High countrate anger camera design for electronically collimated SPECT

Second detectors for Compton cameras will need to accommodate countrates on the order of 2-4 Mcps for good performance. A new high countrate Anger camera design for electronically collimated SPECT is being developed to recover position and energy information from a scintillation waveform typically resulting from the high likelihood for pileup at these countrates. Signal outputs from each PMT of the scintillation camera are digitized continually at 100 MHz into a ring buffer. When a Compton coincidence occurs, a snapshot of the digitized data is retrieved by a host computer for processing where correlations among the neighborhood PMT outputs are used to recover scintillation events from pileups and where position and energy information are subsequently computed. A new digital event detection algorithm is applied by using moving average filters and differentiator. The event signals generated from the new event counting algorithm are utilized to detect the starting time of each piled up event. Subsequent to detection and time estimation, a maximum likelihood position and energy estimation algorithm has been developed to deal with the highly piled up events