Talk:Relative biological effectiveness

Untitled

First, thanks to those who have contributed so far. However, in the version I'm currently looking at, there are no references -- neither in-line nor global (besides one peripheral one about smoking and radiation). Can someone provide some? Thanks. Jespley (talk) 01:03, 31 July 2008 (UTC)

Merge

Almost all the information from equivalent dose and absorbed dose is in this more complete article already. I suggest it all go here (since RBE is the standard abbreviation) and redirect the other terms to here. SBHarris 23:18, 9 January 2011 (UTC)

• I disagree. These are distinct concepts in the nuclear power industry, with force of law behind them (specifically the very long-standing 10 CFR 835). Link between them all you want, but people need to perceive these as distinct entities. Niels Olson (talk) 07:50, 29 March 2011 (UTC)
• Disagree too. The RBE is only one factor in the equivalent dose computation, and it is complicated enough that it deserves its own article. Just as π deserves an article separate from circle...Jorge Stolfi (talk) 22:40, 8 June 2011 (UTC)

Recommendation deleted

I have removed this sentence since it is prescriptive, and Wikipedia is not meant to be a manual:

Due to the uncertainty associated with the RBE for alpha radiation, and the lack of neutron exposure to personnel in almost all settings, to use rems or sieverts as measures of comparative radiation exposure, and instead to use the actual exposure in rads or grays, followed with a description of the type of radiation.

Jorge Stolfi (talk) 22:40, 8 June 2011 (UTC)

W_R, RBE, and Q

One of our editors has undertaken to "disintangle" these by saying that RBE is "represented by" W_R (previously called Q). And changed the tables to W_R tables and banned RBE from them (even though this is an article about RBE-- see title). If there is a difference here, it is subtle, and still is not explained. The reference given is to an out of print book and is not helpful. Would anybody like to explain this? If W_R is merely what you call RBE from in vitro tissue experiments, when you get to dosimetry in a living organism, but otherwise is the same number, then we should say that. But it's sort of ridiculous to have two different terms for the same thing, and insist on them. SBHarris 18:31, 8 May 2012 (UTC)

That would be me, and I'm happy to explain. First of all, the reference given, ICRP publication 92, is certainly not out of print. Paper copies are apparently out of stock at Elsevier, but you can buy electronic copies from a science direct or directly from the ICRP. Not that there would be anything wrong with citing an out of print book, especially one just published in 2003! Anyway, you don't have to buy it to get a sense of the puzzle; the preface's guest editorial is available for free as a Google Books preview.

Briefly put, the RBE is an empirical value; i.e. it is the measured by scientific experiments. (With a lot of statistical analysis thrown in.) The Wr and Q are not experimental results. They are standardized figures used in dosimetry to represent the RBE. Wr and Q are conservatively chosen by regulatory bodies to be higher than most RBE measurements, because there is still a lot of uncertainty and experimental spread about the true RBE values. See for example figure 1 in reference 3. I thought I tried to explain that in the article, but please help out if you see a better way to say it. I don't really like your proposed sentence above because W_R doesn't come from in vitro experiments; it comes from the judgement of regulators based on in vitro and in vivo data. Note, for example that reference 3 proposed a W_R of 5 for animals while 20 is used for humans; the difference essentially represents a reduced safety factor, not a different effectiveness in animals versus humans.--Yannick (talk) 00:45, 9 May 2012 (UTC)

That's very helpful. No, you explain it above far better than the article does. What we need is some tables of both regulatory Wr's and RBEs side by side, so that they can be compared. I'll see what I can do about putting in some additional explanation. I take it that Wr is just a new regulatory name for what used to be called Q? Or is Q still used? SBHarris 01:03, 9 May 2012 (UTC)

