page_title: Sievert
section_title: External dose quantities
hierarchical_section_title: Sievert / External dose quantities
caption_attribution_description: English: Representation of the main dose quantities used in radiation protection based partly on Mattson and Soderberg: "Dose Quantities and Units for Radiation", Ch2 of "Radiation protection in nuclear medicine" Springer Verlag 2013. That in turn is based on ICRU report 57. This final graphic also incorporates an image by Rensselaer Polytechnic Institute entitled VIP-Man phantom developed by Dr. Xu and team at Rensselaer Polytechnic Institute in Troy, NY published in Wikimedia commons ref - Voxel Phantom - Visual Photographic Man (VIP-Man).jpg the purpose being to introduce the concept of a anthropomorphic phantom by using an image.
context_page_description: The sievert is a derived unit of ionizing radiation dose in the International System of Units and is a measure of the health effect of low levels of ionizing radiation on the human body. The sievert is important in dosimetry and radiation protection, and is named after Rolf Maximilian Sievert, a Swedish medical physicist renowned for work on radiation dose measurement and research into the biological effects of radiation.
  The sievert is used for radiation dose quantities such as equivalent dose and effective dose, which represent the risk of external radiation from sources outside the body, and committed dose which represents the risk of internal irradiation due to inhaled or ingested radioactive substances. The sievert is intended to represent the stochastic health risk, which for radiation dose assessment is defined as the probability of radiation-induced cancer and genetic damage. One sievert carries with it a 5.5% chance of eventually developing fatal cancer based on the linear no-threshold model.
context_section_description: When the sievert is used to represent the stochastic effects of external ionizing radiation on human tissue, the radiation doses received are measured in practice by radiometric instruments and dosimeters and are called operational quantities. To relate these actual received doses to likely health effects, protection quantities have been developed to predict the likely health effects using the results of large epidemiological studies. Consequently, this has required the creation of a number of different dose quantities within a coherent system developed by the ICRU working with the ICRP.
  The external dose quantities and their relationships are shown in the accompanying diagram. The ICRU is primarily responsible for the operational dose quantities, based upon the application of ionising radiation metrology, and the ICRP is primarily responsible for the protection quantities, based upon modelling of dose uptake and biological sensitivity of the human body.
caption: External radiation dose quantities used in radiological protection
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