X-ray irradiation of the organism, with the machine cells, the interaction of tissues, body fluids and other substances, which cause the atom or molecule ionization of the material, can directly destroy some macromolecular structures in the organism, such as making the protein molecule chain break, RNA or deoxyribonucleic acid break, destroying some enzymes that have important meaning to the substance metabolism, and even damaging the cell structure directly. In addition, the rays can be used to form some free radicals by ionization of a wide range of water molecules in the body, thereby damaging the organism through the indirect effects of these free radicals.
The pathogenesis of radiation damage, like other diseases, the pathogenic factor acts on the organism, besides causes the molecular level, the cell level change, but also may produce a series of secondary effect, finally causes the organ level barrier and the whole level change, in the clinical can appear the radiation damage the sign and the symptom. The damage to human cells is limited to the individual itself, causing the body effect. The damage of germ cells affects the offspring of the individual and produces the genetic effect.