For helical CT scans with a pitch smaller or equal to one the redundancy in the helical projection data can be used to generate images at the identical spatial position for multiple time points. As the scanner moves across the thorax during the scan, these images do not have a fixed time point, but a well-defined temporal distance inbetween the images. Using image based registration a motion vector field can be estimated based on these images. The motion artefacts are corrected in a subsequent motion compensated reconstruction. The method is tested on mathematical phantom data (reconstruction) and clinical lung scans (motion estimation and reconstruction).
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M. Grass, R. Bippus, A. Thran, D. Schäfer, S. Kabus, K. M. Brown, "Motion compensation for non-gated helical CT: application to lung imaging," Proc. SPIE 10573, Medical Imaging 2018: Physics of Medical Imaging, 105733H (9 March 2018);