On light sharing TOF-PET modules with depth of interaction and 157 ps FWHM coincidence time resolution

M Pizzichemi,S Tavernier,A Polesel,S Gundacker,M Paganoni,E Auffray,G Stringhini,P Lecoq

doi:10.1088/1361-6560/ab2cb0

Abstract

The performance of a light sharing and recirculation mechanism that allows the extraction of depth of interaction (DOI) are investigated in this paper, with a particular focus on timing. In parallel, a method to optimize the coincidence time resolution (CTR) of PET detectors by use of the DOI information is proposed and tested. For these purposes, a dedicated 64-channels readout setup has been developed with intrinsic timing resolution of 16 ps FWHM. Several PET modules have been produced, based on LYSO:Ce scintillators and commercial silicon photomultiplier (SiPM) arrays, with mm2 individual SiPM size. The results show the possibility to achieve a timing resolution of 157 ps FWHM, combined with the already demonstrated spatial resolution of 1.5 mm FWHM, DOI resolution of 3 mm FWHM, and energy resolution of 9% FWHM at 511 keV, with 15 mm long crystals of section mm2 and mm2. At the same time, the extraction of the DOI coordinate has been demonstrated not to deteriorate the timing performance of the PET module.

Highlights

Positron emission tomography (PET) is a clinical and pre-clinical diagnostic technique based on the simultaneous detection of pairs of 511 keV gamma rays emitted from the annihilation of a positron with an electron (Del Guerra et al 2016)
We recently proposed a method to obtain depth of interaction (DOI) information with high resolution, in the order of 3 mm FWHM, based on a simple light sharing and re-circulation scheme in single side readout and without the need for one-to-one coupling between crystals and detectors (Pizzichemi et al 2016, Stringhini et al 2016)
We developed a 64-channels readout setup with excellent timing resolution, to test the performance of a DOI extraction method, previously proposed by our group, based on light sharing

Summary

Introduction

Positron emission tomography (PET) is a clinical and pre-clinical diagnostic technique based on the simultaneous detection of pairs of 511 keV gamma rays emitted from the annihilation of a positron with an electron (Del Guerra et al 2016). This measurement is usually performed by several rings of crystal scintillators, such as L(Y)SO:Ce or BGO, coupled with photo-detectors, like photomultiplier tubes (PMTs) or silicon photomultipliers (SiPMs). Preclinical and organ-dedicated human PET scanners require very high levels of spatial resolutions, typically in the order of 1–2 mm This is usually achieved by developing detectors based on scintillators with small cross-section, to improve the localization of the gamma interaction point in the radial coordinate. Due to the limitations of the acquisition setup, at that time we were not able to investigate fully the timing capabilities of this method, and especially the influence of DOI on coincidence time resolution (CTR)

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