Improvement of the prompt-gamma neutron activation facility at Brookhaven National Laboratory

The prompt-gamma neutron activation facility at Brookhaven National Laboratory was upgraded to improve both the precision and accuracy of its in vivo determinations of total body nitrogen. The upgrade, guided by Monte Carlo simulations, involved elongating and modifying the source collimator and its...

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Bibliographic Details
Published in:	Physics in medicine & biology 1998-02, Vol.43 (2), p.339-349
Main Authors:	Dilmanian, F A, Lidofsky, L J, Stamatelatos, I, Kamen, Y, Yasumura, S, Vartsky, D, Jr, R N Pierson, Weber, D A, Moore, R I, Ma, R
Format:	Article
Language:	eng
Subjects:	Applied radiobiology (equipment, dosimetry...) Biological and medical sciences Biological effects of radiation Fundamental and applied biological sciences. Psychology Gamma Rays Humans Models, Theoretical Monte Carlo Method Neutron Activation Analysis - instrumentation Neutron Activation Analysis - methods Neutrons Nitrogen - analysis Nitrogen Isotopes Nuclear Reactors Phantoms, Imaging Radiation Protection Reproducibility of Results Sensitivity and Specificity Tissues, organs and organisms biophysics
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Summary:	The prompt-gamma neutron activation facility at Brookhaven National Laboratory was upgraded to improve both the precision and accuracy of its in vivo determinations of total body nitrogen. The upgrade, guided by Monte Carlo simulations, involved elongating and modifying the source collimator and its shielding, repositioning the system's two NaI(Tl) detectors, and improving the neutron and gamma shielding of these detectors. The new source collimator has a graphite reflector around the 238PuBe neutron source to enhance the low-energy region of the neutron spectrum incident on the patient. The gamma detectors have been relocated from positions close to the upward-emerging collimated neutron beam to positions close to and at the sides of the patient. These modifications substantially reduced spurious counts resulting from the capture of small-angle scattered neutrons in the NaI detectors. The pile-up background under the 10.8 MeV 14N(n, gamma)15N spectral peak has been reduced so that the nitrogen peak-to-background ratio has been increased by a factor of 2.8. The resulting reduction in the coefficient of variation of the total body nitrogen measurements from 3% to 2.2% has improved the statistical significance of the results possible for any given number of patient measurements. The new system also has a more uniform composite sensitivity.
ISSN:	0031-9155 1361-6560