| CPC A61B 5/0036 (2018.08) [A61B 6/12 (2013.01); A61B 6/463 (2013.01); A61B 6/466 (2013.01); A61N 5/1049 (2013.01); A61N 5/1064 (2013.01); A61N 5/1067 (2013.01); A61N 5/107 (2013.01); A61B 6/025 (2013.01); A61N 2005/1062 (2013.01)] | 20 Claims |

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1. A system for generating a repositioning signal for adjusting a target volume relative to an isocenter of a radiation therapy device, comprising:
a computer processing device configured to:
obtain images from the radiation therapy device, the images having been generated by irradiating the target volume with radiation beams at a series of projection angles;
determine trajectories of radiation beams through the target volume from the generated images;
determine a measure of correlation between the determined beam trajectories and corresponding reference beam trajectories, the reference beam trajectories having been obtained from reference images of the target volume at the series of projection angles;
evaluate the measure of correlation over the series of projection angles;
determine a change in the measure of correlation;
determine a displacement of the target volume based on the determined change in the measure of correlation; and
generate a repositioning signal based on the determined displacement,
wherein the repositioning signal indicates an amount and direction of adjustment for the target volume relative to the isocenter.
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