APD performance in light sharing PET applications

An APD-based, light-sharing detector has been evaluated for use in PET. The detector configuration is a 2 × 2 array of 5 mm × 5 mm Hamamatsu S8664-55 APDs used to readout multi-crystal LSO blocks. Initially, a basic performance study was undertaken with a single APD coupled to a chemically etched 4 mm × 4 mm × 10 mm LSO crystal (teflon wrapped) using a custom, single-channel fast ASIC preamplifier. Timing and energy resolution measurements with a ²²Na source were performed using the monolithic LSO crystal coupled to the APD. The timing resolution of the APD channel in coincidence with a plastic scintillator coupled to a PMT was 870 ps FWHM. The energy resolution of the 511 keV photopeak was 12.1% FWHM. Based on these initial results, a 9 × 9 array of 2 mm × 2 mm × 20 mm LSO crystals was assembled and evaluated with a 2 × 2 APD array. The LSO block had an average energy resolution of 20.9% and a timing resolution of 2.47 ns FWHM. These results show that APDs are promising photodetectors for high-resolution and cost-effective PET systems utilizing light-sharing block detectors.