| radiation risks | The risks to health posed by exposure to radiation. Exposure comes from both natural sources and from man-made ones (medical and occupational). See: background radiation.Because any amount of radiation may cause cellular mutations, considerable effort has been made by government and independent researchers to establish exposure guidelines. In most cases, natural sources account for the bulk of received radiation, with artificial sources adding only a small percentage to the average annual dose. Public perception of the hazards of radiation is often at odds with scientific positions on the matter. In part, equivocal research results (as in attempts to assess the added cancer risk posed by mammograms) contribute to public fears. Some psychological studies have concluded that whether or not public fears of nuclear power plants and other radiation sources are justified, the added stress caused by such fears in itself constitutes a threat to health that should be addressed. (05 Mar 2000) |
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| radiation-sensitizing agents | Drugs used to potentiate the effectiveness of radiation therapy in destroying unwanted cells. (12 Dec 1998) |
| radiation sickness | A systemic condition caused by substantial whole-body irradiation, seen after nuclear explosions or accidents, rarely after radiotherapy. Manifestations depend on dose, ranging from anorexia, nausea, vomiting, and mild leukopenia, to thrombocytopenia with haemorrhage, severe leukopenia with infection, anaemia, central nervous system damage, and death. Synonym: radiation poisoning. (05 Mar 2000) |
| radiation therapy | <radiobiology> Treatment with high energy radiation from X-rays or other sources of radiation. (16 Dec 1997) |
| radiation tolerance | The ability of some cells or tissues to withstand ionizing radiation without serious injury. Tolerance depends on the species, cell type, and physical and chemical variables, including radiation-protective agents and radiation-sensitizing agents. (12 Dec 1998) |
| radiation weighting factor | In radiation protection, a factor weighting the absorbed dose of radiation of a specific type and energy for its effect on tissue. See: equivalent dose. (05 Mar 2000) |
| gamma radiation | Ionizing electromagnetic radiation resulting from nuclear processes, such as radioactive decay or fission. (05 Mar 2000) |
| geniculocalcarine radiation | The massive, fanlike fibre system passing from the lateral geniculate body of the thalamus to the visual cortex (striate or calcarine cortex, area 17 of Brodmann); the fibres follow the retrolenticular and sublenticular limbs of the internal capsule into the corona radiata but they curve back along the lateral wall of the temporal and occipital horns of the lateral ventricle to the striate cortex on the medial surface and pole of the occipital lobe. Synonym: radiatio optica, geniculocalcarine radiation, geniculocalcarine tract, Gratiolet's fibres, Gratiolet's radiation, occipitothalamic radiation, Wernicke's radiation. (05 Mar 2000) |
| recombination radiation | <physics> Radiation produced when a free electron in a plasma is captured by an ion. (09 Oct 1997) |
| Cerenkov radiation | Light given off by a transparent medium when a high energy particle speeds through it at a velocity greater than that of light in that medium. (05 Mar 2000) |
| characteristic radiation | Monochromatic radiation that is produced when an electron is ejected from an atom and another takes its place by jumping from another shell; the energy of the photon is the difference between that of the two shell positions. Synonym: characteristic emission. (05 Mar 2000) |
| Gratiolet's radiation | The massive, fanlike fibre system passing from the lateral geniculate body of the thalamus to the visual cortex (striate or calcarine cortex, area 17 of Brodmann); the fibres follow the retrolenticular and sublenticular limbs of the internal capsule into the corona radiata but they curve back along the lateral wall of the temporal and occipital horns of the lateral ventricle to the striate cortex on the medial surface and pole of the occipital lobe. Synonym: radiatio optica, geniculocalcarine radiation, geniculocalcarine tract, Gratiolet's fibres, Gratiolet's radiation, occipitothalamic radiation, Wernicke's radiation. (05 Mar 2000) |
| microwave radiation | Electromagnetic radiation with wavelengths between 3 millimetres and 300 millimetres. Used in radar, these waves have frequencies between 1-100 gigahertz. Microwaves have also been harnessed for cooking in microwave ovens. (09 Oct 1997) |
| photodynamic radiation therapy | <oncology, technique> A light sensitive drug is given through a vein and concentrates in the tumour. Then, during a surgical procedure, a special light activates the drug. The activated drug kills tumour cells. (31 Dec 1997) |
| coherent radiation | <physics> Any form of radiation in which the phase relationship between sections of the wave at different locations is not random (or incoherent!). Typical example is a laser beam, in which the phase is more or less uniform across the beam and changes along the beam in accordance with the wavelength. Radiation in which the photons tend to correlate with one another, rather than being randomly distributed. (09 Oct 1997) |