Systems analysis of breath-to-breath ventilatory variations in man: Role of CO2 feedback

resulted in improved Monte Carlo simulation efficiency and indicates that variance reduction merits further investigation. These findings demonstrate the power of Monte Carlo simulation for studying scattered radiation in PET. In the future, the simulation will be used to investigate the use of radiotracers that emit cascade photons in addition to annihilation photons, to study the impact of increased time-of-flight resolution, to examine the contribution of scattered coincidences to attenuation scans, to calculate the probability necessary for maximum likelihood reconstructions, and to determine a scheme for eliminating scattered coincidences from images.