摘要：

We have used X rays produced a t two million volts for the treatment of lymphoma since 19451 .I Several physical and clinical advantages result from the use of this higher-energy radiation in local and regionalized cases. The relatively greater penetration, as indicated by its half-value layer (HVL) of 12.5 mm. copper, allows the administration of sufficient radiation to the deeper tumor-bearing regions. Untoward skin effects are almost completely avoided both because of this penetration and because of the fact these highenergy rays achieve their maximum ionization just below the radiosensitive skin? The threshold skin erythema dose with 2-million-volt X radiation is about 3000 r when delivered by the divided-dose technique, as compared with less than 1000 r for conventional deep-therapy rays. In addition, megavolt rays are known to be less strongly absorbed by bone and other high-atomicnumbered components and thus have a lesser effect on the blood-forming organs for the same soft-tissue dose. The Van de Graaff electrostatic X ray source used in this work is a constantpotential unit delivering 80 r/min., measured a t 1 meter. The usual treatment distance of 125 cm. allowed a portal 35 cm. x 35 cm. in size and made possible the treatment of most regions with a single field carefully shaped so as to shield normal structures such as the eyes, teeth, lungs, or genitalia. The focal spot on these units is usually under 3 mm. in diameter and results in a sharply defined X-ray beam. These factors have allowed us to treat most of our lymphoma cases through two portals, one anterior and one posterior, with minimum tumor doses from 2400 r to 3000 r delivered to the primary lesion and the adjacent lymphatics, regardless of the location. Conventional deeptherapy equipment cannot readily provide portals of the dimensions desirable for lymphoma therapy and may elicit excessive skin and systemic reaction if adequate deep irradiation is delivered to such large fields. The histological classification of lymphomas used in this study and the number of cases treated are shown in FIGURE 1. This report covers four series of cases followed for a period of three to five years for all types of lymphoma (FIGURE 2). The 64 cases reported using the 2-million-electron-volt (Mev) X ray were treated a t Massachusetts Institute of Technology (M.I.T.), between 1950 and 1952 and were patients for whom one of us (H. F. H.) cared as a staff member of the Lahey Clinic, Boston, Mass. Another group of 181 cases was composed of patients also treated by H. F. H. between 1939 and 1942; 200-kilovolt-peak (kvp) X rays were used. The third series of 63 cases was treated with 200-kvp and 400-kvp therapy a t Los Angeles Tumor Institute, * Fellow of the Los Angeles Tumor Institute.

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