CHARACTERIZATION AND CORRECTION FOR SCATTER IN 3D PET USING REBINNED PLANE INTEGRALS

The scatter characteristics of three-dimensional (3D) positron emissio n tomography (PET) in terms of the plane-integral scatter response fun ction (SRF) are studied. To obtain the plane-integral SRF and study it s properties, Monte Carlo simulations were carried out which generated coincidence events from point sources located at different positions in water-filled spheres of various sizes. In each simulation, the plan e-integral SRF is obtained by rebinning the detected true and scatter events into two separate sets of plane integrals and then dividing the plane integrals of scatter events by the plane integral of true event s of the plane in which the point source is located. A spherical PET s canner was assumed for these simulations, Examination of the SRF shows that the SRF in 3D PET can be modeled not by an exponential function as in the case of 2D PET, but by a Gaussian with its peak shifted away from the primary peak Using this plane-integral SRF, a scatter correc tion method was developed for 3D PET that first converts an attenuatio n-corrected 3D PET data set into plane integrals, then obtains the sca tter components in the rebinned plane integrals by integral transforma tion of the rebinned plane integrals with the SRF, and finally subtrac ts the scatter components from the rebinned plane integrals to yield t he scatter-corrected plane integrals. From the scatter-corrected plane integrals, a 3D image was reconstructed by using a 3D filtered-backpr ojection algorithm. To test the method, a cylindrical PET scanner imag ing an ellipsoid phantom with a 3-cm cold bar at the center was simula ted, and 3D images of the phantom with and without scatter correction were reconstructed. Comparison of the two images shows that this metho d compensates reasonably well for scatter events. The advantages of th e proposed method are that it treats the scatter in 3D PET in a truly 3D manner and that it is computationally efficient.