Prototype design of readout electronics for In-Beam TOF-PET of Heavy-Ion Cancer Therapy Device

Heavy-Ion Cancer Therapy Device (HICTD) developed by the Institute of Modern Physics of the Chinese Academy of Sciences is an advanced tumor radiotherapy device for nuclear medicine. The time of flight (TOF) positron emission tomography (PET) located on the beam line, called In-Beam TOF-PET, is a key detector in HICTD, which is employed for obtaining time, energy and position information of gamma ray to implement real-time image reconstruction during the treatment. A high performance readout electronics system has been designed for In-Beam TOF-PET. The Data Acquisition Unit (DAQU), a key device of it has been implemented. The signals from the In-Beam TOF-PET are acquired and processed by the DAQU, including 8 energy chains and 2 time chains. A field programmable gate array (FPGA) is adopted as a processor on board for implementing pulse area information extracting algorithm, FPGA-based TDC, and etc. The precision pulsar test indicates that the DAQU system has intrinsic influences on the energy resolution better than 5.5 parts per thousand (full width at the half-maximum, FWHM) and time resolution of 255 ps (FWHM). The Na-22 source test indicates that the overall system of the in-beam TOF-PET has an energy resolution of 14% FWHM at 511 keV and coincidence timing resolution better than 1.12 ns. The good position identification ability is indicated by the flood map, all the 484 crystals in one of LYSO crystal block detectors can be clearly distinguished.