Multi-contrast Images of atherosclerotic plaque with hemorrhage from a patient

are shown at the left. The plaque area indicated by white arrows shows a moderate signal

on T1w, T2w and low ADC value (0.29x10-3 mm2/s). 3D MPRAGE images show the hyper-

intense hemorrhage region in the carotid plaque.

Discussion: The results obtained indicate that multi-contrast black blood images

including DWI (as a new contrast) and 3D MPRAGE may be of substantial value for

carotid plaque identification.

T1w T2w ADC 3DMPRAGE


.

b a Figure 1. Curved reformatted vessel wall images Obtained at a) 1.5T b) 3T.

3.8 3D peripheral vessel wall MRI with flow-insensitive blood suppression and isotropic resolution at 3 Tesla Thanh D. Nguyen, Keigo Kawaji, Pascal Spincemaille, Matthew D. Cham,

Priscilla Winchester, Martin R. Prince, Yi Wang Weill Medical College of Cornell University, New York, NY

Email: [email protected]

Flow-insensitive T2-prepared inversion recovery (T2IR) has been shown to provide

better blood suppression for 2D arterial vessel wall imaging at 1.5T than double inversion

recovery (DIR) in the lower extremities where blood flow is slow (1). T2IR offers global

blood suppression regardless of flow velocity and direction at the cost of reduced wall

SNR. The purpose of this study was to develop a cardiac triggered 3D black blood T2IR

fast spin echo sequence for vessel wall MRI at 3T.

For comparison, 4 normal volunteers (27 ± 8 years) were imaged at both 1.5T and 3T

(GE HDxt) with parameters: TR=1RR, TE=20 ms, FOV=28 cm, matrix=384x384, coronal

slice thickness=1.4 mm (1.5T, interpolated to 1.5 mm) and 0.7 mm (3T), number of

slices=100/200 (1.5/3T), NEX=2/1

(1.5/3T), bandwidth=±62.5 kHz,

ETL=64 (variable flip angles to

increase sampling efficiency), self-

calibrated parallel imaging (ARC)

factor R=1.9, partial kz factor=0.75,

fat suppresion, scan time~8 min, 8-

channel cardiac coil. For T2IR

preparation, T2PREP time=120/150

ms (1.5/3T), and TI~250/300 ms

(1.5/3T).

Figure 1 shows images of

distal superficial femoral and

proximal popliteal arteries obtained at 1.5T and 3T, demonstrating extended bilateral

coverage, excellent arterial blood suppression across large FOV, and good wall

visualization. Note that 3T images offer true 0.7x0.7x0.7 mm3 isotropic resolution with

similar wall SNR. In conclusion, the global blood suppression of T2IR and the higher SNR

afforded by 3D acquisition and higher field strength allow efficient imaging of vessel wall

with sub-millimeter isotropic resolution.

References. Brown R. ISMRM 2009. p3844.

mailto:[email protected]


3.9 A 16 Channel Anterior Neck RF Coil for Cervical Carotid MRA Quinn Tate, Emilee Minalga, Laura C. Bell, J. Rock Hadley

Utah Center for Advanced Imaging Research, Dept of Radiology, University of Utah Purpose: Increased speed in cervical carotid imaging is highly desired to reduce the

artifacts from occasional motion such as swallowing. Methods: We have developed a 16 channel receive only RF coil array with overlapping

elements placed on a form fitting fiberglass former as shown in Figure 1.

Results: Images shown in Figures 1 and 2 illustrate the improvement for parallel

imaging over the 4 channel bilateral RF coil that we currently use.

Conclusion: The new 16 channel coil shows great potential for rapid carotid MRI.

Figure 1: A 16 channel (8 channels on each side) RF coil array for the neck, with emphasis on the cervical carotid artery. The array was fabricated based on an overlapping element philosophy. A second coil array is being fabricated based upon evaluations of this coil array. Below are shown example images from the 16 channel coil for (left) R=1 (no reduction, 6:44min), (middle) R=2 (3:25min) and (right) R=3 (2:43min) using

2D TSE with DIR prep TE/TR=8/885ms ETL=9 TI=600ms 2 AVG, FOV=130mm matrix=256x256

Figure 2: (left) Head/neck positioner with 4 channel (2 channel bilateral) carotid coil. (right) Comparison 2D DIR TSE images (TE/TR=8.8/885ms, TI= 600ms, 0.5x0.5mm2 inplane, 2mm slice thickness) obtained using the 4 channel coil shown at left (bottom row) and the 16 channel coil shown in Figure (top row). With a reduction factor of 2, the 16 channel coil images are less noisy.


4.1 Gadobenate dimeglumine vs gadopentetate dimeglumine for peripheral MR angiography: comparison with DSA

SC Gerretsen1, T le Maire2, S Miller3 , SA Thurnher4, CU Herborn5, H Michaely 6, H Kramer 7, A Vanzulli 8 , J Vymazal 9, M Wasser 10, T Leiner1

1. Maastricht University Hospital, Maastricht, The Netherlands; 2 Catharina Hospital, Eindhoven, Netherlands; 3. Eberhardt Karls University, Tuebingen, Germany; 4. Hospital Brothers of St. John of

God, Vienna, Austria; 5. University Medical Center, Hamburg-Eppendorf, Germany, 6. University Hospital, Mannheim, Germany, 7. Ludwig Maximilians University, Munich, Germany, 8. Ospedale Niguarda Ca' Granda, Milan, Italy, 9. Na Homolce Hospital, Prague, Czech Republic, 10. Leiden

University Medical Center, Leiden, Netherlands

Purpose: To prospectively compare equivalent 0.1 mmol/kg doses of gadobenate dimeglumine and gadopentetate dimeglumine in patients undergoing contrast-enhanced MR angiography (CE-MRA) of the peripheral arteries. Methods: 96 adult subjects with suspected moderate-to-severe peripheral arterial occlusive disease (PAOD) were enrolled at 7 sites. Patients underwent 2 identical 1.5-T, 3-station, CE-MRA examinations from the aortic bifurcation to the lower leg with randomized 0.1 mmol/kg bodyweight doses of gadobenate dimeglumine and gadopentetate dimeglumine. Diagnostic performance (sensitivity, specificity, accuracy, positive predictive value [PPV], negative predictive value [NPV]) was determined in a subset of patients (n=31) that also underwent conventional DSA. The presence and extent of steno-occlusive disease on DSA images was determined on a segmental basis using a 4-point scale (1=stenosis ≤25%; 2=stenosis >25–≤50% 3=stenosis >50–99%; and 4=occlusion). Statistical analyses were performed using the Wilcoxon Signed Rank, McNemar, and Wald tests. Results: A total of 397 segments were evaluated by DSA. Of these 397 segments, 270 (68.0%) had stenoses of ≤50% while 127 (32.0%) had hemodynamically-relevant (>50%) stenoses. All 3 blinded readers reported significantly (p≤0.0017) better diagnostic performance with gadobenate dimeglumine compared to gadopentetate dimeglumine, with increases of 11.0–18.1% in sensitivity, 4.4–9.3% in specificity, and 7.8–10.1% in overall accuracy (Table 1). Readers also reported significantly (p≤0.0028) higher PPV and NPV with gadobenate dimeglumine, with differences ranging from 12.7–19.3% for PPV and 5.5–7.9% for NPV. Conclusion: In patients with suspected PAOD referred for CE-MRA, use of 0.1 mmol/kg bodyweight gadobenate dimeglumine results in significantly better diagnostic performance than use of an equivalent dose of gadopentetate dimeglumine.


4.2 Dose Comparison between Conventional and High Relaxivity Contrast Agents in Peripheral MRA

Jeffrey H. Maki1, George R. Oliveira1, Gregory J. Wilson2 1 - University of Washington Dept of Radiology, Seattle, WA. 2 - Philips Medical Systems, Cleveland, OH.

Purpose Evaluate the utility of standard dose (~0.1 mmol/kg) high relaxivity (SDHR)

gadolinium contrast for peripheral MRA (pMRA), and compare this to high dose high

relaxivity (~0.2 mmol/kg) (HDHR) and high dose conventional relaxivity (HDCR)

gadolinium contrast.

Methods 60 patients undergoing 3 station moving table pMRA for suspected peripheral

vascular occlusive disease received one of three contrast agents/doses (20 each): 17 cc

gadobenate dimeglumine (MultiHance; Bracco Diagnostics), 34 cc gadobenate

dimeglumine, or 34 cc gadoteridol (ProHance; Bracco Diagnostics). Imaging was

performed on a 1.5T system (Gyroscan NT, Philips Medical Systems) using a prototype

18 channel coil and a SNR/timing optimized pulse sequence designed to maximize SNR

while avoiding venous contamination1. Upper/middle scan times ranged from 5-12.5 sec,

with lower station 45-60 sec. Arterial contrast ratios (CR: arterial SI minus muscle SI

divided by muscle SI) were calculated for each station and corrected for differences in

TR/TE. Subjective image quality and venous enhancement were evaluated. Statisitical

analysis was performed using the Student t-test and Mann Whitney U tests.

Results All studies were diagnostic and high quality. Contrast ratio was uniformly higher

for HDHR contrast in all stations, but only significant in the lower station. Interestingly,

upper station HDHR image quality was rated significantly worse than the others despite

its higher CR. This trend has been noted in other studies, where high dose gadobenate

dimeglumine appears to decrease MRA image quality/diagnostic efficacy2. There was no

significant contrast ratio or image quality difference between SDHR and HDCR, however

lower station venous enhancement was significantly less than the others for SDHR.

Conclusion Excellent quality peripheral MRA can be performed with standard dose

gadobenate dimeglumine, as overall quality is equivalent to or better than double dose

conventional contrast. Increasing HR contrast dose improves CR, but may not improve

image quality. Further investigation into this phenomenon is underway.

References 1. Potthast et al. J Magn Reson Imag 29:1106-1115, 2009.

2. Schneider et al. J Magn Reson Imaging. 26(4):1020-32, 2007.


4.3 Peripheral MRA With Continuous Table (CTM) Movement in Combination with High Temporal and Spatial Resolution TWIST-

MRA With 0.1 mmol/kg Gadobutrol at 3.0 T Voth M1, Haneder S1, Gutfleisch A1, Schoenberg SO1, Michaely HJ1

1Institute of Clinical Radiology and Nuclear Medicine, University Medical Center Mannheim, Medical Faculty of Mannheim, University of Heidelberg, Germany

Purpose: To prove the concept of peripheral CTM-MRA in combination with high spatial

and temporal resolution time-resolved TWIST-MRA in a single MR-exam at 3.0T with a

single dose (0.1 mmol/kg) of gadobutrol in total.

Methods: 22 consecutive patients (15m/7f, mean age 64 years) referred for peripheral

MRA with clinical symptoms of peripheral arterial occlusive disease (PAOD) Fontaine

stages II–IV underwent both CTM-MRA (TR 2.4ms/ TE 1.0ms/ flip angle 21°) of the run-off

vessels and TWIST-MRA (TR 2.8ms/ TE 1.1ms/ flip angle 20°) of the calf station during a

single MR-exam at 3.0T (Siemens Tim Trio). Spatial resolution of the CTM-MRA datasets

was 1.2mm isotropic. The TWIST-MRA was acquired with 1.1x1.1x1.35mm³ and

reconstructed to 1.1mm isotropic with a temporal resolution of 5.5 s. A total of 0.1 mmol/kg

BW gadobutrol diluted 1:1 with saline was injected at a flow rate of 1.5 mL/s of which

0.07 mmol/kg was administered for the CTM-MRA and 0.03 mmol/kg for the TWIST-MRA.

CTM-MRA run off datasets were qualitatively assessed using a four point scale (4-

excellent, 1-non-diagnostic) followed by TWIST-MRA datasets. Additional relevant findings

only visible in the TWIST-MRA were documented.

Results: All datasets could be evaluated with a total of 397 assessable segments. CTM-

MRA was diagnostic in 99% (393/397) with image quality judged as excellent in 54%

(213/397), good in 42% (14/397), and moderate in 4% (14/397) respectively. Non

diagnostic image quality was seen in 1% (4/397). TWIST-MRA was diagnostic in 100%

(115/115) with good or excellent image quality. In 14 of 22 patients additional relevant

findings were detected by TWIST-MRA.

Conclusion: Single-dose gadobutrol CTM-MRA in combination with a high spatial and

temporal resolution TWIST-MRA at 3.0 T is a reliable technique with good image quality.

Despite the use of single dose contrast agent large field of view coverage and dynamic

images can be acquired. Due to its robustness, this imaging approach of the vasculature

has great potential for a broad clinical use.


4.4 Flow and Motion-Insensitive Unenhanced MR Angiography of the Peripheral Vascular System –A pilot study in the lower

extremity John J. Sheehan 1,2, Ioannis Koktzoglou1, James C. Carr2, Eugene Dunkle1, Robert R. Edelman1 1Department of Radiology, NorthShore University HealthSystem, 2650 Ridge Ave., Evanston, IL 2Cardiovascular Imaging, Northwestern University, 737 N. Michigan Ave, Ste1600, Chicago, IL

Introduction: Current limitations of unenhanced magnetic resonance angiography techniques include sensitivity to flow velocity, cardiac rhythm, and patient motion. We developed an alternative unenhanced method for peripheral magnetic resonance angiography (MRA) with the potential for robust performance over a wide range of physiological conditions. Materials and Methods: Flow-insensitive single shot (FISS) MRA acquires data with a specially modified single shot two-dimensional (2D) balanced steady-state free precession (bSSFP) pulse sequence. A key feature is the use of a quiescent inflow time period (QITP), coincident with systole, which is sandwiched between a saturation module and the bSSFP readout. The QITP provides the opportunity for maximal inflow of unsaturated arterial spins while ensuring suppression of venous signal. The combination of a saturation magnetization preparation with a single shot acquisition minimizes sensitivity to heart rate variations and arrhythmias. In order to test the clinical feasibility of the technique, we performed a pilot study of FISS MRA using contrast-enhanced MRA as the reference standard. A series of 4 healthy subjects (4 male, ages 28-45) and 8 patients (8 male, ages 56-90) with documented peripheral vascular disease were studied. Results: In all subjects, FISS MRA demonstrated the entire length of the peripheral vascular tree from aorta to pedal vessels. Considering CE-MRA as the standard of reference examination and excluding stented arterial segments, the sensitivity, specificity, PPV, and NPV values of FISS MRA for arterial narrowing greater than 50% or occlusion were 92.2%, 94.9%, 83.9% and 97.7% respectively. FISS MRA provided robust depiction of normal arterial anatomy and peripheral vascular disease, irrespective of disease severity, in scan times on the order of eight minutes for the entire peripheral vascular tree. In no subject was there substantial degradation of image quality due to bulk motion or variation in cardiac rhythm. Conclusion: FISS MRA is a fast, flow-insensitive and easy-to-use method for depicting the peripheral arteries. In a small group of patients, the unenhanced technique had excellent negative predictive value and image quality was consistent irrespective of the severity of PVD. Unlike subtraction-based unenhanced 3D MRA, the technique does not need to be tailored for each patient and initial results demonstrate reliable image quality for the pelvic vessels despite the presence of respiratory motion.


4.5 A Comparison of Time-Resolved 3D CE-MRA with Peripheral Run-off CTA in the Calves

CR Haider, JF Glockner, TJ Vrtiska, TA Macedo, EA Borisch, SJ Riederer MR Laboratory, Mayo Clinic, Rochester MN USA

PURPOSE To perform a comparison of time-resolved 3D CE-MRA of the calves using Cartesian Acquisition with Projection-Reconstruction-like sampling (CAPR) with peripheral CTA. METHODS Nine patients who underwent clinically indicated peripheral run-off CTA were recruited for MRA within 48 hours of their CTA. CTA was performed using the standard protocol of our vascular CT clinical practice on a 64-detector row CT scanner (Sensation 64; Siemens Medical Solutions, Forschheim, Germany) resulting in 0.6 mm in-plane resolution with 2 mm thick axial sections and 1.2 mm increment. The CAPR acquisitions were performed on a 3.0 T MRI system (GE Healthcare, Milwaukee, WI.). 3D image sets with 1 mm isotropic spatial resolution were generated for a field of view of 40 cm S/I, 32 cm L/R, and 13.2 cm A/P using a 5 sec frame time and 20 sec temporal footprint [1, 2]. Using CTA as the reference, the MR data sets were evaluated with respect to depiction of any pathology, relative prominence of the luminal signal, and any added value of the time-resolved information.

RESULTS The diagnostic image quality of the MRA results was rated very competitively vs. CTA (example, Figure 1). The CAPR sequence provided clear arterial frames in the case of rapid arterial to venous transit in patients with ulceration of the feet. In no MRA study was any reconstruction artifact observed that adversely affected image quality. CONCLUSION These studies suggest that time-resolved MRA of the calves using CAPR can provide similar information to that generated using CTA.

References: [1] Haider et al., MRM 60:749 (2008); [2] Haider et al., Radiology (in

press).

(A) (B) (C)(A) (B) (C)

Figure 1. CTA vs. CAPR MRA. Vessel noted in CTA (A, arrow) is seen to fill retrograde in consecutive 5 sec frames in MRA (B-C).


4.6 3D Time-Resolved MR Angiography of Lower Extremities using Cartesian Interleaved Variable Density Sampling and HYPR

Reconstruction 1aK. Wang, 2R. Busse, 1aY. Wu, 1aL. Keith, 2J. Holmes, 1a,bF. Korosec

1aMedical Physics, 1bRadiology, University of Wisconsin-Madison, Madison, WI 2Applied Science Lab, GE Healthcare, Madison, WI

Purpose: To simultaneously improve spatial and

temporal resolution of 3D time-resolved MR

angiography (TR-MRA) in lower extremities using

Cartesian interleaved variable density sampling

(VDS) [1] and HYPR [2-4].

Methods: Each time frame, a

subset of k-space views are

acquired with sampling density

proportional to 1/kr as shown in

Fig. 1 and described further in Ref.

[1]. The sub-sampling patterns for

a series of timeframes are

designed to interleave, such that

the data over N timeframes is fully

sampled and HYPR methods in Ref. [3,4] can be used. Imaging parameters include: 0.94

x 0.94 x 1.5mm3 voxel size with matrix size of 512x282x72, 30 time frames with 5.8

sec/frame.

Results: Fig. 2 shows coronal MIP images at arterial (a) and venous (b) phases.

Compared with zero-filling, HYPR reduces the spatial blurring and increases the SNR,

while preserving the temporal fidelity; View-sharing techniques yield early enhancement

(thin arrow) and temporal blurring (thick arrow), as shown in Fig. 2(d).

Conclusion: It is feasible to improve the spatial and temporal resolution in 3D TR-MRA

using Cartesian interleaved variable density sampling and HYPR reconstruction.

References: [1] Busse et al., ISMRM 2009, p4534. [2] Mistretta et al. MRM 55:30 (2006).

[3] Wang et al. ISMRM 2009, p3884 [4] Busse et al., ISMRM 2009, p2834

in B being slightly different. After a short pause, a conventional high spatial resolution MRA (0.1 mmol/kg Gadovist®) was acquired using a 3D spoiled gradient-echo sequence


4.7 3D Noncontrast MRA Using FSD-Prepared Balanced SSFP Z. Fan1,2, J. Sheehan1, X. Bi3, T. J. Carroll1,2, R. Jerecic3, J. Carr1, and D. Li1,2

1Radiology, 2Biomedical Engineering, Northwestern University, Chicago, IL, USA; 3Siemens Medical Solutions USA, Inc., Chicago, IL, USA

Purpose: To develop a 3D noncontrast MRA (NC-MRA) method for peripheral arterial system using flow-sensitive dephasing (FSD)-prepared balanced SSFP (bSSFP). Methods: The FSD preparative module consists of a 90o

x-180oy-90o

-x pulse series and symmetric gradients around the 1800 pulse, which imparts flow sensitization measured by the first-order gradient moment (m1) [1]. An optimal m1 can selectively suppress the fast-flow arterial blood signal during systole while having little effect on the slow-flow venous blood and static tissues. Subtraction between a bright-artery scan using bSSFP and a dark-artery scan using FSD-bSSFP will result in an artery-only dataset. The new technique was tested in multiple peripheral arterial territories of healthy volunteers and patients at 1.5-T. Contrast-enhanced (CE) MRA was performed in patient studies for reference. Parameters: 3D coronal acquisition, FSD gradients applied in the readout direction, isotropic high spatial-resolution (0.8 -1.2 mm), TE/TR =1.5-1.9/ 3.1-3.8 ms, flip angle = 70-90o, centric phase encoding, GRAPPA factor =2, m1 range 17-87 (leg), 58-156 (hand), 195-390 (foot) mT.ms2/m. Results: Proof of principle was obtained from the lower extremities and hands (Fig. 1-3). The value of m1 was shown to be critical for suppressing blood signal and achieving excellent MRA quality. Comparable depiction of stenosis/occlusion and superior visualization of patent segments were achieved using NC-MRA vs. CE-MRA. Conclusion: The feasibility of this NC-MRA approach has been successively demonstrated. Systematic optimization of m1 is warranted for clinical applications. References: [1] Koktzoglou I, et al. JCMR 9:33 (2007).

Fig.3 NC-MRA of the feet in a healthy volunteer.

Fig.2 NC-MRA (b) demonstrated more arterial vessels (in red) and detail than CE-MRA (a) in a patient with Raynauds disease.

b a

Fig.1 Both CE-MRA (a) and NC-MRA (b) demonstrate significant calf artery occlusion in a patient with PAD. The large collateral vessels are better depicted by NC-MRA. However, image artifacts due to metallic clip (arrow) and field inhomogeneity (arrowhead) are also appreciable.

a b


4.8 Non Contrast MRA of the Hand in Patients with Raynauds disease using Flow Sensitized Dephasing Prepared SSFP

J. C. Carr1,2, J. J. Sheehan1, Z. Fan2, A. Davarpanah2, and D. Li2 1Cardiovascular Imaging, Northwestern Memorial Hospital, Chicago, IL, United States, 2Cardiovascular

Imaging, Northwestern University, Chicago, IL, United States

Introduction: Raynauds disease is vasospastic disorder of the digital arteries. 3D contrast-enhanced (CE) MRA is increasingly utilized for patients with Raynauds. Safety concerns with contrast administration in patients with renal insufficiency have led to a renaissance of non-contrast MRA (NC-MRA). NC-MRA strategies employing 3D half-Fourier FSE [1] or SSFP [2] have shown great promise but various challenges remain. The aim of this study was to retrospectively assess the diagnostic quality and accuracy of a new NC-MRA method for hand MRA based on flow-sensitized dephasing (FSD)-prepared SSFP. Materials and Methods: The proposed NC-MRA method acquires a bright-artery scan using ECG-triggered SSFP and a dark-artery scan using ECG-triggered, FSD-prepared SSFP [3]. Subtraction of the two scans results in bright arteries and suppression of the background and veins. 8 patients with clinically established Raynauds disease who have been imaged at 1.5T (Avanto, Siemens) using a 16-element peripheral matrix coil and spine coils, were retrospectively reviewed with IRB approval. Phase-contrast flow imaging was first performed to derive the arterial flow peak time T. Each patient subsequently underwent a time resolved TWIST MRA (TR MRA) and a high resolution MRA (HR MRA) with Gadolinium-BOPTA. The FSD subtraction images along with the TR MRA and HR MRA were reviewed and compared. Diagnostic quality was assessed by giving a per vessel score for the 17 segments per hand (1, poor; 2, fair; 3, good; 4, excellent) and adding them together for each hand (full score: 36). The degree of stenosis for each vascular segment was characterized using a four-point scale (grade 0, normal; grade 1, luminal narrowing <50%; grade 2, luminal narrowing >50%; grade 3 occlusion). Results: The mean qualitative score for TR MRA, HR MRA and FSD were similar: 3.8, 3.4 and 3.5, respectively (t-test, P>0.05). Differences were more apparent when comparing the distal digital arteries. Of 90 possible arterial segments, 6 (7%) were not adequately depicted with all techniques because of severe venous overlay. FSD identified 95% of luminal narrowings ≤50% and ≥50% that were identified on contrast enhanced MRA. Non-contrast FSD identified all of the arterial occlusions identified on contrast enhanced MRA. The mean quantitative scores were similar for the degree of stenosis for TR MRA, HR MRA and FSD were: 1.9, 1.9 and 2.0, respectively (t-test, P>0.05). Conclusion: Hi-resolution non contrast FSD MRA of the hand in patients with Raynauds compares favorably with contrast enhanced time resolved TWIST and high resolution static MRA and in many cases demonstrates improved resolution and visualization of normal and vasospastic vessels. References: 1. Miyazaki M, et al. Radiology 227:890 (2003). 2. Stafford R, et al. MRM 59:430 (2008). 3. Koktzoglou I, et al. JCMR 9:33 (2007).


4.9 Two-Station Time-Resolved CE-MRA of the Lower Legs CP Johnson, CR Haider, EA Borisch, RC Grimm, PJ Rossman, SJ Riederer

Department of Radiology, Mayo Clinic, Rochester MN 55902 USA Purpose: Contrast-enhanced MRA of the calves with high spatiotemporal resolution has

recently been demonstrated [1,2]. The goal of this work was to demonstrate the technical

feasibility of acquiring time-resolved extended field-of-view arteriograms of the thighs and

calves, nearly doubling the longitudinal coverage of the calf studies while maintaining

similar quality.

Methods: Acquisition was based on the CAPR method [3] on a GE 3.0T MRI system.

Two stations covering the thighs and calves of a volunteer were imaged with identical

imaging parameters using a stepping table approach. 8x 2D SENSE was achieved with

two high-performance eight-channel receive arrays

[4], one placed at each station. A 2 mL timing bolus

was used to determine the bolus transit time to the

calves. The diagnostic scan was then acquired

using 1.0 mm isotropic resolution with a 5.0 second

image update time. 18 mL of Multihance followed by

a 20 mL flush were injected intravenously at 3

mL/sec. Prior to the time-resolved sequence, a two-

station calibration scan was acquired.

Results: A maximum intensity projection of select

arterial frames overlapped using a weighted sum is

shown in Figure 1, demonstrating good image

quality.

Conclusion: Time-resolved CE-MRA of the lower

legs using CAPR may allow for extended field-of-

view arteriograms with diagnostic quality comparable

to that achieved in single-station studies.

References: [1] Haider CR, ISMRM 2009, #2734. [2] Wu Y, JMRI 2009, 29:917-23.

[3] Haider CR, MRM 2008, 60:749-60. [4] Johnson CP, ISMRM 2008, #1079.

Figure 1: MIP of select arterial frames.


5.1 An Update on the Clinical Experience with Gadofosveset Stephen Schmitz1; Edward Parsons2; Mark G. Hibberd1

1Lantheus Medical Imaging, N. Billerica, MA, USA; 2Independent Consultant, Burlington, MA

Purpose: The clinical use of gadofosveset trisodium is reviewed in light of over three

years’ use in Europe and Canada, the recent US-FDA approval of gadofosveset trisodium,

and the establishment of a new clinical registry in the United States.

Methods: The post-marketing registry that samples the clinical experience of roughly

70,000 exposures of gadofosveset trisodium in Europe was reviewed. The adverse event

profile was summarized and compared with the data found in clinical trials and scientific

literature describing gadofosveset and gadolinium contrast agents in general. The

physiochemical and pharmacokinetic properties of gadofosveset were reviewed in

consideration of leading hypotheses on the mechanism of NSF, and a new clinical registry

in the US was proposed.

Results: To date, only one blood-pool contrast agent (gadofosveset) has been registered

for use in MRA. The utility of gadofosveset in vascular MRI has been detailed both by

well-controlled clinical trials and by investigator-initiated studies. The adverse event profile

reported in post-market assessments is consistent with that reported in clinical trials. The

properties and pharmacokinetics suggest a relatively low risk of NSF, and no cases of

NSF have been associated with gadofosveset to date. A new prospective registry will

assess ongoing adverse event risks.

Conclusion: Over three years of experience has expanded knowledge of the safety and

efficacy of gadofosveset since its introduction in Europe and Canada. This information

should benefit the decision-making of clinicians considering its use. The impeding

introduction of gadofosveset to the US market will bring many of these advances to a large

new group of physicians and patients.


5.2 A Re-analysis of MS-325 (gadofosveset trisodium) Clinical Trial Data in Support of US-FDA Approval

Edward Parsons1, Neil Rofsky2, Gary Stevens3, Margaret Uprichard1, Kirsten Overoye-Chan1, Andrew Uprichard1.

1EPIX Pharmaceuticals, Inc.; 2Beth Israel Deaconess Medical Center, Harvard Medical School; 3Dynastat, Inc.

Purpose: To verify the clinical efficacy of MS-325 (gadofosveset trisodium) in terms of

sensitivity and specificity for detection of stenotic lesions in MRA, as demonstrated in

phase 3 clinical trials [1,2], fulfilling current US-FDA regulatory requirements for efficacy.

Methods: Image data collected in support of registration of gadofosveset was re-read

according to a rigorous interpretation protocol. The protocol was developed in consultation

with the FDA and included additional steps for specific training of blinded MRA readers,

use of a consistent paradigm for image assessment, strict categorization of any image

artifacts that precluded diagnostic assessment, and a conservative statistical analysis with

precise conditions on unanimous gains in sensitivity and non-inferiority of specificity.

Three readers assessed non-contrast and gadofosveset-enhanced MRA data from two

trials of patients with suspected aorto-iliac arterial occlusions. Assessments were

compared to DSA results as a gold standard.

