Sampling the point-spread-function of a positron emission tomograph

A procedure has been developed for decreasing the sampling interval for positron emission tomographs (PETs). For this procedure to be incorporated into a PET, the gamma ray detectors of the PET must provide depth-of-interaction (DOI) information for the detection of the gamma ray. Four radial, as well as an angular, address were provided for each scintillation detector in the tomograph ring for the PET tested. By tilting each detector toward its neighbor, the four radial segments subtended an angle that is one quarter of the angle between the untilted detectors. The utility of the improved sampling has been demonstrated by measuring the point-spread-function (PSF) for a 1 mm source placed at two locations 4 mm apart near the axis of the PET under test. With the untilted detectors, each of the PSF peaks was difficult to identify with its 3 sampling points. With the tilted detectors, the 12 sampling points clearly delineated each of the two PSF peaks. It should be noted that only the sampling, and not the spatial resolution, of the PET has been improved by tilting the detectors