Spatial Resolution Measured by a Prototype System of Two Four-Layer DOI Detectors for jPET-RD

We are developing a small animal PET scanner, "jPET-RD" to achieve high sensitivity as well as high spatial resolution by using four-layer depth-of-interaction (DOI) information of the detector. The jPET-RD is designed with two detector rings each composed of six DOI detector modules arranged hexagonally. The diameter of the field-of-view (FOV) is 8.8 mm, which is smaller than for typical small animal PET scanners. Each detector module consists of a 32 times 32 times 4 LYSO (Lu: 98%, Y: 2%) crystal array and a 256-channel flat panel position sensitive photomultiplier tube. The size of each crystal element is 1.46 mm times 1.46 mm times 4.5 mm. The crystal block consisting of a crystal array and reflector is placed on the central area of the 256ch FP-PMT (49 mm times 49 mm useful area) and coupled with silicone rubber. Previously, we developed a prototype detector for the jPET-RD and successfully implemented crystal identification for the detector module. In the present work, we develop a prototype imaging system for the jPET-RD. The system is composed of two prototype detectors and electrical circuits. We evaluated the spatial resolution of reconstructed images with the one-pair system of the two four-layer DOI detectors for the jPET-RD. The spatial resolution of 1.5mm was obtained at the center of FOV by the filtered back projection algorithm. The spatial resolution of better than 2 mm in the whole FOV was also achieved.