Results: The sensitivity endpoints were similar to those of the prior reads, with smaller

gains in specificity. All three readers showed statistically significant (p<0.001) gains in

sensitivity (+20.4%, +12.2%, +14.9%%) with at least non-inferior specificity (+0.4%,

+7.9%, +0.2%). Significantly fewer contrast-enhanced MRAs were considered

uninterpretable when compared with non-contrast images (average of 8.6% vs 1.4%).

Conclusion: The efficacy of gadofosveset was affirmed, resulting in US-FDA marketing

approval [3]. More standardized reading guidelines produced more consistent results.

References: [1] Rapp et al. Radiology. 2005 Jul; 236(1):71-8. [2]. Goyen et al.

Radiology. 2005 Sep; 236(3):825-33. [3] Drug Approval Package: Vasovist.

http://www.accessdata.fda.gov/drugsatfda_docs/nda/2008/021711s000TOC.cfm


5.3 Gadofosveset Excretion into Human Breast Milk Malene S. Thomsen1, Walter Gössler2, Uwe Lang3 Manuel Aigner1,

and Manuela Aschauer1

1 Division of Vascular and Interventional Radiology, Department of Radiology, Medical University of Graz, Auenbruggerplatz 9, 8036 Austria, 2 Institute of Chemistry, Analytical Chemistry, Karl-Franzens

University, Universitaets-platz 1, 8010 Graz, Austria, 3Department of Obstetrics & Gynaecology, Medical University of Graz

Purpose - Gadolinium (Gd) based contrast agents are generally accepted as

pharmaceutical agents with few adverse effects. However, for the contrast media

gadopentetate (Magnevist®) it is common practice that nursing mothers interrupt

breastfeeding, and discard the milk the first 24 - 48 hours after injection of gadopentetate [1]. The aim of this current investigation was to evaluate if this guideline can be applied as

well when using the contrast agent gadofosveset (Vasovist®).

Methods - The Gd-content of breast milk was monitored up to 51 hours after injecting

gadofoveset to a lactating patient (indication: objective evaluation of pulmonary artery

embolism and deep venous thrombosis to plan the cava filter implantation) by collecting

the breast milk with intervals of 2-4 hours and analyzing samples for the Gd-content

applying inductively coupled plasma mass spectrometry (ICP-MS)

Results - A significant result found was that gadofosveset was excreted from the body

with a half-life time of around 26 hours, which was twice that of gadopentetate [2,3]. That

gadofosveset stays longer in the blood circulation can most likely be explained by the fact

that gadofosveset reversibly bind to proteins[4] whereas gadopentetate is highly water

soluble and has low binding to proteins.

Conclusion - From the study it was discovered that gadofosveset stays in the body twice

as long as gadopentetate. Therefore the guideline might not be directly applicable. We

recommended no brest feeding in this case for 48 hr.

References - 1) Lin & Brown, J. Magn. Reson. Imaging, 2007 25, 884-899

2) Schmiedl et al, Am. J. Roentgenol., 1990, 154, 1305-6

3) Rofsky et al, J. Magn. Reson. Imaging, 1993, 3, 131-132

4) Goyen, Vasc. Health Risk Manag., 2008, 4, 1-9


5.4 Overview of Gd-BOPTA Phase III Trial for CERMA: What are the results, and how do we move forward? Thomas M. Grist, M.D. University of Wisconsin – Madison

PURPOSE Contrast-enhanced magnetic resonance angiography (CE-MRA) is widely used for

imaging atherosclerotic disease in the carotid, renal, and peripheral arteries yet few multi-

center trials have been reported that document the safety and efficacy of modern CE-MRA

techniques. Studies were recently initiated to assess the safety and efficacy of a single

0.1 mmol/kg bw dose of gadobenate dimeglumine (Gd-BOPTA; MultiHance) for MRA in

these three vascular territories. The objective of this presentation is to review the results

of a multi-center trial and highlight the potential impact of the salient findings on MRA

practice in the future.

MATERIALS AND METHODS

A total of 825 patients from Europe (63%), North America (27%), and South America

(10%) were evaluated. Imaging of the carotid (N=247), renal (N=291) and peripheral

(N=287) vessels was performed. 2D TOF and CE MRA was performed, and compared to

intra-arterial DSA as a reference standard. Assessment of MRA images was performed at

an independent core imaging laboratory by 3 experienced, fully-blinded radiologists per

study unaffiliated with any study center. DSA images were reviewed in a similar fashion

by a single reader. McNemar’s test was used to compare sensitivity, specificity, and

accuracy of TOF and CE-MRA for detection of clinically significant steno-occlusive

disease (>50% or 60% for carotid).

RESULTS AND DISCUSSION

The diagnostic accuracy of CE-MRA was significantly greater than TOF-MRA for most

vessel territories and readers (p<0.05). Likewise, inter-observer agreement for CE-MRA

was greater than 2D-TOF MRA. However, lower sensitivity values than anticipated were

observed for CE-MRA due to methodological issues encountered in the study. The results

and potential impact of these findings on acceptance of CE-MRA techniques will be

discussed.


5.5 Safety of Gadobenate dimeglumine (Gd-BOPTA) in Cardiovascular Imaging of Pediatric Patients Guenther Schneider, Hellmut Schürholz, Arno Bücker, Peter Fries

Homburg University Hospital, Homburg/Saar, Germany

Purpose: The advent of nephrogenic systemic fibrosis (NSF) has brought the safety of

Gd-based contrast agents into sharp focus. Nowhere is safety of greater concern than

among pediatric patients who frequently require multiple contrast-enhanced (CE) MR

examinations over an extended period of time. Gadobenate dimeglumine (MultiHance) is a

contrast agent that has proven extremely safe among adult subjects for a variety of

indications. Due to its increased relaxivity and the stability of the complex it seems to be

well suited for cardiovascular imaging in pediatric patients. The present retrospective

analysis was performed to determine the safety of gadobenate dimeglumine in pediatric

subjects referred for routine cardiovascular MRI.

Material and Methods: Gadobenate dimeglumine is routinely used off-label with IRB

approval at our center for this specific patient population because of its beneficial

properties. A total number of 88 pediatric patients (134 studies; 0 years - 15 years)

underwent CE-MRA studies with a gadobenate dimeglumine dose of 0.1 mmol / kg

bodyweight. Since only in-patients were studied, monitoring for adverse events was

performed up to at least 24 hours post injection. Laboratory measurements, vital signs and

ECG determinations were made before and after CE-MRA.

Results: No severe or serious adverse events were noted in our series. No significant

changes of creatinine, bilirubin, vital signs or ECG parameters were noted. No patients

exhibited symptoms of NSF even after repeat doses of gadobenate dimeglumine. Image

quality was excellent especially in patients that underwent CE-MRA for evaluation of CHD.

Conclusion: Gadobenate dimeglumine at a dose of 0.1 mmol/kg bodyweight is a safe and

effective contrast agent for cardiovascular imaging of pediatric patients. Concerning the

safety of Gd-based MR contrast agents, the lower required dose of gadobenate

dimeglumine seems to be beneficial for vascular imaging.


5.6 Retrospective 7 year Study of the Incidence of Nephrogenic Systemic Fibrosis in Patients Investigated with Gadolinium

Contrast-Enhanced Renal Magnetic Resonance Angiography Collidge T A, Brown, M, Rao, A, Thomson P C, & Roditi G Glasgow Royal Infirmary, Alexandra

Parade, Glasgow G31 2ER

Purpose: There is now well documented association between the development of the

condition Nephrogenic Systemic Fibrosis (NSF) and high dose gadolinium contrast MRI

examinations in patients with severe renal failure. We set out to assess the incidence of

NSF in patients with differing degrees of renal impairment investigated by contrast-

enhanced renal MRA.

Methods & Materials: Patients from 1998 to 2005 assessed through retrospective

analysis of electronic patient record (EPR). Patients excluded if follow-up < 90 days.

Analysis included renal function (CKD stage) at time of scan, time to first follow-up, total

follow-up time, number of follow-up episodes, EDTA diagnoses, diagnoses of NSF, reports

of pruritus or other skin disorder, episodes of gadolinium-enhanced MRI and cumulative

gadolinium doses.

Results: Of 1200 patients who underwent gadolinium-enhanced renal MRA studies 500

had follow-up documented > 90 days with average follow-up of 1326 days.

CKD eGFR MRA NSF

5 <15 67 1

4 15-29.9 169 2

3 30-60 222 0

1 & 2 >60 31 0

Normal >90 11 0 (potential live renal donors)

The 3 patients who developed NSF during the course of follow-up had estimated GFRs of

<1, 16 & 18. One patient with initial CKD stage 4 at time of renal MRA developed NSF at

a significantly later stage following a peripheral run-off MRA when clinically unwell in CKD

stage 5. 5 other patients were noted at clinic follow-up to be complaining of pruritus but

none of these was ever diagnosed as suffering from NSF.

Conclusion: This study confirms that NSF is not seen in patients undergoing contrast-

enhanced MRA with less severe degrees of renal failure than CKD stages 4 & 5


5.7 Risk Factors for NSF: a Meta-analysis Martin R. Prince1, 2, MD, PhD, Hong Lei Zhang1, MD, Giles H. Roditi3, MD

Tim Leiner4, MD, Walter Kucharczyk5, MD From Departments of Radiology at Weill Medical College of Cornell University1, Columbia College of

Physicians and Surgeons2, New York, Glasgow Royal Infirmary, Scotland3, Maastricht University Hospital, Maastricht, the Netherlands4, and University of Toronto, Toronto, Canada5

Purpose: To investigate who can safely undergo Gd MRA with minimal risk of NSF.

Method: Pubmed was searched for ‘Nephrogenic Systemic Fibrosis’ to identify papers

with detailed clinical information from January, 2003 to June, 2009. Patient age, gender,

race, type of Gd enhanced imaging, Gd type and dose, interval between Gd and NSF

onset, GFR, dialysis, interval between Gd and dialysis, acuteness of renal failure, kidney

transplant, serum phosphorus, acidosis, epoetin, pro-inflammatory events and NSF

symptoms, were recorded and analyzed. Corresponding authors were contacted for

corroboration and to provide as much missing data as possible.

Results: 77 papers with detailed information on 290 patients were included in the final

analysis. The gender distribution was approximately equally weighted. Very young (<10

yrs) and old (> 60 yrs) patients are at less risk. In 244 patients for whom MR exam history

was investigated, 217 (89%) were noted to have GBCA injections prior to NSF symptom

onset including use of gadodiamide (n = 167), Gadopentetate dimeglumine (n = 11),

gadoversetamide (n = 5), multiple agents (n = 8) and unspecified/unknown (n = 26). All

NSF patients had renal dysfunction with highest prevalence for dialysis and for GFR < 15

mL/min. Acute renal failure was an NSF risk factor with odds ratio of 13:1. In 182 cases

for which data on GBCA dose were available or could be estimated, 90% (n = 163)

received high dose. Other risk factors include pro-inflammatory events, epoetin, acidosis

and hyperphosphatemia. Risk of NSF is small compared to the risk of iodinated contrast

induced nephropathy and the risk death from NSF was small compared to the risk of death

from allergic reactions.

Conclusion: Order of magnitude reductions in NSF risk can be attained by 1) avoiding

high dose, 2) avoiding nonionic linear chelates, 3) dialyzing within 24 hours of Gd

administration for patients already on dialysis, 4) avoiding injecting acute renal failure

patients while serum creatinine is rising.


5.8 Extracellular matrix metabolism in organ-cultured skin from patients with end-stage renal disease: Response to gadolinium

based MRI contrast agents James Varani, Marissa DaSilva, Monica O’Brien Deming, Kent Johnson and 1Richard Swartz;

Departments of Pathology and 1Medicine, University of Michigan, Ann Arbor, Michigan, 48109

Purpose: Nephrogenic systemic fibrosis (NSF) is a clinical syndrome linked with

exposure in renal failure patients to gadolinium - based MRI contrast agents (GBCAs).

The present study addresses potential patho-physiological mechanisms.

Methods: Here we have examined human skin from normal subjects and individuals with

end stage renal disease for response to GBCA stimulation in organ culture.

Results: Omniscan, one of the clinically used GBCAs, had no effect on type I

procollagen production, but increased levels of both matrix metalloproteinase-1 (MMP-1)

and tissue inhibitor of metalloproteinases-1 (TIMP-1). The level of TIMP-1 was

significantly higher than the level of MMP-1 and there was no detectable collagenolytic

activity. Qualitatively, there were no differences in the responses of skin from renal failure

patients as compared to controls. However, basal responses were higher in skin from

subjects in renal failure as compared to control.

Conclusion: These data suggest that GBCA exposure does not directly stimulate

collagen production but, rather, modulates an enzyme-inhibitor system responsible for

regulation of collagen turn-over in the skin. We speculate that heightened responses in

subjects with end-stage renal disease may reflect elevated basal activity.


MDCC

MECC pre MnCl2 MDCC MECC (30 minutes after i.v injection)

5.9 Manganese Based Biodegradable Macromolecular MRI Contrast Agents for Cardiovascular Imaging Zhen Ye1, Eun-Kee Jeong1, Dennis L. Parker1, Zheng-Rong Lu1,2

1Department of Pharmaceutics and Pharmaceutical Chemistry, University of Utah, Salt Lake City, Utah; 2Department of Biomedical Engineering, Case Western Reserve University, Cleveland, Ohio

Purpose: This study was intended to develop Mn(II) based biodegradable

macromolecular contrast agents for cardiovascular MRI.

Methods: The polymeric contrast agents (CAs), Mn(II)-DTPA cystamine copolymers

(MDCC) and Mn(II)-EDTA cystamine copolymers (MECC), were synthesized and

characterized(1). Their in vivo contrast enhanced MR cardiovascular imaging was

evaluated in mice on a Siemens 3T MRI scanner with MnCl2 as a control.

Results: The number average molecular weight of MDCC and MECC was 30.5 and 60.8

KDa, respectively. The T1 relaxivity of MDCC and MECC was 4.7 and 6.41 mM-1s-1 at 3T,

respectively, in the same range of that of MnCl2 (5.2 mM-1s-1)[2]. Contrast enhancement

was observed in the vasculature with MDCC and MECC in the initial period post injection.

Significant enhancement in the myocardium was also observed for MECC and MnCl2, not

for MDCC. The difference in myocardium enhancement between MDCC and MECC might

be attributed to the different coordination chemistry and the stability of two contrast

agents[3].

Conclusion: The Mn(II) based biodegradable macromolecular contrast agents MDCC and

MECC are promising for contrast enhanced cardiovascular imaging with MRI.

Reference: [1] Intl. J. Nanomed. 2007, 2, 191-9. [2] Chem. Rev. 1987.87.901-927; [3]

Cur.Pharm.Biotech, 2004, 5, 539-549

NN

NNH

SS

-OOCO

-OOC

HN

COO-

O nMn2+

NNH

NNH

SS

O

-OOC

HN

COO-

O n

Mn2+


6.1 Non-invasive Trans-Stenotic Pressure Measurements with 3D Phase Contrast MRA: Validation against Endovascular Pressure

Measurements in Swine 1, 3T Bley, 2K Johnson, 1C François, 1,2S Reeder, 1M Schiebler, 2O Wieben, 1T Grist

Departments of 1Radiology and 2Medical Physics, UW Madison, WI, USA 3Department of Radiology, University Medical Center Hamburg-Eppendorf, Germany

Purpose

To evaluate trans-stenotic pressure gradients (TSPG) in renal artery stenosis (RAS)

noninvasively utilizing a 3D phase contrast acquisition with vastly under sampled isotropic

projection reconstruction (PC-VIPR) MRA in a porcine study.

Methods

Respiratory gated PC-VIPR MRA (dual echo, 18,000 projection angles, 10˚ flip, TR/TE

(first echo) = 11.4/3.7 msec, BW = ±62.5kHz, imaging volume: 260x260x160mm3,

acquired isotropic spatial resolution: 1.0x1.0x1.0mm3, venc = 150cm/s) of renal arteries

with surgically created RAS in 12 swine was performed on a 1.5T clinical system (Signa

HDx, GE Healthcare, Waukesha, WI). NCE MRA and TSPG were calculated directly from

the magnitude and velocity measurements using the Navier-Stokes equation.

Endovascular pressure measurements were used as the gold standard for pressure

gradient quantification, performed under DSA guidance.

Results In 19 renal arteries, the TSPG analysis demonstrated excellent correlation between the

non-invasive TSPG utilizing PC-VIPR and endovascular pressure measurements (average

stenosis = 62%, r = 0.977; 95% CI: 0.931, 0.998; p < 0.001). In 5 arteries with severe RAS

(mean 86%), the residual lumen within the stenosis was so small that TSPG could not be

determined using PC-VIPR and they were excluded from the statistical analysis. However,

the angiographic reformats from those data readily revealed severe, hemodynamically

significant RAS. Conclusion Noninvasive assessment of hemodynamic significance of RAS in swine was feasible

utilizing non contrast material enhanced PC-VIPR MRA. Excellent correlation between

TSPG measurements by PC-VIPR and endovascular guide wires was found. PC-VIPR

has the potential to become a major advance in the noninvasive evaluation of RAS and,

as a result, in the management of patients with renal hypertension.


Fig. 1: Vortical flow patterns (white arrows) observed in 15/24 patients after treatmen of aortic coarctation. This finding could be observed irrespective of the treatment methodology. This patient also shows flow acceleration over a mild re-stenosis (openwhite arrow).

Fig. 2: Different stages of aneurysm development were detectable. (A) represents flow patterns in a 10yo boy before treatment of an otherwise not symptomatic coarctation. Clearly, the elongated aortic arch, the vortical flow acceleration (white arrowheads) before the stenosis (white arrow, moderate flow acceleration during late systole) can be apreciated. In (B), a hypoplastic arch (white arrow) gives rise to a flow acceleration taht enters a highly vortical flow through a small aneurysm that distributes greatly helical flow in the Dao (yellow arrows).

6.2 Analysis of aortic hemodynamics after treatment for coarctation using flow-sensitive 4D-MRT at 3T

A. Frydrychowicz1, D. Hirtler2, R. Arnold2, A. Berger1, A.F. Stalder1, J. Bock1, M. Langer1, J. Hennig1, M. Markl1

1Department of Diagnostic Radiology, Medical Physics, University Hospital Freiburg, Germany, 2Department of Pediatric Cardiology, University Hospital Freiburg, Germany 3Department of

Cardiology, University Hospital Freiburg, Germany\

Purpose: To evaluate the hemo-dynamic alterations in aortic blood flow after coarctation repair by flow-sensitive, time-resolved 3D MRI at 3T and to compare findings to acquisitions in volunteers. Methods: Flow-sensitive 4D MR was performed in 28 patients after coarctation repair (16.5±8.0years, range 4-36) and 19 volunteers (35.3±18.1 years, range 20-75) from a previous analysis were included as a reference [3]. Results: The operative site showed a relative re-stenosis with a diameter of 13.3 ± 4.0mm (range 6-24) and a post-stenotic dilatation of 18.8 ± 6.5mm (range 7-43). Next to accelerated flow in all patients, there were additional helices, an increased rate of vortices and most noticeably, in the majority of all patients unexpected vortices in the supraaortics that might attribute to intimal thickening were found. Quantitative analysis showed significantly elevated wall shear stress levels and decreased oscillatory shear indices in the patients that hint towards an influence concerning arterial remodeling. Conclusion: Flow-sensitive MRI revealed marked changes in the hemodynamics after CoA repair. Follow-up examinations have to clarify, whether a predictive value can be attributed to hemodynamics or derived vessel wall parameters. References: 1. Oliver JM J Am Coll Cardiol 2004, 44:1641-1647. 2. Wigström L, et al. MRM 1999;4:793-799, 3. Frydrychowicz A, ISMRM 2008


B

6.3 Flow assessment of arterial dissections using 3D radial phase contrast MR angiography

Christopher J François, Kevin M Johnson, Benjamin Landgraf, Mark L Schiebler, Scott B Reeder, Thomas M Grist, Oliver Wieben

University of Wisconsin, Madison, WI, USA

Purpose: The ability to predict the progression and complications of dissections (eg.

aneursymal dilatation and rupture) is a limitation of current diagnostic methods.

Differences in the flow patterns in the true and false lumina may be important in the

outcomes of dissections1-3. Our aim was to develop a 3D phase contrast (PC) radial pulse

sequence that can be peformed in less than 10 minutes to assess the hemodynamics of

dissections, as a potential prognosticator of dissection

evolution.

Methods: 3D PC VIPR was performed in patients with

arterial dissections. Parameters for PC VIPR were: ±62.5

kHz receiver bandwidth, 1.00-1.25mm3 isotropic spatial

resolution, 8-10 min of free breathing with 50% respiratory

gating efficiency, imaging volume: 32x32x16 cm3, VENC of

80-100 cm/s, retrospective cardiac gating with a temporal

filter for radial acquisitions. PC VIPR data were acquired after obtaining patient consent

according to our IRB protocol. Datasets were analyzed using EnSight (CEI, Inc., Cary,

NC).

Results: Flow patterns in true (arrows) and false (open arrows) lumina were laminar and

non-laminar, respectively. In a patient with celiac and superior mesenteric artery

dissections (A), the flow in the false lumina was vortical. In a

patient with chronic descending thoracic aortic dissection

(B), flow in the false lumen was very slow and turbulent.

Conclusion: Using PC VIPR it is possible to detect

differences in flow patterns between true and false lumina of

arterial dissections, which should permit a more

comprehensive quantitative hemodynamic assessment and

could have prognostic implications in addition to improving our understanding of the

underlying pathophysiology.

References: 1. Markl M, et al. JCAT 2004;28:459. 2. Strotzer M, et al. Acta Radiol

2000;41:594. 3. Mohri M, et al. Clin Cardiol 1985;8:225.

A


6.4 High Temporal and High Spatial Resolution Perfusion Imaging of Hepatocellular Carcinoma in the Liver

Scott B. Reeder, MD, PhD; Ethan K. Brodsky, PhD; Eric Bultman, BS; William Schelman, MD, PhD; Yin Huang, PhD; Sean F Fain, PhD; Walter F. Block, PhD

Departments of Radiology, Medical Physics, Biomedical Engineering and Medicine University of Wisconsin, Madison, WI, USA

Introduction: The field of cancer therapeutics has been shifting from traditional “cytotoxic”

agents to targeted anti-angiogenic therapies. This trend requires biomarkers of early tumor

response. Here we aim to develop high spatial and temporal resolution imaging methods

for quantitative perfusion imaging as a biomarker of tumor response.

Methods: Patients with known hepatocellular carcinomas (HCC) were imaged on a 3.0T

scanner (MR750, GE Healthcare) with a 32 channel abdominal coil, after single dose

injection of gadobenate dimeglumine (Bracco, Princeton, NJ). A time-resolved 3D radial

sequence collected whole abdomen data using one interleaved sub-frame/sec,

reconstructed in real-time1, allowing fluoroscopic monitoring of the contrast bolus. Real

time bolus tracking permits timing of breath-holding during 1) contrast arrival during the

arterial phase, 2) portal venous phase (50-70s), and 3) delayed phase from 1:40-2:00

minutes. Using temporal filtering through density compensation filters2, time-resolved

image volumes at full spatial resolution (1.6x1.6x1.6mm3) were reconstructed with an

effective temporal resolution of 8s. Using the high temporal resolution images, quantitative

perfusion modeling can be performed using a dual input model of the hepatic blood flow

that includes the portal vein and hepatic arterial input3.

Results and Discussion: Figure 1 shows images of a 1.5cm HCC, identified on

surveillance MRI. Arterial phase shows brisk enhancement and rapid washout during the

portal venous phase, highly characteristic of HCC. Spatial resolution is 1.6mm isotropic

with 8s temporal resolution. High spatial and temporal resolution will allow clinicians to

accurately capture contrast uptake in the tumor contrast kinetics, the portal vein and

hepatic artery, necessary for dual input modeling of perfusion to the HCC3.

References: 1. Brodsky et al, MRM, 2006 2. Barger et al, MRM, 2002 3. Materne et al, MRM, 2002

Figure 1: Pre-contrast, arterial phase, and portal venous phase images through a 1.5cm HCC (arrow). Brisk arterial enhancement and rapid washout is highly characteristic of HCC. Spatial resolution is 1.6mm isotropic with 8s temporal resolution.


6.5 Stack of Stars 4D Phase Contrast Velocimetry of the Circle of Willis

Steven Kecskemeti, Kevin Johnson, Yijing Wu,Warren Chang, Charles Mistretta, Patrick Turski Departments of Medical Physics and Radiology, University of Wisconsin, Madison, WI

INTRODUCTION: In addition to angiograms, cardiac gated phase contrast (PC) MR

velocimetry provides hemodynamic information such as pulsatility, flow streamlines,

relative pressure, and estimates of wall shear stress. In certain cases, such as

aneurysms in the circle of Willis (COW), high resolution over a moderate excitation slab

(40mm) can be achieved using a stack of stars hybrid PR acquisition.

METHODS AND RESULTS: A cardiac gated (both retrospective and prospectively)

gated PC stack of stars (SOS) sequence was developed with radial readout in the xy-

plane and traditional phase encoding in the z-direction. A bitreversed projection ordering

allows for retrospective viewsharing in multiples of the minimum temporal width of 4TR

for four point velocity encoding. Exams have been performed on a 3T clinical scanner

with 8-channel head coil. Parameters were FOV: 220x220x50mm,

resolution:0.43x0.43x1.0mm, reconstructed voxel size: 0.43x0.43x0.43mm, TR/TE =

9.3/4.1ms, tip angle = 20, BW = 62.5kHz, scantime 7:03+30s calibration scan. Full MIPs

have been shown for the axial (a) and coronal(d) views, while limited MIPS of sagittal

are displayed to distinguish left (c) and right (d) hemispheres.

We conclude that 4D cardiac gated PC SOS a practical method to study flow normal and

pathological flow conditions within the Circle of Willis.

High Resolution Perfusion Weighted Imaging

0 200 400 600 800 10002

2.2

2.4

2.6

2.8Mean Flow

time [ms]

flow

[ml/s

]


6.6 High Resolution Perfusion Weighted Imaging Meng Li, MS and E. Mark Haacke, PhD

Wayne State University, Detroit, MI, USA

Purpose: Perfusion-weighted imaging (PWI) using dynamic susceptibility contrast (DSC)

is a useful tool to evaluate various diseases of the brain. But current low resolution PWI is

unable to easily show differentiation between gray matter and white matter. We plan to

use susceptibility weighted imaging (SWI) and MR angiography (MRA) to remove major

vessel information from a high resolution PWI approach to better reveal gray matter

perfusion without the confounding major vessel effects.

Methods: HR PWI images of 1 x 1 x 4 mm3 were acquired on a 1.5T Siemens Sonata with

an 8-channel head coil. The imaging parameters used were:

TR/TE/FA/Resolution/BW=2200ms/98ms/60°/1x1x4mm3/752Hz/pixel, the acquisition

matrix was 256x256 (interpolated to 512x512). Both MRA and SWI data were acquired.

MRA was obtained pre-contrast with TE/TR/FA = 7ms/37ms/25°, SWI was acquired pre

and post-contrast with TE/TR/FA = 40ms/49ms/20°.

Results: High resolution PWI was successfully obtained with parallel imaging. Compared

to the usual 2mm in-plane resolution, the following advantages were observed on CBF

and CBV maps: the blurring of blood vessels was minimal, fine details of blood vessels

were observed, gray matter was clearly separated from blood vessels, and small vessels

like the medullary veins could be seen. Using the HR PWI data it was possible to remove

the blurring associated with the major blood vessels. This is accomplished by using both

the MRA and SWI data. The major vessels were then removed from the HR PWI CBV

map in an attempt to create a segmented vessel free image. This made it possible to

focus on just gray matter or white matter and made it easier to filter the gray matter data

without interference from major vessels.

Conclusion: The separation of gray matter and white matter in PWI can be achieved by

increasing the in-plane resolution of conventional PWI data to 1mm. Combination of high

resolution maps of PWI, SWI and MRA can provide additional information about macro

and micro circulations and vasculature of the brain.


6.7 Accelerated velocity imaging using compressed sensing L. Marinelli1, K. Khare1, K. F. King2, R. Darrow1, T. K. F. Foo1, and C. J. Hardy1

1GE Global Research, Niskayuna, NY, 2GE Healthcare, Waukesha, WI

Purpose: Accurate measurement of blood velocity in complex flows can improve the

diagnosis and characterization of a variety of cardiovascular diseases. We have

developed a 2D Fourier velocity encoding (FVE) M-mode MRI pulse sequence to probe

multi-dimensional velocity distributions. Unlike in conventional MRI, parallel imaging

cannot be used to shorten FVE scan time. We have instead developed a compressed

sensing (CS) approach to accelerate 2D FVE, which exploits the sparsity of the blood

velocity distribution.

Methods: Following localization of the mitral valve, 2D FVE M-mode MRI was performed

with a VENC of 64 cm/s. A 2-cm pencil of spins was excited and 16 velocity-phase-

encoding steps were applied in each velocity-encoding direction. The 16x16 velocity

encodings were undersampled by various factors and we compared uniform random,

Gaussian random, and Poisson disk distributions.

Results and Conclusions: Figure 1 shows a typical temporal evolution of the blood

velocity distribution near the mitral valve. Frame (a) was acquired 20ms after the QRS

complex and in frame (c) we note that there was some flow towards the aortic valve.

