TM8381V6.pdf

This report is the sixth volume of a series in which specific absorbed fractions ( ’s) in various organs of the body ("target organs") from sources of monoenergetic photons in various other organs ("source organs") are tabulated. The first volume (ORNL/TM-8381:Vol. 1) outlines various methods used to compute the -values and describes how the "best" estimates recommended by us are chosen. In this volume -values are tabulated for a newborn or 3.4-kg person. In companion volumes -values are tabulated for ages 1, 5, 10, and 15 years, an adult female and for an adult male. These -values can be used in calculating the photon component of the dose-equivalent rate in a given target organ from a given radionuclide that is present in a given source organ. The methods used to calculate are similar to those used by Snyder et al. (1974) for an adult. However, an important difference involves the dosimetry for radiosensitive tissues in the skeleton. The International Commission on Radiological Protection recognizes, in the radiation protection system of its Publication 26 (1977), that the endosteal, or "bone surface," cells are the tissue at risk for bone cancer. We have applied the dosimetry methods that Spiers and co-workers developed for beta-emitting radionuclides deposited in bone to follow the transport of secondary electrons (freed by photon interactions) through the microscopic structure of the skeleton. With these methods we can estimate in the endosteal cells and can better estimate in the active marrow; the latter is overestimated with the methods of Snyder et al. at photon energies below 200 keV.