Development of Single-Ended Readout DOI Detector With Quadrisected Crystals

In this article, we developed the novel single-end readout depth-of-interaction (DOI) detector with quadrisected crystals comparable in size to a single photo sensor. The proposed DOI detector consists of 784 gadolinium aluminum gallium garnet (GAGG) crystals, which are arranged in four layers of $14\times14$ arrays coupled with an $8\times8$ multipixel photon counter (MPPC) array. The size of each GAGG crystal is $1.45\times 1.45\times4.5$ mm3. Also, each MPPC has a surface area of $3.0\times3.0$ mm2. One pair of four-layered crystals coupled with a partial optical window is arranged across two MPPCs. Boundaries without the partial optical window are covered with optical reflectors. Light sharing is done between a pair of four-layered crystals optically coupled at one end. Each pair is coupled with paired silicon photomultipliers of different patterns. Crystal identification from each pair is obtained from the output rate of two MPPCs. From 511-keV uniform irradiation, responses of all crystal elements in the four layers can be separated clearly on a 2-D position histogram after applying the Anger calculation. Also, DOI information can be mapped to each cluster on curved lines. The energy resolution for all crystals is 9.1% after event reduction of intercrystal scatter.