Long acquisition times lead to image artifacts in thoracic C-arm CT. Motion blur caused by respiratory motion leads to decreased\r\nimage quality in many clinical applications.We introduce an image-based method to estimate and compensate respiratory motion\r\nin C-arm CT based on diaphragm motion. In order to estimate respiratory motion, we track the contour of the diaphragm in the\r\nprojection image sequence. Using a motion corrected triangulation approach on the diaphragm vertex, we are able to estimate a\r\nmotion signal.The estimated motion signal is used to compensate for respiratory motion in the target region, for example, heart\r\nor lungs. First, we evaluated our approach in a simulation study using XCAT. As ground truth data was available, a quantitative\r\nevaluation was performed.We observed an improvement of about 14%using the structural similarity index. In a real phantomstudy,\r\nusing the artiCHEST phantom, we investigated the visibility of bronchial tubes in a porcine lung. Compared to an uncompensated\r\nscan, the visibility of bronchial structures is improved drastically. Preliminary results indicate that this kind ofmotion compensation\r\ncan deliver a first step in reconstruction image quality improvement. Compared to ground truth data, image quality is still\r\nconsiderably reduced.
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