A COMPARATIVE-STUDY OF METHODS FOR THE REGISTRATION OF PAIRS OF RADIATION-FIELDS

Accurate techniques for the registration of pairs of radiation fields, usually derived from simulator and portal films, are required if on-l ine portal imaging is to be used with maximum benefit to the patient. We report a quantitative comparison of the performance of three groups of registration techniques applied to field pairs derived from fifty simulator and 135 portal images acquired during the routine radiothera py of seventeen patients. Using the parameters of coverage and overcov erage we conclude that a method based on the combination of geometric moments up to order six outperforms both central plus individual Zerni ke moments up to order four and a generalized field-match-point method .