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 field size dependence of on-axis relative output from a linear accelerator can be well described by a model comprising two components. One component represents radiation emanating from a point source and the other represents radiation from a field size dependent distributed source. In this communication the application of the model is extended to off-axis situations and demonstrates that a good description of the dependence of off-axis output on collimator configuration can be obtained. Of particular clinical relevance in this regard is the beam profile of half blocked fields which are adequately reproduced. The model has also been applied to the study of profiles generated by simulated dynamic wedging.