1. A radiation detector system comprising: plural detector units disposed about a bore configured to accept an object to be imaged, each detector unit configured to acquire imaging information at plural corresponding projection angles; and at least one processor operably coupled to the detector units, the at least one processor configured to: acquire projections at the projection angles of the detector units; organize the projections into groups based on the projection angles; for each group of projections, rotate a corresponding image from an original orientation so that the group of projections are parallel to a first axis of the rotated image, convolute and sum slices from the group of projections using kernels to provide a forward projection; perform a back projection to provide back projections; and rotate the back projections to the original orientation and sum the rotated back projections to provide a back projected transaxial image.