An electron beam pseudoarc technique for irradiation of large areas of chest wall and other curved surfaces.

An electron beam technique has been developed for the treatment of large areas of the chest wall and other curved surfaces employing the stationary field electron beam mode ordinarily available on a linear accelerator. The technique simulates an arc through the use of multiple fixed fields. The electron collimator is not used. Field shaping is achieved through the combined effects produced by the photon jaw settings, the arc limits, and secondary lead shielding on the patient's skin. Thus, there is no limitation on the circumferential extent of the field size that can be used. Electron beam energies of 6 MeV, 9 MeV, 12 MeV, 15 MeV and 18 MeV have been studied. Our findings indicate that, for these energies, this technique produces isodose curves parallel to the cylindrical surface at all depths beyond maximum build-up. This paper discusses the physical characteristics of the single beams, the degree of dose homogeneity achieved with the multiple fields, and the dosimetry technique developed to implement the therapy.