Transcript Improving detectability and quantification

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
For internal use only / Copyright © Siemens AG 2006. All rights reserved.
Lung cancer: response to therapy (Hanna, Nahmias)
Week 1
Week 7
Week 1
3.5
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0.5
SUV
SUV
2.5
Responder
Patient alive 20 months
after end of chemotherapy
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Week 7
Non-responder
Patient survived 2 months
after end of chemotherapy
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Week
Courtesy of David Townsend, Ph.D.
University of Tennessee Medical Center
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Bernard Bendriem, Ph.D., Siemens Medical Solutions
Improving detectability and quantification
1. Hybrid imaging
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Bernard Bendriem, Ph.D., Siemens Medical Solutions
Hybrid imaging
Morphology
Physiology
Metabolism Molecules
CT
Dynamic, Perfusion
US
Dynamic, Flow, Perfusion
106 -108
molecules/cell
MRI, MRS
Dynamic, Flow, Perfusion, Diffusion, Molecules
1 molecule/cell
NM
Perfusion, Molecules
Several
molecules/cell
FluorescenceOptical
Molecules
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Bernard Bendriem, Ph.D., Siemens Medical Solutions
• to image different
aspects of disease
• to identify tracer uptake
• to simplify the image
Form + function
Why combine form and function?
interpretation
• to give added value to
CT and PET
Fused image accurately
localizes uptake into a
lymph node and thus
demonstrates spread of
disease.
CT (anatomy)
Courtesy of David Townsend, Ph.D.
University of Tennessee Medical Center
PET (function)
PET/CT
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Bernard Bendriem, Ph.D., Siemens Medical Solutions
I-131 SPECT•CT:
Residu thyroidien vs.
Metastases ganglionnaires
University of Erlangen
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Bernard Bendriem, Ph.D., Siemens Medical Solutions
Advantages of CT-based correction
•
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
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more tolerable for the patient
•
shorter total scan duration
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Bernard Bendriem, Ph.D., Siemens Medical Solutions
Improving detectability and quantification
1. Hybrid imaging
2. Organ motion
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Bernard Bendriem, Ph.D., Siemens Medical Solutions
Whole-body respiratory gated PET/CT: Simulations
 Spherical VOI
that tracks with
motion over 10
respiratory
phases
VOI value (a.u.)
1.5
1
Phase matched CTAC
Helical CTAC
CINE CTAC
0.5
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0
Courtesy of Dr. Kinahan
University of Washington
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Bernard Bendriem, Ph.D., Siemens Medical Solutions
Whole-body respiratory gated PET/CT: Patients
Static wholebody
Single respiratory phase
(1 of 7, so noisier)
< 1 cc lesion on CT
Respiratory motion is distributed throughout the whole body
Impact is rarely on detection, but often affects quantitation
Courtesy of Dr. Kinahan
University of Washington
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Bernard Bendriem, Ph.D., Siemens Medical Solutions
Improving detectability and quantification
1. Hybrid imaging
2. Organ motion
3. Spatial resolution
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Bernard Bendriem, Ph.D., Siemens Medical Solutions
The clinical importance of spatial resolution
2.0
3.9
1.3
3.3
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Recovery (%)
8 x 8 elements/block
6.4 mm x 6.4 mm
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Low-REZ; 8.6 mCi; 60 min uptake
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Sphere diameter (mm)
HI-REZ; 11.2 mCi; 90 min uptake
13 x 13 elements/block
4.0 mm x 4.0 mm
3.7
8.7
4.1
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Courtesy of David Townsend, Ph.D.
University of Tennessee Medical Center
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Bernard Bendriem, Ph.D., Siemens Medical Solutions
Smaller pixels……Research
HRRT Detector Block Design
2 mm
LYSO (10 mm)
LSO (10 mm)
 8X8 crystal matrix
Light Guide
 128 Single crystals per block
PMT
PMT
1 9.5mm
2
56
63
8
15
0
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0
crystal
block
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 LYSO only used for pulse shape discrimination
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columns
Bernard Bendriem, Ph.D., Siemens Medical Solutions
High Resolution Research Tomograph
Investigation of small dopaminergic structures playing a
crucial rôle in the reward circuit, such as :
- Ventral striatum (Accumbens nucleus)
- Midbrain (SNr & VTA)
Ventral striatum
VTA & SNr
 High spatial PET imaging is promising for the
exploration of subtle modifications in small and
complex brain structures.
Courtesy of Pr Syrota
Service Hospitalier Frederic Joliot, Orsay
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Bernard Bendriem, Ph.D., Siemens Medical Solutions
Improving detectability and quantification
1. Hybrid imaging
2. Organ motion
3. Spatial resolution
4. Number of detected photons
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Bernard Bendriem, Ph.D., Siemens Medical Solutions
Clinical workflow: reduced imaging times
30 sec/bed
2 min/bed
3 min/bed
2.5 min
10 min
Total scan duration (5 beds)
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.
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Bernard Bendriem, Ph.D., Siemens Medical Solutions
How to improve intrinsic sensitivity?
