Preliminary performance evaluation of the prototype system for a brain DOI-PET scanner: jPET-D4

A high-performance brain PET scanner, jPET-D4, which provides depth-of-interaction (DOI) information, is under development. The scanner is designed to achieve not only high spatial resolution but also high scanner sensitivity with the DOI information obtained from multi-layered thin crystals. The scanner has 5 rings of 24 detector blocks each, and the detector block consists of 1,024 GSO crystals of 2.9 mm×2.9 mm×7.5 mm, which are arranged in 4 layers of 16×16 arrays. At this stage, a pair of detector blocks and a coincidence circuit has been assembled into an experimental prototype gantry. In this paper, as a preliminary experiment, we have investigated the performance of the jPET-D4´s inherent spatial resolution and noise characteristics using the prototype system. Spatial resolution and background noise were measured by using a line source and a uniform cylinder phantom respectively. To avoid systematic error and reduce computational cost in image reconstruction, the DOI compression (DOIC) method followed by the ML-EM with accurate system modeling, that we have previously proposed, was applied. Experimental results showed that the JPET-D4 achieves less than 3 mm spatial resolution over the field-of-view. Trade-off results between spatial resolution and background noise also promise an excellent performance of the scanner.