Clinical use of a match-line wedge for adjacent megavoltage radiation field matching

The divergence and sharp penumbra of linear accelerator beams pose notorious problems when joining such beams side by side. One way of reducing the dose distribution nonuniformity in the matching region is to create a wide pseudo-penumbra with the use of a "match-line wedge." A single match-line wedge shape has been developed for 6 MV and 10 MV photon beams. The wide pseudo-penumbra created by the wedge drastically reduces the effect of random set-up errors. Special attention has been paid to ensure simple and reliable clinical use of the wedge. Details of the design, construction, dosimetry, and rules of practical application are presented. Comparisons of several matching methods are made.