Study of low noise multichannel readout electronics for high sensitivity PET systems based on avalanche photodiode arrays

A compact, low noise, and low cost readout system based on commercially available application-specific integrated circuits (ASICs) is under investigation. These front-end circuits have been used to readout a prototype detector module comprising Lutetium Oxyorthosilicate (LSO) scintillation crystals coupled to avalanche photodiode (APD) arrays. A major goal for this work is to build a dedicated high performance breast imaging PET system. Characteristics of signal response, noise, pedestals and gain of the chip have been evaluated. The channels have a linear response to within 2% across a ±50 fC dynamic range. The circuits allow hardware adjustment of bias levels to allow gain uniformity of less than 5% for all channels within a chip and the gain performance is very stable over all channels. Initial tests of the chip when connected to a prototype APD array also showed good performance. 13% energy resolution was obtained with direct 5.9 keV X-ray interactions in an individual APD pixel. Initial performance evaluation indicates that the ASIC may serve as a foundation for front-end readout electronics for the proposed PET system.