CT metal artifact reduction based on sinogram surgery

Abstract

X-ray Computed Tomography (CT) is one of the most widely used technique for medical imaging to provide the anatomical structure of the body invaisively, and is also popular in industrial field to obtain the internal structure of the objects nondestructively. However, the streak artifacts in the CT images caused by the metallic objects (dental implants, surgical clips, or steel-hip) limit the applications of CT images. There have been various approaches to improve the CT images containing the streak artifacts

however, most of them generate additional artifacts or keep the remaining artifacts. In this paper, we propose a novel algorithm to reduce the metal artifact effectively without generating additional artifacts. We find the connected region surrounding the metallic objects and evaluate the average value of the region. Using the average value, we fill in the connected region and the region of metallic objects. Using this modified CT image whose CT numbers are constant near the metallic objects, we generate the sinogram containing the information of anatomical structure. We do the sinogram surgery iteratively to remove the metallic effect in the sinogram using the basic principle of CT image reconstruction. We apply our method to various shape of phantoms and to the real data, and we observe that it reduces the metal artifacts effectively. The results are analyzed both qualitatively and quantitatively. Moreover, we provide the convergence analysis of the proposed algorithm.