TraPET: High performance small animal PET with trapezoidal phoswich detector

In recent years, small-animal PET scanners with depth of interaction (DOI) capability have been developed for molecular imaging research. The aim of this study is to perform simulations to design a high performance small-animal PET, called TraPET. TraPET has an inner diameter of 76.21 mm with 6 dual-layer phoswich detector modules. Each module is composed of a 5.0-mm-thick trapezoidal-monolithic-LSO crystal with a front face (surface facing toward the inside of the scanner) of 44.0×44.0 mm2 and a back face of 50.0×50.0 mm2 and a 25×25 array of LuYAP crystals with a 2.0×2.0 mm2 sensitive area with a 15.0 mm thickness. DOI information is extracted by a pulse shape discrimination method. The ability of event positioning in the trapezoidal-monolithic-LSO was evaluated by modeling the light distribution in the crystal using DETECT2000 and a 16×16 array of silicon photo-multipliers (SiPMs), with a 3.0 mm pixel size, selected as the photo-sensor. Also, the sensitivity and gap filling effect between modules were simulated using the Monte Carlo code, GATE. The new detector showed higher and more uniform sensitivity, as compared to scanners with rectangular-shaped detectors, because the trapezoidal-monolithic-LSO minimizes the dead space within the detector ring. In conclusion, our new detector proved to be a reliable design for small-animal PET with high spatial resolution by DOI information, and high sensitivity by high filling fraction.