Performance evaluation of a four-layer LSO detector for a small animal DOI PET scanner: jPET-RD

Previously we proposed a new depth of interaction (DOI) encoding method and proved that it worked successfully with four-layered Gd₂SiO₅ crystals for a small animal positron emission tomography (PET) detector. We are now planning a small animal PET scanner, jPET-RD (for Rodents with DOI detectors), which has both high resolution and high sensitivity. Scintillator for the scanner will be Lu_2(1-x)Y_2xSiO₅ (LYSO). In this work, we evaluated the DOI detector composed of four layers of 12×12 LYSO (Lu: 98%, Y: 2%) crystal array by irradiating 511 keV uniform gamma rays. For crystal identification, the new encoding method was used. The size of each crystal is 1.44 mm×1.44 mm×4.5 mm. The crystal block was coupled to a 256-channel flat panel position sensitive photomultiplier tube, which has 16×16 multi anodes at intervals of 3.04 mm. In this measurement, all crystals are expressed on a single two-dimensional position histogram without overlapping as we expected. Energy resolution of all events is 21.8 % and time resolution of all events is 0.69 ns in FWHM. The energy resolutions of the first, second, third, and fourth are 11.6%, 12.3%, 13.3%, and 12.5% and the time resolutions are 0.60 ns, 0.59 ns, 0.60 ns, and 0.66 ns, respectively.