Radiation exposure

For other uses, see Radiation exposure (disambiguation).
Types of electromagnetic radiation

Radiation exposure is a measure of the ionization of air due to ionizing radiation from photons.[1] It is defined as the electric charge freed by such radiation in a specified volume of air divided by the mass of that air.[1] 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.[2] 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.[3] Each type of test carries its own amount of radiation exposure.[2] There are two general categories of adverse health effects caused by radiation exposure: deterministic effects and stochastic effects.[2] 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.[2]

Absorbed dose is a term used to describe how much energy that radiation deposits in a material.[4] 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.[4] This is done using tissue weighting factor, which takes into account how each tissue in the body has different sensitivity to radiation.[4] The effective dose is the risk of radiation averaged over the entire body.[4] Ionizing radiation is known to cause cancer in humans.[4] We know this from the Life Span Study, which followed survivors of the atomic bombing in Japan during World War 2.[5][4] Over 100,000 individuals were followed for 50 years.[5] 1 in 10 of the cancers that formed during this time was due to radiation.[6] The study shows a linear dose response for all solid tumors.[6] This means the relationship between dose and human body response is a straight line.[6]

Radiation exposure
Common symbols
X
SI unitC/kg
Other units
röntgen
In SI base unitsA⋅s/kg

The risk of low dose radiation in medical imaging is unproven.[7] It is difficult to establish risk due to low dose radiation.[7] This is in part because there are other carcinogens in the environment, including smoking, chemicals, and pollutants.[7] A common head CT has an effective dose of 2 mSv.[7] This is comparable to the amount of background radiation a person is exposed to in 1 year.[5] Background radiation is from naturally radioactive materials and cosmic radiation from space.[5] The embryo and fetus are considered highly sensitive to radiation exposure.[8] Complications from radiation exposure include malformation of internal organs, reduction of IQ, and cancer formation.[8] The SI unit of exposure is the coulomb per kilogram (C/kg), which has largely replaced the roentgen (R).[9] One roentgen equals 0.000258 C/kg; an exposure of one coulomb per kilogram is equivalent to 3876 roentgens.[9]

  1. ^ a b Hubbell, John H. (January 2001). "Radiation detection and measurement 3rd Edition, Glenn F. Knoll; Wiley, New York, 2000, pp. xiv+802; cloth: alk. Paper, $112.95, ISBN 0-471-07338-5". Radiation Physics and Chemistry. 60 (1–2): 33–34. doi:10.1016/s0969-806x(00)00323-6. ISSN 0969-806X.
  2. ^ a b c d "The 2007 Recommendations of the International Commission on Radiological Protection. ICRP publication 103". Annals of the ICRP. 37 (2–4): 1–332. 2007. doi:10.1016/j.icrp.2007.10.003. ISSN 0146-6453. PMID 18082557. S2CID 73326646.
  3. ^ Lin, Eugene C. (December 2010). "Radiation risk from medical imaging". Mayo Clinic Proceedings. 85 (12): 1142–6, quiz 1146. doi:10.4065/mcp.2010.0260. ISSN 1942-5546. PMC 2996147. PMID 21123642.
  4. ^ a b c d e f Cite error: The named reference :1 was invoked but never defined (see the help page).
  5. ^ a b c d Cite error: The named reference :03 was invoked but never defined (see the help page).
  6. ^ a b c Cite error: The named reference :2 was invoked but never defined (see the help page).
  7. ^ a b c d Cite error: The named reference :3 was invoked but never defined (see the help page).
  8. ^ a b Cite error: The named reference :4 was invoked but never defined (see the help page).
  9. ^ a b Holmes-Siedle & Adams 2002, p. 4