radiation biology

biology

 [bi-ol´o-je]

scientific study of living organisms. adj., adj biolog´ic, biolog´ical.

molecular biology study of molecular structures and events underlying biological processes, including relation between genes and the functional characteristics they determine.

radiation biology scientific study of the effects of ionizing radiation on living organisms.

ra·di·a·tion bi·ol·o·gy

field of science that studies the biologic effects of ionizing radiation.

ra·di·a·tion bi·ol·o·gy

(rā'dē-ā'shŭn bī-ol'ŏ-jē)

Science that studies the biologic effects of ionizing radiation.

biology

scientific study of living organisms. See also biological.

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radiation biology

scientific study of the effects of ionizing radiation on living organisms.

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radiation

1. divergence from a common center.

2. a structure made up of diverging elements, especially a tract of the central nervous system made up of diverging fibers.

3. energy carried by waves or a stream of particles. One type is electromagnetic radiation, which consists of wave motion of electric and magnetic fields. The quantum theory is based on the fact that electromagnetic waves consist of discrete particles, called photons, that have an energy inversely proportional to the wavelength of the wave. In order of increasing photon energy and decreasing wavelength, the electromagnetic spectrum is divided into radio waves, infrared light, visible light, ultraviolet light and x-rays.

Another type is the radiation emitted by radioactive materials. Alpha particles are high-energy helium-4 nuclei consisting of two protons and two neutrons, which are emitted by radioisotopes of heavy elements, such as uranium. Beta particles are high-energy electrons, which are emitted by radioisotopes of lighter elements. Gamma rays are high-energy photons, which are emitted along with alpha and beta particles and are also emitted alone by metastable radionuclides, such as technetium-99m. Gamma rays have energies in the x-ray region of the spectrum and differ from x-rays only in that they are produced by radioactive decay rather than by x-ray machines.

Radiation with enough energy to knock electrons out of atoms and produce ions is called ionizing radiation. This includes alpha and beta particles and x-rays and gamma rays.

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radiation biology

study of the effects of ionizing radiation on living tissues.

corpuscular radiation

particles emitted in nuclear disintegration, including alpha and beta particles, protons, neutrons, positrons and deuterons.

radiation detection

special equipment, including Geiger-Müller tubes and a scintillation crystal, is available to detect radiation which may be accidental, or detect small amounts where this is expected but it needs to be measured in terms of accumulated dose.

electromagnetic radiation

energy, unassociated with matter, that is transmitted through space by means of waves (electromagnetic waves) traveling in all instances at 3 × 10¹⁰ cm or 186,284 miles per second, but ranging in length from 10¹¹ cm (electrical waves) to 10⁻¹² cm (cosmic rays) and including radio waves, infrared, visible light and ultraviolet, x-rays and gamma rays.

radiation exposure

means more than the patient being exposed intentionally to an x-ray beam. Technical persons in the vicinity will also be exposed to a much less dangerous but perniciously cumulative load of radiation.

infrared radiation

the portion of the spectrum of electromagnetic radiation of wavelengths ranging between 0.75 and 1000 μm. See also infrared.

radiation injury

is caused by exposure to radioactive material. High doses cause intense diarrhea and dehydration and extensive skin necrosis. Median doses cause initial anorexia, lethargy and vomiting then normality for several weeks followed by vomiting, nasal discharge, dysentery, recumbency, septicemia and a profound pancytopenia. Death is the most common outcome. Chronic doses cause cataract in a few. Congenital defects occur rarely.

interstitial radiation

energy emitted by radium or radon inserted directly into the tissue.

ionizing radiation

corpuscular or electromagnetic radiation that is capable of producing ions, directly or indirectly, in its passage through matter. Used in treatment of radiosensitive cancer, in sterilization of animal products and food for experimental use.

radiation necrosis

see radionecrosis.

radiation physicist

the person responsible for the administration of radiation therapy including estimating the dose required for a treatment, arranging for the dose to be delivered and making arrangements for safety of the patient and staff, and disposing of any residual radioactive material. Technical aspects of the work include computer estimations, preparation of isodose curves, preparation of wedge and compensating filters, and calibration of teletherapy equipment.

primary radiation

radiation emanating from the x-ray tube which is absorbed by the subject or passes on through the subject without any change in photon energy.

radiation protection

includes proper control of emissions from the x-ray machines, proper protective clothing for staff, keeping unnecessary people out of the way while the tube is actually generating its beam, the wearing and regular examination of a dosimeter and the proper storage of radioactive materials or residues.

pyramidal radiation

fibers extending from the pyramidal tract to the cortex.

radiation sensitivity

tissues vary in their sensitivity to the damaging effects of irradiation. The rapidly growing tissues are most susceptible, e.g. the embryo, rapidly growing cancer, gonads, alimentary tract, skin and blood-forming organs.

radiation sickness

see radiation injury (above).

solar radiation

see solar.

radiation striothalamica

a fiber system joining the thalamus and the hypothalamic region.

tegmental radiation

fibers radiating laterally from the nucleus ruber.

thalamic radiation

fibers streaming out through the lateral surface of the thalamus, through the internal capsule to the cerebral cortex.

radiation therapist

a person skilled in radiotherapy. See also radiation therapy (below).

radiation therapy

see radiotherapy.

ultraviolet radiation

the portion of the spectrum of electromagnetic radiation of wavelengths ranging between 0.39 and 0.18 μm. See also ultraviolet rays.