New filter being derived from the modification of projection filter is proposed and its performances are also investigated. It takes the correlation coefficients among the pixels into account in the case of designing the filter algorithm, then the mean square error between the original image and the image obtained by this restoration method decreases. When the space to be projected is different from the range space of the conjugate form of the matrix which generates blurred image, the proposed filter can reduce the zebra lattice which is caused by the projection filter.
The scatter fraction near the boundary for various stepped phantoms was measured using the segment method. If the difference in thickness of both sides of the step were great, the measured distribution of scatter fractions near the boundary of stepped phantoms were similar to boundary. However, if the difference in thickness of both sides of the step become smaller, the measured values of scatter fraction near the boundary of the stepped phantoms were almost equal to that near the center of each step.