apd quantum efficiency - ndipndip.in2p3.fr/ndip08/presentations/2monday/a-midi/117...snm 2008, new...

5th NDIP CONFERENCE New Developments in Photodetection

Aix-les-Bains – France, June 15-20, 2008

APD Quantum Efficiency

Development of a 64-channel APD Detector Module with

Individual Pixel Readout for Submillimeter Spatial Resolution in PET

Philippe Bérarda, Mélanie Bergerona, Catherine M. Pepina, Jules Cadorettea, Marc-

André Tétraultb, Nicolas Viscogliosib, Réjean Fontaineb, Henri Dautetc, Murray

Daviesc, Pierre Deschampsc, Roger Lecomtea

aDepartment of Nuclear Medicine and Radiobiology, Université de Sherbrooke, Sherbrooke, QC, CANADAbDepartment of Electronic and Computer Engineering, Université de Sherbrooke, Sherbrooke, QC, CANADA

cPerkinElmer Optoelectronics, Vaudreuil-Dorion, QC, CANADA



LabPETLabPET ScannerScanner

�� PET sensitivity PET sensitivity ↓↓↓↓↓↓↓↓

Detector module :Detector module :

•• 4 individual 4 individual APDsAPDs

•• ∼∼∼∼∼∼∼∼ 16 channels/cm16 channels/cm22

•• Dimension : 1.8 Dimension : 1.8 ×××××××× 4.4 mm4.4 mm22

•• Active area : 1.1 Active area : 1.1 ×××××××× 3.6 mm3.6 mm22

•• Coupling fraction : Coupling fraction : 40.5 %40.5 %

•• ModuleModule’’s surface : 10.3 x 4.8 mms surface : 10.3 x 4.8 mm22

•• Packing fraction : Packing fraction : ∼∼∼∼∼∼∼∼ 65 %65 %

LYSO

LGSO

Design Parameters:Design Parameters:

•• 16.2 cm diameter ring16.2 cm diameter ring

•• FOV:FOV: 10 cm diameter 10 cm diameter 3.75 or 7.5 cm axial3.75 or 7.5 cm axial

•• 3072 or 6144 crystals3072 or 6144 crystals

•• 1536 or 3072 APD detectors1536 or 3072 APD detectors

•• 2 2 ×××××××× 2 2 ×××××××× 12 mm12 mm33 pixelspixels

•• Massively parallel digital processingMassively parallel digital processing

High resolution molecular imaging toolSNM 2008, New Orleans



Main PurposeMain Purpose

208 g rat208 g rat

Na18F

75 kg 75 kg humanhuman

Philips

Gemini

TF

LabPETTM

20.6 g mouse20.6 g mouse

Submillimeter spatial resolution in PET is desirable for small animal molecular

imaging such as transgenic mice



( ) ( ) 0022.0 2 2222

rDbdaFWHM +++=

Physical limit

≈0.35 - 0.4 mm

GeometricGeometricDetector

size(triangular)

*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. 25-40.

PositronPositronrangerange

18F : ∼∼∼∼ 0.3 mm

Spatial Resolution in PETSpatial Resolution in PET

NonNon--colinearitycolinearity

Ring diameter

80-120 mm

Detector

d ∼∼∼∼ 1.2 mmFWHM ∼∼∼∼ 1 mm

Need Higher channel density � APD array design

CodingCoding

Individual: ~0 mm

Packing fraction is an issueLabPETTM detector design



LabPET II module

A novel 64-channel avalanche photodiode

(APD) detector module with individual

crystal readout

LabPET II ModuleLabPET II Module

1. Building block of a high spatial resolution small animal

PET system

2. Provide anatomic localization by performing photon

counting CT

Objectives :Objectives :



