Development of a detector module for Time-of-Flight PET with improved timing performance

The propagation time of the photons inside the scintillators, to a large degree, is responsible for degradation of Coincidence Timing Resolution (CTR) in PET scanners. This effect is a liming factor to reach a timing resolution suitable for Time-of-Flight (TOF) applications. We have developed a single sided readout detector module with Depth of Interaction (DOI) capability where the DOI information is used to correct for this degradation in timing. The detector module is composed of an array of $4 \times 4$ pixelated LYSO crystal with a pixel size of $3 \times 3 \times 20$ mm 3 in one to one coupling with an array of SiPM from Hamamatsu and readout with TOFPET2, a high performance front-end ASIC with integrated TDC (time binning of 30ps). The lateral surfaces of the crystal pixels are optically depolished and separated by a reflective foil, but scintillation photons can be shared between the pixels by having a light guide on top of the crystal. With this method, which is investigated and validated in the previous study, the DOI information can be extracted. In this study, this DOI information is used to estimate and correct for the the delay in arrival time of the photons inside the crystal to improve the CTR. The results have shown an improvement of 64 ps.