Optimum Bandwidth Usage In Digital Coincidence Detection For PET

In positron emission tomographs (PET), the ratio of time coincident events to single events is less than one out of twenty. A significant reduction in the bandwidth necessary to transmit the coincident events to a histogramming circuit can be achieved by using this fact. Since the coincident events occur randomly, there is a finite chance that no coincident events occur within a clock cycle. We present an architecture that uses the vacant clock cycles to transmit any extra events that occur during non-zero clock cycles. An analysis of this architecture along with a Monte Carlo simulation show that a reduction in complexity can be achieved while maintaining virtually no event loss at coincidence rates near channel saturation. This architecture has been implemented in a VLSI gate array and is presented in the paper.