Improving DOI information using 3-layer crystals for small animal PETs

Improving the spatial resolution without sacrificing the sensitivity is one of the most challenging goals for small animal PETs. The 3-layer configuration that we propose consists of 7 mm long LuYAP and 7 mm long LSO crystals aligned with each other, and 5 mm long LSO crystals with an offset of 1.15 mm. The LuYAP crystals are attached to Hamamatsu H7546B multi-anode PMTs, and the sensitive cells of which are aligned to match the 5 mm long LSO crystals. To estimate the improvement of the spatial resolution, we also simulated the 2-layer configuration of LSO and LuYAP, each with a 9.5 mm length. The Monte-Carlo simulation shows that the 3-layer configuration has a potential to improve the spatial resolution by about 30-40% at 40.0 mm from the central axis over the 2-layer configuration. To study the 3-layer configuration, we started to test the 2-layer and 3-layer configurations and presented preliminary test results.