ABSTRACT
In regard to radiation effects on small blood vessels, the early radiation-induced changes in endothelial cells include degeneration, swelling, and necrosis. Radiation induction and advancement of progressive fibrosis of the fine vasculature leads eventually to premature narrowing and obliteration of vascular lumens and usually to a reduction in the total extent of fine vasculature or a reduction in its effective function. Marked changes in dependent tissues can be caused by subtle radiation-induced changes in fine vasculature and interstitial connective tissue, despite their initial inconspicuous character. The advancement of cicatrization of the fine blood vessels by irradiation involves the gradual replacment of the muscle tissue of the small arteries by fibrous tissue, a tissue that is less resilient and less resistant to stress. The severe damage to the fine vasculature caused by very large radiation doses results in poor support for continuing viability or regeneration of any kind of dependent cell, radiosensitive or radioresistant.
