Study of spatial resolution and depth of interaction of APD-based PET detector modules using light sharing schemes

Using 4 × 8 Hamamatsu S8550 APD matrices with 1.6 mm × 1.6 mm pixels and a 2.3 mm pitch, we compared the spatial resolution of light sharing schemes using block detectors to detector modules using 1-to-1 coupling between individual 2 mm × 2 mm × 10 mm LSO crystals and APD pixels. In addition, depth of interaction (DOI) measurement capabilities of the block detector were studied. Using neural network methods to determine the interaction position in a 10 mm thick LSO block, we achieved an intrinsic spatial resolution of 1.5 mm FWHM compared to 2.06 mm for individual readout. The DOI resolution varied between 1.8 and 3.0 mm FWHM.