During diastole, the aortic valve closes and the mitral valve opens; flow near the mitral

valve becomes more directional towards the valve (frame (e)) and then relaxes back to

zero velocity sweeping an arc in velocity space (frame (f) and (a)). This is the only

technique that provides multi-dimensional velocity distribution data that may have impact

in the assessment of valvular disease and regional intravascular wall pressure.

Figure 1. (a)-(f)Time evolution of the 2D blood velocity distribution

near the mitral valve (green arrow in (g)). vx (resp. vz) is the velocity

component parallel (perpendicular) to the pencil beam. (g) Left

ventricular outflow tract view with M-mode pencil prescribed through

the mitral valve. (h) 2D FVE pulse sequence diagram.

R = 2

R = 4

R = 6

R = 2.5 R = 4 R = 2.7

R = 4

(b) R = 2

R = 4

R = 6

R = 1

e

R = 2

R = 4

R = 6

R = 2.5 R = 4 R = 2.7

R = 4

(b) R = 2

R = 4

R = 6

R = 1

e

R = 2

R = 4

R = 6

R = 2.5 R = 4 R = 2.7

R = 4

(b) R = 2

R = 4

R = 6

R = 1

e

R = 2

R = 4

R = 6

R = 2.5 R = 4 R = 2.7

R = 4

(b) R = 2

R = 4

R = 6

R = 1

e

R = 2

R = 4

R = 6

R = 2.5 R = 4 R = 2.7

R = 4

(b) R = 2

R = 4

R = 6

R = 1

e

R = 2

R = 4

R = 6

R = 2.5 R = 4 R = 2.7

R = 4

(b) R = 2

R = 4

R = 6

R = 1

e

R = 2

R = 4

R = 6

R = 2.5 R = 4 R = 2.7

R = 4

(b) R = 2

R = 4

R = 6

R = 1

e

R = 2

R = 4

R = 6

R = 2.5 R = 4 R = 2.7

R = 4

(b) R = 2

R = 4

R = 6

R = 1

e

g

h

vx vz a b c d e f

1/32 3/32 8/32 11/32 18/32 21/32 g

h


6.8 Wall Shear Stress in Normal and Atherosclerotic Carotid Arteries

M. Markl, S. Bauer, J. Bock, A. F. Stalder, A. Frydrychowicz, A. Harloff 1 Diagnostic Radiology, Medical Physics, University Hospital Freiburg, Germany

Introduction: Hemodynamic conditions in the carotid bifurcation resulting in low wall shear stress (WSS) and high oscillatory shear index (OSI) can predict plaque development1,2. The normal distribution of segmental WSS and OSI was evaluated in 32 normal volunteers and compared to findings in 6 patients with moderate internal carotid artery (ICA) stenosis < 55%. Methods: Flow-sensitive 4D-MRI3,4 (a=15°, venc=150cm/s,TRes=45.6ms, 1.1x0.9x1.4mm³) was performed to estimate time-averaged absolute WSSmag and OSI in 7 analysis planes (figure 1)5. To identify areas at risk for plaque development segments representing the individual upper 15% of OSI and lower 15% WSSmag were determined. Results: 64 normal carotid bifurcations (figure 2) revealed high inter-individual consistency and a high incidence of low WSSmag and high OSI in segments corresponding to the proximal ICA bulb. Patients showed a more heterogeneous distribution and a spatial relocation of critical wall parameters to proximal regions distal to the ICA stenosis. Discussion: Atherogenic low WSSmag and high OSI in the normal ICA bulb may explain why ICA plaques often develop at this site. The presence of ICA stenosis can alter wall parameter distributions which may help to predict the direction and extent of progression of the disease.

Fig. 1: Assessment of wall parameters in 7 analysis planes (left) and extracted systolic velocity profile and wall shear stress vectors (WSS) for analysis plane 3 in the ICA bulb (right).

Fig. 2: Distribution of critical wall parameters for n=64 normal carotid arteries and n=6 patients with moderate ICA stenoses. In normal controls critical wall parameters were predominately located in the posterior ICA bulb while patients showed critical WSS in more distal segments.

References: 1. Cheng C et al. Circulation. 2006;113:2744-2753; 2. Lee SW et al. Stroke. 2008;39:2341-7; 3. Harloff A, et al. MRM 2009, 61:65-74; 4. Markl M, et al. JMRI 2007, 25:824-831; 5. Stalder AF et al MRM. 2008;60:1218-1231.


6.9 MR imaging and significance of flow reversal and carotid atherosclerosis: Initial results

J. Scott McNally3, Seong-Eun Kim1,3, John Roberts1,3, Gerald S. Treiman2,4, Dennis L. Parker1,3

1Utah Center for Advanced Imaging Research, 2VA Salt Lake City Health Care System, 3Radiology, 4Surgery, University of Utah, Salt Lake City, Utah, 84108

Introduction Reports suggest that atherosclerotic plaque at the carotid bifurcation correlates with areas

of flow reversal and low wall shear stress. MRI can be used to delineate plaque

components including ulceration, erosion, and hemorrhage, which are thought to correlate

with symptoms. Using MRI, our goal is to determine if areas of flow reversal correlate with

these markers of plaque vulnerability and plaque location at the carotid bifurcation.

Methods VA subjects scheduled for carotid endarterectomy are being scanned with a 3T MRI using

the following sequences: 2D T1w (0.5 x 0.5 x 2mm3) and 2D TSE to measure plaque

location, ulceration and erosion, 3D MPRAGE (0.5 X 0.5 x 1mm3) to measure

hemorrhage, 3D TOF (0.3 x 0.6 x 0.6mm3) and 2D Phase Contrast (0.8 x 0.8 x 3.0mm3)

with dual VENC to measure flow reversal. After tracing the regions of interest, areas of

these components are calculated.

Results and Discussion Results obtained to date on subjects with atherosclerosis (16 diseased and 7 normal

carotid arteries) have shown: 1) Flow reversal in normal carotid arteries occurs along the

proximal internal carotid artery (ICA) and downstream of plaques. 2) Plaque area is

largest along the outer wall of the ICA. 3) Ulceration, erosion and hemorrhage occur

preferentially in areas exposed to flow reversal.

Conclusion Initial results suggest that flow reversal correlates with plaque location and markers of

vulnerability. This study may help determine the significance of flow reversal in the

progression of atherosclerosis.


7.1 4D-MRA in combination with arterial spin labelling for selective and functional information in patients with AVMs

W. A. Willinek1,G.M. Kukuk1, D.R. Hadizadeh1, J. Gieseke1, 2, J. Bergener1, G. Beck2, L. Geerts2, P. Mürtz1, A. Boström3, H. Urbach1, J Schramm3, H. H. Schild1

1 Dpt. of Radiology, University of Bonn, Germany, 2 Philips Healthcare, Best, Netherlands, 3 Dpt. of Neurosurgery, University of Bonn, Germany

Purpose: Arterial spin labelling with selective labelling pulses is a promising method providing selective and functional information regarding brain perfusion territories, regional cerebral vascular supply and functional collateral circulation. The purpose of this study was to prospectively evaluate 4D-MRA in combination with selective arterial spin labelling for perioperative assessment of cerebral AVMs. Methods: In a prospective intraindividual comparative study 10 patients (6 female, 4 male; mean age 35.8 years ± 12.2; range 20-58 years) diagnosed with symptomatic cerebral AVMs underwent pre- and postoperative 4D-MRA, regional brain perfusion imaging using selective arterial spin labelling and DSA. Institutional ethics committee approval and written informed consent were obtained. 4D-MRA was performed using CENTRA keyhole in combination with view sharing yielding a temporal resolution of 572 msec, whole brain coverage and an isotropic voxel size of 1.1 x 1.1 x 1.1 mm³. Selective arterial spin labelling was performed using the PULSAR labelling sequence for selective labelling of both carotid arteries and the vertebrobasilar complex. All images were pre- and postoperatively assessed by two radiologists in consensus regarding technical success rate, preoperative assessment (Spetzler-Martin classification, identification of arterial feeders, existence of anatomic variants / functional crossfilling) and completeness of resection. In all cases DSA served as the standard of reference. Results: 4D-MRA was successfully performed in 20/20 exams and enabled the same Spetzler-Martin classification as DSA in all cases (100 %). 11/13 (85 %) feeding arteries were identified by 4D-MRA. Selective arterial spin labelling was successful in 16/20 (80 %) exams. Selective arterial spin labelling provided additional functional or anatomic information in 2/16 exams and enabled the diagnosis of a cross-filling feeding artery that was not identified by 4D-MRA but by DSA, thus improving the sensitivity of MRI in identification of arterial feeders from 11/13 (85 %) to 12/13 (92 %). Postoperative assessment confirmed complete resection of all AVMs in 100 % yielding a 100 % concordance between 4D-MRA in combination with selective arterial spin labelling and DSA. Conclusion: 4D-MRA in combination with selective arterial spin labelling is a promising tool for pre- and postoperative assessment of cerebral AVMs providing functional information that so far has been gained only with selective DSA. References: [1] Golay X, Petersen ET, Hui F. Pulsed star labeling of arterial regions (PULSAR): a robust regional perfusion technique for high field imaging. Magn Reson Med 2005;53:15-21. [2] Hendrikse J, van der Grond J, Hanzhang L et al. Flow territory mapping of the cerebral arteries with regional perfusion MRI. Stroke 2004;35:882-887. [3] Lim CC, Petersen ET, Ng I et al. MR regional perfusion imaging: visualizing functional collateral circulation. AJNR 2007;28:447-448. [4] Willinek WA, Hadizadeh DR, von Falkenhausen M. 4D time-resolved MR angiography with keyhole (4D-TRAK): more then 60 times accelerated MRA using a combination of CENTRA, keyhole and SENSE at 3.0T. JMRI 2008;27:1455-1460. [5] Hadizadeh DR, von Falkenhausen M, Gieseke J et al. Cerebral arteriovenous malformation: Spetzler-Martin classification at subsecond-temporal-resolution four-dimensional MR angiography compared with that at DSA. Radiology 2008;246:205-213.


7.2 Intraindividual comparision between multislice CT and 4 D TWIST MRA in the assessment of residual cerebral

arteriovenous malformations – a prospective study protocol Authors: M. Essig, M. Voth, A. Zabel-Du-Bois, L. Schuster

Institution: Department of Radiology, German Cancer Research Center, Heidelberg, Germany Rationale and Objectives Small or residual cerebral arteriovenous malformations (AVMs) are hard to visualise with MR angiographic techniques. Although MRA techniques like TOF or contrast enhanced MRA allow high resolution they are not able to visualize small or slow flowing vessel segments. However, these small vascular structures and their intra cranial course are important for radiotherapy planning and follow-up assessments. Therefore MS-CTA is used to assess complete obliteration if MRA proved negative. The aim of the presented study protocol was now to assess the validity of a time resolved 3D contrast enhanced MRA technique in direct comparision with CTA. Methods In an ongoing dual centric prospective study protocol we used a combination of high temporal resolution (250ms) and high spatial resolution (1x1x1 mm) CE MRA using a standard dose (0,1mmol) of the macrocyclic Gadobutrol (Gadovist®, Bayer, Berlin) for a TWIST (Time-Resolved Imaging with Stochastic Trajectories) acquisitions. The new 4 D MRA technique was intraindividually compared with MS CTA to assess the visibility of residual small AVM compartments and the presence of arteriovenous shunting. The imaging data were evaluated in a qualitative matter by two independent readers with special attention to the morphologic features of the malformation and the influence of the dynamic MRA studies. Results So far we were able to include 12 patients with no residual AVM components on conventional TOF-MRA examinations (inclusion criteria). In10 out of these patients residual AVM components could be visualized on the dynamic and high resolution contrast enhanced MRA sequences. The MS CTA was able to visualize residual vessel components in only 8 patients. In two patients massive artifacts from previous embolisation hindered the visualisation. In two patients no vascular components were seen on both CTA and contrast enhanced MRA. In the MRA studies the hemodynamic information from the TWIST technique was found to be very helpful in the differentiation between physiologic and pathologic vessels. Conclusion In conclusion these preliminary results could prove that high temporal and spatial resolution 4D MRA is able to assess even small residual AVM compartments at a high sensitivity. Based on the initial patient studies, Gadobutrol with its unique high molar concentration seems to be the ideal contrasting agent in this study concept. The high concentration allowed for a small bolus which is ideal for the high temporal resolution of the MRA, the higher relaxivity was found to be ideal for the vessel assessment in the high resolution MRA.


7.3 Our Strategy for the Surgical Planning with 3T MRA in Detecting Unruptured Cerebral Aneurysms

Keiji Igase1), Ichiro Matsubara1), Masamori Arai1), Jyunji Goishi1), Hitoshi Miki2), Kazuhiko Sadamoto1)

1) Department of Neurosurgery, Washokai Sadamoto Hoapital 2) Departments of Radiology, Ehime University School of Medicine

Purpose: Subarachnoid hemorrhage is the most disastrous and irrevocable disease out of

many cerebrovascular diseases except for a few fortunate cases, thus it has been

overwhelmingly emphasized to detect unruptured intracranial aneurysms (ANs) with less

invasive examination. Therefore, we made our original 3T MRA-centered strategy for the

surgical planning on detection of unruptured cerebral ANs and verified the detection

capability of them compared with flat-panel detector digital angiography (FD-DA).

Methods: In order to screen unruptured intracranial ANs 3T MRI (Signa Excite: GE) was

aggressively exploited in our hospital. First of all, out-patients with some cranial problems

can undergo 3T-MRI for the screening of cerebrovascular diseases including cerebral

ANs, and in the case of patients with ANs suspected on MIP (Minimum Intensity

Projection) image of MR Angiography, VR (volume rendering) images are briefly created,

with which if ANs are definitely diagnosed, there are two options to proceed treatments

depending on their size. For ANs over 5mm in size flat- panel detector digital angiography

(FD-DA) is planned for scrutinizing both size and shape of the aneurysms because of its

having an indication for the operation, on the other hand for ANs less than 5mm 3D-CT

Angiography precedes FD-DA. Objective was all out-patients initially underwent 3T MRI

during one year in 2006, where patients with ANs have been followed for 3 years.

Results: Out of 3318 of out-patients 286 patients were found to have unruptured ANs,

and 3 years after 157 patients were followed, in which 2 patients (1.3%) had the rupture of

ANs, 15 patients (5.2%) the operation for unruptured ANs, 19 (12.1%) patients the

enlargement of ANs, and 121 (77.1%) no change of the ANs. All of the operated 15

patients underwent both 3T-MRI and FD-DA, revealing that VR images of 3T MRI closely

coincided with 3D-images of FD-DA in size and shape of ANs.

Conclusion: In detecting unruptured cerebral ANs for surgical treatment 3T-MR

Angiography, especially VR images, are sufficiently useful and our strategy with 3T MRI-

centered system should be reasonable and beneficial for less invasive examination.


7.4 Hybrid of Opposite Contrast MR Angiography of the Brain Faïza Admiraal-Behloul1 , Evert Blink1, Tokunori Kimura2,

1Toshiba Medical Systems Europe, Zoetermeer, the Netherlands, 2MRI Systems Development Department, Toshiba Medical Systems Corp., Otawara-Shi, Tochigi-Ken, Japan

Purpose: To compare a new non-contrast enhanced MR angiography technique, to an

optimized Time of Flight technique (TOF) with MTC pulse, in the visualization of fast and

slow flow brain vessels using comparable scan time on a 1.5T MR system.

Methods: The Hybrid of Opposite

contrast (HOP) technique is a dual-

echo 3D gradient-echo sequence

where the first echo is used to

generate a TOF white blood image

and the second echo generates a

Flow Sensitive Black Blood image

using motion-probing gradients to

introduce intra-voxel flow dephasing

[1]. In this work, the 2-echo images are combined using a frequency weighted subtraction

that enhances slow-flow (small) vessels [1]. Fifteen volunteers (8 men, mean age 46.2 y,

range 31 to 77 y) were imaged on a 1,5T System (Vantage ZGV Atlas, Toshiba) using a

13-channel Atlas-head coil with a Parallel Imaging factor of 2. Both TOF and HOP images

were obtained using a matrix of 256x256, FOV of 22x22cm, in-plane resolution of

0.86x0.86mm, slice thickness of 1mm and a slab thickness of 7cm. For TOF, TR = 30ms,

TE = 8ms and acquisition time = 5min12s. For HOP, TR = 34ms, TE1 = 7.5ms, second

TE2 = 24.9ms, and acquisition time = 5min30s. Water excitation technique was used for fat

suppression. A slice-selective off-resonance sync pulse was used in TOF or optimal

background signal suppression. No MTC pulse was used in HOP.

Results: HOP and TOF were visually comparable in the depiction of fast flow vessels in

all subjects. The low-flow vessels were better visualized by HOP in 13 subjects (see fig.1

for a representative case) and comparable in 2 subjects.

Conclusion: HOP-MRA is a promising technique for the visualization of small collateral

vessels which is technically difficult with a standard TOF technique especially at 1.5 T.

Reference: 1. T. Kimura et al, Magn Reson Med. 2009 Aug; 62(2):450-8.

Figure 1: (a) HOP image (b) TOF image.


4 cm

A

B

Fig. 1. Axial targeted MIPs (35 mm thick) at the left internal carotid artery before (A) and after (B) re-synthesis, with improvements in vessel depiction noted (arrows).

7.5 High Resolution Fast Inversion Recovery MRA (FIR-MRA) E. T. Tan, N. G. Campeau, J. Huston III, S. J. Riederer

Department of Radiology, Mayo Clinic, Rochester, MN 55905 USA Purpose – Compared to 3D time-of-flight (TOF), the FIR-MRA technique provides

superior vessel conspicuity in imaging of the intracranial arteries [1]. However, the intrinsic

signal modulation of FIR-MRA causes loss of vessel sharpness and small vessel signal.

The FIR angiogram is obtained by a difference between the acquired, un-subtracted

bright-blood and black-blood data. Interestingly, the bright-blood signal is larger than the

difference signal at k-space periphery, while the dark-blood signal is negligible at k-space

center. We hypothesize that these properties of the un-subtracted data may be harnessed

to improve vessel depiction of high-resolution FIR-MRA by re-synthesizing the FIR-MRA

data.

Methods – Two data re-synthesis steps are proposed. First, the use of the difference data

for central k-space and the un-subtracted bright-blood

data for k-space periphery reduces signal modulation and

improves sharpness. Second, an additional subtraction of

a fraction λ of magnitude dark-blood data with a threshold

at zero reduces the level of residual tissue signal. The

optimum value for pass band frequency in step one was

determined to be 70% of maximum k-space, and that for

λ of step two was 10%. This technique was evaluated in

vivo at 3T.

Results – Fig. 1 shows improvements in the smoothness

and sharpness of large vessels, and in the conspicuity of

small vessel branches. The background noise and

residual tissue signal are also noticeably reduced.

Conclusion – Re-synthesis of FIR-MRA data results in

superior vessel depiction, as well as reduction in residual

tissue signal and background noise.

References – [1] Tan ET et al. ISMRM 2009, #91.


7.6 3D Dual V E NC P C MR A us ing S piral P rojection Imaging N. R. Zwart1, and J. G. Pipe1

1Keller Center for Imaging Innovation, Barrow Neurological Institute, Phoenix, Arizona, United States

P urpos e: The dual-VENC method of unaliasing a low VENC with a high VENC MRI data

set allows for a significant improvement in the velocity to noise ratio of PCMRA [1]. The

collection of additional data necessitates the use of a rapid imaging technique to maintain

feasible scan durations. The proposed method is a 3D k-space sampling trajectory called

Spiral Projection Imaging (SPI) [2]. This work demonstrates the effectiveness of SPI while

maintaining a short sample window and increased

undersampling. The synthesis of high VNR images is

explored with attention to problematic areas of dephasing.

Methods : S P I: Variable density spiral interleaves are

critically sampled up to 1/8 of the k-space radius (Fig. 1a).

At the edge of k-space, spirals are separated by a factor of 4

times the critical sample distance. Spiral planes are rotated

about kz to fill 3D k-space (Fig. 1b). The scan parameters

are: 24cm FOV, 0.8mm3 voxel, 300 dia. matrix, 20

interleaves, 120 planes, 19.5msec TR, and a 6min total scan

time for 7 volumes. Dual VE NC : Velocity encoded sets

were collected for a 100cm/s and 20cm/s VENC. High

velocity gradients at vessel walls cause vessel narrowing in

unaliased low VENC images. This is addressed by a

weighted combination of the high and low VENC data.

R es ults and Dis cus s ion: SPI PCMRA scans were

collected with a GE 3T Signa Excite system (Fig. 1c).

Blurring near the sinuses becomes problematic with longer sampling windows than what is

used. Aliasing due to undersampling causes some smaller vessels to appear inconsistent.

Vessel diameter in high flow areas is regained by partial combination of high VENC data

with the unaliased low VENC data.

C onclus ion: This method provides short scan times that make the added time required

by dual VENC techniques less prohibitive.

R eferences : [1] Lee, A. MRM, 33:122, 1995; [2] Irarrazabal, P. MRM, 33:656, 1995;


7.7 High Resolution Simultaneous Angiography and Venography (MRAV) with a Single Echo

Samuel Barnes, MS1,2, E. Mark Haacke, PhD1,2

1. Wayne State University, Detroit 2. Loma Linda University, Loma Linda, CA

Purpose: In this work we develop novel acquisition and post processing techniques to

improve the quality of single echo MRAV acquisition using susceptibility weighted imaging

(SWI). Techniques recently presented have focused on double echo acquisitions which

will be harder to implement at very high fields.

Methods: All SWI images were acquired at 3T with TR/TE/FA/Resolution/BW =

30ms/20ms/15°/0.5x0.5x0.5mm3/50Hz/pixel or 160Hz/pixel. To visualize veins the data

was downsampled to a resolution of 0.5x0.5x2.0mm3 before the SWI processing.

Results: Using a higher bandwidth of 160 Hz/pixel as compared with 50 Hz/pixel

dramatically reduces flow dephasing, improving larger vessel visibility at the cost of a

reduced signal-to-noise ratio (Fig. 1). The high isotropic resolution also helps to reduce

dephasing across a voxel improving the MRA. The original isotropic resolution data

showed poor venous contrast due to the non-optimal aspect ratio of 1:1 which causes the

phase for certain orientations of veins to have the opposite sign (Figure 2). This lost

contrast is fully recovered by downsampling the high resolution data to a more optimal

aspect ratio of 1:4 (0.5x0.5x2 mm3). The downsampling takes advantage of the high

resolution data by reconstructing the slices in an overlapping pattern so the optimal partial

voluming of smaller structures is guaranteed thus improving image quality.

Conclusion: By collecting data with high isotropic resolution and higher bandwidth, flow related losses from higher order uncompensated effects can be reduced improving the quality of the MRA extracted from the SWI data even at long echo times (20ms).

Figure 3. Maximum intensity projection (left) over isotropic data showing arteries and minimum intensity projection (right) over SWI processed downsampled image.

Figure 2. Isotropic phase image (left) shows veins switching from bright to dark depending on orientation. Downsampled image (right) shows higher SNR and more homogenous veins producing a better venography.

Figure 1. 50 Hz/pixel (left) shows almost complete loss of the MCA and losses in the middle of smaller vessels while 160Hz/pixel (right) shows minimal flow losses.


7.8 Low Dose 3D Time-Resolved MR Angiography of the Supraaortic Artery: Correlation to High Spatial

Resolution 3D Contrast-Enhanced MRA Yoon-Joo Lee, So-Lyung Jung, Kook-Jin Ahn, Bum-soo Kim

Department of Radiology, Seoul St.Mary Hospital, The Catholic University of Korea

Purpose: To evaluate the effectiveness of low-dose, contrast-enhanced, time-resolved,

three dimensional (3D) magnetic resonance (MR) angiography (TR-MRA) in the

assessment of supraaortic vessel, and to compare the results with high-resolution contrast

enhanced MRA (HR-CEMRA).

Materials and Methods: 45 consecutive patients underwent contrast enhanced 3D TR-MRA and high spatial

resolution 3D CE-MRA for evaluation of neurovascular disease at 3T. Gadolinium-based

contrast medium was administered at a constant dose of 1ml for TR-MRA, and

0.1mmol/kg for HR-CEMRA. Two readers evaluated image quality using a four point scale

(from 0=excellent to 3=non-diagnostic), artifacts and findings on both datasets.

Results: The overall image quality for low dose TR-MRA was in the diagnostic range

(median 0, range 0-3). Two cases showed non-diagnostic image quality due to severe

motion in patients with acute ICA occlusion. Readers demonstrated additional

hemodynamic information on TR MRA in 3 patients with severe stenoocclusive lesions.

For the evaluation of arterial stenosis, TR-MRA well correlated with HR-CEMRA (r=0.668,

p<0.001). Of the 675 supraaortic arterial segments evaluated for stenosis or occlusion,

TR-MRA agreed with HR-CEMRA in 611 of 675 (90.5%), overestimated in 41 of 675

(6.1%), and underestimated 23 of 675 (3.4%).

Conclusion: TR-MRA can be achieved by administration of small contrast dose (1cc,

0.1mmol), and yields rapid and important functional and anatomical information in the

evaluation of supraaortic arteries. Due to limited spatial resolution, TR-MRA is has

tendency to overestimated the stenosis or occlusion of smaller intracranial arteries.


7.9 Obstruction of IJV by Asymmetry of Lateral Mass of Atlas on Head and Neck CEMRA and Contrast CT

Tae-Sub Chung, MD1, Hye Mi Gweon, MD1, Sang Hyun Suh, MD1 Department of Diagnostic Radiology, Gangnam Severance Hospital 1

Yonsei University, Seoul 135-720, Republic of Korea

Purpose; To evaluate that asymmetry of lateral mass of atlas could be the cause of high level

internal jugular vein (IJV) obstruction on head and neck contrast enhanced 3D MR

angiography (CE-MRA) and contrast enhanced computed tomography (CE-CT).

Materials and Methods; Thirty cases among 1800cases which examined both head and neck CE-MRA and CE-

CT were enrolled during last 5 years. The eleven cases had IJV obstruction and nineteen

cases had no IJV obstruction on CE-MRA. We defined obstruction group which had IJV

obstruction and control group which had no IJV obstruction on CE-MRA. The following

parameter was measured from axial images of CE-CT: 1) the diameter of IJV; 2) the

distance between styloid process and ipsilateral lateral mass of atlas; 3) maximum area of

lateral mass of atlas.

Results; The incidence of IJV obstruction was 28% (504/1800 cases) of all reviewed head and

neck CE-MRA. The diameter of IJV and distance between styloid process and lateral

mass of atlas at IJV obstruction side in obstruction group were 1.6 ± 1.0mm and 4.1 ±

2.1mm. The diameter of IJV and distance between styloid process and lateral mass of

atlas were significantly narrower than those of contralateral normal side in obstruction

group (3.5 ± 1.7mm and 3.7 ± 3.2mm, p<0.001). The maximum area of lateral mass of

atlas at IJV obstruction side was significantly larger than that of contralateral normal side

in obstruction group (24.2 ± 10.5 mm2, p<0.001).

Conclusion: The cause of high level IJV obstruction on head and neck CE-MRA was

narrowing space between styloid process and lateral mass of atlas resulting from larger

area of lateral mass of atlas and induced IJV compression.


8.1 Evaluation of Gd-DOTA (DOTAREM®) enhanced MRA compared to time-of-flight MRA in the diagnosis of clinically significant

non-coronary arterial disease at 1.5 and 3.0 Tesla. Dipan J. Shah1, Lim Tae-Hwan2, Steven Wolff3.

1 Methodist DeBakey Heart & Vascular Center, The Methodist Hospital, Houston, TX. 2 Department of Radiology, Research Institute of Radiology, University of Ulsan, College of Medicine,

Asan Medical Center, Seoul, Korea. 3 Advanced Cardiovascular Imaging, New York, NY.

PURPOSE: To assess the diagnostic accuracy and safety of meglumine gadoterate (Gd-

DOTA)-enhanced MRA over non-enhanced Time-of-Flight (TOF) MRA at 1.5 and 3.0

Tesla for clinically significant non-coronary arterial disease by comparing of each

technique with x-ray angiography.

MATERIAL AND METHODS: Multicenter, open-label, paired trial in 192 subjects (100 at

1.5 Tesla and 92 at 3.0 Tesla), age >18 years, (140 men, 52 women; mean [±SD] age,

63.7 ± 13.9 years) with suspected non-coronary arterial disease and scheduled to undergo

x-ray angiography were included and received an iv bolus of 0.1 mmol/kg Gd-DOTA.

Renal insufficiency was present in 15 (7.8%) of subjects. The percent agreement was

defined as the number of stenosis grades measured with MRA in agreement with x-ray at

segment level / total number of segments evaluated for the patient x 100. Sensitivity and

specificity were assessed at the segment level.

RESULTS: The arteries imaged were: aorto-iliac (39.6%); renal (18.2%); calf (13.0%);

femoral (12.5%); carotid (12.0%); and popliteal (4.7%). There was a statistically

significantly greater mean (± SD) percent agreement of MRA to x-ray with Gd-DOTA MRA

vs TOF MRA (85.8% ± 19.8% vs 78.3% ± 24.9%, respectively; difference 7.4% ± 22.1%

[p<0.0001]). The sensitivity and the specificity of Gd-DOTA MRA were significantly greater

than TOF MRA (93.3% vs 85.7% [p=0.0004] and 89.7% vs 84.4%, [p=0.0019]

respectively). There were no serious drug-related adverse events and no spontaneously

reported cases of nephrogenic systemic fibrosis.

