ionizing radiation (redirected from Atomic radiation)

radiation /ra·di·a·tion/ (ra″de-a´shun)

1. divergence from a common center.

2. a structure made up of divergent elements, as one of the fiber tracts in the brain.

3. energy transmitted by waves through space or through some medium; usually referring to electromagnetic radiation, when used without a modifier. By extension, a stream of particles, such as electrons or alpha particles.

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acoustic radiation  a fiber tract arising in the medial geniculate nucleus and passing laterally to terminate in the transverse temporal gyri of the temporal lobe.

radiation of corpus callosum  the fibers of the corpus callosum radiating to all parts of the neopallium.

corpuscular radiations  streams of subatomic particles emitted in nuclear disintegration, such as protons, neutrons, positrons, and deuterons.

electromagnetic radiation  see under wave.

ionizing radiation  corpuscular or electromagnetic radiation capable of producing ionization, directly or indirectly, in its passage through matter.

occipitothalamic radiation , optic radiation a fiber tract starting at the lateral geniculate body, passing through the pars retrolentiformis of the internal capsule, and terminating in the striate area on the medial surface of the occipital lobe, on either side of the calcarine sulcus.

pyramidal radiation  fibers extending from the pyramidal tract to the cortex.

tegmental radiation  fibers radiating laterally from the red nucleus.

thalamic radiations  fibers which reciprocally connect the thalamus and cerebral cortex by way of the internal capsule, usually grouped into four subradiations (peduncles): anterior, central, inferior, and posterior.

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i·on·i·zing radiation (-nzng)

n.

High-energy radiation capable of producing ionization in substances through which it passes.

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Ionizing radiation

Radiation that can damage living tissue by disrupting and destroying individual cells at the molecular level. All types of nuclear radiation—x rays, gamma rays and beta rays—are potentially ionizing. Sound waves physically vibrate the material through which they pass, but do not ionize it.

Mentioned in: Abdominal Ultrasound, Hypogonadism, Interstitial Microwave Thermal Therapy, Magnetic Resonance Imaging, Recurrent Miscarriage

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ionizing radiation,

high-energy electromagnetic waves (such as x-rays and gamma rays) and particles (such as alpha and beta particles, neutrons, protons, and heavy nuclei) that cause substances in their paths to dissociate into ions. The spatial distribution of the ionization depends on the kind of radiation, its penetrating power, the location of the source, and the nature of the irradiated material. High-energy x-rays penetrate deeply, most beta particles penetrate only a few millimeters, and alpha particles penetrate only a fraction of a millimeter. However, all three produce intense ionization along their tracks. Ionizing radiation directly affects living organisms by killing cells or retarding their development and by producing gene mutations and chromosome breaks. Tissues containing elements with relatively high atomic masses, such as calcium in bones and teeth, absorb much higher doses of ionizing radiation than do soft tissues.

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radiation (rā´dēā´shn),

n 1. the process of emitting radiant energy in the form of waves or particles.
n 2. the combined processes of emission, transmission, and absorption of radiant energy.

radiation, actinic,

n radiation capable of producing chemical change (e.g., effect of light and roentgen rays on photographic emulsions).

radiation, background,

n radiation arising from radioactive material other than the one directly under consideration. Background radiation resulting from cosmic rays and natural radioactivity is always present. Background radiation may also exist because of radioactive substances in other parts of a building (e.g., building material).

Radiation.

radiation, backscatter,

n radiation that deflects off its target at an angle of deflection greater than 90°, possibly affecting those who may be off to the side of or behind the main beam. See also radiation, scattered.

radiation, biologic effectiveness of,

n the ability of a particular type of ionizing radiation to produce biologic effects on an organism with small absorbed doses. See relative biologic effectiveness.

radiation, bremsstrahlung

n (white), describes the distribution of roentgen rays from extremely low energy photons to roentgen rays originating from the highest kilovoltage applied to a radiographic tube.
Bremsstrahlung translates to “braking radiation,” referring to the sudden slowing of electrons that occurs when they encounter nuclei with a high positive charge.

radiation caries,

n a type of tooth decay caused by the reduction in saliva that may result from the use of ionizing radiation in the treatment of oral and facial malignancies. Radiation caries is an unfortunate side effect of a necessary radical procedure to cure or prevent the spread of cancer.

radiation cataract,

n a cataract that is caused by extended exposure of the eye to ionizing radiation in the course of treating facial cancers.

radiation, characteristic,

n radiation that originates from an atom after removal of an electron or excitation of the nucleus. The wavelength of the emitted radiation is specific, depending only on the element concerned and on the particular energy levels involved. Also refers to the specific type of secondary radiation resulting when rays from a radio ray tube strike another substance, such as copper.

radiation, coherent scattering,

n See coherent scattering.

radiation, Compton scatter,

n See Compton scatter radiation.

radiation, corpuscular

n subatomic particles, such as electrons, protons, neutrons, or alpha particles, that travel in streams at various velocities. All the particles have definite masses and travel at various speeds. The properties are in opposition to electromagnetic radiations, which have no mass and travel in wave forms at the speed of light. See also radiation, electromagnetic.

radiation, cosmic,

n See ray, cosmic.

radiation, cumulative effect of

n reactions vary depending on the dosage; if the radiation received is in several smaller doses, the reaction is not as severe as if the same amount of radiation is received all at once. Unless a tissue is completely destroyed by the radiation, some or all of it will be repaired, although cumulative damage may cause some irreparable conditions.

