Performance characterization of a novel thin position-sensitive avalanche photodiode-based detector for high resolution PET

We are developing advanced dedicated breast and small animal positron emission tomography (PET) systems with detectors comprising arrays of 1times1times3 mm³ LSO crystals coupled to novel, extremely thin position-sensitive avalanche photodiodes (PSAPD). This thin PSAPD is essential for achieving high crystal packing fraction for a PET system design which has 2 cm effective LSO crystal thickness, 1 mm transaxial spatial resolution and 3 mm directly measured photon DOI resolution. These properties facilitate high detection efficiency and three dimensional positioning capability in the detector. With this very thin PSAPD, preliminary results indicated that we can expect 1 mm³ intrinsic spatial resolution. We have observed an average of 1.1 mm transaxial and 3 mm DOI spatial resolution, ~11% energy resolution and ~2 ns temporal resolution. We have also implemented a position algorithm for reducing the effect of pincushioning on events detected over the face of the PSAPD