CONCLUSION: Gd-DOTA-enhanced MRA provided significantly greater diagnostic

accuracy than TOF MRA at 1.5 and 3.0 Tesla in the diagnosis of non-coronary arterial

disease.


8.2 Pulmonary MRA in 75 patients with dyspnea ML Schiebler1, SK Nagle1, CJ Francois 1, RF Busse4, ACS Brau4,

JH Brittain4, TM Grist1, and SB Reeder 1, 2, 3 1. Department of Radiology, UW- Madison 2. Department of Medicine, UW-Madison

3. Department of Medical Physics, UW-Madison 4. Applied Science Lab, General Electric, Waukesha, WI

Purpose: Review of our clinical experience with a new contrast enhanced pulmonary

MRA (CE-MRA) sequence with 2D parallel imaging (ARC) 1 for the detection of

pulmonary embolism (PE) performed in 75 dyspneic patients.

Methods: A total of 75 CE-MRA (accelerated with 2D-ARC) pulmonary MRA exams in

patients with dyspnea were reviewed for the presence of emboli (PE), perfusion defects

within the lungs, and artifacts limiting diagnostic quality. These artifacts fell into 4

categories: central vessel signal drop-out (CVSDO), central field-of-view (FOV) blurring,

bolus timing issues, and residual aliasing.

Results: 20 pulmonary emboli were detected in 11 patients. 27 lung perfusion defects

were demonstrated. Lobar (n=8), segmental (n=7) and sub-segmental (n=2) PE were

identified. Only 5 cases contained artifacts that required follow-up imaging with computed

tomography angiography (CTA) to exclude PE. In most cases of CVSDO, use of multi-

phasic imaging allowed differentiation from PE. Central FOV blurring and residual aliasing

were only a problem when the entire AP dimension of the patient was not included in the

FOV. Bolus-timing issues were not a significant problem.

Conclusion: CE-Pulmonary MRA with 2D-ARC allows near-isotropic high-resolution

whole chest coverage in a14s breath hold. This is now being used routinely to evaluate

young patients with suspected pulmonary embolism in order to limit radiation dose to this

vulnerable population at our institution.

Figure 1: Pulmonary embolus in patient with dyspnea. A). Pulmonary infarct (arrow) on

pre-contrast 2D ARC, B). Perfusion defect seen on dextro-phase of CE-MRA in left lower

lobe (arrow), C). Segmental embolus in LLL lateral segmental artery (arrow) causing the

perfusion defect seen in A and B.

A B C References: 1. Schiebler et al, ISMRM 2008, Poster # 3928


8.3 Origin and Frequency of artifacts in Contrast Enhanced Pulmonary MRA in 80 patients with dyspnea ML Schiebler1, SK Nagle1, CJ Francois 1, RF Busse4, ACS Brau4,

JH Brittain4, TM Grist1, and SB Reeder 1, 2, 3 1. Department of Radiology, UW- Madison 2. Department of Medicine, UW-Madison

3. Department of Medical Physics, UW-Madison 4. Applied Science Lab, General Electric, Waukesha, WI

Purpose: Clinical use of a new contrast enhanced pulmonary MRA sequence with 2D

parallel imaging (ARC) 1 for the detection of pulmonary embolism (PE) requires a careful

understanding of the normal range of artifacts to help prevent a false positive

interpretation.

Methods: A total of 80 CE-MRA (accelerated with 2D-ARC) pulmonary MRA exams in

patients with dyspnea were reviewed for the presence of significant artifacts (Gibbs

ringing, cardiac motion induced blurring, aliasing, respiratory motion) necessitating further

imaging with CTA to rule out the presence of PE.

Results: Of the 80 exams, only 5 cases had artifacts on pulmonary MRA requiring further

imaging with CTA. These artifacts (4 cases) appeared as central hypo-intense foci that

resembled PE. The origin of these artifacts may be a Gibb’s ringing phenomenon or from

mixing of contrast (from the SVC) with un-opacified blood from the IVC. These occurred

most commonly in the right and left lower lobe (LLL) pulmonary arteries. In addition,

cardiac motion occasionally obscured the right middle lobe and lingular branches (1 case).

In this series, respiratory motion and aliasing were not problematic artifacts.

Conclusion: Understanding the artifacts is necessary when interpreting pulmonary MRA.

With understanding of these artifacts, highly diagnostic pulmonary MRA can be performed

in the vast majority of patients, greatly reducing the use of unnecessary radiation.

Figure 1: A. Gibbs ringing artifact simulating a central PE in the left lower lobe pulmonary

artery B. Cardiac motion induced blurring of right middle lobe arteries C (arrows).

Respiratory motion in a positive case of pulmonary embolism showing perfusion defect

(arrowhead) in left upper lobe and a LLL PE (proven at CTA).

References: 1. Schiebler et al, ISMRM 2008, Poster # 3928


8.4 Gadolinium Enhanced Magnetic Resonance Angiography for Pulmonary Embolism: Results of PIOPED III

Paul D, Stein, MD Visiting Professor, Department of Medicine, School of Osteopathic Medicine, Michigan State University,

East Lansing, MIchigan Purpose PIOPED III is a multi-center prospective study of contrast-enhanced magnetic resonance

angiography (MRA) and venography (MRV) accuracy for diagnosis of acute pulmonary

embolism (PE). The study rationale was the assumed safety of MRA in the large number

of patients who have contraindications to CT angiography (CTA) related to iodine allergy,

impaired renal function, or ionizing radiation.

Materials and Methods Patients were eligible for the study if they were suspected of having PE. Exclusions

included age under 18, inability to complete MRA within 72 hr of the reference test,

contraindications to MRA, critical illness, and other standard exclusions. All patients had

Wells’ score, MRA and one or more reference imaging tests (CTA, V/Q scan, digital

subtraction pulmonary angiography or lower extremity ultrasound). Basis for confirmation

of PE included CTA showing PE in main or lobar pulmonary arteries; positive DSA; and

either 1] positive CTA (not main or lobar) or positive CTV; or 2] high probability V/Q scan;

or 3] positive lower extremity US; in combination with high or intermediate Wells’ score.

Basis for exclusion of PE included the inverse of the confirmatory criteria, and patients

who did not meet the confirmatory or exclusionary criteria were classified as PE uncertain.

Results During the course of the study, a novel disorder (nephrogenic systemic fibrosis) was

attributed to use of gadolinium in the presence of impaired renal function, and this

impacted recruitment negatively. A total of 818 patients were enrolled. The high

prevalence of relative contraindications to CTA noted in the PIOPED II study was

confirmed. The image quality, sensitivity and specificity of MRA were assessed. The

results will be presented in detail.

Conclusions The use of MRA in patients with impaired renal function continues to evolve, while patients

with iodine allergy and radiation issues remain candidates for MRA. The role of MRA in

diagnosis of PE will be discussed.


8.5 4D time-resolved MR angiography for non-invasive pulmonary post-embolization AVM patency assessment

L Boussel, A Cernicanu, D Gamondes, C Khouatra, V Cottin, D Revel, P Douek. Lyon, France Purpose: In Rendu-Osler disease, post-percutaneous embolization recurrence of

pulmonary arteriovenous malformation (AVM) patency is often difficult to assess non-

invasively using CT because of its poor temporal resolution. We assess the capability of a

post IV Gd 4D time-resolved MR angiography (MRA) sequence to distinguish between

patent AVMs and healthy normal vessel by analyzing pulmonary arterial and venous

enhancement kinetic.

Methods: After IRB approval, 8 patients with 8 documented pulmonary AVMs (3

previously embolized (recurrence) and 5 untreated), prospectively underwent: a thoracic

MDCT scanner to localize the AVMs; a pulmonary digital substracted angiography (DSA)

to assess AVMs patency and a 4D time-resolved MRA with keyhole and view sharing

compression method at 3T (Philips Achieva). MRA was performed after IV injection of 15

ml of Gadovist (Bayer-Schering) at a 2cc/s rate with the following parameters: FOV:

500x350x240 mm, spatial resolution: 1.2x1.2x1.4 mm, keyhole factor: 20%, viewsharing

compression: 100%, dynamic scan time (temporal resolution): 1.2 s, total acqusition time:

22.7 s for 6 dynamic images. All images were consensually reviewed by two experienced

radiologists. Signal value of cross section AVMs afferent pulmonary arteries and efferent

veins were compared to reference arteries and veins located in an healthy pulmonary area

at the same distance from the hilum than the studied AVM vessels. The difference in Time

to Peak (dTTPav) for each couple artery/vein was calculated. A Mann Whitney test was

used to compare dTTPav for AVMs and reference vessels and recurrent and untreated

AVMs.

Results: A complete thoracic coverage with 6 dynamic time points was obtained for each

patient within a single breath hold and with sufficient spatial resolution to analyze distal

arteries and veins. dTTPav was significantly smaller in AVM (0.45 +/- 0.9 s) than in

reference vessels (3.75 +/- 1.35 s), p=0.0006. No significant difference was found

between recurrent and untreated AVMs, p=0.4.

Conclusion: 4D time-resolved MR angiography is a promising tool for non-invasive

thoracic AVM post-embolization patency assessment.


8.6 Radial Sliding Window MRA in Pulmonary Hypertension Timothy J. Carroll1,2, Amir Davarpanah2, James C. Carr2, Michael Cuttica3,

John Sheehan2, Sanjiv Shah4, and Hyun Jeong1 1Biomedical Engineering, 2Radiology, 3Internal Medicine, and 4Cardiology,

Northwestern University, Chicago, IL

Purpose: To develop an MRI imaging protocol for the quantification of hemodynamic

changes resulting from pulmonary hypertension.

Methods: We have developed an approach to CE-MRA which is based on a previously

reported radially sampled MR fluoroscopic technique using sliding mask subtraction (1, 2,

3). This allows for better A/V separation which aids in the identification of pulmonary

branches (Figure 1). We tested

the hypothesis that bolus transit

times are indicators of

pulmonary hypertension in

patients. A series of patients

(n=17, male=8, female=9,

<age>=46 ± 9.7) were studied

with elevated mean arterial

pressure (mPAP> 25 mm Hg)

measured in a right heart

catheterization study which

confirmed the diagnosis of

pulmonary arterial hypertension. ROIs were place to cover the proximal and distal

branches of the pulmonary arteries and veins. Arterial and venous transit times were

calculated individually as a test of the improved separation of the arterial and venous

phases.

Results/Discussion: We found that bolus transit times, as measured with our high frame

rate pulse sequence, were significantly (p<0.05) increased in pulmonary hypertension

patients.

Conclusions: CE-MRA of the pulmonary arteries may serve as an adjunct to cardiac

catheterization.

References: (1) Reiderer et all MRM 1998, (2) Cashen MRM 2007, (3) Jeong MRM 2009.

(a) (b)

Sliding Window Mask-Mode Subtractions Improves the Depiction ofThe Distal Branches of the Pulmonary Veins.

(a) (b)

Sliding Window Mask-Mode Subtractions Improves the Depiction ofThe Distal Branches of the Pulmonary Veins.

Figure 1. Mask mode subtraction using (a) a pre-contrast mask image and (b) a “sliding mask” that is a fixed time lag behind the angiogram. The improved depiction of the pulmonary veins (arrows).


Fig. 1. Sequence diagram.

8.7 Non-Contrast Enhanced Pulmonary Vein MRI with a Spatially Selective Slab Inversion Preparation Sequence

Peng Hu1, Michael L. Chuang1, Kraig V. Kissinger1, Beth Goddu1, Lois A. Goepfert1, Neil M. Rofsky2, Warren J. Manning1, Reza Nezafat1

1Departments of Medicine and 2Radiology, Beth Israel Deaconess Medical, Boston, MA Purpose: With recent reports of adverse effects of use of contrast agents, non-contrast

pulmonary vein (PV) imaging has been of interest [1,2]. We propose a non-contrast

enhanced free-breathing ECG-gated 3D thin-slab gradient echo sequence with a sagittal

slab-selective inversion for PV angiography.

Methods: A sagittal inversion slab was applied prior to

data acquisition to suppress cardiac structures adjacent to

the left atrium (LA) and PV (Fig. 1) thereby, improving

PV/LA conspicuity. The feasibility of the proposed method

was demonstrated in 5 healthy subjects. Contrast-to-noise

ratio (CNR) between LA and right atrium (RA), ascending

aorta and pulmonary artery was measured and compared

with conventional non-contrast imaging without inversion.

Results: Figure 2 shows improvement of PV and LA conspicuity using our method. Figure

3 shows an example volume view of PV image. Compared to the conventional GRE

without inversion, our technique increased the CNR between LA and RA and pulmonary

artery by 20 and 4 fold (p<0.01), respectively.

Conclusions: The proposed technique enhances the conspicuity of the PVs and LA with

minimal loss of SNR.

Fig 2: A comparison of images acquired using a conventional GRE (top row) and the proposed technique (bottom row).

Fig 3: 3D volume view of PV and LA acquired using the proposed method.

References: 1. Francois et al., Radiology 2009; 250:932-939 2. Krishnam et al., Invest. Radiology, 2009,June 25, ePub.

References: 1. Francois et al., Radiology 2009; 250:932-939 2. Krishnam et al., Invest. Radiology, 2009,June 25, ePub.


8.8 MRA with the “No Phase Wrap” Grace Choi, Martin R. Prince

New York, NY

PURPOSE: Aliasing artifact in the phase encoding direction, also known as wrap-around

artifact, occurs when patient anatomy extends beyond the field of view (FOV). Tissues

outside the FOV wrap around to the opposing edge in the phase-encode direction

superimposing unwanted signals on the area of interest which may interfere with

diagnosis. Aliasing has become more problematic in abdominal and thoracic MRA

utilizing parallel imaging which may wrap the arms onto the middle of the torso

superimposing on major vessels. Metallic, e.g. aluminum foil, sleeves have been

successful in eliminating wrap-around but heating of the metal and cumbersome

application of the foil has prevented this from being a viable clinical option. We have

developed sleeves that are convenient to apply and eliminates phase aliasing artifact with

negligible heating.

MATERIALS AND METHODS: Sleeves were constructed using silver and carbon fabrics

of varying mesh geometry and weights and treated with liquid silicone to absorb excess

heat. The opening diameter for the shoulder was minimized with an elastic liner to adjust

to patient size. Imaging was performed on 1.5T and 3.0T systems (GE HDx 14.0) using an

8-channel body array coil. Coronal and axial single shot fast spin echo (SSFSE), axial

steady state free precession and spoiled gradient echo sequences were performed with

and without sleeves to identify the optimal fabric. A final design was evaluated on

abdominal, thoracic and unilateral upper extremity MR Angiography studies.

RESULTS: Phase wrap-around artifact was present on all images scanned without sleeves. Corresponding images using sleeves showed no wrap-around artifact. MRA was possible with smaller FOV without wrap around artifact from the arms on all studies. MRA with parallel imaging was possible with smaller FOV. CONCLUSION: Silver and carbon sleeves effectively eliminate phase wrap-around

artifact from arms in patients who cannot tolerate elevating arms overhead for abdominal,

thoracic and unilateral upper extremity MRA.


8.9 Unruptured Intracranial Aneurysms; Detection and Follow-up on 3.0T MRA

Hitoshi Miki1, K Igase3, I Matsubara3, I Kiriyama2, Kazuhiko Sadamaoto3 1Department of Radiology, Ehime University School of Medicine,

Department of Radiology2 and Neurosurgery3, Sadamoto Hospital, JAPAN Purpose: To evaluate the frequency, size, location and enlargement of unruptured

intracranial aneurysms (UIAs) found during screening with 3.0T MR angiography (MRA) at

our hospital.

Methods: 3D time-of-flight (TOF) MRA was performed for 3,414 cases (1,453 men, 1,961

women, a mean age of 65.7 years) without neurological sign during January to December

2006 at our hospital. All screening MRA was performed with a 3.0T MR system by using

an eight-element phased array head coil.

Results: The UIAs were found in 286 (8.4%) of the 3,414 cases, 93 men and 193 women,

with a mean age of 65.7 years. The locations of the UIAs of single aneurysm cases were

as follows: anterior cerebral artery (ACA) including anterior communicating artery (A-com)

in 43 lesions, middle cerebral artery (MCA) in 68 lesions, C1 portion of internal carotid

artery (ICA) in 44 lesions, C2 portion in 7 lesions, C3-5 portion in 79 lesions, and basilar

artery (BA) in two lesions and vertebral artery (VA) in 15 lesions. In 30 cases, multiple

UIAs were observed. Aneurysm size varied as follows: 143 lesions (50.5%) were less than

3 mm, 94 (33.2%) were ranged from 3 to 5 mm in size, 34 (12%) from 5 to 7 mm, 11

(3.8%) from 7 to 10 mm, and 4 (1.4%) were greater than 10 mm. The frequency of UIAs

on screening 3.0T MRA was higher than that of past screening reports with 1.5T MRA.

Especially, the frequency of small aneurysms less than 3mm markedly increased in our

study. One hundred forty of 286 cases were followed with serial MRA. Frequency of

enlargement was 13.6% (Nineteen cases).

Conclusion: 3.0T 3D TOF MRA should be excellent modalities for screening and

following up unruptured intracranial aneurysms.


9.1 Comprehensive PC MR Imaging in Congenital Heart Disease Oliver Wieben1,2, Kevin M. Johnson1, Elisabeth Nett1, Ben Landgraf1,2, Scott Reeder1,2, Mark Schiebler2, Sharda Srinivasan3, Carter Ralphe3, Darren Lum2, and Chris Francois2 Depts. of Medical Physics1, Radiology2 & Pediatric Cardiology3 - University of Wisconsin

Purpose: To further develop and validate highly accelerated radially sampled phase

contrast imaging (PC VIPR) for clinical use in congenital heart disease [1].

Methods: 24 consecutive CHD patients (range 9 weeks – 67 years) with a variety of

pathology including aortic coarctation (9), bicuspid aortic valve (6), tetralogy of Fallot (5),

atrial septal defects (3) among others were scanned at 1.5T and 3 T. Typical scan

parameters: imaging volume = 320 x 320 x 180 mm3, readout = 256-320, (1.0-1.25 mm)3

acquired isotropic spatial resolution, VENC = 50-150 cm/s, TR/TE = 8.7/2.8 ms, flip = 10º ,

retrospective cardiac gating, scan time ~ 10 min (50% respiratory gating efficiency). CE-

MRA and 2D PC images were used for comparisons when available. Data processing in

customized analysis and visualization tools (Matlab & Ensight).

Results: PC VIPR data sets were successfully acquired in all patients. All anatomical

structures visualized on CE MRA images were identified on the angiograms derived from

the PC VIPR images. On a case-by-case basis, additional hemodynamic information was

obtained including visualization of flow patterns, flow quantification, and transstenotic

pressure gradients. PC VIPR flow measurements were more accurate than the clinical

routine targeted 2D PC measurements.

Conclusion: The radially undersampled 10 min PC MRI acquisition coupled with the

developed post-processing tool has proven to be a versatile tool for imaging in CHD.

Coupled with an efficient motion correction it can possibly replace exams in the young

currently performed under anesthesia with more patient friendly sedation.

Fig 1: (a-d) Pulmonary venoblar syndrome – (a) posterior view, (b) atrial defect: 1.34 L/min, (c) analomous pulmonary venous return “Scimitar Vein”: 0.42 L/min, (d) abnormal systemic artery: flow to the right lung., (e-f) Double inlet left ventricle status post bidirectional Glenn – particle traces and flow waveforms, (g) Aortic coarctation - pressure map.

SVC

RPA LPA

e f g


9.2 Ultrasound-guided Cardiac Gating for Coronary MRA G. Liu1, R. Walcarius2, X.L. Qi2, A. Dick2, G. A. Wright1

1Medical Biophysics, University of Toronto, Toronto, Ontario, Canada, 2Sunnybrook Health Sciences Centre, Toronto, Ontario, Canada

Purpose: Mistakes on the order of tens of milliseconds in the timing of imaging windows

can incur significant motion artifacts in coronary MRA. We present a new, ultrasound-

based method for identifying quiescent periods by monitoring the velocity of the inter-

ventricular septum (IVS), a correlate of flow into and out of the left ventricle [1]. We

demonstrate that, compared with using a cine SSFP pre-scan, our determination of gating

parameters produces sharper coronary MRA images.

Methods: Right coronary artery (RCA) imaging was performed on four healthy volunteers

using a GE Signa 1.5T system. Two sequences were used: (1) T2-prep spiral GRE during

6 to 15s breath-holds with 0.77 x 0.77 x 3.6 mm resolution; and (2) respiratory navigated

3D fat-sat SSFP, with 1.4 x 1.4 x 2.0 mm resolution. ECG gating parameters were

determined by, first, ultrasound imaging of the IVS, and second, a SSFP cine of the

4-chamber view [2]. Differences in gating parameters produced different results in RCA

visualization. Two experienced observers chose the better images of the two data sets in

a blinded, head-to-head comparison. Results: One observer always favoured the MRAs guided by the ultrasound pre-scan.

The second observer found image quality to be better for the ultrasound method in 7 out of

8 comparisons, and equal between the two methods in the remaining case. Figures 1 and

2 show some sample comparisons.

Figure 1: 2D RCA MRA (74 bpm) ECG gating parameters obtained by (left) an ultrasound pre-scan [onset: 600ms; duration: 53ms], and (right) a cine MR pre-scan [onset: 432ms;duration: 158ms].

Figure 2: 3D RCA MRA (62b pm) ECG gating parameters obtained by (left) an ultrasound pre-scan [onset: 650ms;duration: 158ms], and (right) a cine MR pre-scan [onset:561ms;duration:165ms].

Conclusion: In this study, RCA MRA produced sharper images under the guidance of an ultrasound pre-scan versus the guidance of a MR cine pre-scan. References: [1] Mundigler G et al., JClinBasicCardio 2002 (5). [2] Jahnke et al., Radiology 2006 (239).


9.3 Contrast-Enhanced Whole-Heart Coronary MRA at 3T Using Gradient Echo Interleaved EPI (GRE-EPI)

Himanshu Bhat1, Sven Zuehlsdorff2, Debiao Li1. 1Northwestern University, Chicago, IL, 2Siemens Medical Solutions, Chicago, IL

Purpose: Whole-heart coronary MRA is a promising technique for detecting coronary

artery disease; however its major drawback is the long scan time on the order of 10-15

minutes. The goal of this work was to reduce the

scan time of whole-heart coronary MRA by using

a GRE-EPI [1] sequence at 3T.

Methods: 6 echoes (TR = 10.6 ms) were

acquired after each RF pulse. To minimize k-

space modulations, scan parameters were

selected using simulations of the Bloch equation.

A dual reference scan phase correction

technique was used for accurate echo alignment

in the presence of increased off-resonance

effects at 3T. The GRE-EPI readout was

combined with GRAPPA [2] for a further

reduction in scan time.

Results: Whole-heart coronary artery images

were acquired in 7 volunteers with a spatial

resolution of 1.0 x 1.0 x 2.0 mm3 in an average

scan time of 2.6 ± 0.6 minutes with an average

navigator efficiency of 41.7 ± 9.7%. Fig. 1 shows

coronary artery images from 2 volunteers using

the contrast-enhanced GRE-EPI (a-c) and GRE

(d-f) techniques acquired in separate sessions

for comparison purposes. The imaging times with

GRE-EPI were 1.6 and 2.6 minutes and those

with GRE were 4.2 and 8.7 minutes. Both

sequences show similar depiction of the

coronary arteries.

Conclusion: Compared with current techniques, the proposed GRE-EPI method

represents a factor of 3 reduction in scan time and a factor of 2 reduction in contrast dose.

References: [1] MRM 30(5):609-16, 1993. [2] MRM 47(6):1202-10, 2002.

Fig 1. Coronary artery images using a contrast-enhanced GRE-EPI sequence (a-c) and a contrast-enhanced GRE sequence (5d-f), acquired in separate scan sessions.


9.4 Feasibility of Whole-Heart Coronary MRA on 3 Tesla Using Ultrashort-TR SSFP VIPR

J. Xie1, P. Lai1, H. Bhat1, and D. Li1 1Departments of Radiology and Biomedical Engineering, Northwestern University, Chicago, IL, United

States

Purpose: The purpose of the work was to evaluate the feasibility of whole-heart coronary

MRA on 3.0T using SSFP and verify that ultrashort TR with VIPR allows good coronary

MRA image quality with SSFP.

Methods: Eight healthy volunteers were studied on a 3.0 Tesla Siemens whole-body

scanner during free breathing. An ECG-triggered, navigator-gated SSFP VIPR sequence

was used for data acquisition. The imaging parameters were: TR/TE = 3.0 ms/1.5 ms,

bandwidth/pixel was 868 Hz, resolution = 1.3*1.3*1.3 mm3.15360~16720 projections, 512

readout points per projection were collected. With the SAR limitation, a flip angle of 50~60

degree was used. Adiabatic T2 preparation scheme was used with a T2-prep time of 40

ms [3]. SPIR (Spectral Presaturation Inversion Recovery) was used to suppress the fat

signal.

Results: The acquisition time of whole-heart MRA ranged between 9 to 13 min. Both left

and right coronary arteries

from four volunteers were

successfully visualized. Figure

1 is a multiplanar reformatted

(MPR) image delineating

LAD, RCA, and LCX.

Excellent contrast between

blood and myocardium is

observed and no banding

artifacts are present. Average

image quality scores were

3.10 with a SD of 0.41.

Conclusion: With non-slab-selective excitation for VIPR, TR could be decreased to 3.0

ms as compared to 4.0 ms usually required for slab-selective SSFP. As a result, no

apparent image artifacts were observed in the region of interest and excellent delineation

of coronary arteries were obtained in our volunteer studies.

References: [1] Bi X, et al. JMRI 2005;22:206-212

[2] Shea SM, et al. JMRI 2002;15:597-602

[3] Nezafat R, et al. MRM 2006;55:858-864

Figure 1. MPR images acquired with ultrashort-TR SSFP VIPR from two volunteers. Note the good delineation of coronary arteries.


9.5 Cardiac Imaging: Methods for the Detection of Intramyocardial Fat

James W Goldfarb PhD Saint Francis Hospital, Roslyn, NY and Stony Brook University, Stony Brook, NY

Purpose: Detection and characterization of myocardial infarction has been shown to be

critical for both the right and left ventricles. While the primary technique for detection of

fibrosis and necrosis is late gadolinium-enhanced (LGE) imaging, chronic myocardial

infarction is often associated with fatty replacement. In this presentation, we will discuss

the available methods for detection of intramyocardial fat along with their advantages and

disadvantages. Examples from each technique will be presented.

Methods and Results: Techniques considered include T1 weighted imaging (native T1

weighting or use of inversion or saturation pulses)(1), bSSFP CINE, opposed phased

imaging, water-fat separation (2), chemical fat saturation preparation pulses, and late

gadolinium-enhanced water-fat separated imaging(3). Accurate sizing of myocardial fat

deposition, may only be achievable using “in-phase” MR images due to the loss of signal

at water-fat tissue boundaries in opposed phase images. Opposed phase images may

offer increased sensitivity for small fat deposits due to this “artifact” at tissue boundaries.

Reliability, ease of use, accuracy, sensitivity, specificity, availability and speed are all

important issues for widespread clinical usage. Due to its simplicity, precontrast CT

imaging (4) is a quick, high resolution, accurate technique, but does not have the

specificity for fat detection as does MR imaging. Though CT techniques are under

development, MR imaging currently has better methods for contrast-enhanced infarct

detection and the quantitative assessment of ventricular function.

Conclusions: MR imaging has many techniques for the detection of intramyocardial fat.

Though water-fat separation and CT imaging provide the best images, other techniques

may be relevant if detection rather than accurate sizing is needed.

1. Goldfarb J, Arnold S, Roth M, McLaughlin J, Reichek N. Magnetic Resonance Shows Fatty Replacement of Left Ventricular Myocardium after Myocardial Infarction. Circulation 2005; 112:II-470.

2. Reeder SB, Markl M, Yu H, Hellinger JC, Herfkens RJ, Pelc NJ. Cardiac CINE imaging with IDEAL water-fat separation and steady-state free precession. J Magn Reson Imaging 2005; 22:44-52.

3. Goldfarb JW. Fat-water separated delayed hyperenhanced myocardial infarct imaging. Magn Reson Med 2008; 60:503-509.

4. Zafar HM, Litt HI, Torigian DA. CT imaging features and frequency of left ventricular myocardial fat in patients with CT findings of chronic left ventricular myocardial infarction. Clin Radiol 2008; 63:256-262.


9.6 3D spiral high-resolution late gadolinium enhancement Dana C. Peters, Peng Hu, Reza Nezafat, Warren J. Manning

Beth Israel Deaconess Medical Center, Dept of Medicine, Harvard Medical School

Purpose: Late gadolinium enhancement (LGE) is peerless among imaging modalities for

visualizing scar/fibrosis in the heart. High resolution LGE imaging is an important goal to

improve visualization of small regions of scar, such as papillary muscle scar, complex scar

related to ventricular tachycardia, and RF ablation scar. Spiral imaging with spectral

spatial pulses is attractive for high-resolution LGE because it provides excellent fat-

suppression, high SNR efficiency, and good motion ghosting properties. We compared a

high resolution 3D spiral LGE sequence with our current 3D Cartesian protocol.

