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

In recent years, the detection of multiple photon timestamps and their processing for gamma time of arrival (ToA) estimation in PET systems has been a hot topic of research. These works have consistently shown that using multiple timestamps can improve the system timing resolution, which is especially useful in time-of- flight PET. In this paper, we make use of a recently proposed fully digital 8×16 SiPM array with per-pixel time-to-digital converters (TDCs) to compare single- and hardware-friendly, multiple-timestamp ToA estimators for PET in terms of Coincidence Resolving Time (CRT). The experimental setup includes two acquisition boards placed one on top of the other, with the sensors coupled to a LYSO scintillator. We acquired and processed 100k coincidence events to extract the performance of the system. Pre-processing steps were applied to the data to remove scattered events and correct the TDC values. Results show a 7% improvement in CRT of the suggested multiple timestamp estimator with respect to the best performing single-timestamp estimator