Programmable High Voltage Distribution for Photodetectors in a 1 mm Resolution Clinical PET System

We present a scalable, cost-effective, and compact high voltage (HV) distribution design for a system that requires many HV channels for photodetector biasing. A digital-to-analog converter (DAC) with a 100 V output range is floated with its reference at -1800 V, providing outputs between -1800 V and -1700 V. As a consequence, the DAC control and power signals are referenced to -1800 V. This design was implemented in our 1 mm resolution clinical PET imaging system with detectors comprised of LYSO scintillation crystals coupled to position-sensitive avalanche photodiodes (PSAPDs). The programmable bias voltage outputs have only 20 m V_pp of bias ripple. This design enables all PSAPDs to be biased at their optimal bias voltage, allowing us to achieve a standard deviation of only 2.3% in the energy resolution measured across all 512 PSAPDs in the subsystem.