GATE Optical Simulation of a Dual-Ended Readout DOI PET Detector with Trapezoid Geometry

Abstract

GATE Monte Carlo optical simulation has been used widely as an excellent tool for the design and optimization of positron emission tomography (PET) detectors. Recently, our group has started to develop a small animal depth-of-interaction (DOI) PET scanner with a trapezoid geometry crystal for highresolution and high-sensitivity small animal imaging. However, modeling of a DOI PET detector with a trapezoid geometry crystal has not been studied yet because of the complex geometry. The aim of this study was to model this trapezoid geometry detector with a mixed SiPM pitch using GATE Monte Carlo optical simulation. The trapezoid geometry dual-ended readout PET detector consisted of a 13 × 11 LYSO crystal array, a 7×6 SiPM array (pixel pitch = 2.4 mm) and an 8×4 SiPM array (pixel pitch = 3.2 mm). The 20 mm long LYSO crystal had front and back pitches of 1.18 mm and 1.87 mm, respectively. The effect of the crystal surface roughness on the DOI resolution was investigated. The DOI resolution was calculated by using the signal amplitude ratio of the two SiPMs. We analyzed the GATE optical simulation output file by using a custom-written MATLAB code. In conclusion, we could identify all crystals in the 13×11 LYSO crystal array in the 2D flood map. The DOI resolution of 1.1 mm could be obtained by using a saw-cut LYSO crystal. In the future, we plan to validate the GATE optical simulation results by experimental results.