Premium
Verification of radiosurgery target point alignment with an electronic portal imaging device (EPID)
Author(s) -
Dong Lei,
Shiu Almon,
Tung Samuel,
Boyer Arthur
Publication year - 1997
Publication title -
medical physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.473
H-Index - 180
eISSN - 2473-4209
pISSN - 0094-2405
DOI - 10.1118/1.598070
Subject(s) - isocenter , linear particle accelerator , imaging phantom , centroid , medical imaging , radiosurgery , offset (computer science) , optics , image guided radiation therapy , computer science , fiducial marker , nuclear medicine , physics , medical physics , computer vision , artificial intelligence , radiation therapy , beam (structure) , medicine , radiology , programming language
A procedure has been developed using an electronic portal imaging device (EPID) to verify that the center of a patient's lesion is aligned with the center of a treatment cone prior to treatment in a linac‐based stereotactic radiosurgery procedure. The coordinates of the lesion center are set on the Brown–Roberts–Wells phantom base using a target simulator. A 3 mm tungsten ball, mounted on the target simulator, is used as the reference point for the planned isocenter. The target simulator is then attached to an adapter mounted on the linac couch, and an EPID image of the simulated target is acquired. The center of the circular‐shaped radiation field is calculated from the centroid of the segmented EPID image, and the center of the tungsten ball is identified by an automated computer search algorithm. A summation filter is used to find the position of the lowest radiation intensity coincident with the center of the ball. The alignment error is defined as the difference between the center of the radiation field and the center of the ball. The accuracy of this method was tested and found to be within 0.2 mm. The advantage of the EPID‐based procedure is that it can give quantitative offset values quickly for immediate readjustment. We have found that the method is also a convenient tool for testing room laser alignment and the accuracy of the treatment cones.