A Novel Readout Approach with Multiplexed Timing for High Timing Resolution TOF-PET Detector

It is challenging to read out the tens of thousands of signal channels in a TOF-PET system based on SiPMs. To reduce the complexity and meanwhile achieve the high timing resolution, we developed a scalable readout scheme that multiplexes timing signals of multiple SiPMs into one channel using a summing circuit and performs the one-to-one readout of energy signals by a Sigma-Delta circuit. When tested on a piece of 3×3×3 mm
³
LYSO crystal, the proposed scheme achieved a high coincidence timing resolution (CTR) of 109.45±1.24 ps FWHM with 9 SiPMs multiplexed (corresponding to a total effective detection area of 331.60 mm
²
). The degradation in CTR was only 22.06 ps from the single SiPM readout scheme. CTRs measured at different multiplexing ratios indicate our readout scheme is promising in effectively simplifying the readout electronics while providing excellent coincidence timing performance.