An algorithm for the reduction of metal clip artifacts in CT reconstructions

Abstract

Implanted surgical metal clips often produce objectionable artifacts in CT reconstructions. The artifacts appear as streaks which emanate radially from the site of the clip. It is shown in this paper that these artifacts stem primarily from motion of the clip during the scan. An algorithm is described which reduces the intensity of these artifacts. The procedure attempts to remove the metal object entirely from the scan data by replacing the measured projection values of rays that passed through a neighborhood of the clip with calculated values consistent with an object whose density is an average of the surround. Examples are given for head and body scans as well as for computer simulations which show substantial reduction of the streak intensity. Key words: computed tomography, artifacts, reconstruction algorithms, surgical clip streaks, starburst artifacts