APD Quantum Efficiency

Transcription

1 APD Quantum Efficiency Development of a 64-channel APD Detector Module with Individual Pixel Readout for Submillimeter Spatial Resolution in PET Philippe Bérard a, Mélanie Bergeron a, Catherine M. Pepin a, Jules Cadorette a, Marc- André Tétrault b, Nicolas Viscogliosi b, Réjean Fontaine b, Henri Dautet c, Murray Davies c, Pierre Deschamps c, Roger Lecomte a a Department of Nuclear Medicine and Radiobiology, Université de Sherbrooke, Sherbrooke, QC, CANADA b Department of Electronic and Computer Engineering, Université de Sherbrooke, Sherbrooke, QC, CANADA c PerkinElmer Optoelectronics, Vaudreuil-Dorion, QC, CANADA

2 LabPET Scanner Design Parameters: 16.2 cm diameter ring FOV: 10 cm diameter 3.75 or 7.5 cm axial 3072 or 6144 crystals 1536 or 3072 APD detectors mm 3 pixels Massively parallel digital processing LYSO LGSO Detector module : 4 individual APDs 16 channels/cm 2 Dimension : mm 2 Active area : mm 2 Coupling fraction : 40.5 % Module s s surface : 10.3 x 4.8 mm 2 Packing fraction : 65 % SNM 2008, New Orleans PET sensitivity High resolution molecular imaging tool

3 Main Purpose Na 18 F Philips Gemini TF LabPET TM 75 kg human 208 g rat 20.6 g mouse Submillimeter spatial resolution in PET is desirable for small animal molecular imaging such as transgenic mice

4 Spatial Resolution in PET ( ) 2 2 d 2 + b + ( D) FWHM = a + Geometric Detector size (triangular) Coding Individual: ~0 mm 2 Non- colinearity Ring diameter mm r 2 Positron range 18 F : 0.3 mm FWHM 1 mm Detector d 1.2 mm Physical limit mm LabPET TM detector design Packing fraction is an issue Need Higher channel density APD array design * Derenzo & Moses, Critical instrumentation issues for resolution < 2 mm, high sensitivity brain PET, in Quantification of Brain Function, Tracer Kinetics & Image Analysis in Brain PET, Elsevier, 1993, pp

5 LabPET II Module LabPET II module A novel 64-channel avalanche photodiode (APD) detector module with individual crystal readout Objectives : 1. Building block of a high spatial resolution small animal PET system 2. Provide anatomic localization by performing photon counting CT

6 Custom ceramic pin grid array 2 APD chips (4 8 pixels array) bump-bonded on ceramic Reach-through structure with common anode / divided cathode Pixel pitch : 1.2 mm Active area single APD : mm 2 Fill factor : 84.0 % 41 channel/cm 2 APD Schematic

7 APD Characterization

8 APD Characterization APD #1 : V QE (430 nm) : 0.43 T : 30.5 o C APD #2 : V QE (430 nm) : 0.44 Multiplication Gain Dark Current Dark Noise APD 2 APD 2 APD 2 APD 1 APD APD 1 APD 1 APD 2 APD 1 APD 2 APD 1 APD 2 Centre 95.6 ± ± 7.9 Centre 23.2 ± ± 0.8 Centre 0.13 ± ± 0.04 Side 95.9 ± ± 10.5 Side 36.7 ± ± 1.8 Side 0.13 ± ± 0.01 Corner 95.1 ± ± 11.7 Corner 55.8 ± ± 3.1 Corner 0.14 ± ± 0.04 Total 95.7 ± ± 9.8 Total 34.0 ± ± 10.2 Total 0.13 ± ± 0.03

9 Design of Scintillator Array 4 prototype units manufactured by mm mm 1.36 mm 8 8 LYSO scintillator array 12 mm 3M VM2000 Radiant Light Film reflector 1.2 mm Non-conventional tapered geometry PET sensitivity radial axial Coupling fraction : 84.0 % (LabPET TM : 40.5 %) Packing fraction : 74.6 % (LabPET TM : 64.4 %) radial axial

10 LabPET II Module a) Ceramic b) Ceramic + 2 APD chips c) LYSO array d) LabPET II module

11 Custom designed analog test board 4 x 16 channel CSP Programmable gain Electronics BACK Digital LabPET TM board MHz dual-channel ADC FRONT

12 Energy Spectra 68 Ge (511 kev) 240 V Mean energy resolution : 27.5 ± 2.1 % Mean photopeak position (bin number) : 87.3 ± 13.8

13 Timing Spectra 68 Ge (511 kev) 270 V Timing resolution with LabPET TM digital electronics Two modules 12 cm apart Timing spectrum obtained over 100 LOR kev energy window Timing resolution : 5.0 ± 0.2 ns

14 Intrinsic Spatial Resolution Na Ф : 0.3 mm 12 cm kev energy window Coincidence pair # FWHM (mm) FWTM (mm) All LORs are clearly identified Nearly triangular shape FWTM < 2 FWHM Quadratic subtraction non-colinearity and source size 0.73 mm FWHM detector resolution Mean STD

15 Counting CT? 241 Am (59.5 kev) 260 V Mean energy resolution : 47.5 ± 3.3 % A B C D E F G H Mean photopeak position (bin number) : 18.9 ±

16 Future Work Light collection, Light cross-talk Higher APD QE desirable Electronic architecture PET/CT implementation Feasibility of PET / Counting CT Image Fusion with LabPET TM I Detectors and Electronics Counting CT Mouse 21 g Will be presented at WMIC 2008 in Nice, France, September 10-13

17 Conclusion A high density APD PET detector was successfully designed with low dead space All 511 kev photopeak could easily be identified suitable timing resolution was obtained 5.0 ns Intrinsic spatial resolution of 0.8 mm was measured

18 Acknowledgments LabPET II Scanner Developments GRAMS,, Faculty of Engineering, UdeS LabTEP,, Faculty of Medicine and Health Sciences, UdeS