Ionizing Radiation Injury

Extract

[...] HERITABLE (GENETIC) EFFECTS OF RADIATION On the basis of the existing evidence, it is inferred that a dose of at least 1 Sv is required to double the rate of heritable mutations in human germ cells and that, consequently, less than of all genetically determined disease is attributable to natural background irradiation. CARCINOGENIC EFFECTS OF RADIATION Many but not all types of benign and malignant growths have been observed to be inducible by irradiation; however, the induced growths characteristically take years or decades to appear and possess no features to distinguish them from growths arising through other causes. [...]

[...] Clinical Manifestations Ionizing radiation injuries encompass a diversity of tissue reactions that vary markedly in dose-response relationships, manifestations, timing, and prognosis. Except for mutagenic and carcinogenic effects, the reactions generally result from the killing of sizable numbers of cells in the exposed tissues and are not detectable unless the dose of radiation exceeds a substantial threshold. Clinical Manifestations For this reason, the reactions are called nonstochastic (or deterministic) effects, in contrast to mutagenic and carcinogenic effects, which are presumed to have no thresholds and are considered to be stochastic in nature. [...]

[...] Treatment In managing radiation injury, good medical judgment and first aid are the priorities. Even if the patient has been heavily irradiated, the patient should be evaluated for other forms of injury, such as burns, mechanical trauma, and smoke inhalation. If radioactive contamination is known or suspected, rescue and medical personnel who handle the patient should wear gloves and other protective clothing and take precautions to isolate all contaminated objects. Treatment Apart from symptomatic treatment, management of the hematologic form of acute radiation syndrome is similar to that used for pancytopenic leukemia, including reverse isolation, antibiotics to combat infection, granulocyte and platelet transfusions as needed, and intravenous fluids as required to combat dehydration and electrolyte loss. [...]

[...] Pathogenesis Ionizing radiation colliding randomly with atoms and molecules in its path gives rise to ions and free radicals that break chemical bonds and cause other molecular alterations, ultimately injuring the affected cells. Any molecule may be altered, but DNA is the critical biologic target because of the limited redundancy of its genetic information. A dose of radiation large enough to kill the average dividing cell Sv) causes hundreds of lesions in its DNA molecules. Pathogenesis Most lesions are reparable, but lesions produced by a densely ionizing radiation (e.g., proton or a-particle) are generally less reparable than lesions produced by a sparsely ionizing radiation. [...]

[...] caused by ionizing radiation include mutagenic, carcinogenic, and teratogenic effects and various acute and chronic tissue reactions, such as erythema, cataract of the lens, sterility, and depression of hematopoiesis. Etiology The biologic effects of ionizing radiation result from damage to DNA and other vital molecules by locally deposited energy. Doses of ionizing radiation are measured in terms of energy deposition. Etiology All humans are exposed continuously to natural background ionizing radiation from cosmic rays; radium and other radioactive elements in the earth's crust; potassium-40, carbon-14, and other radionuclides normally present in human tissues; and inhaled radon and its daughter elements. [...]