Wedge field isodoses without wedge filters.

Wedge filters are now extensively used to produce skewed isodose patterns which can be combined for uniform treatment of a region such as the maxillary antrum. Overlapping fields can be employed to imitate such a treatment pattern, but there is relatively little mention of this method in the literature. Murphy (1) showed a diagram of two fields superimposed, indicating that these give a wedge effect, and Moss (2) has suggested a similar arrangement. We had believed that with a three-field combination a more homogeneous dose distribution would be achieved, and this method has given satisfactory uniform reactions. The purpose of this paper is to describe how, with cobalt-60 radiation, variations in incident doses and in field arrangements affect the dose distribution, and to show that two overlapping fields from each side can give a satisfactory distribution if certain combinations of doses are delivered. The dose diagram in Figure 1 is a typical example obtained with the field arrangement used originally, ...