Fast implementation of the single scatter simulation algorithm and its use in iterative image reconstruction of PET data

In positron emission tomography (PET), scatter correction is generally performed prior to image reconstruction using a more or less exact model of the scatter processes. Those models require estimates of the correct emission and attenuation distribution in the imaged object, neglecting the fact that these estimates already contain scattered events, since they are computed from uncorrected data. The purpose of this work was to bypass this problem by incorporating scatter characteristics directly into the process of iterative image reconstruction. This could be achieved by an optimized implementation of the Single Scatter Simulation (SSS) algorithm which results in a significant speedup of the scatter estimation procedure. The scatter simulation was then included into the forward projection step of maximum likelihood image reconstruction. Results demonstrate that this approach leads to a more exact estimation of the scatter component which can not be obtained by a simple sequential data processing strategy.