A local coincidence triggering system for PET tomographs composed of large-area position-sensitive detectors

A local triggering system composed of small overlapping triggering channels has been designed for use in PET (positron emission tomography) tomographs composed of continuous position-sensitive detectors. This triggering system functionally divides the continuous detectors into smaller subdetectors for the purposes of event detection and coincidence timing. Such a system is necessary in tomographs with a continuous detector ring, such as a cylindrical NaI(Tl) detector, where it is necessary to detect two coincident events in the same detector. A preliminary version of the local triggering system has been designed, and the effect of triggering channel size and overlap has been tested on a single large-area NaI(Tl) detector. Based on these tests it is concluded that such a coincidence triggering system is feasible and that the local triggering system may reduce coincidence triggering system deadtime significantly