Simulation of imaging with sodium iodide crystals and position-sensitive photomultiplier tubes

The imaging characteristics of miniature gamma cameras that consist of a single sodium iodide (NaI(Tl)) crystal coupled to a position-sensitive photomultiplier tube (PSPMT) have been studied via Monte Carlo simulations. Images obtained with such cameras with the use of conventional position calculations exhibit considerable distortions, particularly compression. This study demonstrates that the distortions result primarily from nonuniform sensitivities of PSPMTs and secondarily from nonlinear responses of PSPMTs, light-reflection properties resulting from the treatments of crystals, and light-refractive properties of glass interfaces between crystals and photocathodes. Simulation results are compared to images obtained with a prototype miniature gamma camera