A cross-stack quasi-monolithic detector with DOI capability for a small animal PET

We report on the new design of a detector module with depth of interaction (DOI) based on a quasi-monolithic LSO crystal, a multi-channel sensor, and a maximum-likelihood position-estimation (MLPE) algorithm. In our detector design, two layers of quasi-monolithic crystal elements are stacked crosswise. Each layer consists of eight crystals which are separated from each other in one direction, and are monolithic in the other direction. The size of each crystal is 2.0×16.0×10.0 mm. The light transport and detection in the cross-stack quasi-monolithic detector were modeled using DETECT2000 code, and the lookup tables (LUTs) were built using simulations. Events were well separated by applying the MLPE method with a 2.0 mm spatial resolution in the X-Y plane and for four depths in the DOI direction. The results demonstrated that the proposed detector provides dependable positioning capability for a small animal PET.