Biomedical Engineering Reference
In-Depth Information
Fig. 16.10
Decay-scheme data for
131
I as given in ICRP
Publication 38. [Reprinted with permission from
Radionuclide
Transformations
, ICRP Publ. 38, p. 453, International
Commission on Radiological Protection, Sutton, England
(1983). Copyright 1983 by ICRP.]
be close to the total value [Eq. (16.45)] obtained from the detailed scheme shown
in Fig. 16.10. The close agreement results because (1) we were not far off in esti-
mating
Y
R
E
R
from Appendix D for the beta particles plus conversion electrons
and (2) most of the photon energy escapes from the small thyroid. As is more often
the case, however, self-absorption of photons in an organ is important and simple
estimates are not reliable. When the source and target organs are different, then
the detailed Monte Carlo calculations offer the only feasible way of obtaining all of
the needed specific absorbed fractions reliably. As mentioned in connection with
Fig. 16.2, some absorbed-fraction computations have been checked experimentally.
Today, detailed decay data for more than 800 radionuclides are maintained in
computer files by the Dosimetry Research Group at the Oak Ridge National Lab-
oratory.
4)
The data base has been assembled over the years in conjunction with
Publications 30 and 38 and subsequent work of the ICRP and publications of the
MIRD Committee of the Society of Nuclear Medicine, mentioned earlier. An associ-
ated program, which can be run on a personal computer, calculates age-dependent
4 K. F. Eckerman, R. J. Westfall, J. C. Ryan, and
M. Cristy,
Nuclear Decay Data Files of the
Dosimetry Research Group
,Report
ORNL/TM-12350, Oak Ridge National
Laboratory, Oak Ridge, Tenn. (Dec., 1993).
