An FBP-type reconstruction method for CBCT with significantly displaced detector

In conebeam CT (CBCT), detector displacement is an efficient way to enlarge the field of view (FOV). When the displacement is severe, existing analytical methods will suffer artifacts induced by insufficient sampling. In this work, pre-weighting, post-weighting and Katsevich-type filter backprojection (FBP) as well as backprojection filtration (BPF) methods are investigated for the reconstruction task in dental CBCT. A simple but efficient continuity correction method is proposed for the post-weighting and Katsevich-type FBP. During the padding step, the conjugated projection is scaled by a factor to keep the padded projection continuous. The improved FBP-type algorithm greatly reduced the artifacts brought by the detector displacement. Simulation data and clinical dental CBCT data are used to verify the proposed procedure.