A Simulation Study on Optically Decoding Reflecting Windows for PMT Quadrant Sharing Scintillation Detector Block

A large number of decodable crystals per photomultiplier tube (PMT) can be achieved by using the PMT-quadrant-sharing (PQS) technique with proper optically reflecting windows to channel light distribution in scintillation detector block. However, to develop brand new optically decoding reflecting windows for a detector block with different crystal material, PMT size or decoding resolution, is still very time-consuming and also requires much experience. This study is to develop a computer software tool that can simulate an expected two-dimensional (2-D) crystal decoding map before implementing a real detector block with a new set of decoding reflectors. After comparing the experimental decoding data to the simulated results with the same reflector set on a block, data are feed to adjust the software parameters. More accurate decoding reflectors will then be created by the adjusted parameters. Our result shows the decoding simulation of a 10times10 BGO block can be finished within a few minutes, which is much faster than using the Monte Carlo simulation with "DETECT". This software has been evaluated by five different PQS blocks. Our preliminary study shows this simulation tool is very promising which can significantly reduce a new product developing time; only about two-three development cycles are needed to get to the final optimized decoding reflectors

I. Introduction

Alarger number of decodable scintillation crystals per photomultiplier tube (PMT) can increase spatial resolution in PET detectors without an accompanying increase in cost. High resolution crystal identification can be achieved by properly controlling the distribution of light to the PMTs. Many documents about high-resolution crystal decoding have been published in the past decade [1]–[4]. Some crystal decoding even involves multi-layer blocks using position-sensitive PMTs [5], [6].