Performance evaluation of a staggered 3-layer DOI PET detector using a 1 mm LYSO pitch with PETsys TOFPET2 ASIC: comparison of HAMAMATSU and KETEK SiPMs.

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In this study, we propose a staggered 3-layer depth-of-interaction (DOI) detector with a 1 mm crystal pitch and 19.8 mm total crystal thickness for a high-resolution and high-sensitivity small animal in-beam PET scanner. A three-layered stacked LYSO scintillation array (0.9 × 0.9 × 6.6 mm3crystals, 23 × 22 mm2surface area) read out by a SiPM array (8 × 8 channels, 3 × 3 mm2active area/channel and 50 μm microcell size) with data acquisition, signal processing and digitization performed using the PETsys Electronics Evaluations kit (based on the TOFPET v2c ASIC) builds a DOI LYSO detector block. The performance of the DOI detector was evaluated in terms of crystal resolvability, energy resolution, and coincidence resolving time (CRT). A comparative performance evaluation of the staggered 3-layer LYSO block was conducted with two different SiPM arrays fromKETEK and HAMAMATSU. 100 % (KETEK) and 99.8 % (HAMAMATSU) of the crystals were identified, by using a flood irradiation the front- and back-side. The average energy resolutions for the 1st, 2nd, and 3rd layers were 16.5 (± 2.3) %, 20.9(± 4.0) %, and 32.7 (± 21.0) % (KETEK) and 19.3 (± 3.5) %, 21.2 (± 4.1) %, and 26.6 (± 10.3) % (HAMAMATSU) for the used SiPM arrays. The measured CRTs (FWHM) for the 1st, 2nd, and 3rd layers were 532 (± 111) ps, 436 (± 108) ps, and 447 (± 111) ps (KETEK) and 402 (± 46) ps, 392 (± 54) ps, and 408 (± 196) ps (HAMAMATSU). In conclusion, the performance of the staggered 3-layer DOI detector with 1 mm LYSO pitch and 19.8 mm total crystal thickness was fully characterized. The feasibility of a highly performing readout of a high resolution DOI PET detector via SiPM arrays from KETEK and HAMAMATSU employing the PETsys TOFPET v2c ASIC could be demonstrated.

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Authors: Tim Maximilian Binder, Han Gyu Kang, Munetaka Nitta, Florian Roland Schneider, Taiga Yamaya, Katia Parodi, Florian Wiest, Peter G Thirolf