Optimization of a Staggered 3-Layer DOI PET Detector with a 1 mm LYSO Pitch for High-Resolution Small Animal PET Imaging

Small animal positron emission tomography (PET) requires a submillimeter resolution for better quantification of radiopharmaceuticals. The aim of this study was to develop a staggered 3-layer depth-of-interaction (DOI) PET detector with a 1 mm crystal pitch for realizing a 0.5 mm small animal PET scanner of 52 mm ring diameter. The proposed small animal DOI PET detector had 3-layer staggered LYSO crystal arrays, an acrylic light guide with a 1 mm thickness, and a 4×4 SiPM (Hamamatsu, S13361-3050NE-04, Japan) array with a pixel pitch of 3.2 mm. The LYSO crystal had dimensions of 0.9 × 0.9 × 5.0 mm3 with a pitch of 1 mm. The 1st (10 × 9), 2nd (10 × 10), and 3rd (11 × 11) LYSO layers were stacked with a staggered configuration to encode DOI information in the 2D crystal map. In order to investigate the optimal reflector material and light guide thickness, the performance of the PET detector module was evaluated with different reflectors (ESR and BaSO4), and different light guide thicknesses (0.5, 1.0, and 2.0 mm). Sixteen SiPM anode signals were multiplexed into four positional signals by using a resistive network. The SiPM analog signals were digitized by CAMAC DAQ. The BaSO4 reflector resulted in better crystal identification than the ESR did. However, the energy resolution with the BaSO4 reflector (15.8±2.0%) was worse than that of the ESR reflector (11.1±1.0%). The acrylic light guide thickness of 1 mm resulted in the best crystal identification for both BaSO4 and ESR reflectors. In conclusion, a staggered 3-layer DOI PET detector with a 1 mm crystal pitch was developed by using a 1 mm thick light guide and BaSO4 reflector. In the near future, a prototype high-resolution small animal DOI PET scanner will be developed.2019 IEEE Nuclear Science Symposium and Medical Imaging Conferenc