recent innovations in pet and hybrid modality technologies

For internal use only / Copyright © Siemens AG 2006. All rights reserved.

Recent Innovations in PET and hybrid modality technologies

Bernard Bendriem, Ph.D.

Vice President, PET R&D

9th International SAC Seminar on New trends on PET

2 Bernard Bendriem, Ph.D., Siemens Medical Solutions

Week 1 Week 7

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Week

SU

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ResponderPatient alive 20 monthsafter end of chemotherapy

Week 7Week 1

Non-responder

Patient survived 2 monthsafter end of chemotherapy

Lung cancer: response to therapy (Hanna, Nahmias)

Courtesy of David Townsend, Ph.D.University of Tennessee Medical Center


Improving detectability and quantification

1. Hybrid imaging


Morphology Physiology Metabolism Molecules

CT

US

MRI, MRS

NM

Fluorescence-Optical

Dynamic, Perfusion

Dynamic, Flow, Perfusion

Dynamic, Flow, Perfusion, Diffusion, Molecules

Perfusion, Molecules

1 molecule/cell

106 -108 molecules/cell

Molecules

Several molecules/cell

Hybrid imaging


CT (anatomy) PET (function)PET/CT

• to image different

aspects of disease

• to identify tracer uptake

• to simplify the image

interpretation

• to give added value to

CT and PET

Why combine form and function?

Fused image accuratelylocalizes uptake into alymph node and thus demonstrates spread of disease.

Form + function



I-131 SPECT•CT:

Residu thyroidien vs.

Metastases ganglionnaires

University of Erlangen


• standard transmission sources not required

• much higher statistical quality (400 MBq vs 2·109 MBq)

• much faster scan (20 s compared with 20 min)

• less patient movement during scan

• more tolerable for the patient

• shorter total scan duration

Advantages of CT-based correction



1. Hybrid imaging

2. Organ motion


Spherical VOI that tracks with motion over 10 respiratory phases

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phase

VO

I v

alu

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a.u

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Phase matched CTACHelical CTACCINE CTAC

Whole-body respiratory gated PET/CT: Simulations

Courtesy of Dr. KinahanUniversity of Washington


Respiratory motion is distributed throughout the whole bodyImpact is rarely on detection, but often affects quantitation

Static wholebody Single respiratory phase(1 of 7, so noisier)

< 1 cc lesion on CT

Whole-body respiratory gated PET/CT: Patients

Courtesy of Dr. KinahanUniversity of Washington



1. Hybrid imaging

2. Organ motion

3. Spatial resolution


The clinical importance of spatial resolution

Low-REZ; 8.6 mCi; 60 min uptake

8 x 8 elements/block

6.4 mm x 6.4 mm

HI-REZ; 11.2 mCi; 90 min uptake

13 x 13 elements/block

4.0 mm x 4.0 mm

Sphere diameter (mm)

Rec

ove

ry (

%)100

50

010

37282217

13

2.0

3.9

1.3

3.3

3.7

8.7

4.1

8.6



8X8 crystal matrix

128 Single crystals per block

P TP T

19.5mm

02

13

columns

crystalblock

MM

0 7

8

63

15

56

2 mm

HRRT Detector Block DesignLYSO (10 mm)

LSO (10 mm)

Light Guide

Smaller pixels……Research

LYSO only used for pulse shape discrimination


Investigation of small dopaminergic structures playing a crucial rôle in the reward circuit, such as :

- Ventral striatum (Accumbens nucleus)- Midbrain (SNr & VTA)

High spatial PET imaging is promising for the exploration of subtle modifications in small and complex brain structures.

VTA & SNr

Ventral striatum

Courtesy of Pr SyrotaService Hospitalier Frederic Joliot, Orsay

High Resolution Research Tomograph



1. Hybrid imaging

2. Organ motion


4. Number of detected photons


2.5 min 10 min 15 min

79 year-old female (103 lbs) referred for restaging of colon cancer. PET/CT identifies uptake in left pelvic mass increasing since previous scan. Also interval development of soft tissue mass in right gluteal region and mild focally increased FDG activity in the region of the ninth thoracic vertebra. Scan acquired at 5 bed positions; 10 mCi, 92 min pi.

30 sec/bed 2 min/bed 3 min/bed

Total scan duration (5 beds)

Clinical workflow: reduced imaging times


• thicker crystals

• extended axial FOV

AD

B

C (511 keV)

3D (no septa)

20 mm to 30 mm

16.2 cm to 21.6 cm

sensitivity increase: 40%

sensitivity increase: 77%

How to improve intrinsic sensitivity?


• higher sensitivity = shorter imaging per bed (or more counts)• larger axial FOV = fewer bed positions for same axial coverage

Standard:

Extended FOV:

5 15 min

4 8 min

bed #

Advantages of the extended axial field-of-view


27 year-old female (123 lbs) with metastatic melanoma. Uptake in left lower extremity and in left axillar node positive for melanoma.

