TOTAL-SKIN irradiation with mega-voltage electrons of uniform dose and low x-ray contamination represents one of the newer and more effective therapeutic modalities available for the management of generalized cutaneous lymphomas. Linear and Van de Graaff accelerators are commonly employed as the electron sources for these radiation therapy units. Two problems attendant on total-body irradiation with superficial and conventional x rays in the treatment of lymphoma cutis are bone-marrow depression resulting from the more penetrating elements of the radiation and technical difficulties inherent in the use of multiple ports of treatment. Low-megavoltage electron therapy proves more advantageous than roentgen rays because (a) the penetration of the electrons can be restricted to the superficial pathologically involved skin, minimizing radiation effects to the underlying normal tissue, (b) the inherent x-ray background is low, and (c) total-body irradiation is technically easy. The biological effect of high-energy electrons is similar to that of x rays (1). The purpose of this paper is to review three years experience with total-skin electron-beam therapy in the management of 37 patients with exfoliative erythroderma, mycosis fungoides, lymphosarcoma with secondary skin involvement, and generalized psoriasis. The instrumentation and technics are reviewed, and the adverse hematologic, cutaneous, and subcutaneous reactions which occur during the course of therapy are discussed. Instrumentation A Varian linear accelerator, the technical details of which have been previously reported (2, 3), is employed at the University of California at Los Angeles Center for the Health Sciences. The electrons are generated by a cathode gun, injected into a traveling-wave tube, and accelerated by a microwave beam to energies between 3 and 8 MeV. The electrons may be converted to supervoltage x ray by interaction with a gold target. By magnetically deflecting the electron beam away from this target, however, a uniform source of high-energy, low-mega-voltage electrons can be produced. Various electron energy levels have been used in therapy, but at present electrons with an energy of approximately 3 MeV are employed. Their maximum penetration in tissue is 1.5 cm, with a 50 per cent depth dose at 8 mm (Fig. 1). The standard method of treatment involves positioning the patient 6 m from the unit (Fig. 2). At that distance, the uniformity of dose distribution in a field 6 ft. in diameter is ±6 per cent (Fig. 2). The patient's head (when uninvolved) and eyes are shielded from the electrons by a helmet and goggles with sufficient tissue-equivalent material. Since the general requirements for therapy demand the homogeneous irradiation of the entire skin surface, it is necessary to expose to the electron beam, by appropriate positioning, the incident as well as the inter-triginous surfaces.
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Grollman et al. (1966) studied this question.