Design of compact gamma imager based on pixellated crystal array with high resolution

Abstract

For scintillation camera, recently there have been many research of gamma imager based on position-sensitive photomultiplier tube (PSPMT) coupled with optical guide and pixellated crystal array. For its design, there is a need to optimize several parameters of collimator, crystal with high sensitivity and high spatial resolution. In this study, theoretical investigation and experimental analysis have been performed for the better design of a small gamma camera based on PSPMT through several experiments. The optical photon transport within a scintillating crystal and the emitted photon distribution were simulated by using Monte Carlo method. Based on this simulation, we estimated final photon images from the PSPMT model(R2486) by accounting for the resistive network method. As using this program composed of Monte Carlo method and the resistive network method, we described the whole system of gamma imager and decided many parameters effecting sensitivity and spatial resolution for design of gamma imager. From the simulation results, we found that the images using a pixellated crystal array gives much better positioning accuracy and smaller dead zone than a disk crystal. The detailed simulation results will be discussed in this thesis. Gain variations and position capabilities for the surface of PSPMT by LED scanning test were acquired before experiments and the records were used for correction. Based on the simulations, a prototype gamma imager was developed and then tested by acquiring point and line source images for 662 keV gamma ray. It was found that the images using CsI(Tl) array could give small geometric compression in the image and it means that the images using CsI(Tl) array has the possibility of high spatial resolution because the resolution has the limitation to be able to be achieved by correction method. As last results, it was demonstrated that pixel lookup table using pixellated crystal array easily corrected the images.