1. A computed-tomography (CT) apparatus, comprising: processing circuitry configured to receive projection data representing an irradiance of radiation detected at a plurality of detectors, the projection data corresponding to a plurality of parallel scan slices measured at a non-zero tilt angle, reconstruct a plurality of thin-slice images, wherein each thin-slice image of the plurality of thin-slice images corresponds to a respective scan slice of the plurality of parallel scan slices, and the thin-slice image of the plurality of thin-slice images lies in a plane corresponding to the non-zero tilt angle, group the plurality of thin-slice images into thick-slice groupings corresponding to subsets of nearest-neighbor thin-slice images, and shift the thin-slice images within a thick-slice grouping based on a distance calculated using the tilt angle.