Monte Carlo simulation study on the time resolution of a PMT-quadrant-sharing LSO detector block for time-of-flight PET

We developed a detailed Monte Carlo simulation method to study the time resolution of detector for time-of-flight positron emission tomography (TOF PET). The process of gamma ray reaction in detector, scintillation light emission and transport inside the detector, the photoelectron generation and anode signal generation in the photomultiplier tube (PMT), and the electronics process of discriminator are simulated. We tested this simulation method using published experimental data, and found that it can generate reliable results. Using this method, we simulated the time resolution for a 13×13 detector block of 4×4×20 mm³ lutetium orthosilicate (LSO) crystals coupled to four 2-inch PMTs using PMT-quadrant-sharing (PQS) technology. We analyzed the effects of several factors, including the number of photoelectrons, light transport, transit time spread (TTS), and the depth of interaction (DOI). The simulation results indicated that system time resolution of 300–350ps should be possible with currently available fast PMTs. This simulation method can also be used to simulate the time resolution of other detector design method.