Optimized raw data selection for artifact reduction of breathing controlled four-dimensional sequence scanning

•Optimized raw data selection can improve image quality and anatomical correctness without additional dose exposure by replacing missing or incorrect inspiration data with respective expiration data.•Approximately 2–5% of all scans show artefacts that are due to individual significantly longer breathing cycles and would benefit from the optimized reconstruction.•By replacing missing inspiration information with expiration data, the optimized binning approach ignores differences in tumor trajectory, potentially leading to contouring errors.•An improvement in radiotherapy treatment planning due to the avoidance of artefacts and consequently better image quality can be expected. Even with most breathing-controlled four-dimensional computed tomography (4DCT) algorithms image artifacts caused by single significant longer breathing still occur, resulting in negative consequences for radiotherapy. Our study presents first phantom examinations of a new optimized raw data selection and binning algorithm, aiming to improve image quality and geometric accuracy without additional dose exposure. To validate the new approach, phantom measurements were performed to assess geometric accuracy (volume fidelity, root mean square error, Dice coefficient of volume overlap) for one- and three-dimensional tumor motion trajectories with and without considering motion hysteresis effects. Scans without significantly longer breathing cycles served as references. Median volume deviations between optimized approach and reference of at maximum 1% were obtained considering all movements. In comparison, standard reconstruction yielded median deviations of 9%, 21% and 12% for one-dimensional, three-dimensional, and hysteresis motion, respectively. Measurements in one- and three-dimensional directions reached a median Dice coefficient of 0.970 ± 0.013 and 0.975 ± 0.012, respectively, but only 0.918 ± 0.075 for hysteresis motions averaged over all measurements for the optimized selection. However, for the standard reconstruction median Dice coefficients were 0.845 ± 0.200, 0.868 ± 0.205 and 0.915 ± 0.075 for one- and three-dimensional as well as hysteresis motions, respectively. Median root mean square errors for the optimized algorithm were 30 ± 16HU2 and 120 ± 90HU2 for three-dimensional and hysteresis motions, compared to 212 ± 145HU2 and 130 ± 131HU2 for the standard reconstruction. The algorithm was proven to reduce 4DCT-related artifacts due to missing projection data without further