[Effects of ionising radiation on tissues]

Radiation effects are divided into four groups: a. acute somatic, b. late somatic, c. genetic and d. teratogenic effects. Rapidly proliferating non-differentiated cells are the most radiosensitive. Well known representatives of this class of cells are the stem cells of the hematopoietic tissues and the cells of the intestinal crypts. The differentiated fixed postmitotic cells are the most radioresistant. This class includes the long-lived neurons, skeletal muscle cells and erythrocytes. Carcinogenesis is the most important late effect of ionizing radiation. For low dose rate radiation cancer risk after 1 mSv is estimated to be about 5 extra death cases per 100.000.