Inter-crystal scatter identification for a depth-sensitive detector using multi-anode outputs

In conventional PET detectors, detected events are projected to a 2D position histogram using the Anger calculation for crystal identification. Inter-crystal scatter (ICS) events causes mispositioned crystals because peaks with projected each crystal in the histogram are blurred. A depth of interaction (DOI) detector has been developed for the small animal PET scanner: jPET-RD. This DOI detector uses four-layered arrays of 32 x 32 crystals and a 256-channel multi-anode flat panel photomultiplier tube (FP-PMT). Each crystal element is 1.45 mm x 1.45 mm x 4.5 mm. The FP-PMT has a large detective area and small anode pitch. We think that the FP-PMT has a potential for the trace of the scattered gamma rays in the crystals. In this study, we therefore propose a novel method for ICS estimation using the principle component analysis (PCA). The PCA is applied to multiple-anode outputs in order to discriminate photoelectric events from ICS events. The 1st principle component depends on number of anode outputs deposited energy through the preprocessing. Numerical simulation results shows that the rate of the ICS identification by the proposed method is about 77.6 % at a 511 keV uniform irradiation. Also, PCA method can be identified only events which have large effect on spatial resolution in the ICS events. The proposed method can archive a true subtraction of ICS from measured events.IEEE 2006 Nuclear Science Symposium, Medical Imaging Conferenc