Count rate analysis of PET scanner designs based on a GSO depth of interaction detector with a large-area PS-PMT

We have estimated count rate properties of three-dimensional (3-D) positron emission tomography (PET) scanners based on a Gd₂SiO₅:Ce (GSO) detector with depth of interaction (DOI) capability using a large-area position-sensitive photomultiplier tube (PS-PMT). The proposed detector unit consists of 64 crystal blocks with four stages of 2×2 GSO arrays coupled to a 52-mm square PS-PMT which has small dead space. With appropriate light control in the crystal block, DOI information can be obtained using simple Anger-type positioning logic. Thus, dead-time factors can be calculated using a count rate model with standard acquisition architecture. Compton and photoelectric interactions in the scintillator and uniform cylindrical phantoms were tracked by Monte Carlo simulation programs. Since the DOI detector can provide high resolution throughout the entire field of view, 3-D PET scanners with a large solid angle covered by the detectors with relatively small ring diameters were simulated. The preliminary results suggest that, compared to current PET scanners, high noise equivalent count rate can be obtained by the proposed scanner designs despite the relatively large size of the detector module. The count rate performance can be improved by the reduction of single events that cause block dead-time losses at the cost of a slight decrease in sensitivity.