Exposure (radiation) in the context of Technetium (99mTc) sestamibi

⭐ Core Definition: Exposure (radiation)

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. As of 2007, "medical radiation exposure" was defined by the International Commission on Radiological Protection as exposure incurred by people 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.

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⭐ Core Definition: Exposure (radiation)
Exposure (radiation) in the context of Irradiation
Exposure (radiation) in the context of X-ray detector
Exposure (radiation) in the context of Rad (unit)

Exposure (radiation) in the context of Irradiation

Irradiation is the process by which an object is exposed to radiation. An irradiator is a device used to expose an object to radiation, most often gamma radiation, for a variety of purposes. Irradiators may be used for sterilizing medical and pharmaceutical supplies, preserving foodstuffs, alteration of gemstone colors, studying radiation effects, eradicating insects through sterile male release programs, or calibrating thermoluminescent dosimeters (TLDs).

The exposure can originate from various sources, including natural sources. Most frequently the term refers to ionizing radiation, and to a level of radiation that will serve a specific purpose, rather than radiation exposure to normal levels of background radiation. The term irradiation usually excludes the exposure to non-ionizing radiation, such as infrared, visible light, microwaves from cellular phones or electromagnetic waves emitted by radio and television receivers and power supplies.

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Exposure (radiation) in the context of X-ray detector

X-ray detectors are devices used to measure the flux, spatial distribution, spectrum, and/or other properties of X-rays.

Detectors can be divided into two major categories: imaging detectors (such as photographic plates and X-ray film (photographic film), now mostly replaced by various digitizing devices like image plates or flat panel detectors) and dose measurement devices (such as ionization chambers, Geiger counters, and dosimeters used to measure the local radiation exposure, dose, and/or dose rate, for example, for verifying that radiation protection equipment and procedures are effective on an ongoing basis).

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Exposure (radiation) in the context of Rad (unit)

The rad is a unit of absorbed radiation dose, defined as 1 rad = 0.01 Gy = 0.01 J/kg. It was originally defined in CGS units in 1953 as the dose causing 100 ergs of energy to be absorbed by one gram of matter. The material absorbing the radiation can be human tissue, air, water, or any other substance.

It has been replaced by the gray (symbol Gy) in SI derived units. The rad is still used in the United States, although this is "strongly discouraged" in Chapter 5.2 of the Guide to the SI, which was written and published by the U.S. National Institute of Standards and Technology. However, the numerically equivalent SI unit submultiple, the centigray (symbol cGy), is widely used to report absorbed doses within radiotherapy. The roentgen, used to quantify the radiation exposure, may be related to the corresponding absorbed dose by use of the F-factor.

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