Methods: Four subjects were imaged 20-30 minutes after injection of 0.2mmol/kg Gd-

DTPA. Spiral scan parameters include 3D, ecg-gating, and NAV-gating, water-selective

RF pulses, 1.3 x 1.3 x 5 mm3 spatial resolution, imaging time = 60 heart-beats (neglecting

dead time), 14 interleaves, 14 ms acquisition window, and 38 slice-encodings. The

sequence acquires 5 TRs per heart-beat, using a kz-centric acquisition, TRTEq=

23ms/3.6ms/40°.

Results: Scans were diagnostic in all subjects. Figure 1 compares the spiral LGE

sequence with the Cartesian sequences. The image quality and sharpness is similar to

the 3D LGE sequence which took 3x longer. Conclusions: The high resolution 3D LGE

spiral approach is promising for visualizing scar in the heart.

A B CA B C

Figure 1: A) Low resolution 3D LGE (2 x 2 x 5 mm) acquired in 2 minutes. B) 3D Cartesian LGE with 1.2 x 1.2 x 5 mm resolution, in 6 minutes. C) Spiral 3D LGE with 1.3 x 1.3 x 5 mm spatial resolution, acquired in 2 minute. All times assume 50% NAV-efficiency.


9.7 Temporal Filtering for Sliding Window Time-resolved Angiography: Beyond Density Compensation Solutions

Grabow B, Wu H, Block WF, Samsonov AA University of Wisconsin–Madison, Madison, WI USA

Introduction: Methods such as “tornado filtering” [1-2] and KWIC [3] exploit the variable sampling density in k-space trajectories such as radial acquisitions to produce a temporal or parametric series of images from a single acquisition. A gridding reconstruction utilizes a density compensation function (DCF) to limit the aperture of oversampled spatial frequencies to a specific time point or contrast-weighting. The sampling aperture widens with the k-space radius to limit the effects of undersampling artefacts as the sampling density decreases. The filters are poorly compatible with iterative reconstruction because of: 1) suboptimal SNR; 2) mixing of temporal information, especially in smaller objects. We present a method to design such filters for iterative methods that is not based on using a DCF. Methods: The DCF in [1-2] is designed to minimize errors in the spatial point spread function (psf). As the k-space radius increases and data become undersampled, these approaches weight data across the widening temporal footprint [4] evenly, degrading temporal fidelity. We instead use an iterative reconstruction that derives an image

estimate if that fits the acquired data s and the encoding matrix E :

( )( )1/2

2argmin ii=

ii f

fWEf-s . The minimization is weighted with a specially

designed function iW that emphasizes the current time frame over all spatial frequencies

while minimizing the influence of adjacent temporal data and simultaneously providing optimized image SNR relative to conventional DCF. The implementation provide benefits from parallel imaging by including coil sensitivity information in E .

Results and Discussion: The figure to the right shows four simulated contrast-enhancing vessels over a background of linearly enhancing peripheral tissue at a midpoint in scan where the peak vessel enhancement is at the distal (inferior) point of the image. There is no horizontal variation between the vessel enhancement patterns. Notice that that with the traditional filter, the larger vessels show variation vertically across the vessel but the smallest vessel shows no change across the image. The iterative methods show a much closer depiction of the actual enhancement for all widths of blood vessel. The iterative method gives more flexibility in the design of the temporal filter, as the minimization process essentially corrects errors due to variations in sampling density. There is a cost in noise amplification, which ultimately limits increases in temporal fidelity. 1) Barger et al MRM 2002 2) Liu et al IEEE-TMI 2006 3) Song et al, MRM 2000 4) Mostardi and Riederer et al, MRM, 2009.


10.1 Angiographic and Hemodynamic Assessment of the Hepatic Vasculature in Portal Venous Hypertension

using High Resolution PC VIPR Kevin M. Johnson, Oliver Wieben, Chris Francois, Ben Landgraf, Scott B. Reeder

Departments of Medical Physics and Radiology, University of Wisconsin, Madison, WI, USA

Purpose: Several investigators have proposed the use of non-invasive flow measurement

techniques such as PC MR [1,2] for the evaluation of hepatic flow patterns and rates in

patients with portal venous hypertension; however, with existing techniques evaluation of

the entire hepatic vasculature can be challenging due to long scan times and limited

coverage. In this work, we present initial results using an accelerated 3D radial sequence

for whole abdomen CINE, 3D PC (PC VIPR).

Methods: Both normal volunteers and patients with liver disease were scanned on a 3T

MR scanner (MR750, GE Healthcare) using a 32-channel torso array coil. PC VIPR was

performed using adaptive bellows

respiratory gating with 50% efficiency,

1.25mm isotropic resolution, 32 x 32 x

24cm3 FOV, Venc = 25cm/s, retrospective

cardiac gating, for a total scan time of

approximately 10minutes.

Results: Figure 1, shows example

anatomical images derived using PC

VIPR. Both arteries and veins are well

visualized with high resolution. In Figure 2,

vortical flow can be observed in a

representative visualization of the portal

vein.

Conclusion: Whole abdomen PC VIPR allows

anatomical and hemodynamic visualization of

the entire liver vasculature, the splenic and

renal vasculature, making it a very promising for

non-contrast enhanced evaluation of the hepatic

vasculature in portal venous hypertension.

References: 1. Yzet et al. EJR 08 In Press.

2.Stankovic et al. ISMRM 09 #3856

Figure 1. Example PC VIPR anatomical images of the hepatic artery (left) and portal vein (right). Top images show axial limited MIPs while bottom images show coronal limited MIPs.

Figure 2. Example visualization on the flow in the portal vein, demonstrating laminar mixing from the splenic vein (blue) and SMV (red)


10.2 Renal MR angiography: multicenter intraindividual comparison of gadobenate dimeglumine and gadofosveset

trisodium G Schneider1, M Pasowicz2, J Vymazal3, Z Seidl4, M Aschauer5,

M Konopka6, D Bilecen7, R Iezzi8, C Ballarati9

1. Homburg University Hospital, Homburg/Saar, Germany; 2. John Paul II Hospital, Krakow, Poland; 3.

Na Homolce Hospital, Prague, Czech Republic; 4. Neurologicka Klinika, Prague, Czech Republic; 5. University of Graz, Graz, Austria; 6. NZOZ Slaskie Centrum Diagnostyki Obrazowej, Katowice, Poland;

7. University of Basel, Basel, Switzerland; 8. Università G. D'Annunzio, Chieti, Italy; 9. Hospital Valduce, Como, Italy

Purpose: To prospectively compare gadobenate dimeglumine and gadofosveset trisodium

for contrast-enhanced MR angiography (CE-MRA) of the renal arteries.

Methods: 38 subjects with renal vascular disease underwent a first CE-MRA exam with

0.1 mmol/kg gadobenate dimeglumine followed 3-12 days later by a second exam with

0.03 mmol/kg gadofosveset. For both agents, identical T1w SPGR sequences were used

to acquire first-pass (FP) coronal images during breath-hold. In 16/38 patients additional

steady-state (SS) sagittal and axial images were acquired with gadofosveset. DSA was

performed in 34 patients. Images were evaluated by 3 blinded readers in terms of

sensitivity, specificity, accuracy, and positive and negative predictive values (PPV and

NPV) for detection of significant (≥51%) renal artery stenosis compared to DSA. Findings

were compared using McNemar and Wald tests; assessments of FP diagnostic preference

were evaluated using the Wilcoxon Signed Rank test; and reader agreement (kappa [])

was determined. A full safety evaluation was performed.

Results: Gadobenate dimeglumine was consistently superior to gadofosveset (sensitivity:

76-87% vs 68-76%; specificity: 92-99% vs 91-94%; accuracy: 89-96% vs 86-90%; PPV:

70-94% vs 65-76%; NPV: 94-97% vs 92-94%). Significant superiority for gadobenate

dimeglumine was noted by 2 readers for specificity (P≤0.02), accuracy (P≤0.005), and

PPV (P≤0.018). SS images provided no additional benefit for gadofosveset. Three-reader

agreement was excellent (=0.776-0.855). Readers 1, 2, and 3 preferred gadobenate

dimeglumine in 11, 17, and 13 patients and gadofosveset in 5, 4, and 5 patients; no

preference was expressed for the remaining subjects. Adverse events were reported for

2/38 [5.3%] with gadofosveset but 0/39 [0%] with gadobenate dimeglumine.

Conclusion: Better reader preference and diagnostic performance was obtained with 0.1

mmol/kg gadobenate dimeglumine vs 0.03 mmol/kg of the intravascular blood pool agent

gadofosveset for CE-MRA of the renal arteries.


10.3 FINESS (Flow Inversion-prepared Non-contrast Enhancement in the Steady State): a novel technique for non-contrast renal MRA

Manojkumar Saranathan1, Ersin Bayram1, and James Glockner2 1GE Healthcare, Rochester MN & 2Dept. of Radiology, Mayo Clinic, Rochester MN

Purpose: To evaluate a novel balanced SSFP-Dixon technique for non-contrast MRA of

the renal vasculature in a single breath-hold Methods: A 3D dual-echo bipolar readout balanced SSFP pulse sequence with a robust

two-point Dixon algorithm1 for fat-water separation was developed. This enabled use of

radial fan-beam segmentation in ky-kz. Each fan-beam was acquired after a slab selective

180° pulse that effected venous and background suppression2. The radial fan-beam

scheme enabled us to acquire the 3D volume in a single 20-22s breath-hold, eliminating

the need for respiratory triggering, which is sub-optimal in some patients. Parameters: 70°

flip, TR/TE1/TE2 6.2/1.4/2.8 ms, 256x224 matrix, 35 cm FOV, 2 mm thick, 32-40 slices,

TI=900ms. All subjects were imaged on a GE Excite system with a 8-channel torso array

coil under an IRB-approved protocol.

Results and Discussion: Fig. 1 Right renal artery stenosis depicted using a 22s BH

FINESS volume rendering (top) and confirmed on conventional x-ray angiography

(bottom). Fig. 2. Right renal artery stenosis depicted using a 23s BH FINESS sequence

(top) compared to MR contrast enhanced angiography (bottom). FINESS afforded

excellent visualization of stenoses in a short 20-22s breathhold with marked insensitivity to

Bo inhomogeneities. Preliminary results are encouraging, and suggest that this technique

may have clinical utility for rapid, breath-held non-contrast MRA.

Figure 1

a

Figure 2

Refs: [1] Ma et al. MRM. 52:415-419 (2004) [2] Takei et al. Proc ISMRM, p3420 (2008)


10.4 Magnetic Resonance Angiography of the skin for perforator-based autologous breast reconstruction

Tiffany Newman, MDI, Julie Vasile MD II, Joshua Levine, MD II, David Greenspun, MD II, MSc, Robert J. Allen M.D., A.P.M.C, F.A.C.S II, Minh-Tam Chao B.S.R.T(R) MR I, Martin R. Prince, MD, PhD I

I Radiology, Weill Cornell Imaging at New York Presbyterian, New York, NY, United States, II The Center for Microsurgical Breast Reconstruction, New York, NY, United States.

Purpose: Autologous breast reconstruction after mastectomy using abdominal and gluteal perforator artery flaps has gained popularity due to preservation of the donor site muscle and function. We evaluate skin MRA accuracy for the preoperative mapping of perforating arteries and flap volume estimation. Methods – Pre-operative MRA on 25 consecutive patients undergoing perforator artery based autologous breast reconstruction was performed at 1.5 Tesla using axial 3D LAVA of the skin overlying abdominal and/or gluteal regions with 20ml gadobenate. Perforator artery size and coordinates relative to umbilicus or top of gluteal crease on 3D MRA were compared to findings at surgery. Reconstructed breast volume estimates from volume rendered MRA images were also compared to weights at harvesting. Results – One hundred twenty-five perforator arteries were found at surgery to be located within 1cm of the coordinates measured on MRA and were surgically verified to be suitable for flap perfusion. Surgery verified the arterial course and caliber through the rectus and gluteal muscles visualized on MRA in 47 of 48 arteries. Volume rendering of 3D MRA accurately predicted breast reconstruction volumes. Conclusion - This study of 25 patients undergoing breast reconstruction shows that 1.5T MRA safely and accurately identifies precise location measurements and vascular anatomy of abdominal wall and gluteal perforator arteries for guiding autologous flap harvesting.

a a

Figures: Preoperative MRA of the skin of the abdomen (top 2 images) and gluteal (bottom 2 images) regions in different patients undergoing perforator based breast reconstruction


10.5 Time-SLIP versus DSA in Patients with Renal Artery Stenosis Isabelle Parienty1, Faïza Admiraal-Behloul2 , Francis Jouniaux1 , Guy Rostoker3

1Centre d’Imagerie du bois de verrière, Antony, France. 2Toshiba Medical systems, Zoetermeer, the Netherlands. 3Service de Néphrologie, Centre Hospitalier Claude Galien,

Paris, France.

Purpose: To compare the findings in non-contrast enhanced MRA using the Time Spatial

Labeling Inversion Pulse (Time-SLIP) technique [1]

to those of Digital Subtraction Angiography (DSA) in

patient with significant renal artery stenosis (>60%).

Methods: Thirty Patients (12 man, mean age 72 ± 11

y) with renal insufficiency and suspected renal artery

stenosis were explored. Time-SLIP images were

obtained on a 1.5T MRI system (Vantage, TOSHIBA,

Tokyo), using an SSFP sequence with respiratory-

gating and the following parameters: TR=5.2 ms,

TI=1200 to 1800 ms, TE=2.6 ms FA 120, FOV 35x35

cm, Matrix 256X256, Speeder Factor 2 , 35 slices,

Fat Sat on, and time= 4.30 min. The image quality

was visually assessed by an experienced radiologist

and scored as: poor: no contrast in the distal

branches but interpretable, moderate: moderate

contrast in the distal branches and good: strong

contrast from the ostium to the segmental arteries.

the degree of stenosis was estimated using

measurement tools on a post-processing workstation

(GPW, Toshiba Medical Systems). A degree of

stenosis of 60% or higher was considered as

significant. In all patients with a significant stenosis, a

DSA was performed.

Results: The Time SLIP images were scored as good in 24 patients, moderate in 5

patients and poor in 1 patient. We detected 18 significant stenosis in 17 patients. In all 17

patients the DSA confirmed our findings . Figure 1 shows a representative case.

Conclusion: Time-SLIP is a reliable technique for renal artery stenosis screening and

diagnostic in patients with moderate to severe renal dysfunction. A quantitative

comparative study where different degrees of stenosis, from 20% to total occlusion, is on-

going.

Reference: 1. D. Utsunomiya et al. Circ J 2008; 72: 1627–1630 .

Figure 1 :. (a) Time-SLIP image (scored as moderate) revealed an ostial stenosis on the right main renal artery estimated at 60%, (see arrow). (b) DSA confirming the findings.


Figure 2. Time course data from ROIs and model fits.

Figure 1. MIP from a single time frame.

10.6 Simultaneous Renal Angiography and Perfusion Measurement Using Time-Resolved MRA

Katherine L. Wright1, Raymond F. Muzic1,2, Nicole Seiberlich2, Yu-Hua Fang1, Stephen R. Yutzy1, Mark A. Griswold1,2, Vikas Gulani2

1Dept. of Biomedical Engineering, Case Western Reserve University, Cleveland, OH 2Dept. of Radiology, University Hospitals of Cleveland and Case Western Reserve University,

Cleveland, OH Purpose Time resolved angiography with stochastic trajectories (TWIST), a 3D view

sharing technique, with GRAPPA is used to achieve sufficient spatial and temporal

resolution to simultaneously acquire an angiography exam and perfusion measurement

with a single contrast dose.

Methods Two normal subjects underwent a TWIST renal MRA

exam at 3T (Magnetom Verio, Siemens, Erlangen, Germany)

according to local IRB protocol. Imaging parameters: FLASH; 0.05

mmol/kg of Gd-BOPTA (Multihance; Bracco Diagnostics Inc.,

Princeton, NJ), pA=0.2, pB=0.4 [1], TR/TE/FA=2.5ms/0.95ms/21°,

TA=3.7s/volume, Res=1.4x1.4x1.5mm3, FOV=350x284x108mm3,

GRAPPA R=3. Contrast dynamics were evaluated for manually

segmented tissues using a two-compartment model [2].

Results A representative MIP from a single angiographic frame for

an asymptomatic volunteer is shown in Fig 1. This confirms the

feasibility of using this method for renal angiography. Fig 2 depicts time course data and

model fits for the same volunteer. The rate constant Ktrans was measured as 4.24 (cortex)

and 0.14 (medulla), yielding perfusion measurements of 6.63 and 0.22 ml g-1 min-1,

respectively.

Conclusions The initial feasibility of this method has been demonstrated. This could have

significant clinical benefit, as it could potentially assess perfusion deficits created by renal

artery stenosis with a gadolinium dose several times smaller than previously needed

forperfusion and angiography measurements

[3].

References [1] Song, et al. MRM 2009; 61:12428. [2] Tofts, et. al. JMRI 1999; 10:223-32. [3]. Michaely et al. Radiol 2006; 238:586-96.

Figure 2. Time course data from ROIs and model fits


Figure 1 Sagittal control, tag, and difference image at delay time of 1.4 sec.

Control Tag DifferenceControl Tag Difference

Time Frames During Inflow

Cortical ROI Signal vs. Time during Blood Inflow

Tag

ControlNull

Delay Time (sec)

Sign

al (a

.u.)

0.6 1.1 1.6

Time Frames During Inflow

Cortical ROI Signal vs. Time during Blood Inflow

Tag

ControlNull

Delay Time (sec)

Sign

al (a

.u.)

0.6 1.1 1.6

10.7 Assessing Kidney Perfusion using Arterial Spin Labeling and Radial Acquisition for Rapid Characterization of Inflow Dynamics

N. Artz1, K. Johnson1, Y. Huang1, E. Sadowski2, S. Fain1,2 1Medical Physics and 2Radiology, University of Wisconsin, Madison, WI, United States

Purpose: Quantifying arterial spin labeling (ASL) perfusion measurements, especially in

diseased subjects who may demonstrate a wide range of blood flows, benefits from data

at multiple delay times1. This research aims to efficiently acquire data at multiple delay

times using a radial approach.

Methods: FAIR ASL was performed on a healthy volunteer in a 1.5 T MR scanner. From

0.1 to 2.1 seconds following inversion, a 2D radial balanced SSFP readout acquired

unique projections with the following parameters: slice orientation = oblique-sagittal, slice

thickness = 8 mm, TR/TE/flip = 5.4/2.7ms/30°, BW = 250.33 kHz, FOV = 34 cm, and

matrix = 128 x 128. Control (non-selective inversion) and tag (selective inversion) were

alternated until 55 pairs were acquired in 11 minutes. The unique radial lines from all

related inversions were combined and partitioned into twenty time frames, each with a

temporal window of 55 ms. A cortical ROI was

used for signal analysis.

Results: The perfusion-weighted difference

image (at a delay of 1.4s) suffers from poor SNR

[Fig 1]. However, the cortical ROI signal vs. time

frame curve demonstrates the correct trend for

perfusion with the tag showing higher signal than

the control [Fig 2]. Further pulse sequence development could reduce the TR, BW and

off-resonance effects. HYPR related reconstruction

techniques may improve SNR and further reduce scan

time.

Conclusion: Preliminary results suggest that a radial

approach may efficiently acquire perfusion data at

multiple delay times in a clinically feasible scan time.

References: 1Parkes et al. Magn Reson Med. 2002; 48(1): 27-41.

Figure 2 Tag and control inversion recovery signal vs time for a cortical ROI during the blood inflow period. Scan time: 11 minutes


10.8 Imaging Capabilities for Real-time Guidance and Verification of Transcatheter Arterial Chemoembolization (TACE) Procedures

WF Block, EK Brodsky, E Bultman, H Wu, A Samsonov, SB Reeder, O Unal University of Wisconsin–Madison, Madison, WI USA

Introduction: Transcatheter arterial chemoembolization (TACE) provides targeted

delivery of chemotherapy and embolizing agents to liver lesions using X-ray fluoroscopic

guidance. The inability of X-ray to adequately visualize the tumor and the tumor’s vascular

supply can cause mistreatment, and thus potentially unnecessary damage to healthy liver

tissue or incomplete tumor treatment. Our long term aim is to develop an integrated MR

real-time imaging system which can visualize liver tumors and adjacent vasculature

through dynamic 3D imaging while also verifying the treatment area. Here we describe

milestones reached as we move towards system integration.

Methods: MR-guided TACE will require catheter tracking, tumor localization, vascular

visualization, and treatment validation. Tumor localization has previously been described

at the Angio Club. Examining the vascular territory distal to the catheter position is

performed via an intra-arterial contrast injection with a 3D stack of stars sequence which

can be oriented obliquely in relation to the hepatic vasculature. Verification of the

treatment region in TACE is normally performed with a followup CT that is sensitive to the

iodine in the ethiodized oil that is preferentially taken up in the treated region. We

demonstrate how treatment can be verified immediately by detecting the oil in ethiodized

oil in the fat images generated by a single breath-hold MR IDEAL scan.

The imaging tasks for this procedure require both real-time, near real-time, and

non-real-time capabilities with multiple contrast mechanisms. We are porting catheter

tracking (described by Brodsky and Unal at this meeting), vascular imaging, and

treatment verification using the virtual scanner capabilities provided by the RtHawk

imaging platform (HeartVista, Palo Alto, CA) onto a GE 1.5T HDx system. In the RtHawk

paradigm, users exert imaging control through a stand-alone processor which modifies a

very simple and flexible imaging sequence.

Results and Discussion: Oblique time-resolved CE-MRA of the hepatic vein is shown at

2 s intervals using a stack of stars sequence in Figure a, with time frames advancing left to

right. Using an MR IDEAL fat image to validate

the treatment region after TACE is shown in Fig.

c, where the hyperintense region corresponds to

the hyperintense region shown in the CT

followup (Fig b).


11.1 Non-Contrast-Enhanced MR Identification of DVT M Louis Lauzon, Houman Mahallati, Linda Andersen, and Richard Frayne Seaman Family MR Research Centre, University of Calgary, Calgary, AB

Purpose: Pulmonary embolism is the 3rd most common cause of death in US hospitals. Common sources of emboli come from pelvic or lower extremity deep vein thrombosis (DVT). We hypothesize that identifying thigh-to-calf DVT is clinically important, so we are investigating high-resolution non-contrast-enhanced (NCE) thrombus MR imaging.

Methods: We adapted a 3D direct thrombus imaging sequence1,2 by adding a flow-suppressing bipolar gradient. All images were acquired on a 3.0T scanner (Signa VH/i; GE Healthcare) using a 4-channel torso phased-array coil, coronal orientation, 15º flip angle, 40 cm FOV, 9.2 ms TR, 320×320 in-plane matrix, 90-120 slices for the thigh and calf/knee regions, 2.0 mm slice thickness, velocity suppression of 20 cm/s and above, TE of 2.0/5.4 ms without/with flow suppression, and one signal average, leading to scan times of 4.5 to 6.0 minutes per region. The internal review board approved the study protocol, and each subject gave written informed consent before imaging. Certified body radiologists interpreted the MR thrombus images to determine the presence of clots.

Results: The figure below is from a patient with known DVT in the superficial femoral vein. The conspicuity of clot in a given slice is similar without (A) or with (B) flow suppression, but the maximum intensity projection (MIP) image provides significantly better thrombus identification with (D) than without (C) flow suppression.

Conclusion: The visualization of lower extremity DVT using high resolution NCE MR imaging is feasible, and shows great clinical promise and potential.

References: 1Moody. Lancet 1997,350:1073. 2Moody. J Thromb Haemost 2003,1:1403.

A B C D


11.2 Susceptibility mapping as a means to image veins E. Mark Haacke, PhD1,2, 3 and Jin Tang2

1. Wayne State University, Detroit, MI, USA 2. McMaster University, Hamilton, Ontario, Canada

3. The MRI Institute for Biomedical Research, Detroit, MI, USA Introduction: The ability to image oxygen saturation is tantamount to being able to follow

tissue function in the brain. This is important for monitoring patients with stroke, multiple

sclerosis and even tumors. Recently, a new approach to susceptibility weighted imaging

(SWI) called susceptibility mapping (1,2) has been proposed. We refer to this new

approach as SWIM. This method offers the ability to monitor susceptibility and correlate it

with oxygen saturation, the focus of this work.

Materials and methods: In order to extract the susceptibility, the phase from a gradient

echo sequence is required. In this study, we use the high pass filtered phase image from

an SWI scan. This phase image is then Fourier transformed back to k-space, filtered with

an inverse regularized filter, and then forward transformed back to the image domain. The

resulting image is now a susceptibility map of the veins and the tissue in the brain. High

resolution SWI data with isotropic resolution of 0.5mm at 4T were collected. Three echo

times were used: 11.6ms, 15ms and 19.2ms.

Results: The susceptibility maps for all three echoes give similar results. Although the

agreement is not perfect, the susceptibility values appear to be independent of echo time

as they should be. They also predict that the oxygen saturation is roughly 0.5ppm in SI

units which is consistent with expected in vivo values.

Discussion and Conclusion: The ability to map veins throughout the entire brain and to

extract venous oxygen saturation is an important adjunct to MRI methodology in the study

of diseases that affect the brain’s hemodynamics. We have presented here an approach

that promises the ability to provide this information for veins much larger than a voxel. The

method is fast and simple and can be applied to any SWI data with phase.

References: 1. Deville G, Bernier M, Delrieux J. NMR multiple echoes observed in solid

3He. Physical Review B 1979;19:5666-5688. 2. Salomir R, Senneville BD, Moonen CT. A

Fast Calculation Method for Magnetic Field In homogeneity due to an Arbitrary Distribution

of Bulk Susceptibility. Concepts in MR Part B (MR Eng) 2003;198:26-34.


Fig. 1. Sagittal MIPs of one arterial time frame (A) and the subsequent venogram (B) both taken from the modified acquisition.

AA

B

11.3 Modified CAPR MRA: Improved Imaging of the Arterial and Venous Phases

P. M. Mostardi, C. R. Haider, N. G. Campeau, S. J. Riederer Department of Radiology, Mayo Clinic, Rochester, MN 55905 USA

Purpose – Acquisition parameters for time-resolved MRA are typically constant

throughout a scan. We hypothesize that the image quality of the arterial and venous

phases of an intracranial MRA can be substantially improved by dynamically changing

acquisition parameters, optimizing spatial resolutions and frame rates as dictated by the

relevant physiology. Tailoring acquisition parameters to match the specific demands of

temporal and spatial resolution of the vascular region of interest is essential in the

development of a Comprehensive Neurovascular Exam (CNVE).

Methods – The CAPR pulse sequence [1] was modified to allow dynamic change of

matrix size, SENSE acceleration, k-space center size, and view sharing factor at a

specified time during the acquisition. Volunteer studies were performed in which a view-

shared time-resolved view order (2.25 sec/frame, 0.86 x

1.38 x 2.00 mm3) was executed to capture the arterial

phase, and then by seamlessly switching to a high spatial

resolution single-phase view order (25 sec, 0.86 x 0.86 x

1.00 mm3) a venogram was acquired. The reconstruction

was modified to automatically account for the change of

CAPR acquisition parameters.

Results – Fig. 1 shows images from a single time-

resolved MRA scan in which several distinct arterial

frames were captured as well as a venogram. The arterial

images are optimized for high temporal resolution,

whereas the venous phase accentuates spatial resolution

and SNR.

Conclusion – By dynamically changing view order

parameters, the intracranial arterial and venous systems

can be imaged with high quality in a single scan. Further

enhancements to the CNVE will allow modification of the

FOV from a large aorta-based FOV to one limited to the

brain.

References – [1] Haider CR, MRM 60:3(2008).


Figure 1: 4D MRA of an AVM using

CAMERA. NRO=192, Nproj=192,

Npartition=30 (10% OS), Nechoes=4,

FA=45°, TR=6ms, TE=1.5, 2.5, 3.5,

4.5 ms, FOV=220x220x3 mm.

Temporal footprint=9s. Arrows

indicate early drainage.

11.4 CAMERA: Contrast-enhanced Angiography with Multi-Echo and RAdial k-space

Hyun Jeong1, Christopher Eddleman2, Saurabh Shah3, Guilherme Dabus4, Timothy J. Carroll1,4 1Biomed. Engineering, 2Neurosurgery, and 4Radiology, Northwestern University, Chicago, IL

3Siemens Medical Solutions, Chicago, IL

Purpose: A new fast acquisition technique for 4D contrast-enhanced MRA is introduced.

It allows a shorter temporal footprint, which samples the contrast bolus more frequently

than previous techniques for more accurate dynamic information.

Methods: 3D radial “stack-of-stars” k-space is acquired with multiple echoes in partition

direction (kz), similar to in a centric segmented EPI (1), which shortens the temporal

footprint by up to 60%. Intracranial MRA images of healthy volunteers and AVM patients

were acquired on a Siemens 3T Trio, using CAMERA and the previously developed radial

sequence. Sliding window reconstruction (2, 3) was used to increase apparent frame rate.

AVM patient images were correlated with X-Ray angiography.

Results and Discussion: The images acquired with CAMERA (Nechoes=4) resulted in

significantly higher CNR values than single-echo acquisition. Flip angle optimization is a

known problem with high field CE-MRA, due to SAR. With our multi-echo approach, we

are able to increase the TR while reducing temporal footprint. The longer TR used in

multi-echo acquisitions allows more flexibility in the choice of flip angles for optimal

contrast weighting of the FLASH sequence. Figure 1 shows arterial, nidal, and venous

phases of the time-resolved MRA of an AVM, and a corresponding X-Ray angiogram.

Conclusion: A novel fast 4D MRA technique based

on radial k-space and multi-echo has been developed.

