Wedge design and dosimetry for 25-MV X rays

The design and construction details of wedge filters for 25-MV x-ray beams are presented. The authors studied how the characteristics of wedged fields affect their clinical use with 25-MV x-rays, paying particular attention to the effects of (a) the wedge angle, (b) the variation of the wedge angle with field size, (c) the variation with depth of the isodose angles relative to the central axis, and (d) the wedge factor. The analysis of the data pertinent to the above parameters is presented for 30°, 45°, and 60° wedges. In addition, the authors experimentally confirmed the accuracy of Tatcher's method (7), by which a wide range of wedge angles smaller than the nominal angle can be generated by using a combination of open and wedge beams.