Optimum Bandwidth Usage In Digital Coincidence Detection For PET

Abstract

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.