Re: Mice and elephants

[JMUCKERHEIDE@delphi.com]

Note that in the context of the subject, this is not important. The issue is
the effect of 'dose' to cells (dose-significant cells). Whether that is from
internal or external exposure, attentuated or not, wasn't the point, even
though the specific analysis of that dose in relation to the entry dose
(whether gamma- or x-rays) is a valid issue. 

Thanks.

Regards, Jim Muckerheide
jmuckerheide@delphi.com


> On Sun, 6 Jul 1997 Ccja@aol.com wrote:
> > In re the question of the radiobiological equivalencies of exposure: in
> > health physics, for the purposes of routine protection of persons (in
> > contrast to, let's say, basic research into dosimetry) the value most
> > commonly used, where exposure to penetrating external radiation is the
> > concern, is the deep dose equivalent (DDE). That is, the dose equivalent at a
> > depth of 1 gram/sq.cm. (i.e., 1 cm.) in soft tissue, starting at the exterior
> > of the body. This is merely a convenient indexing point. Most of the organs
> > which we are really protecting, e.g., the lungs, thyroid, female gonads, red
> > bone marrow, etc., are at much greater depths, and sometimes pretty well
> > shielded (RBM). Even the male gonads are well shielded, in the lateral view.
> > Also, occupationally exposed individuals, and the general public, are not
> > usually exposed to, for instance, the direct beam of a medical linac, in
> > which electronic equilibrium may not be achieved before a depth of several
> > centimeters.
> > 
> > So, I would think that a sumo wrestler (or an elephant), would receive less
> > "real" exposure, if the DDE is the measure of said exposure, than a jockey,
> > or, more to the point, a small child (or a mouse), for the same reason that
> > fetuses receive rather less exposure than the expectant (or unknowing)
> > mother, in most cases.
> > 
> > chris alston
> > ccja@aol.com
> > 
>         For gamma rays and neutrons, the attenuation length is about 10-15
> cm (depending on their energy) which makes shielding much less important
> than Chris implies. For X-rays. of course, Chris has an excellent point.