Obliquely incident electron beams for irradiation of the internal mammary lymph nodes.

For irradiation of the internal mammary lymph nodes, together with irradiation of the breast, a number of more or less standardised techniques are used. Regarding some disadvantages of these techniques, a modified method is discussed, that uses an obliquely incident electron beam for the mammary lymph node irradiation. Dose distributions of obliquely incident electron beams are measured and compared with the results of a treatment planning program. A procedure to match this obliquely incident beam to the adjacent tangential photon beams, that irradiate the breast, is described and the resulting dose distribution is compared with a standard technique. Applications with this technique and its usefulness are discussed.