Tissue Changes in the Brains of Cats and Monkeys Following Cobalt 60 Irradiation

Abstract

Areas of the cerebral cortices of cats and monkeys were irradiated, utilizing a small segment of Co60 fastened to the tip of a 17-gauge needle. A standard dose of 4000 (measured at 5 mm) was used in both species. Specimens were obtained at varying intervals from zero to 256 days and studied microscopically. Radiation produced complete liquefaction of all elements (neural, glial, and vascular) for a short distance immediately around the source. Vascular degeneration resulted in hemorrhage and edema. Gitter cells removed the debris and fibroblasts and astrocytes combined to produce a fibroglial scar. Secondary necrosis was found at 64 days around the original defect, and focal perivascular areas of demyeliniza-tion appeared at 96 days in the white matter. The size of the lesion and the time sequence of the changes were strikingly different in the two species.