A nondivergent three field matching technique for breast irradiation.

Effective radiation therapy to intact breasts requires the delivery of adequate dose to a large target volume using complex beam arrangements. A semi-empirical method is described to determine the correct gantry, collimator, and couch positions for a geometrically accurate field match among adjoining radiation beams. The technique uses a metal rod and chain combination to aid determination of the proper couch setting under remote fluoroscopy control. A couch position error of more than half a degree is easily detectable by this technique.