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Title: Monte Carlo simulation of {sup 40}K in-vivo body-count spectra for different body shapes

Abstract

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 resultsmore » of these calculations qualitatively agree with the observations and support our hypothesis.« less

Authors:
;  [1]
  1. Los Alamos National Laboratory, NM (United States)
Publication Date:
OSTI Identifier:
394064
Report Number(s):
CONF-9607135-
Journal ID: HLTPAO; ISSN 0017-9078; TRN: 96:028742
Resource Type:
Journal Article
Journal Name:
Health Physics
Additional Journal Information:
Journal Volume: 70; Journal 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
Subject:
56 BIOLOGY AND MEDICINE, APPLIED STUDIES; RADIATION DOSES; M CODES; SHAPE; CORRELATIONS; WHOLE-BODY COUNTING; BODY; PHANTOMS; PHOTONS; SPECTRA; POTASSIUM 40; MASS DISTRIBUTION; COUNTING RATES

Citation Formats

Schillaci, M E, and Brown, T H. Monte Carlo simulation of {sup 40}K in-vivo body-count spectra for different body shapes. United States: N. p., 1996. Web.
Schillaci, M E, & Brown, T H. Monte Carlo simulation of {sup 40}K in-vivo body-count spectra for different body shapes. United States.
Schillaci, M E, and Brown, T H. 1996. "Monte Carlo simulation of {sup 40}K in-vivo body-count spectra for different body shapes". United States.
@article{osti_394064,
title = {Monte Carlo simulation of {sup 40}K in-vivo body-count spectra for different body shapes},
author = {Schillaci, M E and Brown, T H},
abstractNote = {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.},
doi = {},
url = {https://www.osti.gov/biblio/394064}, journal = {Health Physics},
number = Suppl.6,
volume = 70,
place = {United States},
year = {Sat Jun 01 00:00:00 EDT 1996},
month = {Sat Jun 01 00:00:00 EDT 1996}
}