Accounting for singles rate related phenomena in PET Monte Carlo-based simulations

Monte Carlo-based PET simulators are powerful tools to accurately generate projections of tracer distributions given scanner specifications and attenuating media distribution. Most of the available programs aim at simulating only the scattered and unscattered components of the PET signal and do not account for singles rate related phenomena such as random events and event losses that may occur at different levels of the event detection and data processing steps. In fact, such an algorithm would involve a dramatic increase in computation time. We have developed a model which gives the rate of the detected singles for each block of the scanner across time, according to the known activity levels and distributions of the different structures. We have integrated our singles rate model into an existing PET Monte Carlo simulator and validated the whole process against measured count rate performances. Simulated and measured data were found to be in good agreement.