An investigation of methods of pileup rejection for 2-D array detectors employed in high resolution PET

Two methods of rejecting pileup events in 2-D array detectors used in positron emission tomography (PET) are investigated. Since the methods are based on different physical properties, they were investigated separately and in combination. Method one is based on the fact that valid events in the 2-D array detector occur only in a limited pulseheight range for each detector element, and by rejecting events outside these energy ranges, many of the pileup events can be rejected. Method two is based on the fact that most pileup event pairs have a time differential, which will cause a difference in the shape of the signal which increases the rise time of an integrated signal or the crossover time of a bipolar signal from a shaping amplifier. Method two proved to be somewhat better than method one. However, the ideal system would most likely use both methods simultaneously.