Characterizing Single- and Multiple-timestamp Time of Arrival Estimators with Digital SiPM PET Detectors

In this paper, we make use of a recently proposed fully digital 8x16 SiPM array with per-pixel time-to-digital converters (TDCs), the SPADnet-I, to compare hardware-friendly, single-and multiple-timestamp time-of-arrival (ToA) estimators for PET. Two SPADnet-I sensors are used in coincidence, each coupled to a 3x3x5 mm(3) LYSO crystal wrapped in Teflon. We acquired and processed 100k coincidence events to extract the coincidence resolving time (CRT) of the system. Pre-processing steps were applied to the data to remove low-energy events and correct the TDC values. Results show a 8% improvement in CRT of the suggested multiple timestamp estimator with respect to the best performing single-timestamp estimator (from 313 ps to 288 ps).