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Study of readout for groups of position sensitive avalanche photodiodes used in a 1 mm3 resolution clinical PET system

We are developing a 1 mm3 resolution, high sensitivity PET system for breast cancer imaging. The system comprises two 16cm × 9cm × 2cm detector panels each containing 2304 position sensitive avalanche photodiodes (PSAPDs) coupled to 8×8 arrays of 1×1×1 mm3 LYSO scintillation crystal elements for a total of 294,912 crystal elements. The LYSO-PSAPD detectors are multiplexed in pairs (“dual LYSO-PSAPD modules”) to reduce the number of channels, resulting in 9216 channels per panel. The readout system has a modular data acquisition structure based on a 36-channel readout ASIC. This system design has multiple dual LYSO-PSAPD modules read out by a single ASIC, with each dual module having an adjustable high voltage bias and gain. This paper characterizes performance when groups of dual LYSO-PSAPD modules are read out simultaneously.