References: (1)Beck G et al. MRM, 2001 (2)Riederer et al. MRM, 1988 (3)Cashen et al. MRM, 2007


11.5 Time-Resolved, Vessel-Selective, Cerebral Angiography Using Arterial Spin Labelling

Philip M. Robson1, Weiying Dai1, Ajit Shankaranarayanan2, Neil M. Rofsky1, David C. Alsop1

1Beth Israel Deaconess Medical Center, Boston, MA, 2Global Applied Science Laboratory, GE Healthcare, Menlo Park, CA

PURPOSE: X-ray Digital Subtraction Angiography (DSA) is the conventional, yet highly

invasive method for morphologic and haemodynamic assessment of the cerebral

vasculature [1-2]. The purpose of this work is to assess an Arterial Spin Labelling (ASL)

MRI method capable of time-resolved inflow visualisation and vessel-selective labelling of

feeding vessels, similarly to X-ray DSA, without the use of contrast material.

METHODS: Temporally resolved image frames were obtained by varying the duration of

labelling before commencing imaging. A modification of pulsed-continuous labelling

(pCASL) incorporating additional gradient pulses, allowed labelling to be targeted to the

ICA [3]. Labelled signal was acquired whilst in the lumen using a bSSFP read-out.

Background suppression was used to provide robust subtraction images. Imaging time

was 1.5 min. Quantitative measurements included arterial transit time to vessel segments,

residual contralateral signal, and labelling efficiency for vessel-selective labelling.

RESULTS: MIP images with temporal resolution of 200 ms (Figure), and high selectivity

and efficiency were obtained (5% contralateral signal, 73% relative efficiency). Normal

variations of the vasculature were identifiable by ASL-MRA in our cohort of 6 healthy

volunteers.

CONCLUSION: This non-invasive ASL technique provides high quality angiographic

images of the vasculature, able to show haemo-dynamic function; it may be of particular

importance for assessing conditions exhibiting altered or differen-tial arterial transit and

collateral flow pathways.

REFERENCES: 1) Borisch I et al., AJNR 2003;24(6):1117-1122; 2) Grzyska U et al.,

Neuroradiology1990;32(4):296-299; 3) Dai W et al., Proc. ISMRM 2008:184.

Left to right: labelling durations of 600, 800, 1000, and 2000 ms


11.6 Quantifying L umen G eometry from R outine C arotid C E MR A

Payam B. Bijari1, Luca Antiga, PhD2, Bruce Wasserman, MD3, David A. Steinman, PhD1 1Biomedical Simulation Laboratory, University of Toronto, Toronto, ON, Canada

2Bioengineering Department, Mario Negri Institute for Pharmacological Research, Ranica, Italy 3Department of Radiology, Johns Hopkins University, Baltimore, MD, USA

Purpose: Recent work has demonstrated a strong relationship between the exposure of the normal carotid bifurcation to disturbed flow and its three-dimensional (3D) geometry [1]. Insofar as 3D contrast-enhanced MRA (CEMRA) is now almost routine, it becomes possible to consider large-scale studies of local risk factors for atherosclerosis. Before this happens, however, it is important to assess the repeatability of these geometric measurements from routine CEMRA.

Methods: As part of the ARIC Carotid MRI study’s repeatability protocol, the left or right carotid bifurcations of 60 participants were scanned twice at a mean(±SD) interval of 65±36 days. 3D contrast-enhanced MR angiograms were acquired at 1.5T using bilateral phased-array RF surface coils at the following spatial resolutions: a coronal slab partitioned into 56 2-mm thick slices, zero-padded to 1 mm; and 200-mm2 field-of-view acquired at 256x160, zero-padded to 512x512. Our Vascular Modeling ToolKit (www.vmtk.org) was used to segment the lumen surface rapidly (typically < 5 minutes) and with minimal operator interaction, from which a number of geometric parameters were extracted automatically as described by Lee et al. [1]. Results: Of the 60 pairs, 9 were excluded because one or both carotid bifurcations resisted segmentation by the rapid protocol. Intra-class correlation coefficients (ICC), tabulated to the right and based on analysis of the remaining pairs, revealed excellent repeatability for three of the four geometric factors despite the relatively coarse CEMRA spatial resolutions, possible repositioning effects, and purposefully rapid segmentation protocol. These results were found to be insensitive to operator’s grading of the segmented lumen surface as excellent (37%), adequate (41%) or poor (22%). Interestingly, area ratio and tortuosity, the geometric parameters that together best predict the burden of disturbed flow [1], were found to have the best repeatability. Conclusion: In most cases 3D level set segmentation and geometric factor extraction can be performed reproducibility, with minimal operator intervention, from non-ideal CEMRA data. This opens up the possibility for cost-effective retrospective or prospective studies on the role of local risk factors in vascular disease. [1] Lee SW, Antiga L, Spence JD, Steinman DA. Geometry of the carotid bifurcation

anticipates its exposure to disturbed flow. Stroke 2008 Aug; 39(8): 2341-7.

Parameter ICC Angle 0.80 Planarity 0.54 Area Ratio 0.93 Tortuosity 0.89


11.7 Magnetic source MRI for quantitative brain iron mapping L. de Rochefort, T. Liu, I. Khalidov, J. Liu, B. Kressler, J. Wu, M.R. Prince, Yi Wang

Departments of Radiology and Biomedical Engineering, Cornell University, New York

Purpose: Iron deposition in the brain can result from cerebral microbleeds (CMB), which

may be associated with an increased risk of devastating intracerebral hemorrhage (ICH),

especially in patients anticoagulated with medicines such as warfarin. Studies have

indicated that the severity of CMB is strongly related to the occurrence of ICH (1).

Quantification of iron deposition in CMB may help quantitatively manage the risk of

warfarin associated ICH. Currently, dark regions in T2* weighted MRI have been used to

identify the presence of iron (2). This hypointensity caused by intravoxel variation of local

magnetic fields depends on imaging parameters and source-voxel geometry, may be

confused with other signal voids such as those caused by calcium deposits.

Method/Results/Conclusions: We propose a novel magnetic source MRI (msMRI)

approach to generate quantitative susceptibility maps for quantitative assessment of CMB

iron deposits. The average local magnetic field in a voxel is a convolution of a dipole field

kernel with the iron magnetization (mass density X B0 X iron susceptibility). So the

susceptibility as a tissue material property can be determined by solving the inverse

problem from magnetic field to susceptibility source. Unfortunately, straightforward

inversion generates no meaningful susceptibility mapping because of severe noise

propagation near the zero points of the dipole kernel. We propose to develop a novel

robust inversion method by making full use of all information in the T2* gradient echo

image data. The phase image (typically neglected in MRI) contains the intravoxel average

field information and is used to generate a local magnetic field map. The magnitude image

contains intravoxel field variation information and is used to guide the inverse algorithm

through a regularization term. We have obtained very encouraging preliminary data

indicating that our inverse approach is highly viable for mapping CMB susceptibilities.

References: 1. Lee SH, et al. Neurology 2009; 72:171-176. 2. Haacke EM, et al. Magn

Reson Imaging 2005; 23:1-25.


11.8 Targeted Glyco-Magnetic Fe3O4 Nanoprobes for Detection and Molecular Imaging of Atherosclerosis

Kheireddine El-Boubbou,a,d Medha N. Kamat,a,d David C. Zhu,b Ruiping Huang,c George Abela,c Xuefei Huang*a

Department of Chemistry,a Departments of Radiology and Psychology,b Department of Medicine,c Michigan State University, East Lansing MI 48824

Cardiovascular diseases, often associated with atherosclerosis, are the leading cause of morbidity and mortality in the world. Despite the significant progress in cardiology, there remain large unmet needs to early detect atherosclerotic plaques, especially those which are prone to ruptures causing heart attacks and strokes. One of the major causes of such dramatic event is “inflammation” which occurs during early onset of the disease leading to over-expression of adhesion molecules. This initiates an immune response that eventually leads to the formation of the plaque. Such adhesion cell-surface glycoprotein receptors including the cluster of differentiation (CD44) expressed on leukocytes presents a unique opportunity for the detection of the disease in its preliminary state. Our proposed work is based on the surveillance that hyaluronic acid (HA) is upregulated in atherosclerotic lesions and CD44, its principal receptor, is involved in several atherogenic processes. Polyvalent HA is expected to displace native HA from cell surface CD44 to reduce the development of atherosclerosis. Thus, we engineered novel highly dispersed hyaluronic functionalized superparamagnetic iron oxide nanoparticles (HA-DESPIONs) as proficient probes to non-invasively target atherosclerotic plaques using magnetic resonance imaging (MRI). The targeting agents on the external surface of the magnetic nanoparticles will allow the selective labeling of the plaques. Herein, imaging of atherosclerotic plaques in rabbits was successfully examined. Due to the paramagnetic nature of the nanoparticles, their binding with the plaques greatly enhances the contrast from the surrounding tissue, allowing ready plaque detection by MRI. We anticipate that such novel nanoprobes HA-DESPIONs will not only deepen our fundamental understanding of the molecular and cellular events characterizing unstable atherosclerotic plaques, but also be potentially developed into a highly innovative therapy for atherosclerosis.


12.1 4D DSA and Fluoroscopy: A New Challenge for MRA? C A. Mistretta, E Oberstar, B Davis, E Brodsky and CM Strother

When DSA was first introduced, it was hoped that X-ray angiography could be accomplished with intravenous injections. Ultimately, the overlap occurring in the 2D projections led to the need for repeated injections and image quality was often marginal due to poor SNR. In recent years 3D rotational DSA techniques, based on rotating C-arm gantrys and large area flat panel detectors have been developed. 3D angiographic non-time-resolved volumes are reconstructed following IV or IA injection of Iodine. Image quality is excellent due to the combination of information over the course of a 5-20 second injection and rotation. In recent years accelerated MRA methods have been developed to permit temporal resolution of about 0.75 seconds over isotropic 320 x 320 x320 voxel volumes. These methods have been modified to permit the acquisition of time resolved 4D DSA data sets with matrices up to 512 x 512 x 512 with frame rates of 20 per second using either the intrinsic projection information in the 3D rotational DSA acquisition or using a combination of these data and an auxiliary conventional single projection DSA run using an IV or IA injection. Real-time fluoroscopic catheter information can be embedded within a roadmap formed from any of the 4D DSA time frames and can be viewed from any angle without gantry rotation. Methods Rotational DSA data are acquired using either intra-arterial or intravenous injections of iodine using typical rotation time of 5-20 seconds. Temporal information is embedded in the reconstructed 3D rotational vascular system using multiplicative projection processing (MPP) using time resolved information from either a separate conventional DSA examination or using the intrinsic projections used to form the rotational reconstruction. Whereas conventional reconstruction from projections typically requires a number of projections dictated by the Nyquist theorem, one or two projections suffice to embed the temporal information in the rotational DSA vessels due to the sparsity of angiographic data sets. Shadowing artifacts occur when signals from the time resolved data set are projected through. However the use of biplane acquisition or the use of separated projections from the intrinsic data set are effective in resolving these. In the latter case temporal resolution is reduced in proportion to the required angular separation. Artifacts can also be reduced based on analysis of contrast time curves where shadowing artifacts will appear as anomalies. .4D fluoroscopy is implemented using MPP using a subtracted catheter-only data set that is multiplied into the vascular tree. Results are shown below. Figure 1 shows the AP and Lateral MIP images of the acquired 3D rotational study formed with a 5 second rotation following an intra-arterial contrast injection. The first four frames of the time resolved AP and lateral MIPS through the 4D DSA data set are also shown. The spatial resolution of the images shown has been reduced by a factor of eight relative to what is possible due to memory limitations of the MATLAB software used to reconstruct these images. This study was performed using a single AP conventional DSA acquisition.


Figure 1 Rotational DSA MIPS and MIPS through the 4D DSA time frames. All time frames can be rotated in arbitrary directions. Figure 2 illustrates two orthogonal views of a single fluoroscopic time frame obtained using single plane fluoroscopy. The catheter can be viewed from arbitrary directions without gantry rotation. When biplane fluoroscopy is used the catheter representation is accurate from all views. When a single projection is used the catheter position is constrained to be in the center of the vessel in the orthogonal view since the projection from the acquired view produces a sheet of intensity through the vessel. This may provide no disadvantage since the position of the catheter in a normal fluoroscopic view is also unknown in one

direction. In spite of this, the advancement of the catheter tip is well represented. Figure2 Orthogonal views of a single fluoroscopic time frame from single plane fluoroscopic exposure. The catheter is shown in white and can be view from arbitrary directions without gantry rotation.

Figure 3 shows a color display of the time to ½ maximum intensity for the vessels contained in one of the 4D DSA time frames. Figure 3 Color display of time to ½ peak. The color scale is in units of 0.25 seconds. 4D DSA is the result of an approximate reconstruction method and typically suppresses parenchymal information, so semi-quantitative impressions of perfusion deficits will have to be inferred based on localized models involving the differences in calculated vascular transit times combined with already available cerebral blood volume maps.


12.2 MR Angiography of muscular and collateral arteries in peripheral arterial disease: reproducibility of morphological and

functional vascular status Bas Versluis1,4, MD; MD; Patty J. Nelemans3, MD, PhD; Joachim E. Wildberger1,4, MD, PhD; Walter H.

Backes1,4, PhD; Tim Leiner1,4, MD, PhD Maastricht University Medical Center, Departments of Radiology1 and Epidemiology2 and

3Cardiovascular Research Institute Maastricht (CARIM), 5Atrium Medical Center Heerlen, 6University Medical Center Utrecht

Purpose: Vascular adaptations contribute to the recovery of peripheral arterial disease

(PAD). The aim of this study was to determine the reproducibility of the number of arteries

in the upper leg as well as arterial flow.

Methods: 10 patients with proven PAD (Fontaine stage II) and 10 healthy volunteers were

included. All subjects underwent CE-MRA covering the entire muscular volume of the

upper legs twice, with a time interval of at least 72 hours. Reproducibility was evaluated in

terms of the smallest noticable difference by the repeatability coefficient (RC), the

coefficient of variation and the intraclass correlation coefficient between the two scans and

the two readers.

Results: Interscan RC for the number of vessels was 1.1 for both patients and volunteers,

meaning an increase of 1 vessel per measurement plane between two scans would

already indicate a significant effect. Interscan RC for flow was 1.5 mL/s for patients and

1.6 mL/s in volunteers. Interreader repeatability coefficient was approximately four times

higher, indicating that the same reader is recommended for follow-up studies.

Conclusions: Quantification of the morphologic vascular status using artery count and

flow measurements proved reproducible in both patients and healthy volunteers. Because

of the high reproducibility, CE-MRA might be helpful in quantifying the development of

arterial collateral formation in patients with PAD and can help to understand to complexity

of this process.


12.3 Multicenter Studies: Lessons Learned from ADNI Matt A. Bernstein, Jeffrey L. Gunter, and Clifford R. Jack Jr

Mayo Clinic, Rochester, MN, USA

The Alzheimer’s Disease Neuroimaging Initiative (ADNI) [1, 2] is a six-year, 800-subject

observational study to assess how well the combined information obtained from MRI, PET,

other biological markers, as well as from clinical and neuropsychological assessment can

measure the progression of mild cognitive impairment (MCI) and early Alzheimer’s

disease (AD). All of the subjects are imaged with 1.5T MRI, and a subset (25%) with 3T

MRI. Half of the subjects also receive FDG PET, and a smaller subset of 120 subjects

receives PIB PET. A total of approximately 5500 MRI exams are planned over the

Execution Phase of the study, which is scheduled to be completed in 2010. All of the

image data are readily available via the Internet to any researcher.

Details about the ADNI MR imaging protocol and its development process are

documented in [2]. A total of 89 scanners with 38 discrete combinations of vendor/field

strength/software revision/hardware configuration are supported. Detailed lists of imaging

parameters for those configurations are posted and are publicly available at

http://www.loni.ucla.edu/ADNI/Research/Cores/ . The wide variety of supported platforms

greatly increases the complexity of the management of the study.

In this talk, with benefit of hindsight, a few lessons learned about managing the MR

portion of a large, multicenter study will be discussed. In particular, the following points will

be covered:

- Quantitative and automated QC and standardization methods [3,4].

- Advantages of a phased approach, i.e. a “prep phase” or mini-dry run for a large study.

- Collaboration with MRI equipment vendors and how it can be mutually beneficial.

Preliminary results from ADNI will also be presented, indicating that the sensitivity of

MRI methods compares very favorably with PET and neuropsychological testing. The

particular experiences reported here relate to an Alzheimer’s disease study, but most of

the lessons learned are quite general and apply to large MR angiography multicenter

studies as well.

1. Mueller SG, Weiner MW, Thal LJ, et al. Alzheimers Dement. 2005 ;1(1):55-66. 2. Jack CR, Bernstein MA, Fox NC et al., J Magn Reson Imaging 2008 ;27(4):685-91. 3. Gunter JL, Bernstein MA, Borowski BJ et al, Med Phys. 2009 Jun;36(6):2193-205. 4. Mortamet B, Bernstein MA, Jack CR et al, Magn Reson Med. 2009 Jun 12;62(2):365-372.


12.4 Imaging Considerations in Serial Studies of Vascular Disease

M Sakamoto, H Kroll, V Rayz, L Boussel, A Martin, and D Saloner Department of Radiology and Biomedical Imaging, VA Medical Center/UCSF

Purpose To investigate strategies for extracting quantitative estimates of important

descriptors of vascular disease that would permit a determination of compositional and

geometric changes in patients with atherosclerotic and/or aneurysmal disease. Methods We selected 18 patients from a large cohort of subjects who underwent two

serial MRA studies of the extracranial carotid arteries and 32 subjects with intracranial

aneurysms who underwent at least two serial studies generally acquired one-year apart.

Quantitative measures of the lumenal volume was measured manually by three

independent readers and using a semi-automated algorithm on TOF- MRA, CE-MRA, and

T1-black blood MRI. Lumen boundaries were determined either using a visual threshhold

or from histogram and/or profile analyses. In order to account for threshholding variation

from factors such as coil sensitivity profiles, a reference segment of normal vessel was

selected for calibration. Results Excellent inter-reader and intra-reader reproducibility was demonstrated. In

carotid disease it was found that appropriate selection of histogram parameters provided

essentially equivalent volume measures for all sequences. In aneurysmal disease, it was

found that volume values were reproducible to within 3% for diameters larger than 5 mms,

to within 10% for diameters greater than 3 mms, and that smaller aneurysms were

associated with substantial uncertainty. Conclusions The combination of MRI and MRA provides information on the temporal

evolution of both the lumenal geometry and disease of the vessel wall such as atheroma

or juxtalumenal thrombus. However, the absence of normalized values for signal

intensities compromises the ability to unambiguously define vessel wall composition and

the precise location of vessel edges. With careful attention to signal intensity

characteristics and using appropriate reference standards it was found that reliable

estimates of serial changes could be extracted from MRI/A. These approaches have

significant advantages in longitudinal studies. One specific example is the ability to use

MRA studies to quantitate the vascular lumen thereby reducing the imperative to obtain

high quality black-blood lumenal definition in studies of atherosclerosis.


12.5 Towards Abdominal MRA at 7 Tesla

Ladd ME, Umutlu L, Maderwald S, Kinner S, Orzada S, Antoch G, Kraff O, Ladd SC, Brote I, Bitz AK, Schaefer L, Quick HH, Lauenstein TC

1Erwin L. Hahn Institute for MRI, University Duisburg-Essen, Essen, Germany 2Department of Diagnostic and Interventional Radiology and Neuroradiology, University Hospital,

Essen, Germany

Purpose: Imaging in anatomic regions with large cross-section is challenging at 7T because of RF wavelength effects in the tissue. Thus far, 7T imaging has therefore been primarily limited to the head or extremities. Only few reports of 7T for cardiac or abdominal imaging are available [1-3]. The purpose of this study was to perform an exploratory study of the potential of 7T for performing MRI and MRA in the abdomen. Methods: All examinations were performed on a 7T whole-body MRI system (Magnetom 7T, Siemens) in a total of 20 subjects. A custom-built flexible 8-channel RF transmit/receive body coil consisting of stripline elements and suitable for static RF shimming was used [4]. Non-contrast-enhanced MRI was performed including T1w 3D FLASH, T1w fat-saturated 2D FLASH, 2D T1w in- and opposed-phase FLASH, 2D TOF, quasi T2w 2D TrueFISP, and T2w TSE. Results: T1w imaging at 7T in general revealed excellent conspicuity of small anatomical structures and the hepatic and renal vasculature (Fig. 1). The arterial system was bright and the venous system primarily dark regardless of slice orientation. TrueFISP provided unexpectedly good image quality (Fig. 2); however, both it and TSE remained challenging due to SAR restrictions. Conclusions: These results are promising for the future of performing abdominal MRA at 7 Tesla. The inherently high signal of the arterial system in T1w imaging shows the potential for MRA without contrast agent. Subsequent studies in healthy volunteers and patients will further assess these sequences and the 7T appearance of pathologies.

References: [1] Vaughan JT, et al. MRM. 2009;61:244-8. [3] Maderwald S,et al. ISMRM 2009, p. 821. [2] Snyder CJ, et al. MRM. 2009;61:517-2 [4] Bitz AK, et al. ISMRM 2009, p. 4767.

Fig. 2: TrueFISP provides good overview of the liver vasculature. TR/TE = 3.5/1.5 ms, flip 50°, BW 975 Hz/pixel, FOV 400x400 mm2, matrix 256x320, 21 slices, thickness 4 mm, TA 18 s.

Fig. 1: Non-enhanced T1w imaging. Left and middle: FLASH 2D of the upper abdomen. Note the inherently high vasculature signal. TR/TE = 130/3.6 ms, flip 70°, BW 405 Hz/pixel, FOV 400x400 mm2, matrix 512x512, 13 slices, thickness 2 mm, Grappa R=2, TA 31 s. Right: TOF MIP in a further subject.


12.6 7 Tesla Cardiac MRI in Humans

Harald H. Quick1,2, S.Maderwald1, S.Orzada1, A.K.Bitz1, I.Brote1, O.Kraff1, L.C.Schaefer1, M.E.Ladd1,2 1Erwin L. Hahn Institute for MRI, UNESCO World Cultural Heritage Zollverein, Essen, Germany

2University Hospital Essen, Department of Diagnostic and Interventional Radiology, Essen, Germany

Purpose: Human cardiac MRI at 7 Tesla is a potentially challenging endeavor due to inhomogeneous RF signal transmission [1] caused by the heart’s position deep within the body and due to the reduced Larmor wavelength at 7 T of approximately 12 cm, which is shorter than the dimensions of the human body and may thus lead to destructive B1 interference (signal voids). Additionally, the specific absorption rate (SAR) at this field strength often constrains the choice of imaging sequence parameters [2]. The purpose of this study was to transfer initial experiences in animal cardiac MRI at 7T [3, 4] to human in vivo cardiac imaging using a custom-built flexible 2x4-channel RF transmit/receive body coil.

Methods: All examinations were performed on a 7T whole-body MRI system (Magnetom 7T, Siemens, Erlangen). A custom-built flexible 2x4-channel RF transmit/receive body coil for 7T human imaging was used for RF signal transmission and reception. Seven healthy volunteers (4 male, 3 female) were placed head-first supine with the chest at the isocenter of the magnet and within the sensitive region of the coil. The imaging protocol encompassed cardiac function along standard views using peripheral pulse-triggered Cine FLASH sequences with 20 phases per RR-interval. The image quality was visually assessed for signal homogeneity and myocardium-to-blood contrast.

Results: All seven subjects could be successfully examined. The coil, driven in CP mode, qualitatively provided relatively homogeneous B1 signal over the sensitive volume. Some regions in the images, however, showed destructive interference with associated signal voids. The Cine FLASH sequence provided good imaging quality and signal homogeneity over almost the entire heart and with good myocardium-to-blood contrast; the achieved spatial resolution was 1.4 x 1.4 x 4 mm3. For perfectly timed and triggered cardiac images, however, ECG triggering seems mandatory. Peripheral pulse gating, as used in this study, in part was associated with imprecise triggering leading to mild motion artifacts.

Fig. 1: Cine FLASH images of the human heart in vivo at 7T. a) short axis, b) 2-chamber, c) 4 chamber, d) LVOT, and e) LVOT 2nd. 1 out of 25 cine phases is shown for each orientation. Conclusion: These initial results can be considered as a first step towards human in vivo cardiac imaging at 7 Tesla high-field MRI. Subsequent studies in patients will further assess these sequences in high-field cardiac imaging and additional cardiac protocols including late enhancement. References: [1] DelaBarre et al.; ISMRM 2007, p. 3867; [2] Maderwald et al.; ISMRM 2008, p. 2716.[3] Quick et al.; MRA-Club 2008, Graz, p. 84.;[4] Quick et al.; ISMRM 2008, p. 1023.


12.7 The Role of Cholesterol Crystals in Acute Cardiovascular Events: Identifying the Cause for Gender Differences in Clinical

Presentation George S. Abela MD, Ameeth Vedre MD, Fadi Shamoun MD, Majid Moughal MD, Department of

Medicine, Division of Cardiology, Michigan State University, East Lansing, MI Purpose: Plaque rupture has been seen more frequently in men and erosion in women.

To explain this we evaluated the physical factors related to cholesterol crystallization.

Methods: The amount of cholesterol, temperature, hydration and pH were varied and rate

and amount of volume expansion measured in vitro. Cholesterol powder (1,2,3 g) was

dissolved in corn oil at varying temperatures (22-44°C) and allowed to crystallize. Effect of

pH and hydration of cholesterol were also evaluated. Fibrous membranes (rabbit

pericardium) with similar thickness and composition to the plaque cap were placed in the

path of growing crystals to assess potential for damage. Tissue preparation for scanning

electron microscopy (SEM) was performed without ethanol to avoid dissolving the

cholesterol crystals.

Results: The volume and rate of cholesterol expansion was directly related to the amount

of cholesterol present (r=0.98; p<0.01, r=0.99; p<0.01 respectively). Low temperature,

hydration and higher pH all significantly increased volume expansion. By gross

examination, the expanding crystals tore the fibrous membrane while in others it just

perforated the membrane. By SEM cholesterol crystals were seen perforating the fibrous

membranes.

Conclusions: Greater amounts of cholesterol result in more crystallization and volume

displacement that can tear fibrous membranes. Thus, the larger necrotic cores seen in

men that probably have higher cholesterol content would result in more rupture. This may

help explain in part the gender difference in clinical symptoms of more ruptures in men

compared to more erosion in women.


P.1 CE-MRA with tailored 3D random sampling patterns and nonlinear parallel imaging reconstruction F. Knoll1, C. Clason2, F. Ebner3, M. Aschauer3, R. Stollberger1

1Institute of Medical Engineering, TU Graz, Austria, 2Institute for Mathematics and Scientific Computing, University of Graz, Austria, 3Department of Radiology, Medical University Graz

Introduction: Variable density 3D random sampling trajectories which were introduced in the context of compressed sensing [1], have great potential for subsampled MR angiography techniques. The goal of this work was to present a parameter-free method to construct tailored variable density sampling patterns, which can be used together with a nonlinear parallel imaging method [2, 3] to allow the use of very high acceleration factors. Methods: A CE-MRA dataset (3D Gradient Echo Sequence, TR/TE=3.74/1.48ms, FA=30°, matrix: 448x352x40, resolution: 0.55x0.55x0.70mm3) of the carotid arteries was acquired on a clinical 3T system and subsampled retrospectively, to simulate an accelerated acquisition. Parallel imaging with 8 receiver coils, comparable to the spatial positions of the individual elements of the receiver head coil that was used in our experiments, was simulated by use of Biot Savart’s law. The proposed method to generate the variable density 3D random sampling pattern is to use the scan of the same anatomic region of a different patient or a healthy volunteer as a template. The power density spectrum of this template can be used as a reference to generate a probability density function which is then used to construct the sampling pattern. Patterns that are generated in this way can be pre-computed for different types of scans or anatomical regions. Image reconstruction was performed with an iteratively regularized Gauss-Newton method (IRGN) [2]. Results and Discussion: Our results show that excellent image quality can be achieved even for very high acceleration factors like R=30 (Fig.1.) without any application of temporal view sharing. Only a slight decrease of SNR and a minimally reduced contrast for the smallest vessels result for an acceleration factor of 30. The mean RMS difference to the original fully sampled data set over all 40 slices was 0.055 with a standard deviation of 0.036. The proposed approach to generate the variable density sampling pattern ensures the sampled ratio of low to high frequency sample points is reasonable for angiography scans. One major advantage is that the method is completely free of any user defined parameters. Our experiments showed that the method is robust regarding the choice of the reference image, as the only information that has to be obtained is an estimate of the ratio of high to low frequency components. The exact anatomical details are not important in this context. References: [1] Lustig et al., MRM 58: 1182-1195 (2007), [2] Uecker et al., MRM 60: 674-682, [3] Knoll et al., ISMRM 2009: 2721

Fig. 1: CE-MRA Dataset of the carotid arteries: (a) Fully sampled data set (b) IRGN reconstruction, R=30


P.2 Handling Motion in Sparse MRI with Whiskers Jason Mendes, Dennis L. Parker, University of Utah, UCAIR, Salt Lake City, Utah

PURPOSE: For dynamic images, pixel intensities that vary smoothly or periodically can

be sparsely represented in a Wavelet-Fourier space and recovered from undersampled k-

space data using Compressed Sensing (1,2). Patient motion that is not periodic or

smooth can therefore be a problem in the reconstruction. We investigate the application

of Compressed Sensing to a novel segmented data sampling technique called Whiskers

(for the whiskers looking pattern in k-space and lack of a clever acronym) to reduce the

effects of patient motion.

