A later report by Eckerman, Cristy, and Ryman5 added a
description for the esophagus for the several ages and modified the
head and neck descriptions to include a distinct neck region.
The Cristy and Eckerman models are presented as quadratic and planar equations for the organ surfaces. Specifications are given for the elemental composition of three tissue types: lung, skeletal, and soft tissue. The soft tissue composition is used for all organs other than the skeleton and lungs. All soft tissue organs thus appear the same to a radiation transport simulation. Unless a soft tissue organ is required as a source or a tally volume, the efficiency of a Monte Carlo transport simulation is improved by the omission of those organs and the filling of their volume by the generic trunk soft tissue.
Cristy and Eckerman also provide tables of volumes that are not
necessarily the volumes calculated from the mathematical surface
descriptions. The volumes are of primary interest for the calculation
of a specific dose from the total activity absorbed by an organ.
In a few cases, we have made very small changes to organ positions
to avoid overlap with other organs. In some cases a very slight overlap
at some ages has been resolved by including the touching surface of the
overlapping organ in the description of the other. In the 1996 models
with a distinct neck, we have raised the bottom of the upper portion of
the spine to avoid overlap with the esophagus.
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1M. Cristy and K. F. Eckerman, "Specific Absorbed Fractions of Energy at Various Ages from Internal Photon Sources. I. Methods," Oak Ridge National Laboratory Report ORNL/TM-8381/VI (1987).
2W. S. Snyder, M. R. Ford, G. G. Warner, and S. B. Watson, "A Tabulation of Dose Equivalent per Microcurie-day for Source and Target Organs of an Adult for Various Radionuclides: Part I," Oak Ridge National Laboratory Report ORNL-5000 (1974).
3M. Cristy, "Mathematical Phantoms Representing Children of Various Ages for Use in Estimates of Internal Dose," U. S. Nuclear Regulatory Commission Report NUREG/CR-1159 (also Oak Ridge national Laboratory Report ORNL/NUREG/TM-367) (1980).
4M. G. Stabin, E. E. Watson, M. Cristy, J. C. Ryman, K. F. Eckerman, J. L. Davis, D. Marshall, and M. K. Gehlen, "Mathematical Models and Specific Absorbed Fractions of Photon Energy in the Nonpregnant Adult Female and at the End of Each Trimester of Pregnancy," Oak Ridge National Laboratory Report ORNL/TM-12907 (1995).
5K. F. Eckerman, M. Cristy, and J. C.
Ryman, “The ORNL Mathematical Phantom Series,” Oak Ridge National
Laboratory Report, available at
http://homer.hsr.ornl.gov/VLab/VLabPhan.html (Dec. 1996).