GPGPU-based optical propagation simulator of a laser processed crystal block for the “X´tal Cube” PET detector

X´tal cube is a next generation DOI detector for PET with high resolution and sensitivity that we are developing. It is constructed from a cubic scintillation crystal and silicon photomultipliers (SiPMs) coupled on various positions of six surfaces of the cube. A laser processing technique is applied to produce 3D optical boundaries composed of micro-cracks inside a monolithic scintillator crystal. In this paper, in order to design optical characteristics properly, we developed a Monte Carlo simulator which is able to arrange laser-processed optical boundaries (LPB) arbitrarily. Optical characteristics of LPB were measured using a set of laser and photo-diode and then modeled for simulator. Effectiveness of the simulator was confirmed from a comparison with the experiment using a cubic LYSO monolithic crystal with 6 × 6 × 6 segments. Furthermore, the simulator was accelerated by parallel computing with a general purpose GPU (GPGPU). Calculation speed with GPGPU was 350 to 430 times faster than that with only CPU.