Computed tomography analysis of the canine brain: effects of hemibrain X irradiation.

Radiation damage induced by megavoltage X irradiation in normal brain tissue can manifest as one of several pathologic processes depending upon the time of brain examination after irradiation. Serial quantitative computed tomography (QCT) analyses were used to study the development of radiation damage in the normal canine brain. Tissue density, volume of low density areas, magnitude and volume of contrast uptake, and ventricular volume were measured following hemibrain irradiation and were correlated with histopathology. Low density areas correlated with edema, demyelination, axonal swelling, and necrosis and appeared 3-4 months after irradiation. Large regions of contrast enhancement (coagulation necrosis and associated vascular changes) appeared 5-6 months after irradiation. Results from this study demonstrated that the pathologic changes induced in the dog brain after single doses of X rays were similar to the changes observed in nonhuman primates and man after exposure to radiation.