pet: new technologies including oncology...pet technology innovations 1953 first coincidence...

AAPM 2012 Summer School on Medical Imaging using Ionizing Radiation

PET: New Technologies & Applications, Including Oncology

Paul Kinahan, PhD, FIEEEImaging Research LaboratoryDepartment of Radiology

University of Washington, Seattle, WA


Paul Kinahan

DisclosuresResearch Contract, GE HealthcareAdvisory Board, Aposense Inc.


Paul Kinahan

Objectives1. Review history and uses of PET/CT2. Understand recent technology developments and challenges3. Learn the context of the potential future applications of PET/CT

imaging in clinical practiceOutline Respiratory motion compensation Time of flight imaging Advanced modeling of PET physics in image reconstruction Extended axial field of view New detector systems PET/MR scanners CT dose reduction methods Cost effective PET/CT scanners


Paul Kinahan

PET Technology Innovations1953

First coincidence positron imaging system

1975

PETT III

1989

whole‐body imaging

1991

3D PET

1998

PET/CT

2005

respiratory gating

2006

time‐of‐flight

2008

PET/MR?

0

500,000

1,000,000

1,500,000

2,000,000

2,500,000

1998 2000 2002 2004 2006 2008

Pro

cedu

res/

yr

0%

20%

40%

60%

80%

100%

% s

cann

ers

Procedures/yr

PET/CT % ofSales


Respiratory motion compensation


Paul Kinahan

Impact of Respiratory Motion

Breath‐hold (BH) PET SUVs are 26% greater than free breathing (FB) PET SUVs

Truth is not known

Kawano, JNM 2008


Paul Kinahan

Impact of Respiratory Motion

The SUV of the lesion goes from 2 in the static image to 6 in one phase of the respiratory‐gated image sequence

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

1 cc lesion on CT


Paul Kinahan

A Hierarchy of Respiratory Motion Compensation Methods

1. Breath‐hold PET2. Cine+Helical CTAC3. Respiratory‐gated PET (4D‐PET)4. Phase‐matched 4D‐PET and 4D‐CTAC5. Quiescent Period Gating6. Respiratory Aligned and Summed Phases (RASP)7. Internal‐External Correlation (INTEX)8. Dual respiratory / cardiac gating9. Reconstruction‐based methods

Increasing complexity


Paul Kinahan

Helical+CINE CTAC Acquisition to Compensating For Patient Motion

1. Standard non‐contrast helical CT (diagnostic beam) for both CT imaging correlation and for CT‐based attenuation correction (CTAC)

2. Cine CT acquired over the diaphragm region for respiratory motion (much like a PET transmission scan: based on method of Pan et al. JNM 2005)

3. Average of helical+Cine CT acquired is used for CTAC of PET data

Sum of all CT scans used for CTAC


Paul Kinahan

lower limit of diaphragm motion

Helical+CINE CTAC Protocol

max inspiration max expiration

upper limit of diaphragm motion

Cine CT range


Paul Kinahan

Helical+CINE CTAC Protocol

area of impact

new cine+helical CTAC standard helical CTAC

reduced 'banana' artifacts


Paul Kinahan

IR LEDs and camera

PC w/ frame grabber + trigger generator

Gating inputs

reflective block

Respiratory Gated PET/CT Imaging

Respiratory trace information

PETCT


Paul Kinahan

Wholebody Respiratory Gated PETNotes:• motion throughout

body• changes in moving

lesion intensity • apparent fixed

diaphragm location QuickTime™ and aYUV420 codec decompressor

are needed to see this picture.


