Computer simulation for design of depth encoding multicrystal detector for PET

A detector proposed by Murayama et al. (IEEE Trans. Nucl. Sci., vol. 45, no.3, p. 1152-7, 1998) for detection of depth-of-interaction (DOI) in PET consists of three-dimensionally arranged crystal blocks with proper optical reflectors and is coupled to an array of photomultiplier tubes. This detector has a great advantage in easiness and cost in fabrication. The authors built a simulator of such a detector which allows them to find appropriate values of parameters such as optical properties of crystal or detector unit geometry before making detectors actually. The simulator is based on the Monte Carlo method which traces the migration of optical photons generated by interaction of a gamma ray with crystal. First, the simulator performance was validated by comparing with the experimental data obtained with some prototype detectors. Then, on some parameters including refractive index of crystal, detector geometry, and light yield per interaction, appropriate values were investigated for accurate block discrimination from PMT output signals.