Improve spatial resolution by projection restoration for CT reconstruction

The finite focal spot size is one of the major physical limitations to the spatial resolution for CT reconstruction. In this paper, a projection restoration based method is proposed to improve the spatial resolution. First of all, the focal spot size is considered into the projection model. Then the equivalence relation between the measured projection and the ideal projection is deduced. Based on such relation, the equivalent ideal projection can be recovered from the measured data before reconstruction. Finally, a high-resolution image is reconstructed using the recovered projection. Furthermore, an improved Nonlocal Mean method is presented to suppress the noise in the highresolution image. Both numerical simulation and experiment results have shown that the proposed method with the outstanding performance and efficiency characteristics can significantly enhance the spatial resolutions.