Automated verification of multileaf collimation using portal imaging

Advances in linear accelerator technology have led to the emergence of conformal radiotherapy, in which complex beam configurations can be utilized to maximize radiation dose to the treatment volume, while minimizing dose to adjacent critical structures. The beam configuration is optimized in terms of position, collimation and intensity in treatment planning. The adequacy of the treatment rests on the verification of the localized treatment volume with respect to the radiation beams. Verification is performed using megavoltage portal imaging on the treatment accelerator or linac. Errors affecting treatment delivery can arise either in the construction of the custom collimation, or in positioning the patient on the linac. The collimation shape is verified using edge detection with respect to a reference point defined by both a user and a user independent template method. Image registration of anatomical landmarks using Chamfer matching is used to compute positioning errors of the patient.