from novel g-2 fast calorimetry to a superior pet scanner bill worstell chief technology officer...
TRANSCRIPT
From Novel g-2 Fast Calorimetry to a Superior PET Scanner
Bill Worstell
Chief Technology Officer
PhotoDetection Systems, Inc.
Talk Overview
• What PET/CT is and why it is important– Brief Summary of Clinical Context
• The PDS PET/CT and its connection with Experimental High-Energy Physics– Detector Design + Implementation– Data Analysis/Processing + Image Algorithms
• The Future of PET/CT– Molecular Imaging + Molecular Medicine
PET Physics
Measure positionsand energies ofcoincident particles whichgenerate triggers –sound familiar?
FDG-PET
• All of clinical PET is currently FDG-PET
• FDG developed at Brookhaven National Laboratory
• Nearly all tumors are FDG-avid
Clinical Applications of PET in Oncology
• Diagnosis• Biopsy guidance• Staging• Radiation Therapy
Planning• Monitoring Response
to Therapy• Monitoring for
Recurrence
Anatomical plus Functional Imaging -> Fusion Imaging
CT Image gives anatomy
PET Image gives function
(-> in-vivo
Quantitative
Biochemistry)
PET is now a $1B/year business,Up from ~$10M/year in 1998
PET/CT was first commerciallyintroduced in 2002, and now makesUp nearly 100% of the PET market
Distinguishing Features of PDS PET component of PET/CT
• Highest Sensitivity available
• Largest bore available (only 90cm PET/CT)
• Matches highest clinical spatial resolution available
• Lowest cost to manufacture• Simple interfaces to
alternative multislice CTs
Largest Bore PET/CT available
Patient Bore (cm)
PDS Resolve 90 90GE Discovery ST 70CTI/Siemens pico-3D 70CTI/Siemens Hi-Res 70Philips Gemini 63
Manufacturer/Model
Large-bore CTs have been introduced to satisfy the needsof radiation therapy planningapplications – there is as yet nocomparably large-bore PET/CT.
Highest SensitivityPET/CT system
• Double the axial field of other scanners (32cm vs 16cm)– Larger coverage
– Larger acceptance
• High stopping power• Clinical applications:
– Lower injected dose
– Emerging radiotracers
Manufacturer Model Sensitivity(kcps/MBq)
PDS Resolve 90 18.1GE Discover ST 9.1Siemens Biograph LSO 6.4Siemens Hi-Rez 5.3Philips Gemini 4.4
length
keV511
Highest PET/CTImage Quality
• Meets or exceeds the performance of competitive systems as quantified by NEMA standard tests and direct imaging comparisons
CTI: Low resolution
GE: Non-uniformintensity
PDS: High resolution and uniform intensity
PDS PET/CT
6.35
2.38
3.18
3.97
4.76
5.56
CTI Hi-Res
BU Physics Prototype WorkAntecedent work:• Muon g-2 fiber
calorimeter prototypes• SSC fiber calorimeter
prototypes• BU wavelength-
shifting fiber PET prototypes– Patent filed 1995– Photonics Center spin-
off start-up 2000
Principle of Wavelength-Shifting Fiber Optic PET Readout
• Wavelength-shifting fiber readout technology familiar and proven by tile calorimeter groups for many years.
• Combination with Anger Logic readout is cost-effective and robust at high event rates.
1. Gamma ray enters crystal from positron annihilation
2. Interaction in crystal releases blue
photons
3. Fiber absorbs blue photons and fluoresces green
4. Fibers carrygreen lightto sensors
5. Other photons pass through mixer to
photomultiplier tube
5. Other photons pass through mixer to
photomultiplier tube
Commercial embodiment of WLS fiber readout
44 field-replaceable optics modules11 field-replaceable electronics modules11 parallel readout commercial PCs
Key to High Sensitivity and Low Cost: CsI(Na) Scintillator
• CsI(Na) developed at Kharkhov in collaboration with Budker Instititute in Novosibirsk
• Much lower cost to manufacture than alternatives– Low melting point– Low cost raw
materials
• But slower decay
Accurate High-Throughput Data Acquisition and Signal Processing
• Fully digital, including digital triggering (unique to PDS)
• Digital waveform signal processing
• Fully buffered to eliminate downstream deadtime effects
• Cost-effective Programmable Logic Array Design
Key to High-throughput Data Processing:Parallel Readout
• Unique to PDS design
• Organizes lines-of-response into ordered pairs.
• Uniformly distributes data acquisition and data processing workload
• Built on a commercial off-the-shelf Linux cluster
2
3
4
5
67
8
9
10
111
3 slaves
2
3
4
5
67
8
9
10
11
1
3 masters
Optimal Use of Measured Data --Diversity Signal
Processing• List mode event data
packet:
• Weight each event by probability it is a True
• Mathematically optimal statistical treatment of diverse events
• Unique to PDS
jijijjjiii tEEzyxzyx ,,,);,,();,,(
Randoms
Trues + Scatters
Total
Statistically principled fully-3D Maximum-Likelihood
Image Reconstruction
• Factorized precalculated formulation unique to PDS
• Based on previously unnoticed symmetry
• Custom hardware parallel processing reconstruction accelerator
Continuous Bed Motion combined
with fully-3D reconstruction
• Coordinate transformation to “virtual detector” which is co-moving with patient.
• PDS first to combine this with fully 3D reconstruction
Axial Direction
Virtual DetectorSide View
Physical DetectorSide View
Virtual DetectorSide View
Physical DetectorSide View
Z
SSpace
ZSpace
Physical DetectorFront View
The Future of PET/CT
• The Multi-slice CT revolution
• Radiation Therapy applications of PET/CT
• New and Emerging Radiotracers– Molecular Imaging and Molecular Medicine– Personalized Medicine
PET/CT and new Multi-slice CTs
Customers are demanding topCT performance in PET/CTs, withCardiac applications leading the way.(CT Angiography)
PET/CT and Radiation Therapy• IMRT – Intensity
Modulated Radiation Therapy directs beams with greater accuracy
• IGRT – Image Guided Radiation Therapy gives direction by imaging organs at delivery time
• FIGRT – Functional Image Guided Radiation Therapy on the near horizon
EmergingHigh-
Specificity Radiotracers
Ga-68 DOTATOCbinds to somatostatinreceptors overexpressedby neuroendocrine tumors
Things I Learned From Larry
• Love what you’re doing and let it show– It’ll make people want to join your team
• Talk fast, life is short– Assume your audience is quick on the uptake
• Put your best foot forward– No one else will do it for you
• Swing for the fences– Who knows how many at-bats you’ll get