Brookhaven Science Associates U.S. Department of Energy 1 Imaging the Awake Rat - RatCAP David J. Schlyer

Brookhaven Science AssociatesU.S. Department of Energy 1

Imaging the Awake Rat - RatCAPImaging the Awake Rat - RatCAP

David J. Schlyer


RatCAP Project CollaborationsRatCAP Project Collaborations

These projects are a collaboration

between several departments and divisions at BNL,

SUNY Stony Brook and LBNL

Weekly meetings within BNL, e-mail

and telephone contact with outside

collaborators


RatCAP- A head mounted PET imager for an awake ratRatCAP- A head mounted PET imager for an awake rat

Mockup of the portable ring on the head of a rat

A septa-less, full-ring tomograph with a diameter of 4 cmand an axial extent of 2 cm, suspended by a tether in a Ratturn bowl to allow nearly free movement of the awake animal


RatCAP- Some Challenges to be OvercomeRatCAP- Some Challenges to be Overcome An Application Specific Integrated Circuit (ASIC)

must be developed which contains all the components necessary to acquire and condition the coincidence events. It must be small enough to be carried by the rat.

The power generated by the electronics must be dissipated without active cooling.

The weight of the entire assembly (125 grams) should not inhibit the motion of the rat and should not stress the rat.

Since the rats head will occupy the entire volume of the scanner, parallax must be accounted for.

Reconstruction of data which is not completely sampled due to small diameter of the ring.

Must be rugged enough to withstand scratching and other manipulation by the rat.


Make the Tomograph SmallerMake the Tomograph Smaller

The light sensor can be a photomultiplier tube

Or it can be a Avalanche Photodiode Array (APD) which matches the crystal array

Craig WoodySean StollPaul Vaska


RatCAPA head mounted PET imager for an awake ratRatCAPA head mounted PET imager for an awake rat

2x2 mm2 LSO crystalsread out with APD arrays

Ring containing 12 block detectors 5 mm deep crystals with APDs and integrated readout electronics


RatCAP Lab Setup for Testing APD and Crystal ArraysRatCAP Lab Setup for Testing APD and Crystal Arrays

Two arrays of 4x8 APDs and crystals Used to measure properties of crystals and APD arrays Computer controlled rotational platform for reconstruction and depth of interaction studies

LSO and APD’sPositioning platform

Preamplifier


RatCAP Comparison of Different Crystal ArraysRatCAP Comparison of Different Crystal Arrays

Three types of arrays have been tested. CTI cut block, Proteus bonded reflector, Proteus unbonded reflector

CTI cut block

Proteus bonded

Proteus unbonded


RatCAP Comparison of Different Crystal ArraysRatCAP Comparison of Different Crystal Arrays

Average Light Output and Resolution of 4x8 LSO arrays

Conclusion: Proteus crystals wrapped and not glued should give good light output and the best energy resolution

manufacturer length note <pe/MeV> <resolution> CTI 8mm slotted block 2918 0.25

Proteus 5mm glued 1513 0.2010mm glued 2356 0.19

Proteus 5mm no glue 3113 0.1910mm no glue 2455 0.17

Proteus 5mm end glued - no mask 4491 0.165mm end glued - mask 2962 0.17

With Silicone cookie

RatCAPModeled Reconstructed ImagesRatCAPModeled Reconstructed Images

Reconstruction Simulations using SimSet

Fully sampled image of four sources of

various dimensions

Image reconstructed using incomplete

data set with linear interpolation

Image reconstructed using characteristic

zero efficiency data set


RatCAPThe Parallax ProblemRatCAPThe Parallax Problem

Human Size PET MicroPET RatCAP


RatCAPDepth of Interaction StudiesRatCAPDepth of Interaction Studies

In the small ring, parallax degrades the resolution

This is a concern due to the fact that the rat brain occupies most of the ring diameter


RatCAPA head mounted PET imager for an awake ratRatCAPA head mounted PET imager for an awake rat

Although RatCAP is a detector system with no depth measurement capability, the parallax effect can be reduced by decreasing crystal length from 10 mm to 5mm at the cost of an approximate factor of 4 in coincidence sensitivity.