• thicker crystals
B
20 mm to 30 mm
sensitivity increase: 40%
C
D
g (511 keV)
• extended axial FOV
16.2 cm to 21.6 cm
sensitivity increase: 77%
3D (no septa)
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Bernard Bendriem, Ph.D., Siemens Medical Solutions
Advantages of the extended axial field-of-view
bed #
Standard:
5 15 min
Extended FOV:
4
8 min
• higher sensitivity = shorter imaging per bed (or more counts)
• larger axial FOV = fewer bed positions for same axial coverage
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Bernard Bendriem, Ph.D., Siemens Medical Solutions
Staging melanoma with extended field-of-view
Total scan duration: 22 min
CT: 30 mAs, 130 kV, 5 mm slices at 0.75 mm
PET: 10 mCi FDG, 108 min pi, 2 min/bed, 11 beds
Courtesy of David Townsend, Ph.D.
University of Tennessee Medical Center
27 year-old female (123 lbs) with metastatic
melanoma. Uptake in left lower extremity and in left
axillar node positive for melanoma.
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Bernard Bendriem, Ph.D., Siemens Medical Solutions
Lung cancer
Biograph
15.1 mCi, 90 min pi
4 min/bed, 5 beds
4i / 8s; 5f
PET/CT
Scan duration: 20 min
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.
Courtesy of David Townsend, Ph.D.
University of Tennessee Medical Center
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Bernard Bendriem, Ph.D., Siemens Medical Solutions
Torso phantom study
4.9 mm
7.8 mm
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
6.2 mm
4.9 mm
7.8 mm
6.2 mm
Imaging time based on equivalent total
acquisition time for whole body scan.
Sphere diameters: 7.8 mm; 6.2 mm, 4.9 mm
Contrast ratio in spheres: 8:1
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Bernard Bendriem, Ph.D., Siemens Medical Solutions
Advantage of extended axial FOV in PET
• 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
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Bernard Bendriem, Ph.D., Siemens Medical Solutions
Improving detectability and quantification
1. Hybrid imaging
2. Organ motion
3. Spatial resolution
4. Number of detected photons
5. Image reconstruction
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Bernard Bendriem, Ph.D., Siemens Medical Solutions
True Counts & Noise
Scatter Coincidence
Trues Coincidence
Random Coincidence
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Bernard Bendriem, Ph.D., Siemens Medical Solutions
Patient MN. 297 lbs (135 kg)
FORE + OSEM, 4i x 8s, 8 mm filter
0 – 21% max window
Scatter corrected
high residual
in left ventricle
No scatter correction
scatter from
liver
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hot lung walls
Bernard Bendriem, Ph.D., Siemens Medical Solutions
Patient MN. 297 lbs (135 kg)
Sinogram profiles
Measured emission
_ _ _ _ Computed scatter
396 MBq injection
157 min uptake
52%
Scatter
54%
Scatter
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Bernard Bendriem, Ph.D., Siemens Medical Solutions
Time-of-Flight Acquisition: Principles
 Time-of-flight reduce noise propagation during image
reconstruction process
TOF filter
Back projection
along the LOR
FOV
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Bernard Bendriem, Ph.D., Siemens Medical Solutions
Time-of-Flight and SNR
t
x  c
2
SNRTOF
Time
Resolution
(ns)
x
D

 SNRconv
x
(cm)
SNR
improvement
(20 cm object)
SNR
improvement
(40 cm object)
0.1
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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
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Bernard Bendriem, Ph.D., Siemens Medical Solutions
Measurements: 27-cm lesion phantom
TOF
60s
6-to-1 contrast
Non-TOF
similar CRC
and noise
TOF
shorter
scan
similar noise
and scan time
TOF
higher
CRC
similar CRC
and scan time
TOF
lower
noise
180s
60s
Courtesy of Joel Karp
University of Pennsylvania
60s
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Bernard Bendriem, Ph.D., Siemens Medical Solutions
Gemini TF - patient study
Rectal carcinoma, metastases in
mesentery and bilateral iliac chains
non-TOF
114 kg; BMI = 38.1
12 mCi; 2 hr post-inj
3min/bed
TOF
Lesion contrast (SUV) improves with TOF reconstruction
Courtesy of Joel Karp
University of Pennsylvania
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Bernard Bendriem, Ph.D., Siemens Medical Solutions
Improving detectability and quantification
1. Hybrid imaging
2. Organ motion
3. Spatial resolution
4. Number of detected photons
5. Image reconstruction
6. Other hybrid imaging
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Bernard Bendriem, Ph.D., Siemens Medical Solutions
Lésion d’un sésamoïde
(premier métatarsien)
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Bernard Bendriem, Ph.D., Siemens Medical Solutions
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)
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Bernard Bendriem, Ph.D., Siemens Medical Solutions
MR-PET Concepts
Analogous to PET-CT
Integrated System
PET-Insert
MR
MR Scanner
 No
PET
Scanner
simultaneous
measurement, no isocentric measurement
 Reduced MR
compatibility demand
(only main field)
MR Scanner
 Upgrade
of existing MR
scanners possible
 Reduced FOV for PET
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PET
PET
Scanner
Integrated
development necessary
Bernard Bendriem, Ph.D., Siemens Medical Solutions
Simultaneous dual-modality data acquisition
 High resolution artifact free PET
images
 High resolution artifact free MR
images
2500.0
[undefined]
2000.0
1.5mm
1.0mm
1500.0
1000.0
500.0
0.0
2.0mm
3.5mm
2.5mm
3.0mm
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Bernard Bendriem, Ph.D., Siemens Medical Solutions
Improving detectability and quantification
1. Hybrid imaging
2. Organ motion
3. Spatial resolution
4. Number of detected photons
5. Image reconstruction
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.
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Bernard Bendriem, Ph.D., Siemens Medical Solutions