Characteristics of Clinac-18 wedged fields for 10-MV x rays

The characteristics of wedged fields which affect their clinical use have been examined for the 10-MV x-ray beam from the Clinac-18. The methods used for obtaining and analyzing the wedged-field data are discussed. These characteristics have been examined in terms of (a) the wedge angle, (b) the variation of the wedge angle with field size, (c) the variation in the angle through which isodose curves between the approximate depths of 5 and 15 cm are turned relative to the central axis as a function of depth, and (d) the variation of wedge central-axis transmission factor with field size. Analysis of the data pertinent to these categories is presented for the 15-, 30-, 45-, and 60-deg wedges. In addition, the effect of the 60-deg wedge upon the position of maximum dose on the central axis was determined.