Occupational Intakes of Radionuclides Part 1 - ICRP

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DRAFT REPORT FOR CONSULTATION
give a more realistic description of the human body than afforded in mathematical (or
stylised) phantoms. Thus, the ICRP decided to use voxel models to define the
reference phantoms to be used in the calculations of dose distribution in the body for
both internal and external exposures. These models (or computational phantoms),
described in Publication 110 (ICRP, 2009), represent the Reference Male and Female,
and have organ masses in compliance with the reference anatomical values compiled
in Publication 89 (ICRP, 2002). These phantoms are designed specifically for the
calculation of the radiological protection quantities corresponding to the effective
dose concept of the 2007 Recommendations.
(27) Equivalent doses to organs and tissues, HT, are calculated separately for the
Reference Male and Reference Female and then averaged in the calculation of
effective dose, E:
Where :
H
H
E
M
T
F
T
T
T
T
M H T H
wT
2
w
w
R
R
D
D
T , R
T , R
F
T
(male)
(female)
(28) It is made clear in Publication 103 (ICRP, 2007) that effective dose is
intended for use as a protection quantity on the basis of reference values and relates to
reference persons rather than specific individuals. The main uses of effective dose are
in prospective dose assessment for planning and optimisation in radiological
protection, and retrospective demonstration of compliance for regulatory purposes.
Sex-averaging in the calculation of equivalent and effective doses, implicit in the past
use of hermaphrodite mathematical phantoms, is now explicit in the averaging of
equivalent doses to adult male and female phantoms. Sex- and age-averaging in the
derivation of tissue weighting factors can be seen to obscure differences in estimates
of absolute radiation detriment between men and women and between adults and
children. However, practical protection would not be improved by calculating
effective dose separately for males and females and to do so might give a misleading
impression of the precision of these quantities.
1.5 Biokinetic models implemented in this report
(29) Biokinetic models for individual elements and their radioisotopes are used to
calculate the total number of transformations occurring within specific tissues, organs
or body regions (source regions) during a given period of time (usually 50 y for
adults, or to age 70 y for children) by determining the time-integrated activity in each
source region. Dosimetric models are used to calculate the deposition of energy in all
important organs/tissues (targets) for transformations occurring in each source region,
taking account of the energies and yields of all emissions (Eckerman, 1994).
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