Novel scatter correction for three-dimensional positron emission tomography by use of a beam stopper device

Modern positron emission tomography scanners generally perform three-dimensional data collection without septa, which increases not only true coincidences but also scattered coincidences. In this study, a beam stopper (BS) device which is made of lead was used to estimate the scatter component in the PET sinogram. Scattered events were then directly measured from those lines of response blocked by stoppers. By assuming that the scatter distribution is a spatially slow-varying function, the scatter component can be recovered using the cubic-spline interpolation from the local measurements. Monte Carlo simulations of an abdomen phantom and the Zubal phantom were performed. Preliminary results demonstrated that the proposed BS method can improve image contrast and quantitative accuracy. Among different configurations, the BS device consisting of twelve lead stoppers with 3 mm radius yielded the optimal result compared to the other BS configurations. This BS method also outperformed the dual-energy window method up to 40% based on the mean squared error. The results indicated that the proposed BS method permits a direct, fast, and accurate scatter correction.