Development of a 64ch SiPM-based TOF-PET Detector with High Spatial and Timing Resolutions Using Multiplexing Architecture

SiPM has excellent potential as a TOF-PET detector because of its fast response. One-to-one connecting of a SiPM and a fast (RF) amplifier is preferable for maximizing timing performance. Custom ASIC is one solution to realize it in a compact front-end electronics of a detector, but a huge development cost and a long development time are required. We developed a 64ch SiPM-based TOF-PET detector using SiPM multiplexing architecture in which SiPMs output signals are multiplexed into one timing signal for reducing timing channels. It causes the degradation of timing resolution due to dark noise and parasitic capacitance of SiPMs, but it can be improved by optimizing the parameter of readout circuit. Timing signal is generated by the leading edge discriminator. Position and energy signals are generated by Anger logic calculator and summing circuits with slow (video rate) amplifiers. Each SiPM is connected the capacitor for timing signals and resistor matrix for position signals. The proposed circuit makes it possible to read the timing signal and position (and energy) signals simultaneously without interference because of the difference in bandwidth of these signals. The developed detector applies four SiPM arrays (S13361-3050NE, 4 × 4 ch of 3 × 3 mm
²
, Hamamatsu) with a scintillator block consists of 2.1 mm × 2.1 mm × 15 mm LFS (Lutetium Fine Silicate, Zecotek) crystal in a 12 × 12 array. The front-end module is composed of two 32ch SiPM signals multiplexing circuits with fast amplifiers and discriminators for timing signal. Coincidence timing resolution of the developed detectors was estimated to be 286 ps (FWHM), and energy resolution was measured as 13.6 %. Moreover, all the crystals (12 × 12) were clearly separated on the 2-D position histogram, so the spatial resolution was estimated to be less than 2.3mm. These results suggest that our new detector is practical for TOF-PET.