Effects of Betatron Radiations on the Brain of Primates

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Abstract
Extensive studies on the effects of high energy X-rays (23 million electron volts (mev)) and high energy electrons (17 mev) from the betatron on the normal brain of monkey and man and on the tumors of the central nervous system of man have been carried out since 1949. The high energy potential of the betatron enables one to produce beams of X-rays which are (1) free from side scatter, (2) more penetrating, and (3) more homogeneous than X-ray beams of low energy. This study was greatly facilitated by the precision of radiation location and the uniformity of dose-distribution through the brain of the monkey which was obtained with the X-ray beam from the betatron by the exptl. technique employed. Adult monkeys (65) were exposed to single total doses of 23 mev X-rays from the betatron via a 1 cm. or 2.5 cm. circular portal. A wide range of single doses from 375-14,000 roentgens (r) was studied. The beams were fired transtemporally or transfrontally. The monkeys were then observed for clinical and eeg. changes. Animals were sacrificed at intervals over a period of 2 yrs. and the perfused brain was removed, imbedded in celloidin, and serially sectioned at 20[mu]. Three series were made, beginning with sections 20, 21, 22 and every 20th section saved thereafter, and Nissl, Weil-van-Gieson, and hematoxylin-eosin prepns. were made. The choice of utilizing small 1 or 2.5 cm. beams of X-rays was made rather than irradiating the entire head so that sufficient non-irradiated brain would be available in each section and adjacent sections to serve as a histologic control for the irradiated areas. The histologic changes as related to dose and time after radiation are tabulated. Neurologic observations are descr. The potential use of high energy X-rays for obtaining a frontal lobotomy is discussed. The problems of radionecrosis in brain tumor therapy are considered. Conclusions from these studies are (1) The central nervous system is more radio-responsive than is generally supposed. (2) The effects of high energy X-rays on the brain of monkey and man appear to be effects of the radiations and are not secondary to vascular occlusion. (3) The brainstem appears to be most responsive to radiation. (4) The white matter of the deep portions of the centrum semiovale, internal capsule, and brainstem are peculiarly responsive to X-irradiation. (5) The cells of the paraventricular and supraoptic nuclei of the hypothalamus are responsive to X-rays. (6) Comparable radiation responses are observed in patients receiving X-ray therapy for tumors of the central nervous system.

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