The weighted-distance scheme: a globally optimizing projection ordering method for art

The order in which the projections are applied in the algebraic reconstruction technique (ART) has a great effect on speed of convergence accuracy and the amount of noise-like artifacts in the reconstructed image. In this paper a new projection ordering scheme for ART is presented: the weighted-distance scheme (WDS). It heuristically optimizes the angular distance of a newly selected projection with respect to an extended sequence of previously applied projections. This sequence of influential projections may incorporate the complete set of all previously applied projections or any limited time interval subset thereof. The selection algorithm results in uniform sampling of the projection access space minimizing correlation in the projection sequence. This produces more accurate images with less noise-like artifacts than previously suggested projection ordering schemes.