Determination of scatter characteristics generated from out of FOV source in FDG-PET studies

Scatter correction is a necessary procedure in quantitative imaging with PET. In HR+, the scatter correction technique is based on estimating scatter ratio in images with the help of the transmission images. However such a technique is not able to correct for scatter originating from scanner out of field of view (OOFOV). In the present work, scatter is characterized with individual and dual sources in and out of the FOV using an HR+ in the usual 3D mode acquisition. The shape of a point source located out of the FOV as seen by detector rings, was found to be dependent on its distance to the scanner. Depending on the ring difference used in acquisition, planes opposite to the source detected approximately no counts, while the nearest planes depended more on the diameter of the scattering medium. An axial line source in FOV measured in the presence of a point source out of FOV, was found to have the shape of the point source and an average amplitude of the line source when both measured separately.