Investigation of low noise, low cost 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 ±75 fC dynamic range and have an intrinsic 120 e-rms noise level in each channel. The chips allow hardware adjustment of bias levels to allow gain uniformity of less than 5% for all channels within a chip. 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 a single APD pixel. The gain performance is very stable over all channels. Initial performance evaluation indicates that the chip has good performance and may be used as front-end electronics for the proposed PET system.