Evaluation of a small field of view SiPM array detector based on a LGSO:Ce pixellated scintillator

Abstract

Introduction Silicon photomultiplier arrays can be used in dedicated small field of view animal imaging detectors and especially in those used to head PET/MR studies in mice due to their small size and flexibility. Ce doped LGSO scintillator crystal is based on a mixture of LSO and GSO orthosilicates (Lu 2x-_ Gd 2-2x_ SiO 5 :Ce – LGSO:Ce) and has attracted researcher’s attention because of high density of 7 g/cm 3 , high light output (∼32000 ph/MeV) and fast scintillation decay time (∼40 ns). Purpose The purpose of this study is to investigate the behavior of the ArraySL-4 (4 × 4 element array of 3 × 3 mm 2 silicon photomultipliers) optical detector coupled to a 6 × 6 LGSO:Ce scintillator array, with 1.9 × 1.9 × 5 mm 3 crystal size elements, for possible applications in small field of view PET imaging detectors. Evaluation was carried out with 137 Cs radioactive source and results regarding energy resolution and peak to valley ratio are presented. Materials and methods We have developed a symmetric resistive charge division circuit to read out the signal outputs of 4 × 4 pixel SiPM array reducing the 16 pixel outputs to 4 position signals. The 4 position signals were acquired using a free running sampling technique. An FPGA (Spartan 6 LX150T) was used for triggering and signal processing of the pulses acquired using free running Analog to Digital Converters. Results and conclusion Evaluation shows a clear visualization of all discrete scintillator elements. The mean peak to valley ratio of the profiles on the image was measured equal to 13 while the mean energy resolution was measured equal to 18%.