Noise Optimization and Monte Carlo Simulation of a PET Detector Based on Continuous LSO Crystal and Large-Area APDs

With the ever increasing demands for higher spatial resolution, sensitivity, and reduced cost in PET, various approaches ranging from using finer crystal arrays to using continuous crystals are being pursued. One such gamma-ray detector consisting of a continuous slab of lutetium oxyorthosilicate (LSO) crystal coupled to large-area avalanche photodiodes (APDs) on both sides had previously been conceived. Preliminary measurements indicated fair spatial resolution of <3 mm FWHM, but better performance was expected based on an analytical detector model. Studies towards improving and understanding the performance of the detector are a current focus with particular attention to minimizing electronics noise. In order to more realistically predict the performance of the detector as a function of electronic noise levels, a detailed Monte Carlo simulation utilizing DETECT2000 has been developed incorporating the reported light output and intrinsic resolution of the scintillator, the optical photon transport mechanism, the quantum efficiency of the APD, excess noise due to the APD gain process, and electronic noise. Preliminary results indicate that with optimized electronics, the achievable spatial resolution using simple Anger logic should be ~1 mm FWHM for interactions at a fixed point in the crystal.