Development of the coincidence sorter for the INSIDE PET system

Positron emission tomography (PET) has gained interest as one of the most reliable techniques for in-vivo range monitoring in particle therapy. The INSIDE project uses a new SiPM based PET implementation that processes individually each single photon acquired by two detector plates placed close to the patient. In order to detect coincidences in the single photons stream, a fast sorter architecture has to be developed. This work proposes an implementation compatible with the Altera Cyclone V available in the main data acquisition board of the INSIDE PET acquisition system. The sorting is performed by several merging steps on the incoming data packets. Two different sorter architectures have been implemented and tested. The first one uses 2-input comparators, the second one uses 3-input comparators. A test-bench is developed to verify the functionality and the performance of the event sorter. The sorter functionality is validated by comparing its results with off-line post-processed data. For the given maximum clock of 200 MHz, 28 MHz throughput rate is achieved with the 2-input comparators and 40 MHz with the 3-input comparators.