Improving the precision and accuracy of Monte Carlo simulation in positron emission tomography

The authors present the methods used to improve the precision and accuracy of Monte Carlo simulations which are executed in different phases for the source distribution and the phantom, the collimators, and the detectors. This has been achieved by giving a more appropriate description of the materials used in the simulations and a better fitting of the Compton scattering and photoelectric effect absorption coefficients of the materials. For many events in which the original rays were directed generally towards the detectors, the precision of the final simulation can be improved by recycling them without reseeding the random number generator, giving them a second or greater chance of being detected. For simulation programs which cascade the simulation process into source, collimator, and detection phases, recycling can improve the precision of the simulation without requiring larger files of events from the source distribution simulation phase