Patent ID: 7728834

Claim:
A method for reconstructing a three-dimensional image volume from a plurality of two-dimensional projection images of a subject, comprising: recording the plurality of two-dimensional projection images from a plurality of different projection directions by rotating a recording system having a real detector about a rotational axis and around the subject; modifying at least one of the projection images to provide a modified projection image which corresponds to a projection image recorded with a virtual detector having an axis aligned parallel to the rotational axis of the recording system so that projections of all voxels in a row and lying on a straight line parallel to the rotational axis are spaced apart an equal voxel spacing distance, this enabling, during consecutive sampling of voxels along the straight line, a determination of consecutive voxel locations by addition of the spacing distance; and calculating grayscale values of voxels of the three-dimensional image volume by back projection of the projection images including the modified projection image wherein, for voxels in the modified projection image (i) projection of each voxel positioned along the straight line is determined relative to a start point along the voxel row with only one addition and with no divisions, and (ii) a grayscale value of a pixel corresponding to one of the voxels in the modified projection image is accumulated to a gray scale value of the voxel with an addition.