A study of intrinsic Crystal-pixel light-output spread for discrete scintigraphic imagers modeling

This paper is focused on the discrete scintillation imaging devices, consisting of crystal arrays and metal-channel dynode Hamamatsu 1" and 2" square position sensitive photomultiplier tubes (PSPMTs). These devices are suitable for nuclear medicine based high resolution applications, and, particularly, for single photon emission computed tomography (SPECT). The model of scintillation light distribution (SLD) previously developed was able to distinguish the responses from crystal-pixels with different side, but it was not detailed enough to explain the influence of crystal-thickness. For this reason the experimental data were reviewed to find a new and more adequate analytical model. The improved SLD model explains the influence both of crystal-side and crystal-thickness on the scintillation light-output spread. The SLD expression is quite simple and its spread depends only on one q-parameter. This expression is well adaptable over the range of examined crystal arrays. Furthermore, in the considered experiments, the SLD q-parameter was found linearly dependent on crystal-pixel shape factor S/V(S=blind-surfacearea,V=volume). An overview of discrete scintillation imager simulator (DISIS) computer code is reported. Major outcomes of this work are: 1) the improved expression of SLD, which consolidates the DISIS performances, and 2) a tool for local SLD-spread control in the imager field of view (FOV).