METHODS: In general, the minimum number of k-space samples required to produce

good results in sparse reconstruction is approximately four times the number of sparse

coefficients (3). It is therefore beneficial to detect and correct as much patient motion as

possible to maximize temporal sparsity and thus reduce the total number of k-space

samples required. This is accomplished using a hybrid Radial-Cartesian sampling

technique called Whiskers. The Whiskers k-space trajectories of a single segment are

shown in Figure 1. Readout and phase encoding directions are alternated each TR.

RESULTS AND CONCLUSION: The new Whiskers design has been implemented with a

Turbo Spin Echo sequence and shown to provide good detection of both translational and

rotational motion. Aliasing artifacts due to Whiskers undersampling are similar to that of

Radial undersampling, but more incoherent, making Whiskers well suited to be used in

conjunction with Compressed Sensing. Additionally, the most distinct artifact of

Compressed Sensing is the loss of low-contrast features in the image (1). Because

Whiskers fully samples the central portion of k-space it should be able to recover much of

that loss. The simulated results look promising and the authors intend next to apply the

technique to vascular imaging.

ACKNOWLEDGMENTS:

1. Lustig M, et. al. Magn Reson Med 2007;58:1182–1195.

2. Lustig M, et. al. ISMRM, Seattle, 2006. p 2420.

3. Tsaig Y, et. al. Signal Process 2006;86:533–548

(a) (b) (c) (c)

Figure 1: Whiskers segment (a) combined with segment (b) yields a radial like coverage while sampling the central part of k-space rectilinearly.


P.3 Improved Carotid imaging with HASTE using a reduced FOV and increased gradient performance

Jordan P. Hulet5, Seong-Eun Kim1,3, Gerald S. Treiman2,4, Dennis L. Parker1,3,5

1Utah Center for Advanced Imaging Research, 2VA Salt Lake City Health Care System, 3Radiology, 4Surgery, 5Biomedical Informatics, University of Utah

Purpose MR imaging of the carotid artery often suffers from motion artifacts. Single shot

sequences, such as HASTE, can reduce the effect of motion artifacts but often produce

blurry images due a long echo train. We have explored the use of both a reduced FOV

technique (shown below) and increased gradient performance in order to shorten the echo

train length, decrease blurring, and improve image quality.

Methods The standard Siemens HASTE sequence was modified to image a reduced field of view

(rFOV) in the phase-encoding direction while preventing aliasing artifacts by moving the

gradient waveforms for the 180° refocusing pulses from the slice select to the phase

encode axis and adjusting gradient amplitude to accommodate the reduced field of view. A

volunteer was scanned using both regular HASTE and rFOV-HASTE.

Results Images obtained using both sequences are shown in Figure 1. rFOV-HASTE resulted in

images with significantly less blurring which more clearly visualize the carotid arteries.

Figure 1: Carotid scans using regular (a) HASTE and (b) rFOV-HASTE. The HASTE images were cropped to match the reduced FOV (25%) of the rFOV-HASTE images.

Discussion Using rFOV with HASTE shortens the echo train resulting in improved carotid images.

Additionally, a custom gradient insert designed to increase gradient performance is

currently under construction. The rFOV-HASTE sequence has been modified to utilize this

increased gradient performance and further shorten the echo train.


P.4 Towards Continuously Moving Table NCE Peripheral MRA Randall B. Stafford1,5, Mohammad Sabati4, Houman Mahallati2,5, Richard Frayne1-3,5

Departments of 1Physics and Astronomy, 2Radiology, 3Clinical Neurosciences, University of Calgary, Calgary, AB, Canada; 4Department of Radiology, University of Miami, Miami, FL, USA; 5Seaman

Family MR Research Centre, Foothills Medical Centre, Calgary, AB, Canada

Purpose: Peripheral arterial disease (PAD) requires large field-of-view (LFOV)

angiography. PAD patients with renal artery stenosis may be at risk of NSF [1,2]. The

purpose of this project is to combine the balanced steady-state free precession (bSSFP)

Dixon method [3,4] with the continuously moving table (CMT) technique [5,6] for LFOV

NCE peripheral MRA. Here, we assess the feasibility through computer simulation.

Methods: A peripheral anthropomorphic

phantom consisting of fat, marrow, arterial

and venous blood, and muscle was

constructed in MATLAB (The MathWorks,

Inc.). Arterial segments were modified with

varying levels of stenosis. LFOV bSSFP

Dixon method [3,4] image data sets were

generated using bSSFP magnetization

evolution with a table velocity of 0.98 cm/s.

Stationary images were generated for

difference comparison. Maximum intensity

projection (MIP) images were produced for

all data sets.

Results: The water-only MIP images [3,4] are shown in Fig. 1. The simulated table

velocity (0.98 cm/s) allowed the tissue to achieve steady-state magnetization, and allowed

for 100% hybrid-space coverage [5]. The blurring artifacts in the CMT images are due to

partial-volume effects associated with the coarse phantom resolution and the table motion.

This blurring effect would be reduced in a real CMT acquisition [5,6].

Conclusion: The simulations presented here have successfully demonstrated the

compatibility of the bSSFP Dixon method with the CMT technique. The next step in this

project is to collect LFOV images in vivo, and assess vessel conspicuity.

References: [1] Albers, Am J Kidney Dis 1994;24:636, [2] Thomsen, Eur Radiol

2006;16:2619, [3] Huang, MRM 2004;51:243, [4] Stafford, MRM 2008;59:430, [5] Kruger,

MRM 2002;47:224, [6] Sabati, PMB 2003;48:2739.

Fig. 1: Simulated bSSFP Dixon method MIP images of anthropomorphic phantom (left) stationary data set, (centre) CMT data set, and (right) difference. Arrows indicate stenoses.


P.5 R2* Calibration Phantoms for Cardiovascular Studies

Matthew T. Latourette and James E. Siebert, Michigan State University, East Lansing

Purpose: R2* quantitation has been applied to assess iron overload and, recently, to

characterize hemorrhage in atherosclerotic plaque.1-3 Calibration reference phantoms exhibiting

long-term chemical stability and temperature-insensitive R2*/T2* signal, needed for longitudinal

studies, have not been adequately addressed in the literature. This study aims to improve R2*

quantitation reproducibility via development of a calibration reference. The availability of a

stable reference standard is important for R2*-based research studies for monitoring data

quality, decreasing the variance of pooled intra-site study data, and detecting and correcting

bias in multi-site studies.

Methods: A gel mixture matching the T1 and T2 of pediatric brain was doped with SPIO

nanoparticles (Feridex) to produce phantoms with varying R2*. NiCl2 was used to modify T1

because its relaxation behavior is largely independent of temperature, unlike other popular

doping agents.4,5 Agarose was used to modify T2 and promote gel formation. Carrageenan

aided formation of strong, tissue-like gels.6 A methylisothiazolinone-based (MIT) preservative

provided long-term antimicrobial protection. Heat and stirring was applied to the mixture of

NiCl2, carrageenan, agarose, and MIT to dissolve it in water. The solution was poured into

polysulfone bottles, chilled, and sealed. Imaging was performed at 0.7T to verify the T1 and T2

of these phantoms. T1 was computed by fitting the mean ROI signal intensity for each of 5

axial SPGR series to S(TR)=S0(1-e-TR/T1). Mean signal intensity in 6 axial spin echo series ROIs

was fit to S(TE)=S0e-TE/T2 to compute T2. R2* calibration phantoms were prepared with the

same underlying composition, varying only the SPIO concentration.

Results and Discussion: Average T1 and T2 for the SPIO-free phantoms at 0.7T was 838 ms

and 89.5 ms respectively. R2* as a function of SPIO concentration of the doped phantoms was

38.5±1.3 s-1 at 63.6 µM, 44.4±1.7 s-1 at 72.7 µM, 55.5±1.9 s-1 at 90.9 µM, and 68.6±1.9 s-1 at

127 µM. Follow-up imaging results describing measurement reproducibility, R2* measurements

for other field strengths, and an evaluation of the thermal stability of phantom R2* will be

presented.

References: 1Siebert JE et al, MR Angio Club, 2006. 2Zhu DC et al, ISMRM, 16:2841, 2008. 3Zhu DC et al, ISMRM, 17:606, 2009. 4Kraft KA et al, MRM, 5:555-562, 1987. 5Waiter GD,

Foster MA, Magn Reson Imaging, 15:929-938, 1997. 6Yoshimura K et al, MRM, 50:1011-1017,

2003.


P.6 Pictorial Review of Supra-Aortic Artery Pathologies as

Visualised with MRA using Blood Pool Contrast Agent Bethapudi S & Roditi G

Glasgow Royal Infirmary, Alexandra Parade, Glasgow G31 2ER

Purpose: Review the appearances of carotid, vertebral & subclavian artery disease as

demonstrated by Contrast-Enhanced Magnetic Resonance Angiography (CE-MRA) with

blood pool contrast agent. To understand the utility of high resolution 3D steady state

phase imaging in adding value to conventional first pass CE-MRA.

Background: The blood pool contrast agent Gadofosveset trisodium allows first pass CE-

MRA at high spatial resolution with low gadolinium dose due to its high specific relaxivity in

human serum. The prolonged blood pool residency further allows very high spatial

resolution imaging during the steady state phase with acquisition of isotropic voxels that

allow reformat in any plane without loss of spatial resolution along with depiction of

adjacent structures not seen on usual CE-MRA.

Procedure Details: Our experience of MRA in patients imaged with blood pool contrast

agent for suspected carotid, vertebral or subclavian disease is presented. Patients were

imaged in usual first pass and subsequently in steady state phase with high spatial

resolution. Results are presented as a pictorial review of the spectrum of pathologies

encountered including atherosclerotic steno-occlusive disease, subclavian steal

syndrome, vertebral dissection, carotid body tumour, surgical endarterectomy sites, large

vessel vasculitis, thoracic outlet syndromes and depiction of extra-anatomical bypass

grafts. Particular emphasis is placed on the utility of high spatial resolution steady state

imaging to extend coverage, delineate the vascular wall and evaluate associated

structures.

Conclusion: Blood pool contrast-enhanced MRA of the supra-aortic vasculature is

effective in allowing comprehensive evaluation of various arterial pathologies, particularly

in demonstrating extraluminal pathology.


Fig.1: Sub-volume MIP of a contrast enhanced trMRA in a child showing a thoracic kidney in the right hemithorax and an aneurysm in the renal artery.

P.7 Robust Clinical Application of Time-Resolved MRA K. A. Blackham, G.S Sandhu, R.C. Gilkeson, M.A. Griswold, V. Gulani1

Department of Radiology, University Hospitals of Cleveland, Cleveland, Ohio, United States

Purpose: To present a review of the clinical applications of time resolved MR

angiography (trMRA) throughout the body.

Methods: A series of patients were imaged with dynamic

contrast enhanced TWIST-MRA (Siemens Verio, 3.0 T,

TR/TE=minimal ; representative 3.28ms/1.51 ms; matrix 256-

320 x 176-256 x 64-80, GRAPPA 2-3, flip angle 21-25˚, TA 1.5-

4 s/ frame, # frames varied according to application).

Results: The TWIST sequence provides a robust clinical tool

for trMRA that can be employed to solve clinical problems non-

invasively. In children, applications included assessment of

arterial inflow and venous outflow in arteriovenous

malformations (AVMs), mapping of thoracic and abdominal

anomalous vessels, and assessment for renal artery stenosis.

The patients were free-breathing, and resolution as high as

0.9x0.7x0.9 cm3 was routinely achieved with a single dose of

Magnevist contrast. Applications in adults included AVMs in the brain and throughout the

body with mapping of feeder/draining vessels, chest pulmonary angiography and

venography, assessment of renal artery stenosis in patients unable to provide breath-

holds, assessment of AV fistulas, dynamic imaging of popliteal artery entrapment

syndrome, pelvic congestion syndrome, assessment of arterial anatomy and disease

when contrast dynamics in two legs were drastically different, and assessment of

perforator anatomy for fibular free-flap transfer operations, often with half the standard

dose of contrast (by weight). Near isotropic datasets allowed multiplanar reconstruction of

images at multiple timeframes, and dynamic MIP images allowed visualization resembling

traditional angiograms.

Conclusion: TWIST-MRA is a rapid, robust technique that is non-invasive and can be

used routinely and for problem solving in a variety of settings throughout the body.

References: 1. Petkova M, et al. J Magn Reson Imaging 2009; 29:7-122. 2. Sandhu G et

al. Proc ISMRM 2009; 589


P.8 Reproducibility of Aortic Pulse Wave Velocity Measurements Obtained with Phase Contrast Magnetic Resonance (PCMR) and

Applanation Tonometry Jonathan Suever, BS,† David Huneycutt, MD,* Enrique Rojas-Campos, MD,* Francesca Cardarelli,

MD,* Sam Fielden, BS,* Arthur Stillman, MD, PhD,* Paolo Raggi, MD,* John N. Oshinski, PhD,*† †Emory/Georgia Tech, Department of Biomedical Engineering, Atlanta, GA

*Emory University School of Medicine, Atlanta, GA

Purpose: Increased aortic pulse wave velocity (PWV) results from decreased vessel

compliance and can be due to increased age, atherosclerosis and/or hypertension (Farrar

et al. Circ. 1991). The goal of this study was to compare reproducibility of PWV

measurements obtained via applanation tonometry (AT), a clinically accepted method, to a

new PCMR method using cross-correlation analysis.

Methods: PWV was measured in seven asymptomatic patients with an elevated CT

coronary calcium score, and ten healthy volunteers. Oblique sagittal images in the plane

of the aorta (“Candy Cane” view) were acquired with a velocity encoding in the foot-head

direction. Cross-correlation was used to determine time shifts between velocity curves at

adjacent points along the aorta. The slope of a regression line fit to the transit time vs.

location data was used to estimate PWV

(Fielden et al. JMRI 2008). For AT, a

Sphygmocor device (AtCor Medical) was

used to measure pressure waveforms at

carotid and femoral locations and the PWV

was determined using a standard transfer

formula. Inter-scan variability for each

method was assessed with the coefficient of

variation (CoV).

Results: PCMR had a significantly lower

inter-scan CoV than AT (Figure 1). The better

reproducibility may allow for the enrollment of

fewer patients for trials of interventions

targeted at vessel wall compliance.

Conclusion: PWV estimates using PCMR

and cross-correlation processing have

superior reproducibility as compared to AT.

Figure 1: Inter-scan coefficient of variation for AT and PCMR


P.9 Motion-compensated, flow-independent, non-contrast-enhanced renal MR angiography

Gregory J. Wilson1,2, George R. Oliveira2, Liesbeth Geerts1, Jeffrey H. Maki2 1 – Philips Healthcare, Cleveland, USA and Best, Netherlands;

2 -- University of Washington Dept of Radiology, Seattle, WA, USA

Purpose Evaluate a new MR technique for high resolution imaging of renal arteries.

While breath-hold contrast-enhanced MRA (CE-MRA) of renal arteries provides useful

images, the achievable spatial resolution can be limited by breath-hold duration, cardiac

motion [1], respiratory motion [2], and the contrast agent bolus profile [3]. The flow-

independent, non-contrast-enhanced method implemented here reduces or eliminates

these resolution-limiting effects.

Methods The technique has been evaluated in 3 healthy volunteers. The cardiac-

triggered, balanced TFE acquisition employed respiratory navigator gating, fat saturation,

and magnetization preparation (T2 Prep). Data was acquired only during diastole, the

most quiescent period of flow and cardiac-related motion, and without inversion pulses. As

a result, the sequence was flow-independent. Axial volumes were acquired with resolution

of 1.68x1.72x2.4mm3 (reconstructed to 0.73x0.73x1.2mm3) in 4:26 with 70% navigator

efficiency and 2 averages.

Results The acquisition was successful in each volunteer. High resolution images were

produced without the limitations of motion or bolus profile blurring. Flow independence

was demonstrated by lack of in-flow signal modulation in coronal acquisitions, and lack of

venous signal suppression by application of in-flow saturation bands. As a consequence,

veins were visible in the images.

Conclusion The new technique provided high resolution images for evaluation of renal

artery lumen morphology. Further study is planned to evaluate the diagnostic value of this

technique.

Figure 1: High resolution, axial source image displaying left renal artery.

Figure2: Curved reformat showing bilateral renal arteries.

References 1-Kaandorp DW, JMRI2000;12:924-8; 2-Vasbinder GB, JMRI2002;16:685-96; 3-Fain SB, MRM1999;42:1106-16.


P.10 Vascular response during visual stimulation at 3T MRI: functional phase contrast angiography (fPCA) study

Sang-Hoon Kim1, Chang-Ki Kang1, Young-Bo Kim1, Zang-Hee Cho1, 2 1. Neuroscience Research Institute, Gachon University of Medicine and Science, Korea

2. Department of Radiological Sciences, University of California, USA

Purpose: The purpose of present study is to investigate direct arterial response with quantitative velocity analysis using phase contrast angiography (PCA) sequence [1,2]. Methods: PCA sequence was used with the following parameters: 0.67x0.67x1.0 mm3 of imaging resolution, 36 slices, and 20 cm/s of velocity encoding (VENC) for all directions. Total acquisition time was 10 m 18 s for 3 sessions, including 2 rests and 1 visual stimulation (a flashing checker board). A custom-built surface coil was designed for angiographic purpose and tuned to 3T. Twelve subjects participated in this study. Circular region of interests (ROIs) consisting of 21 pixels was used to measure the velocity difference on the different diameters. We found the ROI showing a maximum change and defined as peak ROI and distal ROIs for vessels distal to the peak ROI. Velocity changes of the selected ROIs were measured. Results: Fig. 1 showed the vascular change acquired from PCA and calculated the velocity and its percentage change during stimulation. Velocity change during stimulation was clearly delineated, which were indicated with arrows (a). Mean velocity change between rest and stimulation periods were 0.64 and 0.42 cm/s from a peak ROI and distal ROIs (b), respectively, which are corresponding to 42.3 and 29.6 of percentage change as shown in Fig. 1(c). Conclusion: PCA for functional angiography (fPCA) at 3T MRI could provide vascular response during brain function, including the vasculature as well as the velocity changes of related vessels. References: 1. Iadecola C, et al., J Neurophysiol 1997. 2. Cho ZH, et al., Neuroimage 2008.

Fig. 1. Quantitative velocity analysis of fPCA


P.11 Optimization of Phase-contrast MR-based Flow Velocimetry and Shear Stress Measurement

Taeho Kim1, Jihyea Seo1, Seongsik Bang1, Hyeonwoo Choi1, Yongmin Chang2, Tae-Seob Chung3, Jongmin Lee4

Department of 1Biomedical Engineering, 2Molecular Medicine, and 4Radiology, Kyungpook National University; 3Department of Radiology, Yonsei University

Purpose: To measure the pixel-by-pixel flow velocity and shear stress from PC MR

images, an optimized method was suggested and verified.

Material and Methods: A self-developed straight steady flow model was scanned by 3T

MRI with a velocity-encoded PC sequence. The pixel-by-pixel flow velocity and shear

stress was measured using self-made program and were compared with the physically

measured reference data. A comparison between the program and a commercial

velocimetry system was also performed. Subsequently velocity and shear stress were

measured in curved steady flow model to confirm shifted peak velocity and shear stress

toward the outer side of lumen.

Results: The velocity measured with self-made program showed a significant correlation

with the physically measured velocity and was superior to the commercial system (R2 =

0.85 vs. 0.75, respectively). The calculated mean shear stress had a significant correlation

with the physically measured mean shear stress (R2 = 0.95). The curved flow model

showed a significantly shifted peak velocity and shear stress zones toward the outside of

the flow.

Conclusion: The technique to measure pixel-by-pixel velocity and shear stress of steady

flow from velocity-encoded phase-contrast MRI was optimized and verified to be superior

to the use of a commercial system.


P.12 Blood Flow Patterns in the Abdominal Aorta of Mice: Implications for AAA Localization

Smbat Amirbekian1, Robert Long1, Michelle Consolini 3, W. Robert Taylor2,3, John Oshinski1,2

Department of Radiology1, Biomedical Engineering2, and Medicine (Cardiology)3, Emory University School of Medicine, Atlanta, GA

Introduction: Abdominal aortic aneurysms (AAA) localize almost exclusively in the infra-

renal aorta in man. Humans experience a period of reverse flow during early diastole in

the infra-renal aorta during each cardiac cycle. This reverse flow causes oscillatory wall

shear stress (OWSS) to be present in the infra-renal aorta of humans and has been linked

to AAA formation. In contrast to humans, all mouse models of AAA form aneurysms in the

supra-renal aorta. The presence of reverse flow in the mouse aorta is unknown.

Purpose: The goal of this study was to examine flow patterns in the mouse aorta and

evaluate whether reverse flow exist in the infra-renal or supra-renal aorta.

Methods: Blood flow was measured with a phase contrast magnetic resonance (PCMR)

sequence the supra-renal and infra-renal abdominal aorta of 18 wild type C57BL/6 mice

and 15 ApoE-/- mice (most prevalent mouse model of AAA). Measurements were made

using a 4.7T Varian system.

Results: Results indicate that unlike humans, there is no reversal of flow in the infra-renal

or supra-renal aorta of wild type or ApoE-/- mice. Distensibility of the mouse aortic wall as

a percent of diameter (63 + 18%), is higher than reported values for the human aorta.

Conclusion. Wild type and ApoE-/- mice do not experience the reverse flow associated

with OWSS and AAA in the infra-renal aorta that is observed in humans.


a

b

c

a

b

c

P.13 3D Vessel Wall imaging of multiple vascular beds Niranjan Balu1, Jinnan Wang2, Chun Yuan1

1. University of Washington, Seattle, WA 2. Philips Medical Systems, BriarCliff Manor, Ny

Introduction: Black-blood MRI of atherosclerotic plaque allows identification of plaque morphological and compositional features and thereby helps in assessing disease burden and risk of thromboembolism due to plaque rupture. Recently, a fast isotropic 3D black-blood sequence for carotids has been shown to provide comprehensive plaque information in all spatial directions [1]. Since atherosclerosis is a systemic disease, plaque is coexistent in multiple vascular beds. 3D MRI of multiple vascular beds is an ideal tool to study the pathophysiology of atherosclerosis as a systemic disease. Aim: To develop a time-efficient 3D isotropic imaging protocol for carotid vessel wall imaging of the carotids, aorta and femoral arteries Methods: A 3D FLASH sequence with MSDE [2] preparation was optimized (table) for carotid, aorta and femoral imaging. Results: Vessel wall images of diagnostic image quality were obtained in the carotids, aorta and femoral arteries (figure). Scan time was approximately 2 min, 3.5 min and 10 min for coverage of approximately 15 cm, 16 cm and 50 cm in the carotids, femoral and aorta respectively. Conculsions: Time-efficient vessel wall imaging of large arteries can be achieved within a one-hour scan time by use of the new sequence. References: [1] Balu N et al, ISMRM 09 [2] Wang et al, MRM 07;58:973-981

Vascular Bed Carotid Aorta Femoral Acquisition plane Coronal Coronal Coronal Resolution, mm2 0.7 1.4 1.0 Field-Of-View, mm2 250×160 350×300 300×350 Slice thickness , mm 0.7 1.4 1.0 # of slices 100 86 150 TR/TE, ms 10/4.8 7.7/3.7 7.6/3.5 Flip angle, ° 6 6 6 Turbo factor 90 35 100 Bandwidth, Hz/pixel 134.3 269.1 191.6 Number of averages 1 1 1 Number of stations 1 1 3 Scan time, min:s 2:03 3.23 10.24

Representative images (a) Sagittal carotid with calificate (b) Montage from slices to show entire femoral artery covered (c) Cross-section of abdominal aorta


P.14 Feasibility Study of Combining 3D SSFP with T2prep Inversion Recovery (T2IR) for Black Blood Vessel Wall Imaging

Keigo Kawaji1,2, Thanh Nguyen2, Pascal Spincemaille2, Martin R. Prince2, Yi Wang1,2

1 Department of Biomedical Engineering, Cornell University, Ithaca, NY. 2 Department of Radiology, Weill Cornell Medical College, New York, NY.

Background: T2IR preparation vessel wall imaging provides flow-insensitive global

black-blood (BB) suppression at the expense of SNR [1-3]. A recent study [3] has

demonstrated the feasibility of T2IR preparation in 2D Fast-Spin-Echo for BB vessel wall

imaging. In this report, we examine the feasibility of imaging vessel walls using a 3D

Steady-State Free Precession (SSFP) sequence with T2IR preparation.

Methods: 4 healthy volunteers were scanned using a 4-channel cardiac coil for signal

reception. Axial views of the popliteal artery were acquired using gated 3D SSFP with

T2IR preparation on a 1.5T scanner (GE Signa HDx) using the following scan parameters:

imaging matrix 256x256x50, slice thickness=2mm, flip angle=60o, FOV=16cm, NEX=2,

VPS=100, TE=1.6ms, TR=4.0ms, TEeff=120ms,

TI=225-375ms, with a scan time of approximately 4

mins for a nominal heart rate of 60bpm. Fat

saturation was also used.

Results: Figures 1 a,b) show axial views of the

popliteal artery, and 1 c) shows a reformatted view

from the 3D T2IR SSFP images. The vessel walls

were clearly depicted in these images.

Discussion: Preliminary data demonstrate the

feasibility of BB imaging of the vessel wall using a 3D

T2IR prepared SSFP sequence.

References: 1. Brittain et al. MRM 1997; 2. Liu et al.

ISMRM 08 pp3079; 3. Nguyen et al. ISMRM 09 pp607.

Figure 1: a) Axial view of 3D T2IR SSFP image of knee. b) Popliteal artery c) Reformatted view.

a)

b)

c)


0.000.200.400.60

0.801.001.20

0 60 70 80 90 100 110 120 130 140 150

2D Scout

3D Scan

Sign

al In

tens

ity

2D m1= 0 60 80 100 120

3D

V = 20 cm/m

a b

Fig 1. Schematic of the 2D m1-scout scan. A total 11 images were collected. The first uses m1 = 0, while the latter uses incremental m1 values (user specified.)

Fig 2. Corresponding 2D and 3D images (a) and signal intensity measurements (b).

140

First-order gradient moment (mT.ms2/m)

P.15 Identification of Optimal First-Order Gradient Moment for Flow-Sensitive Dephasing (FSD) Preparation

Z. Fan1,2, X. Bi3, and D. Li1,2 1Radiology, 2Biomedical Engineering, Northwestern University, Chicago, IL, USA;

3Siemens Medical Solutions USA, Inc., Chicago, IL, USA

Purpose: The first-order gradient moment, m1, is a measure of the blood signal-

suppression capability of the FSD preparative module. This work aimed to develop an m1-

scout approach to rapidly identify the optimal m1, which may help improve vessel wall

imaging and FSD-based MRA quality.

Methods: FSD-induced signal suppression is voxel size-dependent as its underline

mechanism is the intravoxel velocity variation [1]. For a FSD-prepared 3D isotropic

resolution imaging with major flows in the readout direction, we proposed to run the same

imaging seqence in 2D mode to rapidly identify the optimal m1. This requires the 2D

imaging plane perpendicular to the major vessel of interest, FSD gradient pulses applied

in the slice-select direction, and the in-plane resolution identical to that of 3D imaging. We

hypothesized that the flow-void effects to occur in the 3D case could be reflected by the

2D case with the same m1 used. This approach was tested on flow phantom (Gd-doped

water 0.25mM, a silicone tube of 4.8-mm ID connected to a pump) at various flow rate (15,

20, 30, 40, 50, 60 cm/s). The 2D m1-scout sequence was implemented based on FSD-

prepared balanced SSFP which was also used in 3D imaging for verification. Spatial

resolution: isotropic 0.9-mm for 3D, 0.9-mm in-plane and 5-mm thickness for 2D. The 2D

scan continuously acquired 11 measurements (images) (Fig. 1), whereas the 3D scan

acquired only 6 images due to long scan time.

Results: The lumen signal intensity measurements from the 2D and 3D images were significantly correlated at all the velocities tested (Mean Pearson correlation coefficient = 0.988, p < 0.001). Fig. 2 shows the case of flow rate = 20 cm/s. Conclusion: The optimal m1 value may be identified using the fast 2D scout approach. In vivo experiments are underway to further verify its applicability. References: [1] Nguyen TD et al. JMRI 2008; 28:1092-100.


P.16 Combined Segmentation of Lumen and Intraplaque Hemorrhage in Black-blood T1-Weighted Carotid Imaging

Rahul Sarkar1, General Leung1,2 and Alan R. Moody1,2 1University of Toronto and 2Sunnybrook Health Sciences Centre, Toronto, Ontario, Canada

Purpose: We investigated the use of a novel automatic segmentation approach to allow

localization of intraplaque hemorrhage (IPH) with respect to the lumen in black-blood T1

weighted carotid images.

Methods: From the original image, a fuzzy connectedness map is produced using a

generalized fuzzy spel affinity [1] for lumen detection. The fuzzy thresholded lumen

contour is downsampled to form control points for a b-spline curve to smooth image noise

at the boundary. A radial distance metric from the segmented lumen center of mass is

combined with intensity thresholding for segmentation of IPH. Images used for training

the fuzzy spel affinity and testing were obtained as previously described [2].

