Introduction to Health Physics: Fourth Edition - Ruang Baca FMIPA UB

264 CHAPTER 6
The dose to a single target from a single radionuclide in a single source organ
(for multiple sources and multiple radionuclides, we merely sum the contributions
of each source and each radionuclide.) is given by MIRD, Eq. (6.97) as
D(rk ← rh) = Ãh × S(rk ← rh).
The ICRP formulation is given as
H50,T (T ← S) = US transf. × SEE (T ← S)
where
Sv
, (6.104)
transf.
H50,T(T ← S) is the equivalent dose accumulated during 50 years after intake,
US is the total number of disintegrations during 50 years after intake, and
SEE (T ← S) is the specific effective energy absorbed per gram of target tissue
from each radiation, R, emitted from activity in the source organ.
It is calculated from the following equation:
SEE (T ← S)
=
particles
YR
trans. × (E × w R) effectiveMeV
particle × 1.6 × 10−13 J
MeV × AF(T ← S) 1Sv
R
eff.J
×
mT kg
trans
R
where
= Sv
, (6.105)
trans
YR is the fractional yield, per disintegration, of the radiation under consideration,
w R is the radiation weighting factor (formerly symbolized by Q),
w R = 1 for gamma and beta radiation, and 20 for alphas,
AF (T ← S)R is the absorbed fraction from radiation R in T per transformation
in S, and 3
mT is the mass of T, in kg.
Comparison of Eqs. (6.97) and (6.104) shows that the MIRD and ICRP equations
are essentially the same. There are two differences between them: One is that the
MIRD is the total lifetime dose, expressed in Gy (or rads in traditional units) while
the ICRP dose is the effective dose, expressed in Sv (or rems in traditional units) for
3Tables of specific absorbed fractions may be found in Cristy and Eckerman, ORNL/
NUREG/TM 8381.