Re: Ambient dose equivalent H(10) (ICRU 39)

[nolan Hertel <nolan.hertel@me.gatech.edu>]

According to ICRU 43, page 7 this effect occurs below 0.2 MeV due to the
importance of scattered photons.  Exposure does not include body scatter
and ambient dose does.  They indicate that this effect peaks at 80 keV and
diminishes below it due to the attenuation in the intervening 10 mm of
tissue-equivalent material in the ICRU sphere.  

I have personally found that ICRU Report 43 is invaluable in terms of
trying to interpret ICRU 39, even in terms of understanding the basic dose
equivalent quantity definitions.
Nolan

There is also a somewhat sketchy 11:36 AM 6/15/99 -0500, you wrote:
>Dear RadSafers
>
>Could anyone help me to understand the physical basis for Figure 3 in ICRU39.
>This is the conversion of exposure (roentgen) to ambient dose equivalent
>(cSv).
>Why is it not equal to the ratio of the mass attenuation coefficients for
>tissue and air? For example, near 80 keV, Figure 3 shows about 1.7, whereas
>the ratio of the mass attenuation coefficients is about 1.1. What is the
>physical basis used to obtain Figure 3?
>
>Thank you, mike
>
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Nolan E. Hertel, PhD, PE
Director, Neely Research Center
Professor of Nuclear Engineering and Health Physics
G. W. Woodruff School of Mechanical Engineering
Georgia Institute of Technology
Atlanta, GA 30332-0425
(404)894-3601
facs: (404) 894-9325
email: nolan.hertel@me.gatech.edu
www.me.gatech.edu 
www.nnrc.gatech.edu
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