Sophisticated 32 × 32 × 4-layer DOI detector for high resolution PEM scanner

We are now developing a sophisticated 32times32times4-layer depth of interaction (DOI) detector for a positron emission mammography (PEM) scanner which has both high resolution and high sensitivity. The candidate of scintillator is Lu1.8Gd0.2SiO5 (LGSO) or Lu1.9Y0.1SiO5 (LYSO) and each crystal size is 1.45 mm times 1.45 mm times 4.5 mm. The white plastic reflectors with thickness of 0.125 mm are inserted into a crystal block with different patterns for each DOI layer. The crystal block is coupled to a 256-channel flat panel position sensitive photomultiplier tube which has 16 times 16 at intervals of 3.04 mm. In this work, we evaluated the performance of a DOI detector with LGSO crystals by obtaining a two-dimensional (2D) position histogram of all crystal elements with 511 keV gamma-ray irradiation. Results show that 4,096 crystal elements (32 x 32 x 4) can be clearly identified on the 2D position histogram. As the average over all crystal elements, the energy resolution is 14.7% and the timing resolution is 849 ps in FWHM.