Editing Equivalent dose (section)

==Related quantities==

===Limitation of equivalent dose calculation===
Equivalent dose ''H''<sub>T</sub> is used for assessing stochastic health risk due to external radiation fields that ''penetrate uniformly'' through the ''whole body''. However it needs further corrections when the field is applied only to part(s) of the body, or non-uniformly to measure the overall stochastic health risk to the body. To enable this a further dose quantity called [[Effective dose (radiation)|effective dose]] must be used to take into account the varying sensitivity of different organs and tissues to radiation.

===Relationship to committed dose===
Whilst equivalent dose is used for the stochastic effects of external radiation, a similar approach is used for internal, or [[committed dose]]. The ICRP defines an equivalent dose quantity for individual committed dose, which is used to measure the effect of inhaled or ingested radioactive materials. A committed dose from an internal source represents the same effective risk as the same amount of equivalent dose applied uniformly to the whole body from an external source.

'''Committed equivalent dose''', H <sub>T</sub>(''t'') is the time integral of the equivalent dose rate in a particular tissue or organ that will be received by an individual following intake of radioactive material into the body by a Reference Person, where s is the integration time in years.<ref>ICRP publication 103 - Glossary.</ref>
This refers specifically to the dose in a specific tissue or organ, in the similar way to external equivalent dose.

The ICRP states "Radionuclides incorporated in the human body irradiate the tissues over time periods determined by their physical half-life and their biological retention within the body. Thus they may give rise to doses to body tissues for many months or years after the intake. The need to regulate exposures to radionuclides and the accumulation of radiation dose over extended periods of time has led to the definition of committed dose quantities".<ref>ICRP Publication 103 paragraph 140</ref>

===Equivalent dose V dose equivalent===
There is no confusion between ''equivalent dose'' and ''dose equivalent''. Indeed, they are same concepts. Although the CIPM definition states that the linear energy transfer function of the ICRU is used in calculating the biological effect, the ICRP in 1990 <ref>ICRP publication 60 published in 1991</ref> developed the "protection" dose quantities named ''effective'' and ''equivalent'' dose, which are calculated from more complex computational models and are distinguished by not having the phrase ''dose equivalent'' in their name.

Prior to 1990, the ICRP used the term "dose equivalent" to refer to the absorbed dose at a point multiplied by the quality factor at that point, where the quality factor was a function of [[linear energy transfer]] (LET). Currently, the ICRP's definition of "equivalent dose" represents an average dose over an organ or tissue, and radiation weighting factors are used instead of quality factors.

The phrase ''dose equivalent'' is only used for which use Q for calculation, and the following are defined as such by the ICRU and ICRP:

* ambient dose equivalent
* directional dose equivalent
* personal dose equivalent

In the US there are further differently named dose quantities which are not part of the ICRP system of quantities.<ref>[http://www.wmsym.org/archives/2009/pdfs/9444.pdf - "The confusing world of radiation dosimetry"] {{Webarchive|url=https://web.archive.org/web/20161221205248/http://www.wmsym.org/archives/2009/pdfs/9444.pdf |date=2016-12-21 }} - M.A. Boyd, U.S. Environmental Protection Agency 2009. An account of chronological differences between US and ICRP dosimetry systems.</ref>

===Use of old factors===
[[File:Neutron radiation weighting factor as a function of kinetic energy.gif|thumb|350px|The radiation weighting factor for neutrons has been revised over time, and is different for US NRC, and ICRP.]]
The [[International Committee for Weights and Measures]] (CIPM) and the US [[Nuclear Regulatory Commission]] continue to use the old terminology of quality factors and dose equivalent. The NRC quality factors are independent of linear energy transfer, though not always equal to the ICRP radiation weighting factors.<ref name=NRC1004 /> The NRC's definition of dose equivalent is "the product of the absorbed dose in tissue, quality factor, and all other necessary modifying factors at the location of interest." However, it is apparent from their definition of effective dose equivalent that "all other necessary modifying factors" excludes the tissue weighting factor.<ref>{{cite book|title=10 CFR 20.1003|year=2009|publisher=US Nuclear Regulatory Commission|url=https://www.nrc.gov/reading-rm/doc-collections/cfr/part020/part020-1003.html}}</ref>
The radiation weighting factors for neutrons are also different between US NRC and the ICRP - see accompanying diagram.

===Dosimetry reports===
Cumulative equivalent dose due to external whole-body exposure is normally reported to nuclear energy workers in regular [[dosimetry]] reports.

In the US, three different equivalent doses are typically reported: 
*[[deep-dose equivalent]], (DDE)
* shallow dose equivalent, (SDE)
* eye dose equivalent