When metal objects are present in x-ray computed tomography (CT) scans, they are accompanied by bright and dark shadows and streaks, collectively called metal artifacts. These artifacts are due to physical processes that cause the assumption of linearity in the reconstruction to break down, so that the scanner projections cannot be accurately reconstructed using filtered backprojection or Radon transform inversion. The artifacts obscure information about anatomical structures, making it difficult for radiologists to correctly interpret the images or for computer programs to analyze them. The problem has existed for many years,1,2 and there has been re-