Monte Carlo simulation of {sup 40}K in-vivo body-count spectra for different body shapes
- Los Alamos National Laboratory, NM (United States)
Over the course of several years of measuring in-vivo spectra (whole-body counts) in search of transuranic radionuclides, it has been observed that, relative to the count rate in a region around 80 keV (defined as region 3), large persons have relatively higher count rates than thin persons at around 60 keV (region 2, where an {sup 241}Am line is expected), and relatively lower count rates at around 17 keV (region 1, where both {sup 239}Pu and {sup 241}Am lines are expected). The observed data can be understood in terms of relative amounts of scattering and absorption of the 1.461-MeV photon from {sup 40}K, which occurs naturally in the human body. For larger persons, increased scattering causes the Compton peak to shift to lower energies, thereby increasing the count rate in region 2 relative to region 3. Also, because of increased absorption of very low energy photons, the count rate in region 1 decreases relative to region 3. To test this hypothesis, we compute the Spectrum of photons emerging from cylindrical human phantoms of various dimensions, assuming a variety of distributions of {sup 40}K within the phantom. The calculations are carried out using the Monte Carlo transport code MCNP. The results of these calculations qualitatively agree with the observations and support our hypothesis.
- OSTI ID:
- 394064
- Report Number(s):
- CONF-9607135-; ISSN 0017-9078; TRN: 96:028742
- Journal Information:
- Health Physics, Vol. 70, Issue Suppl.6; Conference: 41. Annual Meeting of the Health Physics Society, Seattle, WA (United States), 21-25 Jul 1996; Other Information: PBD: Jun 1996
- Country of Publication:
- United States
- Language:
- English
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