1.0

1.5

2.0

2.5

3.0

3.5

4.0

4.5

0 2 4 6 8 10 12 14 16Radial Position (mm)

Ra

dia

l F

WH

M S

pa

tia

l R

es

olu

tio

n

(mm

)

Analytical 5mm

Analytical 10mm

Analytical UCLA microPET

SimSET 5mm

SimSET 10mm

approx. edge of rat brain

RatCAPReconstructed ImagesRatCAPReconstructed Images

Measured with a Ge-68 source phantom

dist

ance

(m

m)

distance (mm)

0

2

4

6

8

0 2 4 6 8


RatCAPAnimal StressRatCAPAnimal Stress

Stress testing is in progress at SUNY Stony

Brook

Testing will determine the level of stress and the time to

acclimate the animals to the detector ring


RatCAP Detector cross talk RatCAP Detector cross talk

• Need ADCs or not? • Take block data & process w/

and w/o ADC info which allows cross-talk correction

• w/o ADCs, ~25% loss in coincidence sensitivity

Conclusion: The slightly

increased sensitivity does not justify the added ASIC complexity

0.0%

20.0%

40.0%

60.0%

80.0%

100.0%

Energy Spectra for Crystal 20

0

100

200

300

400

500

600

700

800

900

0 20 40 60 80 100Channel

Co

un

ts

no neighborsincluding neighbors

with correction


RatCAPElectronic DevelopmentRatCAPElectronic Development

No analog information Single ZCD per channel Serial transmission from

on-block electronics to on-enclosure data collection module (DCM)

DCM timestamps each pulse, sends raw addresses/time events to remote coincidence processor

Individual block to DCM links ≈1.5 watt power 3-10 watts power

enc losure

B LO C K 0

B LO C K 1

B LO C K 2

B LO C K n

T D C

A D D RE NC O D E

controls

pow er

LV D S

to co inc . p roc .

LV , HV

tem p senseHV ad jus tthresho ld ad j.anlg . m onito r

9b

24b

330 Mb it/s

P d iss ~ 1W (2 .6 m W /chan) P d iss 3 - 10 W

tim ing c lock

te the r10^7 events /s

on-de tec to r e lec tronics T D C & p rocess ing box

DCM


RatCAPPrototype Chip DevelopmentRatCAPPrototype Chip Development

The fourth iteration chip is being tested


Future PlansFuture Plans Complete animal stress testing in

conjunction with SUNY Stony Brook Test reconstruction with Maximum

Likelihood Statistical methods Design and construct Data Collection

Module and data acquisition system Complete ASIC and front end electronic

design and submit for production Complete design of mechanical support

system Assemble and test the complete system


RatCAPThe RatCAPPERSRatCAPThe RatCAPPERS

Support provided by Université de Sherbrooke and CMC

Funding Provided by the Department of Energy - Office of Biological and Environmental Research,

Physics:Craig Woody

Sean StollBill Lenz

Mike LenzMartin Purschke

Chemistry:David Schlyer

Richard FerrieriMike Schueller

Medical:Paul Vaska, Nora Volkow

SUNY Stony Brook:

Dimitras SamarasXin Li

Sepideh ShokouhiAzael Villanueva

Aarti Kriplani

LBNL:Ron Huesman

Jinyi Qi Greg Klein

Instrumentation:Veljko Radeka, Paul O’Connor, Jean-Francois Pratte, Bo Yu

Acknowledgements: This work was carried out at Brookhaven National Laboratory under contract DE-AC02-98CH10886 with the U. S.

Department of Energy and supported by its Office of Biological and Environmental Research and Grant No. MO-068, T. Ernst PI. The fabrication of ASICs was possible through collaboration with the

University of Sherbrooke and R. Lecomte

Documents

Brookhaven Science Associates U.S. Department of Energy 1 Imaging the Awake Rat - RatCAP David J. Schlyer