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

Monitoring Response to Targeted Therapy

PET/CT Hybrid Scanners

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

PDS/Analogic PET/CT Prototype

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

PET and Molecular Imaging

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