Radiation exposure

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  • Radiation Exposure
definition
  • Exposure to ionizing and nonionizing radiation on humans. Ionizing radiation includes highly energetic electromagnetic radiation (x-rays, gamma rays, or cosmic rays) and particulate radiation (alpha particles, beta particles, neutrons, or heavy charged ions). Nonionizing radiation includes ultraviolet radiation (UV), microwaves, and extralow-frequency (ELF) electromagnetic radiation. These two types of radiation have different modes of action on biological material. Ionizing radiation originates from external sources (medical equipment, computer and TV displays) or from internal sources (ingested or inhaled radioisotopes, such as radon-222, strontium-90 and iodine-131, and is either anthropogenic or natural. Nonionizing radiation originates from natural sources (sunlight, Earth's magnetic field, lightning, static electricity, endogenous body currents) and technological sources (computer and TV video displays, microwave ovens, communications equipment, electric equipment and appliances, and high-voltage transmission lines).
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Abstract from DBPedia
    Radiation is a moving form of energy, classified into ionizing and non-ionizing type. Ionizing radiation is further categorized into electromagnetic radiation (without matter) and particulate radiation (with matter). Electromagnetic radiation consists of photons, which can be thought of as energy packets, traveling in the form of a wave. Examples of electromagnetic radiation includes X-rays and gamma rays (see photo "Types of Electromagnetic Radiation"). These types of radiation can easily penetrate the human body because of high energy. Radiation exposure is a measure of the ionization of air due to ionizing radiation from photons. It is defined as the electric charge freed by such radiation in a specified volume of air divided by the mass of that air. Medical exposure is defined by the International Commission on Radiological Protection as exposure incurred by patients as part of their own medical or dental diagnosis or treatment; by persons, other than those occupationally exposed, knowingly, while voluntarily helping in the support and comfort of patients; and by volunteers in a programme of biomedical research involving their exposure. Common medical tests and treatments involving radiation include X-rays, CT scans, mammography, lung ventilation and perfusion scans, bone scans, cardiac perfusion scan, angiography, radiation therapy, and more. Each type of test carries its own amount of radiation exposure. There are two general categories of adverse health effects caused by radiation exposure: deterministic effects and stochastic effects. Deterministic effects (harmful tissue reactions) are due to the killing/malfunction of cells following high doses; and stochastic effects involve either cancer development in exposed individuals caused by mutation of somatic cells, or heritable disease in their offspring from mutation of reproductive (germ) cells. Absorbed dose is a term used to describe how much energy that radiation deposits in a material. Common measurements for absorbed dose include rad, or radiation absorbed dose, and Gray, or Gy. Dose equivalent calculates the effect of radiation on human tissue. This is done using tissue weighting factor, which takes into account how each tissue in the body has different sensitivity to radiation. The effective dose is the risk of radiation averaged over the entire body. Ionizing radiation is known to cause cancer in humans. We know this from the Life Span Study, which followed survivors of the atomic bombing in Japan during World War 2. Over 100,000 individuals were followed for 50 years. 1 in 10 of the cancers that formed during this time was due to radiation. The study shows a linear dose response for all solid tumors. This means the relationship between dose and human body response is a straight line. The risk of low dose radiation in medical imaging is unproven. It is difficult to establish risk due to low dose radiation. This is in part because there are other carcinogens in the environment, including smoking, chemicals, and pollutants. A common head CT has an effective dose of 2 mSv. This is comparable to the amount of background radiation a person is exposed to in 1 year. Background radiation is from naturally radioactive materials and cosmic radiation from space. The embryo and fetus are considered highly sensitive to radiation exposure. Complications from radiation exposure include malformation of internal organs, reduction of IQ, and cancer formation. The SI unit of exposure is the coulomb per kilogram (C/kg), which has largely replaced the roentgen (R). One roentgen equals 0.000258 C/kg; an exposure of one coulomb per kilogram is equivalent to 3876 roentgens.

    照射線量(しょうしゃせんりょう、英語:exposure)は、乾燥空気に対する電離能力で定義されたX線やγ線の線量(放射線の作用とその影響の因果関係を定量的に論ずるとき、原因の大きさを記述する量)である。照射線量は、自由空気電離箱(free air chamber)で測定される量を1928年に国際的な共通単位として導入した最も歴史のある線量である。現在では、X線やγ線が「仮想的に」乾燥空気に作用したときに発生する二次電子を、「仮想的に」乾燥空気で満たされた空間に放ったとき生成する電離電荷量とX線やγ線が作用した仮想的な空気の質量との比で定義される。1962年以降の照射線量は、X線やγ線と空気の仮想的な相互作用を考えるため、空気中以外の場所(たとえば、水中や真空中)でも定義でき、線量を定義する場所でが成立するか否かにも影響されない量として定義されている。

    (Source: http://dbpedia.org/resource/Radiation_exposure)