Subpixel smoothing by floating grids for ring artefact reduction in fan-beam tomography

The distinctions between the artifacts of the tomographic data acquisition systems with parallel and fan-beam geometry are studied. A new method for suppressing such artifacts on the basis of subpixel smoothing by floating grids is proposed. A non-iterative algorithm based on the classical Shepp–Logan method of filtered back-projection with random shifts (within fractions of a pixel) of each detector element or each pixel of a tomogram is developed. According to the results of mathematical simulation using a variety of models, it is shown that the level of ring artifacts can be reduced by subpixel smoothing comparable to the existing methods of artifact suppression.