Custom ceramic pin grid array

2 APD chips (4 ×××× 8 pixels array) bump-bonded on ceramic

APD SchematicAPD Schematic

Reach-through structure with

common anode / divided cathode

∼ 41 channel/cm2

Fill factor : 84.0 %

Pixel pitch : 1.2 mm

Active area single APD : 1.1 ×××× 1.1 mm2



APD CharacterizationAPD Characterization



APD CharacterizationAPD Characterization

APD #1 : - 308.4 V QE (430 nm) : 0.43 T : 30.5 oC

APD #2 : - 298.4 V QE (430 nm) : 0.44

84.4 ± 11.795.1 ± 13.4Corner

90.0 ±±±± 9.895.7 ±±±± 6.3Total

89.5 ± 10.595.9 ± 6.5Side

92.5 ± 7.995.6 ± 2.8Centre

APD 2APD 1

54.4 ± 3.155.8 ± 10.9Corner

35.3 ±±±± 10.234.0 ±±±± 11.4 Total

39.9 ± 1.836.7 ± 1.9Side

24.2 ± 0.823.2 ± 3.8Centre

APD 2APD 1

0.14 ± 0.040.14 ± 0.02Corner

0.13 ±±±± 0.030.13 ±±±± 0.03Total

0.13 ± 0.010.13 ± 0.04Side

0.13 ± 0.040.13 ± 0.01Centre

APD 2APD 1

Multiplication Gain Dark Current Dark Noise

APD 1

APD 2

APD 1

APD 2

APD 1

APD 2

1.97

1.15

0.01



Non-conventional tapered

geometry ⇒ ↑ PET sensitivity

8 ×××× 8 LYSO scintillator array

4 prototype units manufactured by

Design of Scintillator ArrayDesign of Scintillator Array

Packing fraction : 74.6 %Packing fraction : 74.6 %(LabPETTM : 64.4 %)

Coupling fraction : 84.0 % (LabPETTM : 40.5 %)

10.86 mm 10.86 mm

axial

1.2 mm3M VM2000 Radiant Light Film

reflector

1.36 mm

12 mm

radial

axial

radial



LabPET II ModuleLabPET II Module

a) Ceramic

b) Ceramic + 2 APD chips

c) LYSO array

d) LabPET II module



×32 45 MHz dual-channel ADC

Digital LabPETTM board

Custom designed analog test board

ElectronicsElectronics

4 x 16 channel CSP

BACK

FRONT

Programmable gain



Energy SpectraEnergy Spectra

68Ge (511 keV) 240 V Mean energy resolution : 27.5 ± 2.1 %

Mean photopeak position (bin number) : 87.3 ± 13.8



Timing SpectraTiming Spectra

Timing spectrum

obtained over 100 LOR

68Ge (511 keV) 270 V

Timing resolution : 5.0 ±0.2 ns

450-650 keV energy

window

Two modules 12 cm apart

Timing resolution with LabPETTM digital electronics



Intrinsic Spatial ResolutionIntrinsic Spatial Resolution

0.050.02STD

1.540.82Mean

1.570.808

1.570.807

1.450.806

1.470.835

1.570.814

1.580.823

1.590.822

1.530.841

FWTM

(mm)

FWHM

(mm)

Coincidence

pair #

1 2 3 4 5 6 7 8

� All LORs are clearly identified

� Nearly triangular shape

� FWTM < 2 ×××× FWHM

22Na Ф : 0.3 mm

450-650 keV energy window

12 cm

Quadratic subtraction non-colinearity and source

size ⇒ 0.73 mm FWHM detector resolution



241Am (59.5 keV) 260 V

Counting CT ?Counting CT ?

Mean energy resolution : 47.5 ± 3.3 %

Mean photopeak position (bin number) : 18.9 ± 1.9

A

B

C

D

E

F

G

H

1 2 3 4 5 6 7 8



Future WorkFuture Work

• ↑ Light collection, ↓ Light cross-talk

• Higher APD QE desirable

• Electronic architecture

• PET/CT implementation

Will be presented at WMIC 2008 in Nice, France, September 10-13

Feasibility of PET / Counting CT Image Fusion with LabPETTM I Detectors and Electronics

Counting CT

Mouse21 g



ConclusionConclusion

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



AcknowledgmentsAcknowledgments

LabPET II Scanner DevelopmentsLabPET II Scanner Developments

GRAMSGRAMS, Faculty of Engineering, UdeS, Faculty of Engineering, UdeS

LabTEPLabTEP, Faculty of Medicine and Health Sciences, UdeS, Faculty of Medicine and Health Sciences, UdeS

apd quantum efficiency - ndipndip.in2p3.fr/ndip08/presentations/2monday/a-midi/117...snm 2008, new...

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