Abstract
This paper deals with the metal artifact problem in X-ray computed tomography (CT). If an X-ray opaque structure (metal object) is present in the region to be examined, metal streak artifacts may appear in the reconstructed image, resulting in a non-diagnostic image. In traditional analytical metal artifact reduction (MAR) methods, the part of the projection data affected by the metal object is removed from the original projection data, and the removed part is filled in by interpolation. Then, an image is reconstructed from the interpolated projection data using the filtered back-projection (FBP) algorithm. These methods can considerably reduce metal steak artifacts, but a satisfactory image still may not be reconstructed due to interpolation errors. It is known that the interpolation errors which arise during the interpolation step lead to DC-shift and shading artifacts in the reconstructed images. In the FBP-type MAR algorithm, the interpolated projection data is filtered using a non-local ramp filter before back-projection, which propagates the interpolation errors to the whole projection data. In this paper, we propose a differentiated back-projection (DBP)-type MAR method to reduce the effect of interpolation errors and consequently reduce DC-shift and shading artifacts. We expect image quality to be improved by the proposed method because the DBP reconstruction algorithm is able to apply non-local filtering after back-projection along the preferred Hilbert filter direction. This property helps to reduce the propagation of interpolation errors. A simulation study was performed to evaluate the proposed method.