radiation, dermatitis,

n See dermatitis, radiation.

radiation detector,

n a device for converting radiant energy to a form more suitable for observation and recording. Examples include radiograph films and radiometers.

radiation, direct,

n (primary radiation), radiation emanating from a tube aperture and comprising the useful beam, as compared with any stray radiation, such as that which comes from the tube container.

radiation, electromagnetic,

n forms of energy propagated by wave motion, such as photons or discrete quanta. The radiations have no matter associated with them, as opposed to corpuscular radiations, which have definite masses. They differ widely in wavelength, frequency, and photon energy and have strikingly different properties. Covering an enormous range of wavelengths (from 10⁻⁶ to 10¹⁷ Å), they include radio waves, infrared waves, visible light, ultraviolet radiation, gamma rays, and cosmic radiation. See also radiation, corpuscular.

radiation exposure,

n a measure of the ionization produced in air by roentgen rays or gamma rays. It is the sum of the electric charges on all ions of one sign that are produced when all electrons liberated by photons in a volume of air are completely stopped, divided by the mass of air in the volume element. The unit of exposure is the roentgen.

radiation field,

n See radiographic beam, field size.

radiation, gamma,

n See ray, gamma.

radiation, genetic effects of,

n See genetic effects of radiation.

radiation, grenz,

n See ray, grenz.

radiation, hard,

radiation consisting of the short wavelengths (higher kilovolt peak equals greater penetration).

radiation hazard,

n See hazard, radiation.

radiation, heterogeneous

n a beam or “bundle” of radiation containing photons of many wavelengths.

radiation, homogeneous,

n a beam of radiation consisting of photons that all have the same wavelength.

radiation hygiene,

n See hygiene, radiation.

radiation intensity,

n See intensity, radiation.

radiation, ionizing,

n electomagnetic radiation such as roentgen rays and gamma rays; particulate radiation such as alpha particles, beta particles, protons, and neutrons; all other types of radiations that produce ionization directly or indirectly.

radiation leakage,

n (stray radiation), the escape of radiation through the protective shielding of the radiography unit tube head. This radiation is detected at the sides, top, bottom, or back of the tube head; it does not include the useful beam.

radiation, monochromatic,

n See radiation, homogeneous.

radiation necrosis,

n See necrosis, radiation.

radiation, neutron,

n See ray, neutron.

radiation oncology,

n the study of the treatment of cancer using ionizing radiation

radiation osteomyelitis/osteonecrosis

n an infection of the bone that occurs after exposure to radiation. Most commonly seen in cancer patients when radiation therapy damages healthy tissue surrounding the targeted tumor.

radiation, primary,

n all radiation produced directly from the target in a radiographic tube. See also radiation, direct.

radiation protection,

n provision designed to reduce exposure to radiation. For external radiation, this provision consists of using protective barriers of radiation-absorbing material, ensuring adequate distances from the radiation sources, reducing exposure time, and combinations of these measures. For internal radiation, it involves measures to restrict inhalation, ingestion, or other modes of entry of radioactive material into the body.

radiation quality,

n the ability of a beam of radiographs to allow the production of diagnostically useful radiographs. Usually measured in half-value layers of aluminum and controlled by the kilovolt peak.

radiation quantity,

n amount of radiation. The amount of exposure is expressed in roentgens (R), whereas quantity of dose is expressed in rads.

radiation, relative biologic effectiveness of (RBE),

n a comparison between various types of ionizing radiation with respect to the ability to produce biologic effects with small doses.

radiation, remnant,

n the radiation passing through an object or part being examined that is available either for recording on a radiographic film or for measurement.

radiation, scattered,

n (backscatter radiation), radiation whose direction has been altered. It may include secondary and stray radiation.

radiation, secondary,

n the new radiation created by primary radiation acting on or passing through matter.

radiation shield,

n See shield, radiation.

radiation sickness,

n a self-limited syndrome characterized by varying degrees of nausea, vomiting, diarrhea, and psychic depression after exposure to very large doses of ionizing radiation, particularly doses to the abdominal region. Its mechanism is not completely understood. It usually occurs a few hours after treatment and may subside within a day. It may be sufficiently severe to necessitate interrupting the treatment series, or it may incapacitate the patient.

radiation, soft,

n radiation consisting of the long wavelengths (lower kilovolt peak results in less penetration).

radiation, speed of,

n the speed of light, or approximately 186,000 miles per second.

radiation, stray,

n See radiation leakage.

radiation survey,

n See survey, radiation.

radiation therapy,

n See therapy, radiation.

radiation, total body,

n the exposure of the entire body to penetrating radiation. In theory, all cells in the body receive the same overall dose.

radiation treatment,

n a cancer treatment method that uses roentgen rays to modify or destroy cancer cells; dental patients who are undergoing radiation therapy may exhibit an increased need for certain nutrients. See also therapy, radiation.

radiation, useful,

n the part of the primary radiation that is permitted to pass from the tube housing through the tube head port, aperture, or collimating device. See beam, useful.

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ionizing radiation

high-energy radiation, such as x-rays and gamma-rays which react in a similar manner to produce ion pairs or ionization. Gamma-rays are used in the control of growth of tumors and sterilization of food, in which they have some undesirable side-effects, e.g. they destroy the enzymes in meat that cause tenderizing; off-flavors are also a problem.