CT: 30 mAs, 130 kV, 5 mm slices at 0.75 mm PET: 10 mCi FDG, 108 min pi, 2 min/bed, 11 beds

Total scan duration: 22 min

Staging melanoma with extended field-of-view



Biograph

60 year-old male (187 lbs) with history of NSCLC commencing a seven week course of chemotherapy. Baseline PET/CT scan shows hypermetabolic left hilar mass consistent with known malignancy. Left anterolateral 4th and 5th rib activity is suspicious for metastases.

15.1 mCi, 90 min pi 4 min/bed, 5 beds

4i / 8s; 5fScan duration: 20 min

PET/CT

Lung cancer



Torso phantom study

Brain-torso-bladder phantom scanned with a total of 9 mCi in phantom. Activity in the torso phantom at time of scan is ~3 mCi

Imaging time based on equivalent total acquisition time for whole body scan. Sphere diameters: 7.8 mm; 6.2 mm, 4.9 mmContrast ratio in spheres: 8:1

4.9 mm

7.8 mm

6.2 mm

4.9 mm

7.8 mm

6.2 mm


• scanner operational since late February 2006

• scan time reduced by factor ~2

• equivalently the dose can be reduced by factor of 2

• improved image quality for large patients (up to 450 lbs)

• HI-REZ detectors resolve smaller details (kidney)

• melanoma scan now from head to toe in < 25 min

Advantage of extended axial FOV in PET



1. Hybrid imaging

2. Organ motion



5. Image reconstruction


Scatter CoincidenceTrues Coincidence

Random Coincidence

True Counts & Noise


Scatter corrected

No scatter correction

high residual in left ventricle

scatter from liver

hot lung walls

FORE + OSEM, 4i x 8s, 8 mm filter

0 – 21% max window

Patient MN. 297 lbs (135 kg)


Sinogram profiles

Measured emission

_ _ _ _ Computed scatter

52% Scatter

54% Scatter

396 MBq injection

157 min uptake

Patient MN. 297 lbs (135 kg)


TOF filter

FOVBack projection along the LOR

Time-of-Flight Acquisition: Principles

Time-of-flight reduce noise propagation during image reconstruction process


convTOF SNRx

DSNR

c

tx

2

Time Resolution

(ns)

x

(cm)

SNRimprovement(20 cm object)

SNRimprovement(40 cm object)

0.1 1.5 3.7 5.2

0.3 4.5 2.1 3.0

0.5 7.5 1.6 2.3

1.2 18.0 1.1 1.5

Time-of-Flight and SNR


60s 180s

TOF Non-TOF

similar CRC and noise

TOF shorter scan

60s

similar noise and scan time

TOF higher CRC

60s

similar CRC and scan time

TOF lower noise

6-to-1 contrast

Measurements: 27-cm lesion phantom

Courtesy of Joel KarpUniversity of Pennsylvania


non-TOF

Rectal carcinoma, metastases in mesentery and bilateral iliac chains

114 kg; BMI = 38.112 mCi; 2 hr post-inj3min/bed

TOF

Lesion contrast (SUV) improves with TOF reconstruction

Gemini TF - patient study

Courtesy of Joel KarpUniversity of Pennsylvania



1. Hybrid imaging

2. Organ motion




6. Other hybrid imaging


Lésion d’un sésamoïde(premier métatarsien)


New Hybrid imaging : MR-PET Benefits

Isocentric & simultaneous measurements

Perfect anatomical matching

Important for attenuation correction and motion correction

Good soft tissue contrast

Neuro

Abdomen

No additional ionizing radiation through MR

Enables follow up studies Gating and Motion Correction MR PET

Prospective and retrospective

Functional MR data adds further information

Spectroscopy, fMRI, CE dynamics

(Resolution enhancement due to reduced position range at UHF)


Analogous to PET-CT

MR ScannerPET

ScannerMR Scanner PET

Scanner

MR

PET

Integrated SystemPET-Insert

Upgrade of existing MR scanners possible

Reduced FOV for PET

Integrated development necessaryNo simultaneous

measurement, no iso-centric measurement

Reduced MR compatibility demand (only main field)

MR-PET Concepts


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High resolution artifact free PET images

High resolution artifact free MR images

1.5mm

2.5mm

1.0mm

2.0mm

3.5mm

3.0mm

Simultaneous dual-modality data acquisition



1. Hybrid imaging

2. Organ motion




6. Other hybrid imaging

1. Advancement in term of higher spatial resolution, higher statistics, larger axial coverage and better image reconstruction, including TOF information and other physical characteristics of instrument.

2. New relevant hybrid imaging, new imaging protocol with organ motion correction.

recent innovations in pet and hybrid modality technologies

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