Image reconstruction in asymmetric fan-beam scans with spatially varying focal lengths

We propose a generalized algorithm for image reconstruction from data acquired in an asymmetric fan-beam configuration with a spatially varying focal length. This algorithm is an extension of our previous algorithm for fan-beam computed tomography (CT) that involves a shift-variant filtering. As compared to the existing algorithms, the proposed algorithm involves no additional explicit interpolation and eliminates the spatially-variant weighting factor. Therefore, it retains the spatial resolution and is less susceptible to data noise. We performed computer-simulation studies to validate and evaluate the proposed algorithm, and quantitative results demonstrate that the proposed algorithm possesses desirable noise and numerical properties.