A ROBUST METHOD OF MULTILEAF COLLIMATOR (MLC) LEAF-CONFIGURATION VERIFICATION

We present here a novel and robust method for leaf-position verificati on with a multileaf collimator (MLC). On the portal image associated w ith an MLC-generated treatment field, air true treatment-held-edge lin es are either parallel or perpendicular to each other. This unique fea ture of an MLC treatment held has been fully exploited by our method. Employing a Hough-type transformation as an edge-line-orientation dete ctor and a chamfer-matching method, we can find the best matching para meters (including translation, rotation and scaling) adaptively betwee n a prescribed MLC leaf configuration and the actual treatment-field e dges generated by the MLC system. This works even if the portal image is partially corrupted by noise or covered by compact bony structures. Comparing these parameters with clinically accepted tolerances, we ca n make a 'go-or-no-go' decision quickly.