Paul Kinahan

Single Phase CT‐based Attenuation Correction for 4D PET

CTAC Phase Image Volumes

PET EM phase sinograms

Attenuation corrected PET data

X

X

X

X

Reconstructed PET images

=

=

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irato

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N


Paul Kinahan

Phase‐matched CT‐based Attenuation Correction

CTAC Phase Image Volumes

PET EM phase sinograms

Attenuation corrected PET data

X

X

X

X

Reconstructed PET images

=

=

=

=

1

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Resp

irato

ry p

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Paul Kinahan

Single phase CT attenuation correction (CTAC) image(e.g. helical CT)

Phase‐matched CTAC

QuickTime™ and a decompressor

are needed to see this picture.We see the time average of these images, unless we use respiratory gating




Paul Kinahan

CT PET/CT

4D CT 4D PET/CT

Phase‐matched 4D‐PET and 4D‐CTAC


Time of flight imaging


Paul Kinahan

Time of Flight (TOF) PET/CTc = 3x1010cm/s, so t = 600 ps ~ d = 10 cm in resolutionSurti (JNM 2011) shows improved lesion detection in large patientsLittle information yet on effect on impact on quantitative accuracy

d = c t/2

timing resolution uncertainty

best guess about location (d)

+ + e-annihilation


Paul Kinahan

Impact of TOF PET ‐ Detection




Paul Kinahan

75 kg patient, 120 MBq, 3 min/bed(BG = ~1kBq/cc)

0.25

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VOI & EANM VOI & PSF+TOFMAX & EANM MAX & PSF+TOF

75 kg patient, 120 MBq, 10 min/bed(BG = ~1kBq/cc)

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VOI & EANM VOI & PSF+TOFMAX & EANM MAX & PSF+TOF

Typical coincident count levels High coincident count levels

Courtesy Ronald Boellaard

Impact on quantitation


Advanced modeling of PET physics in image reconstruction


Paul Kinahan

Including improved physics modeling in image reconstruction

In principle can remove detector blurring


Paul Kinahan

Phantom measurements of ringing artifact







Bai, 2010 IEEE MIC conf record

real?


Extended axial field of view


Paul Kinahan

Extended Axial Field of View PET scanner component has 3 rings of detector blocks.

Siemens added one more ring (they quote "extra 33 %") to extend the axial field of view

Increases scanner efficiency and/or allows for shorter scan times


Paul Kinahan

NEMA NU‐2 2001 performance measurements

96 @ 34 kBq/ml

161 @ 31 kBq/ml

Peak NECR

Peak NECR (kcps)

Biograph

Biograph TP

Noise Equivalent Count Rate

Biograph

Biograph TP

Courtesy David Townsend PhD: University of Tennessee at Knoxville


New detection systems

Avalanche photodiodes Solid‐state silicon photomultipliers


Paul Kinahan

Position sensitive avalanche photodiode (PSAPD)

silicon‐based detectors Could ultimately be made cheaply

in high volumes High optical quantum efficiency

(up to 4x higher than PMTs) and wide spectral response

Insensitivity to magnetic fields (used in PET/MR)

Timing resolution of ~3 ns Lower SNR than PMTs Temperature sensitive gains

Flood histogram from coupling a 8 x 8 mm2 PSAPD to an LSO array (1 mm pixels, 20 mm tall)

Shah et al. TNS 2004


Paul Kinahan

The silicon photomultiplier (SiPM)Combine advantages of PMTs and APDs Still very expensive High gain (like PMTs) Insensitive to magnetic fields (e.g. for PET/MR)

Excellent energy and timing resolution

Temperature sensitive gain



Simplified structure of a SiPM composed of G‐APD cells

Roncali and Cherry, Ann Biomed Eng, 2011


PET/MR scanners


Paul Kinahan

PET/CT PET/MR

Clinical PET/MR scanner Siemens mMR first

joint scanner (Philips and GE currently have 'tandem' systems) Uses APDs Expensive Attenuation correction

for bone an open problem for all systems

Clinical results from Drzezga et al, JNM June 2012




CT dose reduction methods


Paul Kinahan

Iterative CT image reconstruction Can be used in CT

like it is in PET Computationally

now tractable Several approaches

under development for CT‐only scanners

Gradually move to PET/CT scanners


Paul Kinahan

FBP

MBIR

RSD Phantom: 120 kVp100 mAs 12 mAs25 mAs

water

water+ contrast

air


Cost effective PET/CT scanners


Paul Kinahan

'Value‐based' PET/CTRefurbished PET/CT scanners Strong market

New systems GE Optima 560 Philips Gemini LXL Siemens Excel 20 mCT Seem to be based on reduced capabilities compared to full‐featured scanners

pet: new technologies including oncology...pet technology innovations 1953 first coincidence...

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