Ultra precise timing with SiPM-based TOF PET scintillation detectors

The combination of SiPMs with fast and bright scintillators, such as LaBr₃:Ce, seems very promising for application in time-of-flight (TOF) PET. We therefore conducted a series of experiments with the goal of obtaining the best possible timing resolution with SiPM-based scintillation detectors in order to establish a bench mark for future experiments with different detector designs. The detectors employed in our measurements consisted of two SiPMs (Hamamatsu MPPC-S10362-33-050C), which were directly coupled to small scintillation crystals, viz. LaBr₃:Ce and LYSO. An excellent coincidence resolving time (CRT) for ²²Na 511 annihilation photons of 99.5 ps ± 0.6 ps FWHM could be achieved at the optimized electronics and digitizer settings with two LaBr₃:5%Ce crystals. A CRT of 171.5 ps ± 0.8 ps FWHM was obtained with L(Y)SO crystals. These results compare well to the predictions of a statistical model which was developed to describe the timing performance of SiPM based scintillation detectors.