A high speed fully digital data acquisition system for Positron Emission Tomography

The availability of compact arrays of high speed analog to digital converters and fast field programmable gate arrays allow much of the complex analog signal processing chain in nuclear pulse processing data acquisition to be replaced with digital algorithms. The fully digital approach allows us to evaluate APD based PET detectors and time of flight (TOF) capable fast PMTs using the same digital data acquisition (DAQ) system. We have developed digital processing algorithms for recording the time, position, and energy from a 511 keV photon interaction with a lutetium-oxyortho-silicate (LSO) crystal array coupled to a Position Sensitive Avalanche Photodiode (PSAPD) or to a XP2020 Photonics PMT as the scintillation light photodector. Implementing these algorithms in a Pixie-4 setup, we compared its performance to an analog setup based on NIM electronics modules, and we evaluated its coincidence time performance using utra-fast PMTs. From our initial experiments, the Pixie-4 system performs well in high spatial resolution, high count rate PET applications with our PSAPD detectors and with fast PMTs that are capable of TOF PET applications.