PURPOSE The aim of this study is to evaluate the tracking accuracy of a commercial ultrasound system under relevant treatment conditions and demonstrate its clinical utility for detecting significant treatment deviations arising from inadvertent intrafractional target motion. METHODS A multimodality male pelvic phantom was used to simulate prostate image-guided radiotherapy with the system un...

Contrary to an earlier report [Anstis and Gregory, Q. Jl exp. Psychol. 17, 173-174 (1965)], we find that the sustained retinal motion caused by tracking a moving target over a stationary grating does not result in a motion aftereffect (MAE) which is equivalent to that resulting from comparable retinal motion caused by actual motion of a grating. The MAE associated with tracking generally occurs...

Two difficult issues in optical flow are motion discontinuities and large interframe motion. We present an algorithm that addresses both issues by first performing feature tracking and motion segmentation and then warping one of the images to reduce the interframe motion and avoid the motion discontinuities. The algorithm consists of three major phases: 1) feature selection, 2) feature tracking...

Motions of organs or extremities are important features for clinical diagnosis. However, tracking and segmentation of complex, quickly changing motion patterns is challenging, certainly in the presence of occlusions. Neither state-of-the-art tracking nor motion segmentation approaches are able to deal with such cases. Thus far, motion capture systems or the like were needed which are complicate...

Tracking accuracy for the CyberKnife's Synchrony system is commonly evaluated using a film-based verification method. We have evaluated a verification system that uses a webcam and a printed calibrated grid to verify tracking accuracy over three different motion patterns. A box with an attached printed calibrated grid and four fiducial markers was attached to the motion phantom. A target marker...

BACKGROUND Intrafractional motion can be a substantial uncertainty in precision radiotherapy. Conventionally, the target volume is expanded to account for the motion. Couch-tracking is an alternative, where the patient is moved to compensate for the tumor motion. However, the couch motion may influence the patient's stress and respiration behavior decreasing the couch-tracking effectiveness. ...