A contribution to the morphological study of acute changes in the blood vessels of the central nervous system of rats following irradiation with high-energy (4 GeV/nucleon) helium ions.

Rats were irradiated with helium ions (4 GeV/nucleon; 2 or 4 Gy). After 4-9 hours or three days, a perfusion was performed and sections of the cerebral cortex were investigated under light and electron microscopes. Changes observed in the vessels of the telencephalic cortex are described. Most of the vessels in the sections analysed showed no signs of damage. In some cases there was a dilated perivascular space; a comparison of its occurrence in irradiated and control animals showed a statistically significant increase in frequency of the phenomenon at a shorter interval after irradiation with a larger dose. Electron microscopical analysis showed that the main locality of damage was the border of the perivascular foot of the astrocytes, which exhibited various degrees of edema. The discussion stresses the peculiarities of the interaction of helium ions with living tissues, particularly the heterogeneity of the distribution of absorbed energy. The consequence is in accordance with the nature of the changes observed.