JAWS .2. A DESCRIPTION OF IN-AIR BEAM PROFILES FOR HALF BLOCKED AND DYNAMICALLY WEDGED RADIATION-FIELDS

in a recent paper [Med. Phys. 19, 1441 (1992)] it was shown that the f ield size dependence of on-axis relative output from a linear accelera tor can be well described by a model comprising two components. One co mponent represents radiation emanating from a point source and the oth er represents radiation from a field size dependent distributed source . In this communication the application of the model is extended to of f-axis situations and demonstrates that a good description of the depe ndence of off-axis output on collimator configuration can be obtained. Of particular clinical relevance in this regard is the beam profile o f half blocked fields which are adequately reproduced. The model has a lso been applied to the study of profiles generated by simulated dynam ic wedging.