# Dosimetry:  equivalent dose vs. effective dose

**URL:** <https://boards.straightdope.com/t/dosimetry-equivalent-dose-vs-effective-dose/657150>\
**Category:** Factual Questions\
**Created:** [April 30, 2013, 9:47pm UTC](https://boards.straightdope.com/t/dosimetry-equivalent-dose-vs-effective-dose/657150 "2013-04-30T21:47:02Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![MikeS](https://avatars.discourse-cdn.com/v4/letter/m/919ad9/32.png) [@MikeS](https://boards.straightdope.com/u/MikeS)\
**Post date:** [April 30, 2013, 9:47pm UTC](https://boards.straightdope.com/t/dosimetry-equivalent-dose-vs-effective-dose/657150/1 "2013-04-30T21:47:02Z")

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I’m teaching a “physics for pre-meds” course this semester, and we’re going to be talking about radiation soon. Since this is a pre-med course, I want to talk about the differences between activity, absorbed dose, equivalent dose, effective dose, etc. But the stuff I’ve found online seems to be inconsistent with what’s in the textbook. The textbook reads, in part,

> [@](#):
>
> The **relative biological effectiveness** (RBE) or **quality factor** (QF) of a given type of radiation is defined as the number of rads of X- or gamma-ray radiation that produces the same biological damage as 1 rad of the given radiation. …
> 
> The **effective dose** can be given as the product of the dose in [grays] and the QF: …
> 
> ```
> effective dose (Sv) = dose (Gy) x QF. 
> 
> ```

My question is mainly about terminology. If you look at the Wikipedia pages on [equivalent dose](http://en.wikipedia.org/wiki/Equivalent_dose) and [effective dose](http://en.wikipedia.org/wiki/Effective_dose_(radiation)), it seems like that quantity that the textbook is calling “effective dose” is what Wiki calls the “equivalent dose”. What Wiki calls the “effective dose” seems to have something to do with the fact that different organs are more or less likely to develop cancer after a given dose in seivert.

Is the textbook closer to the accepted terminology, or is Wiki? Has terminology changed in the last couple of years or something? (The current edition of the text is from 2005, but the first edition is from 1980 and for all I know this verbiage has been in the textbook from the beginning.) I’m perfectly willing to believe that this textbook got it wrong, but I want to make sure of it before I tell the students this.

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**Author:** ![Pasta](https://avatars.discourse-cdn.com/v4/letter/p/ecccb3/32.png) [@Pasta](https://boards.straightdope.com/u/Pasta)\
**Post date:** [May 1, 2013, 12:09am UTC](https://boards.straightdope.com/t/dosimetry-equivalent-dose-vs-effective-dose/657150/2 "2013-05-01T00:09:01Z")

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The wiki definitions are the usual ones.

ETA: Figured I could pull a book off the shelf to provide a cite, if you want one for class: W. R. Leo, “Techniques for Nuclear and Particle Physics Experiments”, which also uses the same notation as the wiki page.

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**Author:** ![yoyodyne](https://avatars.discourse-cdn.com/v4/letter/y/a9a28c/32.png) [@yoyodyne](https://boards.straightdope.com/u/yoyodyne)\
**Post date:** [May 1, 2013, 1:44pm UTC](https://boards.straightdope.com/t/dosimetry-equivalent-dose-vs-effective-dose/657150/3 "2013-05-01T13:44:49Z")

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Equivalent dose and effective dose are the same for whole-body irradiation. Think of effective dose as a way to convert a partial-body equivalent dose to a whole-body equivalent dose.