Optimizing timing resolution of SiPM sensors for use in...

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NDIP – 20 June 2008 Optimizing timing resolution of SiPM sensors for use in TOF-PET detectors Ruud Vinke

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Page 1: Optimizing timing resolution of SiPM sensors for use in ...ndip.in2p3.fr/ndip08/Presentations/6Friday/73-Vinke.pdf · line-of-response (LOR) ... • Hamamatsu SiPM with 1 mm2 effective

NDIP – 20 June 2008

Optimizing timing resolution of SiPM sensors for use in

TOF-PET detectors

Ruud Vinke

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NDIP – 20 June 2008

Overview

• Principle of TOF-PET• Relevant PET detector requirements• SiPM timing characterization

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NDIP – 20 June 2008

The principle of TOF-PET

500 ps → 7.5 cm

uniform probability on line-of-response (LOR)

Δ x=c Δ t2

Moses, W. W., IEEE Trans. Nucl. Sci., vol. NS-50, pp. 1325-1330, 2003

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NDIP – 20 June 2008

2 line sourcesinside water cylinder

TOF-PET: a simulated example

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NDIP – 20 June 2008

TOF-PET: a simulated exampleno TOF TOF

500 ps FWHM

4 cm

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NDIP – 20 June 2008

TOF-PET: a simulated examplesame resolution

improved contrast

non-TOF

TOF

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NDIP – 20 June 2008

PET image deterioration

parallax error

incorrectLOR

measuredepth-of-interaction (DOI)

Comptonscattering

Compton scattering

select full-energy peakenergy resolution < 7 %

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NDIP – 20 June 2008

Conventional detector configuration

Anger logic

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NDIP – 20 June 2008

Monolithic scintillator with photosensor array

Statistics based reconstruction, e.g.:

- Nearest neighbour estimation- Neural network estimation- Maximum likelihood estimation

DOI

M. C. Maas, et al., IEEE Trans. Nucl. Sci.,vol. NS-53, pp. 1071-1077, 2006

Gamma photon entry point estimation -> automatic correction for parallax error

DOI estimation -> correction for DOI-induced time dispersion

(In cooperation with TU Delft)

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NDIP – 20 June 2008

Scintillator materialLaBr3:

• sufficient energy resolution• good timing properties

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NDIP – 20 June 2008

Photodetector

SiPM:• good timing properties

• MRI compatibility

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NDIP – 20 June 2008

Acqiris digitizer

• DC282 high-speed digitizer• 10-bit resolution• 8 GS/s sampling rate

(4 GS/s for 2 ch acquisition) • 2 GHz bandwidth• 50 Ohm input impedance• 1 ps jitter

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NDIP – 20 June 2008

Timing setup

• Hamamatsu PLP10-40 laser• 405 nm peak wavelength• 70 ps pulse width

• Hamamatsu MPPC 25U, 50U, 100U

• Hamamatsu PLP10-40 laser• 405 nm peak wavelength• 70 ps pulse width

• High bandwidth voltage preamp

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NDIP – 20 June 2008

SiPM pulse tracesMPPC 50U; Vop 70.49 V

Afterpulse filtering

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NDIP – 20 June 2008

SiPM risetime spectrum

1.21 ns peak

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NDIP – 20 June 2008

SiPM: single photoelectron sensitivity

1

2

3

4

no. of photoelectrons

MPPC 50U; Vop 69.51 V

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NDIP – 20 June 2008

Breakdown voltage determination

2 phe

1 phe

3 phe

4 phe

MPPC 50U

Breakdown voltage

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NDIP – 20 June 2008

Time pickoff procedure

CF30%

Time mark

Page 19: Optimizing timing resolution of SiPM sensors for use in ...ndip.in2p3.fr/ndip08/Presentations/6Friday/73-Vinke.pdf · line-of-response (LOR) ... • Hamamatsu SiPM with 1 mm2 effective

NDIP – 20 June 2008

SiPM timingMPPC 50U

Page 20: Optimizing timing resolution of SiPM sensors for use in ...ndip.in2p3.fr/ndip08/Presentations/6Friday/73-Vinke.pdf · line-of-response (LOR) ... • Hamamatsu SiPM with 1 mm2 effective

NDIP – 20 June 2008

Single photoelectron timingMPPC 50U

100 ps single photon sigma time res.

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NDIP – 20 June 2008

Coincidence measurements

• 2x2x8 mm3 LYSO crystal• Hamamatsu SiPM with 1 mm2 effective area• Na-22 source → 511 keV anti-parallel gamma emission• Optical coupling needs to be improved

~180 ps fwhm time resolution

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NDIP – 20 June 2008

Coincidence timing resolution (preliminary)

MPPC 100U – Vop 69.77 V (1.14 V above breakdown )

� 600 ps fwhm

1 phe 2 phe

Nr incident photons: ~400

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NDIP – 20 June 2008

Photon detectionefficiency Saturation

Page 24: Optimizing timing resolution of SiPM sensors for use in ...ndip.in2p3.fr/ndip08/Presentations/6Friday/73-Vinke.pdf · line-of-response (LOR) ... • Hamamatsu SiPM with 1 mm2 effective

NDIP – 20 June 2008

Coincidence timing resolution (preliminary)

MPPC 100U – Vop 69.77 V (1.14 V above breakdown )

� 600 ps fwhm

1 phe 2 phe

Nr incident photons: ~400PDE 100U: ~50%→ ~200 photoelectrons→ ~85 pixels fired

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NDIP – 20 June 2008

GATE/GEANT4 simulation of optical transport in crystal

• GEANT4 source code adapted to include effect of scintillation rise time on timing:

• Included detailed physics properties of scintillation emission spectrum; gamma absorption length spectrum; crystal surface reflectivity; SiPM fill factor; etc

Shao, Y. P., Phys. Med. Biol., vol. 52, pp. 1103-1117, 2007

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Summary

• ~ 100 ps single photon sigma timing resolution for Hamamatsu SiPM devices

• Pulse digitization allows flexible determination of timing properties

Page 27: Optimizing timing resolution of SiPM sensors for use in ...ndip.in2p3.fr/ndip08/Presentations/6Friday/73-Vinke.pdf · line-of-response (LOR) ... • Hamamatsu SiPM with 1 mm2 effective

NDIP – 20 June 2008

Outlook

• SiPM photosensor array on monolithic LaBr3 crystal

• MLE determination of 3D gamma interaction position for correcting DOI induced time dispersion