Calibration procedure for a DOI detector of high resolution PET through mixture Gaussian model

A depth of interaction (DOI) detector is developed for the next generation of PET scanners. The detector unit consists of 8×8 crystal blocks with 4 layers of 2×2 Gd₂SiO₅:Ce (GSO) arrays coupled to a 52 mm square position sensitive photomultiplier tube (PS-PMT). Each scintillation event is mapped in a two-dimensional (2D) distribution through the relative ratio of the output signals of the PS-PMT. To facilitate high spatial resolution imaging, accurate crystal identification is needed. A statistical model based on the approach of a mixture Gaussian model (MGM) is introduced for crystal identification. In the MGM, a cluster center and range attributed to individual peaks in the 2D distribution are defined. The MGM method is applied two times, once for the cluster centers and once for determination of the range. These results are used to generate a Look-Up-Table (LUT). This method successfully identifies 288 crystal elements composing 36 crystal blocks.