DATA ACQUISITION DEVICE, PAIR ANNIHILATION GAMMA RAY DETECTOR, AND PAIR ANNIHILATION GAMMA RAY DETECTION METHOD

An apparatus and method for channel count reduction in solid-state-based positron emission tomography that multiplexes read-outs from photo-detectors using a sum delay circuit, including a sum channel and a delay-sum channel. The sum channel sums signals from sensors in an array and is digitized to extract the timing and energy information. A delay-sum channel includes a discrete delay line (305) that introduces a known delay after each sensor, creating a time signature for each sensor (301), followed by a summing circuit (303) that adds delayed signals. The delay-sum channel is digitized using a high speed counter (509) to extract location information. Start and Stop signals for the counter are derived when the sum channel output and the delay-sum channel output cross a pulse ID threshold, respectively. The pulse ID threshold is chosen to minimize the Compton Scatter and not clip photo-peak events.