Thick Continuous Crystal Design for PET

Our goal is to develop a thick continuous detector with high spatial resolution (1-2-mm). We will use simulations with experimental measurements to examine performance of two crystal blocks: a 50x50x25mm(3) and a 25x25x25mm(3) block of LYSO. Based upon the light distribution pattern in the 50x50x25mm(3) crystal, calculations show that a minimum spatial resolution of 2mm can be achieved in the central region of the crystal with some degradation near the edges. Monte Carlo simulations modeling Compton scatter and scintillation photon travel paths indicate that with Anger positioning, a spatial resolution of 2mm is achieved in the central region of the crystal but there is a significant degradation near the crystal edge due to light reflections. We show that we can improve the spatial resolution obtained with Anger positioning at the center and the edges of the crystal by simulating 5mm deep slots cut into the entrance surface of the crystal. Using a maximum-likelihood (ML) positioning algorithm, there is some improvement in the spatial resolution in the central region, but a more noticeable improvement at the unslotted crystal edges. We perform simulations to determine the best spatial resolution that can be achieved in the two continuous LYSO crystal blocks. We measure the energy and timing resolution of both crystals as a first step towards measuring the spatial resolution.