New reconstruction algorithm for stack artifact reduction in breathing-adaptive four-dimensional computed tomography

Background and Purpose: Even with new adaptive four-dimensional computed tomography (4DCT) techniques, artifacts can still occur with strong irregular breathing amplitudes. A new image reconstruction algorithm, currently available for cardiac CT, was tested on 4DCT data for its performance to reduce stack artifacts and thus improve anatomical correctness. Materials and Methods: The ‘ZeeFree' algorithm employs a deformable image registration during reconstruction to reduce remaining stack artifacts. Its performance was evaluated using data of 20 irregular breathing (‘challenging group') and 10 randomly selected (‘verification group') patients with tumors in the thorax. Using a 5-score-scale, image quality in terms of stack artifacts was rated by three physicians and three physicists. Statistical significance was assessed using the Wilcoxon signed-rank test for the mean ratings and the Chi-square test for anatomical correctness.