The use of wedge filters in X-ray therapy

Summary To assist in obtaining uniform irradiation throughout the treated volume, techniques have been developed using wedge filters, i.e., non-uniform (metal) filters whose thickness varies in one direction across the field. Specifications are given of wedges for use with radiation of 1 mm. Cu h.v.l. and field sizes of 5 × 5 cm., 6 × 8 cm., 8 × 10 cm., and 10 × 15 cm. (the wedge directions being along the first of the two dimensions in each case) to produce isodose curves of approximately 45° slope. Measured isodose curves for these applicators are presented, together with field summations for two wedge fields at right angles, two wedge fields and a central normal field in a hemihexagonal arrangement, and two opposed wedge fields with a normal field at right angles. The use of these techniques in larynx, posterior tongue, antrum and ethmoid sinuses, nose, chest, and abdominal wall, limb, and cerebral treatments are discussed and illustrated by photographs. The use of a shallow wedge in superficial treatment of a curved surface is also briefly considered.