Results: Figure 1 shows the segmentation results produced from a representative image

showing intraplaque hemorrhage. The fuzzy segmentation step is highly efficient at gross

lumen detection, but demonstrates sensitivity to noise along border pixels. The derived b-

spline curve is effective in smoothing the border noise without significantly distorting the

lumen shape. IPH is accurately detected by thresholding within a defined radial distance

metric (5mm) from the segmented lumen.

Conclusion: The described approach is effective in automatically segmenting the lumen

and IPH to allow their co-localization in black blood T1weighted images. Figure 1. From left: 1) Original image; 2) Fuzzy detected lumen (red) showing border noise (blue arrow); 3) b-spline corrected fuzzy lumen (red) showing reduced border noise (green arrow); 4) Corrected lumen (red) and automatically segmented IPH (yellow).

References: [1] Carvalho PAA 1999. [2] Leung ISMRM 2009.


P.17 Automatic Registration of Multiparametric T1 Weighted Images Using FOV-Selective Mutual Information

Rahul Sarkar1, General Leung1,2 and Alan R. Moody1,2 1University of Toronto and 2Sunnybrook Health Sciences Centre, Toronto, Ontario, Canada

Purpose: Multiparametric T1weighted imaging may be useful in identifying several

features of atherosclerotic plaque [1]. Here we investigate a technique to automatically

and reliably register the parametric images using normalized mutual information [2].

Methods: All algorithm and user interface development was done in MATLAB (The

Mathworks). Mutiparametric datasets were obtained as previously described [1]. For

each dataset, a normalized mutual information algorithm was applied to register black-

blood post-contrast and bright-blood delayed enhancement images to the reference black-

blood pre-contrast image. Algorithm performance was observed under different field of

view (FOV) selections for reference and non-reference images.

Results: The algorithm was effective in accurately registering images of various non-

reference image FOVs (Figure 1). Reference image FOV was an important factor in

algorithm efficiency. Small reference FOVs (40mm x 40 mm) including the vessel wall and

few surrounding features proved optimal in terms of accuracy and reduced computational

time significantly. Deformable motion effects in large reference FOVs sometimes led to

misregistration that was corrected by reducing the FOV size.

Conclusion: Multiparametric T1 weighted images may be accurately co-registered with a

normalized mutual information algorithm using small reference image FOVs.

Figure 1. Multiparametric T1 images with pre-contrast black blood (left), post-contrast black blood (middle), and bright blood delayed enhancement (right). Top panel shows unregistered images of different FOVs. Bottom panel shows the same images registered to the reference pre-contrast image.

References: [1] Leung ISMRM 2009. [2] Collignon IPMI 1995.


P.18 MR fluid dynamics using 4D-Flow for intracranial aneurysms with growing blebs and a ruptured intracranial aneurysm

Haruo Isoda1, Hisaya Hiramatsu2, Yasuhide Ohkura3, Takashi Kosugi3, Masaya Hirano4, Shuhei Yamashita1, Yasuo Takehara1, Marcus T. Alley5, Harumi Sakahara1; 1Department of Radiology and

2Department of Neurosurgery, Hamamatsu University School of Medicine, Hamamatsu, Japan; 3Renaissance of Technology Corporation, Hamamatsu, Japan; 4GE Yokogawa Medical Systems, Hino,

Japan; 5 Department of Radiology, Stanford University School of Medicine, Stanford, USA.

PURPOSE: The purpose of our study was to investigate the relationship between

hemodynamics and growing blebs or intracranial aneurysm ruptures with the use of MR

fluid dynamics (MRFD) using 4D-Flow (1).

METHODS: This study included an unruptured 6mm right IC-Ach artery aneurysm with

growing bleb, an unruptured 4mm left IC aneurysm (C2 and C3 segment) with growing

bleb and a ruptured 8mm right IC-Ach artery aneurysm with hematoma in the medial

aspect of the right temporal lobe. 4D-Flow was performed by a 1.5T MR scanner. We

calculated and evaluated streamlines, wall shear stress (WSS) and the oscillatory shear

index (OSI) of these intracranial aneurysms based on 4D-Flow with our in-house software.

RESULTS: The top of the spiral flow was near the bleb in the unruptured IC-Ach artery

aneurysm. The WSS was lower and the OSI was higher near the bleb. The top of the

spiral flow was present at the growing bleb of the unruptured IC artery aneurysm and the

WSS was lower and the OSI was higher at this point. A disturbed spiral flow was noted in

the ruptured IC-Ach artery aneurysm. Lower WSS and higher OSI were observed in an

area containing the rupture point.

CONCLUSION: Bleb formation or rupture points were observed near the apex of the spiral

flow with low WSS and high OSI. Based on previously published papers reporting that low

WSS or high OSI causes degeneration and apoptosis of endothelial cells, we

hypothesized that endothelial cells at the apex of the spiral flow in the aneurysms were

much more vulnerable to degeneration or apoptosis.

REFERENCES: 1. Markl M, et al. J Magn Reson Imaging. 2003;17:499-506.


P.19 Phase-Field Dithering for Active Catheter Tracking Charles L. Dumoulin1, Richard P. Mallozzi2, Robert D. Darrow3, and Ehud J. Schmidt4

1Cincinnati Children’s Hospital, 2ONI Medical Systems, Inc., 3General Electric Global Research, and 4Brigham and Women’s Hospital

Purpose: Active MR tracking can become difficult in low Signal-to-Noise (SNR)

conditions, especially when magnetic susceptibility of the device is not well matched to its

surroundings and when unwanted MR signal is coupled into the receive channel (e.g. from

poorly shielded cables). A strategy to increase the robustness of active MR tracking of

micro-coils in these conditions was developed, and tested.

Methods: The method employs dephasing magnetic field gradient pulses that are applied

orthogonal to the frequency encoding gradient pulse used in conventional point-source

MR tracking. In subsequent acquisitions the orthogonal dephasing gradient pulse is

rotated, while maintaining a perpendicular orientation with respect to the frequency

encoding gradient. The dephasing gradient creates a spatially-dependent phase shift in

directions perpendicular to the frequency encoding gradient. Since the desired MR signal

for robust MR tracking comes from the small volume of nuclear spins near the small

detection coil, the desired signal is not dramatically altered by the dephasing gradient.

Undesired MR signals arising from larger volumes (e.g. due to coupling with the body

and/or surface coils), on the other hand, are dephased and reduced in signal intensity.

Since the approach requires no a priori knowledge of the micro-coil orientation with

respect to the main magnetic field, data from several orthogonal dephasing gradients is

acquired and analyzed in real-time. One of several selection algorithms is employed to

identify the “best” data for use in coil localization.

Results and Conclusions: This approach was tested in flow phantoms and animal

models, with several multiplexing schemes, including the Hadamard and zero-phase

reference approaches. It was found to provide improved MR tracking of un-tuned micro-

coils. It also dramatically improved MR tracking robustness in low SNR conditions and

permitted tracking of micro-coils that were inductively coupled to the body coil.


P.20 Interventional Device Tracking and Imaging Using an Extensible Real-Time System

Ethan Brodsky and Orhan Unal Radiology and Medical Physics, University of Wisconsin, Madison, WI, USA

PURPOSE: To demonstrate tracking of interventional devices using RTHawk, extensible

software architecture for real-time MR imaging.

METHODS: RTHawk is a software architecture that permits a variety of pulse sequences,

acquisition trajectories, and reconstruction techniques to be easily developed and

interleaved at run-time on GE scanners [1]. We have previously demonstrated

simultaneously tracking a catheter and imaging an endovascular device using a custom-

designed software solution that was tied to a particular pulse sequence implementation

and was very difficult to modify or extend [2,3]. We have therefore implemented two

catheter tracking techniques in RTHawk – the previously described 3DPR technique that

is amenable to simultaneous tracking and imaging, as well as a simple three-orthogonal-

view tracking acquisition that can easily be interleaved with Cartesian imaging.

RESULTS AND DISCUSSION: Initial testing shows that the previously developed tracking and imaging techniques can be easily adapted to run in this environment, without requiring any pulse sequence programming. A real-time display shows one-dimensional profiles for each axis from which the signal peak is detected and tracked. CONCLUSIONS: Initial results suggest that interventional sequences can easily be adapted to work within this framework. It abstracts away much of the complexity of pulse sequence and reconstruction programming, allowing simple intuitive representations of the acquisition trajectory and reconstruction pipeline. Visualization of final and intermediate results is also greatly simplified.

REFERENCES: [1] Santos et al. Proc IEEE Eng Med Biol Soc. 2:1048,’04 [2] Brodsky et al. MRM 56:247, ‘06 [3] Unal et al. Proc MRA Club 18:4.2, ’06

Figure 2: This plot of peak position over time shows the tip position as the device is moved in a circle in the x-z plane.

Figure 1: These one-dimensional profiles show the signal picked up by the endovascular device’s tip tracking coil for projections along each of the orthogonal gradient axes. Pulse sequences was Fast GRE, 4° flip, 12.5 ms TR, 256 sample readout over a 40 cm FOV for a 1.6 mm resolution.


P.21 Simplified Catheter-based Multimode Coil for Active MR Tracking and Intravascular Imaging Mahdi Salmani Rahimi, Krishna Kurpad, Orhan Unal

Departments of Biomedical Engineering, Radiology and Medical Physics, University of Wisconsin-Madison

PURPOSE: To simplify the design of a multi-mode intravascular MR catheter-based coil

that combines the functionalities of an active tip-tracking coil and an imaging coil and to

resolve the ambiguity of having two tip-tracking signal peaks.

METHODS: Unlike earlier designs [1] that had a separate solenoid at the catheter tip to

provide the localized tracking signal, in this design the inductor in the required matching

network of the tuned imaging coil has been exploited for tip tracking. Quarter-wavelength

π-matching network was placed

at the distal tip with a wire-

wound solenoid as the inductor.

Figure 1a shows the coil

schematic. Cable lengths were

adjusted so that the solenoid in

the matching network is in

resonance during the receive

cycle of the scan. To increase

the number of turns in the

inductor to improve tip-tracking

signal and avoid unwanted

increase in the competing imaging signal, some turns in the imaging coil have been wound

in the opposite direction.

RESULTS: Figure 1b shows a high resolution axial image of a grapefruit obtained with the

imaging loop of the multimode probe using a 2D GRE sequence (FOV=80x80mm,

256X256, TR/TE=200/3.1 ms, FA=90o, and NEX=5). Since there is only one solenoid in

this design, the ambiguity in determining tip position caused by having more than one

localized peak in earlier designs can also be avoided as seen in Figure 1c.

CONCLUSIONS: Our preliminary results suggest that multimode intravascular probes can

be simplified while improving active tip-tracking and imaging functionalities.

REFERENCES: [1] Unal O, et al. ISMRM 1398, 2006.

λ/4 Transformer

Tracking Coil

Imaging Loop

Decoupling Box and GE 1.5T

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Imaging Loop


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λ/4 Transformer

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Figure 1: (a) Schematic of the catheter coil design. (b) 313 micron resolution axial image of a grapefruit obtained with the imaging loop using a 2D GRE technique. (c) Signal profile from manual prescan, TG=100. Tracking coil peak is visible and easily detectable from broader imaging signal in the coil with one counter turn.


P.22 Transmit Power Optimization for Tracking, Wireless Marker and Imaging applications of a Multi-mode Endovascular coil.

Krishna N. Kurpad and Orhan Unal Departments of Radiology and Medical Physics, University of Wisconsin-Madison

PURPOSE: To optimize body coil transmit power settings to manipulate transverse

magnetization in various regions in the vicinity of a MR multi-mode endovascular coil for

optimal operation in tip tracking, wireless marker, and endovascular imaging modes.

METHODS: The multimode coil 1,2 (Fig. 1a), being inductively coupled to the transmit coil,

behaves as a local B1 field magnifier. The series-

connected tip tracking and imaging components of

the multimode coil are constructed with different

conductor densities, resulting in different transverse

magnetization in their vicinity. A series of 21 coronal

images of a tube phantom containing saline solution

doped with copper sulphate (T1=150ms) was

obtained using a FGRE pulse sequence (TR/TE= 200/4 ms, FA=90o, FOV=6cm, 256x256)

on a GE Signa 1.5T clinical scanner. The images were obtained by incrementing the

transmit gain setting in steps of 1 dB between the limits of 0 dB and 20 dB. Graphs of the

mean signal intensity in three small regions (Fig. 1b) located close to 1) the tracking coil,

2) the conductors of the imaging coil, and 3) one cm away from the imaging coil were

plotted against the transmit gain setting for the corresponding images.

RESULTS: The graphs in Fig. 2 show that transmit power settings may be suitably

adjusted to generate 1) distinct tracking

peak, 2) broad region of sensitivity for

imaging, or 3) visualize the conductors of

the multimode coil for wireless marker

applications.

CONCLUSIONS: Preliminary results

show that the current induced in the

multimode coil by the transmitted B1 field

results in varying transverse

magnetization due to the varying

conductor density of its various components. The transmit power may therefore be

optimized for optimal operation of the multimode coil in all three functional modes.

REFERENCES:1Kurpad KN,et al, ISMRM 292, 2007, 2Unal O, et al. ISMRM 1398, 2006


Sponsors

Lantheus Medical Imaging, a worldwide leader in diagnostic imaging for 50 years, is committed to developing innovative solutions for the diagnosis and management of disease. For more information, please visit www.lantheus.com.

"Bayer Schering Pharma AG has a worldwide leading position in developing and manufacturing contrast media for use in x-rays, computed tomography (CT), magnetic resonance imaging (MRI) and in contrast media application systems. www.bayerhealthcare.com

Bracco Imaging S.p.A, is one of the World’s leading companies in the diagnostic imaging business. Bracco Imaging S.p.A products are distributed in USA by Bracco Diagnostic Inc., Princeton. www.braccoimaging.com

GE Healthcare's expertise in medical imaging and information technologies, medical diagnostics, patient monitoring systems, disease research, drug discovery and biopharmaceuticals is dedicated to detecting disease earlier and tailoring treatment for individual patients. For more information visit www.gehealthcare.com

syngo TimCT offers continuous table move for CT-like scanning. Setting the trend in MRI with MAGNETOM ESSENZA, Avanto, Espree, and Verio. Siemens. Answering the questions of life. www.siemens.com/mr

Guerbet is the only pharmaceutical group fully dedicated to medical imaging, offering a comprehensive range of contrast agents for X-ray and MRI worldwide. Guerbet’s innovation focuses on molecular imaging for MRI or nuclear medicine applications, enabling diseases to be targeted earlier and more precisely. www.guerbet.com

http://www.lantheus.com/

http://www.bayerhealthcare.com/

http://www.gehealthcare.com/

http://www.siemens.com/mr

http://www.guerbet.com/


Sponsors

Philips Healthcare is a premier supplier of healthcare solutions. The MR portfolio provides unique, advanced features enabling our users to extend the realms of vascular MR imaging. www.medical.philips.com

TopSpins Inc. is dedicated to helping MR imaging centers implement safe, accurate, state-of-the-art contrast enhanced MR Angiography and dynamic contrast-enhanced MR imaging studies for the benefit of their patients. www.topspins.com

Robarts Research Institute harnesses the power of cell biology, genomics and advanced imaging technologies to investigate disorders of the neurological, cardiovascular and immune systems. It is a research Institute within the Schulich School of Medicine & Dentistry at The University of Western Ontario. www.robarts.ca

Founded in 1878, The University of Western Ontario is one of Canada's oldest universities and today is committed to providing the best student experience among Canada's leading research-intensive universities. A vibrant centre of learning located in London, Ontario, Western is home to more than 30,000 students and attracts external support of over $200 million annually for research projects. www.uwo.ca

As an integral part of the Michigan State University HealthTeam, the Department of Radiology has served the Mid-Michigan community since 1975. Our dedicated team of health care professionals has pioneered research and clinical applications in radiology. www.rad.msu.edu

http://www.medical.philips.com/

http://www.topspins.com/

http://www.robarts.ca/

http://www.uwo.ca/


Insert Lantheus file


Notes


Presenter Index A Page Abela, George The Role of Cholesterol Crystals in Acute Cardiovascular Events: Indentifying the Cause for Gender Differences in Clinical Presentation

118

Admirral - Behloul, Faiza Hybrid of Opposite Contrast MR Angiography of the Brain

73

Artz, Nathan Assessing Kidney Perfusion using Arterial Spin Labeling and Radial Acquisition for Rapid Characterization of Inflow Dynamics

101

Aschauer, Manuela Gadofoveset Excretion into Human Breast Milk CE-MRA with tailored 3D random sampling patterns and nonlinear parallel imaging reconstruction (P1)

54

119

B Balu, Niranjan 3D Vessel Wall imaging of multiple vascular beds (P13)

131

Barnes, Samuel High Resolution Simultaneous Angiography and Venography (MRAV) with a Single Echo

76

Bernstein, Matt Multicenter Studies: Lessons Learned from ADNI

114

Bhat, Himanshu Contrast-Enhanced Whole-Heart Coronary MRA at 3T Using Gradient Echo Interleaved EPI (GRE-EPI)

90

Blackham, Kristine Robust Clinical Application of Time-Resolved MRA(P7)

125

Bley, Thorsten Non-invasive Trans-Stenotic Pressure Measurements with 3D Phase Contrast MRA: Validation against Endovascular Pressure Measurements in Swine

61

Block, Walter Imaging Capabilities for Real-time Guidance and Verification of Transcatheter Arterial Chemoembolization (TACE) Procedures

102

Bousell, Loic 4D time-resolved MR angiography for non-invasive pulmonary post-embolization AVM patency assessment

83

Brodsky, Ethan Interventional Device Tracking and Imaging Using an Extensible Real-time System (P20)

138

C Carr, James Non Contrast MRA of the Hand in Patients with Raynauds disease using Flow Sensitized Dephasing Prepared SSFP

50

Carroll, Timothy Radial Sliding Window MRA in Pulmonary Hypertension

84

Choi, Grace MRA with the “No Phase Wrap”

86

Chung, Tae-Sub Obstruction of IJV by Asymmetry of Lateral Mass of Atlas on Head and Neck CEMRA and Contrast CT

78


Author Index D Page Dumoulin, Charles Phase-Field Dithering for Active Catheter Tracking (P19)

137

E El-Boubbou, Kheireddine Targeted Glyco-Magnetic Fe304 Nanoprobes for Detection and Molecular Imaging of Atherosclerosis

110

Essig, Marco Intraindividual comparison between multislice CT and 4D TWIST MRA in the assessment of residual cerebral ateriovenous malformations – a prospective study protocol

71

F Fan, Zhaoyang 3D Noncontrast MRA using FSD – Prepared Balanced SSFP Identification of Optimal First-Order Gradient Moment for Slow-Sensitive Dephasing (FSD) Preparation (P15)

49

133

Fielden, Samuel Balanced-gradient TSE for Non-Contrast Peripheral MRA

27

Francois, Christopher Flow assessment of arterial dissections using 3D radial phase contrast MR Angiography

63

Frydrychowicz, Alex Analysis of aortic hemodynamics after treatments for coarctation using flow-sensitive 4D MRA at 3T

62

G Ge, Lan Myocardial Perfusion MRI in Canines with Improved Spatial Coverage, Resolution and SNR

32

Geerts, Liesbeth Non-CE Imaging of the Pulmonary Arteries

24

Goldfarb, James Cardiac Imaging: Methods for the Detection of Intramyocardial Fat

92

Grabow, Ben Temporal Filtering for Sliding Window Time-resolved Angiography; Beyond Density Compensation Solutions

94

Grist, Thomas Overview of Gd-BOPTA Phase III Trial for CEMRA: What are the results, and how do we move forward?

55

Griswold, Mark A Simple View of Compressed Sensing and How it Could Change Everything We Do in MRI and MRA

29

H Haacke, Mark High Resolution Perfusion Weighted Imaging Susceptibility mapping as a means to image veins

66

104


Author Index

H Page Hadley, Rock A 16 Channel Anterior Neck RF Coil for Cervical Carotid MRA

42

Haider, Clifton A Comparison of Time-Resolved 3D CE-MRA with Peripheral Run-off CTA in the Calves

47

Hibberd, Mark An Update on the Clinical Experience with Gadofosveset

52

Hu, Peng Non-Contrast Enhanced Pulmonary Vein MRI with a Spatially Selective Slab Inversion Preparation

85

Hulet, Jordan Improved Carotid Imaging with HASTE using a reduced FOV and increased gradient performance (P3)

121

I Igase, Keiji Our Strategy for the Surgical Planning with 3T MRA in Detecting Unruptured Cerebral Aneurysms

72

Isodo, Haruo MR fluid dynamics using 4D-Flow for intracranial aneurysms with growing blebs and a rupture intracranial aneurysm (P18)

136

J Jeong, Hyun CAMERA: Contrast-enhanced Angiography with Multi-Echo and Radial k-space

106

Johnson, Casey Two-Station Time-Resolved CE-MRA of the Lower Legs

51

Johnson, Kevin Accelerated Time Resolved Inflow with 3D Radial bSSFP Angiographic and Hemodynamic Assessment of the Hepatic Vasculature in Portal Venous Hypertension using High Resolution PC VIPR

25

95

K Kang, Chang-Ki Vascular response during visual stimulation at 3T MRI: functional phase contrast angiography (fPCA) study (P10)

128

Kawaji, Keigo Feasibility Study of Combining 3D SSFP with T2prep inversion Recovery (T2IR) for Black Blood Vessel Wall Imaging (P14)

132

Kecskemeti, Steven Stack of Stars 4D Phase Contrast Velocimetry of the Circle of Willis

65

Kerwin, William Fibrous Cap Thickness Assessment: Fact or Fiction?

38

Kim, Bum-soo Low Dose 3D Time-Resolved MR Angiography of the Supraaortic Artery: Correlation to High Spatial Resolution 3D Contrast-Enhanced MRA

77

Kim, Seong-Eun Improved Black Blood Multi-Contrast Protocol for In-vivo Atherosclerotic Imaging

40


Author Index

K Page Kurpad, Krishna Transmit Power Optimization for Tracking, Wireless Marker and Imaging applications of a Multi-mode Endovascular coil (P22)

140

L Page Ladd, Mark Toward Abdominal MRA at 7 Tesla

116

Latourette, Matthews R*2 Calibration Phantoms for Cardiovascular Studies (P5)

123

Laub, Gerhard Low-Dose 4D MR Angiography

26

Lauzon, Louis Non Contrast-Enhanced MR identification of DVT

103

Lee, Jongmin Optimization of Phase-Contrast MR-based Flow Velocimetry and Shear Stress Measurement (P11)

129

Leiner, Tim Gadobenate dimeglumine vs. gadopentetate dimeglumine for peripheral MR angiography: Comparison with DSA

43

Li, Rui Gradient Echo Based Sequence Provides More Information from Ex Vivo Carotid Plaque Specimens

39

Liu, Garry Ultrasound guided cardiac gating for coronary MRA

89

Liu, Jing Self-gated Free Breathing 3D Cardiac Cine Imaging with Data Acquisition During Slice Encoding

28

Lu, Zheng-Rong Manganese Based Biodegradable Macromolecular MRI Contrast Agents for Cardiovascular Imaging

60

M Maki, Jeffrey Dose Comparison between Conventional and High Relaxivity Contrast Agents in Peripheral MRA

44

Marinelli, Luca Accelerated velocity imaging using compressed sensing

67

Markl, Michael Wall Shear Stress in Normal and Atherosclerotic Carotid Arteries

68

McNally, Scott MR imaging and significance of flow reversal and carotid atherosclerosis: Initial results

69

Mendes, Jason Handling Motion in Sparse MRA with Whiskers (P2)

120

Miki, Hitoshi Unruptured Intracranial Aneurysms; Detection and Follow-up on 3.0T MRA

87

Mistretta, Chuck 4D DSA and Fluoroscopy: A New Challenge for MRA?

111-112


Author Index M Page Mostardi, Petrice Modified CAPR MRA: Improved Imaging of the Arterial and Venous Phases

105

N Page Newman, Tiffany Magnetic Resonance Angiography of the skin for perforator-based autologous breast reconstruction

98

O Oshinski, John Blood Flow Patterns in the Abdominal Aorta of Mice: Implications for AAA Localization (P12)

130

Ota, Hideki Carotid Intraplaque Hemorrhage is Associated with Enlargement of Lipid-rich Necrotic Core and Plaque Volume Over TimeL In Vivo 3T MRI Prospective Study

35

P Parienty, Isabelle Time-SLIP versus DSA in Patients with Renal Artery Stenosis

99

Parsons, Edward A Re-analysis of MS-325 (gadofoveset trisodium) Clinical Trial Date in Support of US-FDA Approval

53

Peters, Dana 3D spiral high- resolution late gadolinium enhancement

93

Prince,Martin Risk Factors for NSF: A Meta-analysis

58

Q Quick, Harald 7 Tesla Cardiac MRA in Humans

117

R Rahimi, Mahdi Salmani Simplified Catheter-based Multimode Coil for Active MR Tracking and Intravascular Imaging (P21)

139

Reeder, Scott High Temporal and High Spatial Resolution Perfusion Imaging of Hepatocellular Carcinoma of the Liver

64

Robson, Philip Time-Resolved, Vessel-selective, Cerebral Angiography Using Arterial Spin Labeling

107

Roditi, Giles Retrospective 7 year study of the Incidence of Nephrogenic System Fibrosis in Patients Investigated with Gadolinium Contrast-Enhanced Renal Magnetic Resonance Angiography Pictorial Review of Supra-Aortic Artery Pathologies as Visualised with MRA using Blood Pool Contrast Agent (P6)

57

124


Author Index S Saloner, David Imaging Considerations in Serial Studies of Vascular Disease

115

Saranathan, Manojkumar FINESS (Flow Inversion-prepared Non-contrast Enchancement in the Steady State): A novel technique for non-contrast renal MRA

97

Sarkar, Rahul Combined Segmentation of Lumen and Intraplaque Hemorrhage in Black-blood T1-weighted Carotid Imaging (P16) Automatic Registration of Multiparametic T1 Weighted Images using FOV- Selective Mutual Information (P17)

134

135

Schiebler, Mark Pulmonary MRA in 75 patients with dyspnea Origin and Frequency of artifacts in Contrast Enhanced Pulmonary MRA in 80 patients with dyspnea

80

81

Schneider, Guenther Safety of Gadobenate dimeglumine (Gd-BOPTA) in Cardiovascular Imaging of Pediatric Patients Renal MR angiography: multicenter intraindividual comparison of gadobenate dimeglumine and gadofosveset trisodium

56

96

Seiberlich, Nicole Reconstruction of MR Angiography Images Using Gradient Descent with Sparsification

33

Shah, Dipan Evaluation of Gd-DOTA (DOTAREM) enhanced MRA compared to time-of-flight MRA in the diagnosis of clinically significant non-coronary arterial disease at 1.5 and 3.0 Tesla

79

Sheehan, John Flow and Motion-Insensitive Unenhanced MR Angiography of the Peripheral Vascular System – A pilot study in the lower extremity

46

Stafford, Randall Towards Continuously Moving Table MCE Peripheral MRA (P4)

122

Stein, Paul Gadolinium Enhanced Magnetic Resonance Angiography for Pulmonary Embolism: Results of PIOPED III

82

Steinman, David Quantifying Lumen Geometry from Routine Carotid CEMRA

108

Suever, Jonathan Reproducibility of Aortic Pulse Wave Velocity Measurements Obtained with Phase Contrast Magnetic Resonance (PCMR) and Applanation Tonometry (P8)

126

T Tan, Ek Tsoon High Resolution Fast Inversion Recovery MRA (FIR-MRA)

74


Author Index V Varani, James Extracellular matrix metabolism in organ-cultured skin from patients with end-stage renal disease: Response to gadolinium based MRI contrast agents

59

Velikina, Julia Design of Compressed Sensing Reconstruction for Highly Accelerated Time-Resolved MR Angiography

30

Versluis, Bas MR Angiography of muscular and collateral arteries in peripheral and arterial disease: reproducibility of morphological and functional vascular status

113

Voth, M Peripheral MRA with Continuous Table (CTM) Movements in Combination with High Temporal and Spatial Resolution TWIST – MRA with 0.1 mmol/lg Gadobutrol at 3.0 T

45

W Wang, Jinnan Improved Intraplaque Hemorrhage Detections by a Phase Sensitive IRTFE (SPI) Sequence

37

Wang, Kang 3D Time-Resolved MR Angiography of Lower Extremities using Cartesian Interleaved Variable Density Sampling and HYPR Reconstruction

48

Wang, Yi 3D peripheral vessel wall MRI with flow-insensitive blood suppression and isotropic resolution at 3 Tesla Magnetic source MRI for quantitative brain iron mapping

41

109 Wieben, Oliver Comprehensive PC MR Imaging in Congenital Heart Disease

88

Willinek, Winfried 4D-MRA in combination with arterial spin labeling for selective and functional information in patients with AVMs

70

Wilson, Gregory Motion-compensated, flow-independent, non-contrast enhanced renal MR angiography (P9)

127

Wright, Katherine Simultaneous Renal Angiography and Perfusion measurement Using Time-Resolved MRA

100

Wu, Yijing Low Dose HYPR FLOW

31

X Xie, Jingsi Feasibility of Whole-Heart Coronary MRA on 3 Tesla Using Ultrashort-TR SSFP VIPR

91

Y Yuan, Chun Carotid Plaque Imaging and Clinical Risk Assessment

34


Author Index Z Zhu, David The 3D SHINE Sequence Optimizes the Quantification of Carotid Intraplaque Hemorrhage

36

Zwart, Nick 3D Dual VENC PCMRA using Spiral Projection Imaging

75

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