Late changes in the architecture of blood vessels of the rat brain after irradiation.

The development of vascular changes in the rat brain after a moderate dose of X rays (2000 cGy (rad)) was investigated by means of an angiographic method. The indications are that, even with this dose, a gradual development of vascular abnormalities occurs; these develop between 12 and 14 months after irradiation. It appears that focal telangiectasis in the parts containing white matter is the earliest sign that can be detected with the method employed.