The focal spot model based high spatial resolution iterative reconstruction method for a dual-focus CT

Abstract

The spatial resolution is one the key performance indicators of a CT system. However, in some cases, the scanned specimen is difficult to be penetrated by the x-ray of micro-focus in certain projection views due to its special shapes and the limited energy of the x-ray source, which will eventually lead to the degradation of the spatial resolution. A dual-focus CT system is adopted to address this problem. In the dual-focus CT system, a macro-focus with the higher energy and power can be used for the scanning in the views where the micro-focus source is invalid. The main idea is to combine the high resolution of micro-focus source and the stronger penetration of the high power x-ray source. But the finite focal spot size of the high energy source is another limitation to the spatial resolution of the reconstructed image. In this paper, a focal spot model based iterative reconstruction method is presented to improve the spatial resolution of the dual-focus CT system. The finite focal spot size model is built and the weighted total variation optimization based method is adopted to further suppress the noises or artifacts caused by the inconsistency between the projections of different energies. Preliminary results are shown that significant improvements in spatial resolution have been achieved by the proposed method.