whole-body irradiation

whole-body irradiation,

ionizing radiation exposure that affects the entire body. Short-term whole-body irradiation can cause injury or death in humans, mainly from damage to the GI tract and the bone marrow. However, such injury occurs only with doses far beyond the diagnostic range, such as with exposure to nuclear weapons. The absorbed dose equivalent limit for whole-body occupational exposure is 5 rem per year. The nonoccupational absorbed dose equivalent limit is 0.5 rem per year. Also called total body radiation.

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irradiation [ĭ-ra″de-a´shun]

1. radiation therapy.

2. the dispersion of nervous impulse beyond the normal path of conduction.

3. the exposure of a substance to radiation, which consists of any of numerous kinds of rays that travel at the speed of light. Every living thing is subject to some irradiation by cosmic rays, ultraviolet rays in sunlight, and other natural radiation in the environment, all of which is usually slight and harmless. In large amounts, however, certain kinds of radiation cause direct harm to living cells, especially those rays that have a greater frequency and produce more energy. Irradiation of certain foods, including milk, kills harmful bacteria, prevents spoilage, and sometimes increases its vitamin efficiency. X-ray photography is used in industrial research and in diagnosis of disorders within the body.

Radiation therapy usually refers to treatment by x-rays and gamma rays. X-rays are produced by bombarding a tungsten target with high-speed electrons in a vacuum tube; gamma rays are emitted during the decay of radioisotopes. X-rays may be employed to kill organisms causing skin diseases, for example, or to destroy the abnormal cells that form tumors. Gonads, blood cells, and cancer cells are especially sensitive to radiation, particularly to x-rays and gamma rays.

Other rays are also used medically. Infrared rays produce a radiant heat used for the treatment of sprains and bursitis; tissues such as muscles and joints are relaxed and soothed by the penetration of these rays. Ultraviolet rays are used in sun lamps to treat skin diseases, such as acne and psoriasis. See also discussion of protection against harmful effects of radiation under radiation.

extended field irradiation irradiation of an extended field in radiation therapy for malignant lymphoma.

external beam irradiation radiation therapy in which the radiation is emitted from a source located at a distance from the body.

hemibody irradiation external beam irradiation involving exposure of half the body.

interstitial irradiation see radiation therapy.

involved field irradiation irradiation of only the involved field in radiation therapy for malignant lymphoma.

mantle field irradiation irradiation of a mantle field in radiation therapy for malignant lymphoma.

total body irradiation (whole-body irradiation) TBI; external beam irradiation involving exposure of the entire body.