Editing Absorbed dose (section)

==Stochastic risk - conversion to equivalent dose==
[[File:Dose quantities and units.png|thumb|400px|External dose quantities used in radiation protection and dosimetry]]

[[File:SI Radiation dose units.png|thumb|400px|Graphic showing relationship of "protection dose" quantities in [[SI]] units]]

For [[stochastic]] radiation risk, defined as the ''probability'' of cancer induction and genetic effects occurring over a long time scale, consideration must be given to the type of radiation and the sensitivity of the irradiated tissues, which requires the use of modifying factors to produce a risk factor in [[sievert]]s. One sievert carries with it a 5.5% chance of eventually developing cancer based on the [[linear no-threshold model]].<ref name="ICRP103">{{cite journal|title=The 2007 Recommendations of the International Commission on Radiological Protection|journal=Annals of the ICRP|year=2007|volume=37|series=ICRP publication 103|issue=2–4|url=http://www.icrp.org/publication.asp?id=ICRP%20Publication%20103|access-date=17 May 2012|isbn=978-0-7020-3048-2}}</ref><ref>The ICRP says, "In the low dose range, below about 100 mSv, it is scientifically plausible to assume that the incidence of cancer or heritable effects will rise in direct proportion to an increase in the equivalent dose in the relevant organs and tissues." ICRP publication 103 paragraph 64</ref> This calculation starts with the absorbed dose.

To represent stochastic risk the dose quantities [[equivalent dose]] ''H<sub>T</sub>'' and [[Effective dose (radiation)|effective dose]] ''E'' are used, and appropriate dose factors and coefficients are used to calculate these from the absorbed dose.{{sfn | ICRP | 2007 | loc= paragraphs 104 and 105 }} Equivalent and effective dose quantities are expressed in units of the [[sievert]] or [[rem (unit)|rem]] which implies that biological effects have been taken into account. The derivation of stochastic risk is in accordance with the recommendations of the [[ICRP|International Committee on Radiation Protection]] (ICRP) and [[International Commission on Radiation Units and Measurements]] (ICRU). The coherent system of radiological protection quantities developed by them is shown in the accompanying diagram.

For whole body radiation, with [[Gamma rays]] or [[X-rays]] the modifying factors are numerically equal to 1, which means that in that case the dose in grays equals the dose in sieverts.