The ICRP recommends using Wr, and most scientific articles seem to have followed suit. Unfortunately Q is still used by industry, notably in the US where the Nuclear Regulatory Commission requires its own values different from ICRP recommendations. By the way, I just noticed that our table actually uses the older ICRP60 values for neutrons, not ICRP92. Maybe you could fix that at the same time? There's plenty of things to trip over in dosimetry, so your help is greatly appreciated.--Yannick (talk) 02:02, 9 May 2012 (UTC)

I found this document which tries to document the pre-wikipedia history.--Yannick (talk) 02:58, 9 May 2012 (UTC)

ICRP Publication 103, annex B, para B72 "The weighting factors are intended to take account of different types of radiation and of stochastic effects in different organs in the body" - i.e. WR is an estimate of RBE specifically for stochastic effects and not for tissue reactions. Thus, for protons WR = 2 [ICRP 103 table 2] but for proton radiotherapy a value of RBE = 1.1 is commonly used [Harald Paganetti, Relative biological effectiveness (RBE) values for proton beam therapy. Variations as a function of biological endpoint, dose, and linear energy transferPhys. Med. Biol. 59 (2014) R419–R472] --JohnS (talk) 11:33, 1 December 2014 (UTC)

Angstroms? Really?

I just came across this article and noticed the "too technical" banner at the top. Then in the lead in I see Angstroms being used. Not only are they a non-SI unit, but they're not integral to the topic at hand. I happen to be a chemist, so I know that Angstroms are 1/10 of a nm, but they're probably esoteric for most readers. Since the sentence they occur in is a comparison, no units are really required, it could simply read, "blah blah path left is 1000 times broader for ____ forms of radiation," thereby removing the units altogether. 64.114.134.52 (talk) 20:18, 8 June 2013 (UTC)

Okay, took the Angstroms out and converted all to nm. I also did the ratio you suggest, but this ratio needs to be anchored at some point to tell how far apart the ionizations are in absolute terms. So that had to be left in. The reader now has the choice of looking at it either way. SBHarris 22:28, 8 June 2013 (UTC)

RBE and W_R (Q) are VERY different things

As far as I know, RBE and Q are very different things. RBE is used in context of radiotherapy i.e. high doses, where deterministic effects are considered. For example, RBE for protons is equal to 1.1, which means that we should prescribe either 70 Gy of photon radiation from medical linac, or 63.6 Gy of proton radiation from medical cyclotron to achieve the same TCP (tumor control probability).

W_R (Q) is used in radiation protection, where we want to minimise doses received by person and we consider just stochastic effects (probability of carcinogenesis). For example, alpha particles have W_R = 20, which means that 1 mGy of alpha particles should be considered as 20 mSv, while 1 mGy of gamma radiation is considered 1 mSv. (Also, sieverts are never used in radiotherapy context).

These terms may look alike, but they are not synonyms and should not be mixed.

Weighting factors for 15 KeV neutrons

The text states: Thus, for example, a given amount of energy absorbed in the form of 15 keV neutrons should be assumed to produce 10 times the damage caused by an equal amount of energy absorbed as X-rays or gamma rays. However, using the formula in line 2 (which correctly represents the formula in P103 The 2007 Recommendations of the International Commission on Radiological Protection) yields a weighting factor of 3.5 for 15 KeV (0.015 MeV) neutrons! (in Matlab, E=0.015;2.5+18.2*exp(-(log(E))^2/6) yields 3.46). Indeed the old formula (not energy dependent) used a factor of 10 for 15 KeV neutrons. Am I missing something, or should the text be updated to indicate a factor of 3.5? --PloniAlmoni (talk) 09:33, 24 December 2019 (UTC)

Comment on the graph with title RBE definition

The text in the section "Experimental methods" as well as the description of the figures states, that the LD-30 limit is shown.

I think this statement is wrong, it should be the LD-70 limit.

LD-30 talks about the dose needed to kill 30% of the population. The horizontal line drawn in the graph is at 0.3 of survival fraction, i.e. 30% have survived -> this is the dose, where 70% have been killed. — Preceding unsigned comment added by TheRealMephisto (talk • contribs) 10:36, 4 June 2022 (UTC)