An X-ray computed tomography (CT) image including metallic objects suffers from annoying metal artifacts such as
shades and streaks. In this paper, we propose a novel algorithm for reducing metal artifacts via a reprojectionreconstruction
process. In the proposed algorithm, we first reconstruct a CT image from the original projection data. We
then remove metallic object regions and replace them with the value of soft-tissue; apply total-variation-based smoothing
to the image in order to reduce streak artifacts while preserving the shapes of non-metallic objects; and obtain the
reprojection data of the smoothened image. Even though the reprojection data do not contain metallic objects, remaining
shade artifacts (especially in the regions between metal objects) still affect the reprojection data. Those artifacts are
found to be mainly concentrated in overlapping regions of metal-traces in the reprojection data. Hence, we horizontally
interpolate the overlapping region with intensity values of its boundary pixels. We then replace whole metal trace regions
in the original projection data with the processed reprojection data. The completed projection data are then used for the
reconstruction of the final image. The proposed algorithm can reduce streak and shade artifacts while preserving the
shape of non-metallic objects. It is proved that the proposed algorithm provides noticeably better performance in metal
artifact reduction compared with the algorithms based on linear interpolation and the model image reprojection.
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