Re: Mammo Effective Dose

[Dan Burnstein <npro1@ziplink.net>]

Joel, Chris, and others:

Wondering if there is a chart of risk ratio of various exposures to organs and
whole body on the internet that is reputable?  Understandably, this might
include the 'health giving fruits and vegetables with K-40, a single chest
x-ray, masonary, and so forth.  Don't you think this could help create a class
of educated consumers less prone to blind anxiety and more able to separate
out real risks from imagined ones?  Any references to good charts would be
appreciated.

Thanks,
Dan

Chris Alston wrote:

> Joel
>
> I must respectfully take issue with you on this one. Firstly, if it
> should happen that only one organ/tissue is irradiated, then there would
> be nothing wrong, in principle, with multiplying that single, mean
> glandular dose by the tissue weighting factor (ICRP 26 is still in force
> in the USA), to arrive at a total effective dose equivalent (TEDE). This
> is true exactly because the TEDE is the sum of the EDE's to all the
> irradiated organs (and the DDE, in the occupational arena). So, all
> you're doing is adding zero (0) to whatever EDE you've arrived at for the
> organ/tissue of interest, since there are no other doses of significance.
> Actually, this is the norm in occupational work with radioiodines,
> because the doses to tissues other than the thyroid are negligible, and
> the weighting factor for the thyroid is so large. I do wonder about
> applying the weighting factor (W<smaller><smaller>T</smaller></smaller>)
> for the general population to the exclusively female subpopulation that
> is mammoed. Since the male breast is much less radiosensitive than that
> of the female, it would seem that, for this group, the factor is biased
> low.
>
> Then, it is true that the EDE should not be used to estimate risks to a
> single individual. (I'm not sure how the MGD would be used, though, given
> that these are risks of stochastic effects.) It doesn't follow that the
> EDE is not a useful value, for patient education. It helps people to put
> a medical doses in perspective, if one can relate them, simply, to doses
> received during their everyday lives, e.g., external backgrounds,
> internal doses from the K-40 in the fruits and vegetables that are,
> reputably, so health-giving. Even if one were to misuse the EDE, by
> applying it to an individual (and, I assure you, it's done all the time),
> the risk/benefit ratio, where the benefit would be catching a tumor
> early, would be, clearly, very small.
>
> Someone's probably going to question the meaningfulness of using an EDE
> derived for the general population for a medical subgroup (i.e.
> patients). Whatever the merits of that argument in other contexts, it
> seems to me that this case is not comparable, since essentially all women
> should be getting regular mammograms as a part of routine
> health-monitoring.
>
> I shall now recline in my seat, put up my feet, and eagerly await the
> slings and arrows of my esteemed colleagues in cyberspace.
>
> Cheers
>
> cja
>
> At 03:16 PM 10/19/99 -0500, you wrote:
>
> >I think one should be extremely cautious when attempting to determine
> the
>
> >effective dose for a single organ and single individual.
>
> >
>
> >First of all, ICRP's intention was that the effective dose concept be
> used
>
> >for radiation protection purposes of populations exposed to radiation.=20
> The
>
> >weighting factors for calculating the effective dose are, therefore,
> based
>
> >on a reference population of equal numbers of both sexes and a wide
> range
>
> >of ages.
>
> >
>
> >ICRP 60 states "The effective dose is the sum of weighted equivalent
> doses
>
> >in ALL tissues and oragns of the body" which to my way of thinking
> means
>
> >more than one type of tissue.
>
> >
>
> >The purpose of the effective dose is to be able to estimate a risk of
> fatal
>
> >cancer which would be equivalent to the same dose if given uniformily
> to
>
> >the whole body.
>
> >
>
> >If one is concerned about the risk of breast cancer then effective dose
> is
>
> >not the metric of choice but one should be considering the mean
> glandular
>
> >dose (MGD).  The risk of a developing a fatal cancer can then be
> determined
>
> >based on the MGD and the age at exposure.
>
> >
>
> >          Joel
>
> >
>
> >Joel E. Gray, Ph.D., Consultant
>
> >2804 Second Street Southwest, Suite 334
>
> >Rochester, Minnesota 55902
>
> >
>
> >Business Phone  507-269-4247
>
> >Fax  507-286-8910
>
> >Home Phone  507-286-8910
>
> >e-mail  joelgray@sprynet.com
>
> >
>
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