Respiratory gating and @entity5 tracking for dynamic multileaf collimator delivery require accurate and real-time localization of the @entity2 position during treatment. Deriving @entity5 position from external surrogates such as abdominal surface motion may have large uncertainties due to the intra- and interfraction variations of the correlation between the external surrogates and internal @entity5 motion. Implanted fiducial markers can be used to track @entity5 fluoroscopically in real time with sufficient accuracy. However, it may not be a practical procedure when implanting fiducials bronchoscopically. In this work, a method is presented to track the @entity2 mass or relevant anatomic features projected in fluoroscopic images without implanted fiducial markers based on an optical flow algorithm. The algorithm generates the centroid position of the tracked target and ignores shape changes of the @entity5 mass shadow. The tracking starts with a segmented @entity5 projection in an initial image frame. Then, the optical flow between this and all incoming frames acquired during treatment delivery is computed as initial estimations of @entity5 centroid displacements. The @entity5 contour in the initial frame is transferred to the incoming frames based on the average of the motion vectors, and its positions in the incoming frames are determined by fine-tuning the contour positions using a template matching algorithm with a small search range. The tracking results were validated by comparing with clinician determined contours on each frame. The position difference in 95% of the frames was found to be less than 1.4 pixels (approximately 0.7 mm) in the best case and 2.8 pixels (approximately 1.4 mm) in the worst case for the five @entity1 studied.

XXXX tracking in fluoroscopic video based on optical flow.

@entity5 :: ('MESH:D009369', 'Disease') :: ['tumor', 'tumors'] @entity1 :: ('9606', 'Species') :: ['patients'] @entity2 :: ('MESH:D008175', 'Disease') :: ['lung tumor']
@entity2 :: (MESH:D008175,Disease) :: ['Lung tumor']
