|Shypailo, Roman -|
|Ellis, Kenneth -|
Submitted to: Journal of Radioanalytical and Nuclear Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: February 3, 2007
Publication Date: May 5, 2008
Citation: Shypailo, R.J., Ellis, K.J. 2008. Prompt-gamma neutron activation analysis system design: Effects of D-T versus D-D neutron generator source selection. Journal of Radioanalytical and Nuclear Chemistry. 276(1):71-77. Interpretive Summary: Prompt-gamma neutron activation (PGNA) analysis is used to measure the total amount of nitrogen in the human body, which is related to the amount of protein, an indicator of a person’s health. PGNA uses a neutron source to produce a signal that is measured by detectors. Advancements in portable neutron generator design have made it possible to use a machine as the PGNA neutron source. Two different generators are available – D-D and D-T – each having distinct neutron energy characteristics. We sought to compare the performance of these two units in our present system. We evaluated the nitrogen signal produced within the human body, and estimated the background noise that interferes with the counting system. Our results showed better signal production per unit dose when using the D-D generator, suggesting that it is the more suitable choice for smaller sized subjects. In comparison, the D-T generator produced a greater total signal, and because of its more penetrating neutrons, may be the better choice when examining larger, especially obese, subjects. A clinical PGNA analyzer incorporating both neutron generator options in its design may be the best choice for a system required to measure subjects within a wide range of ages and sizes.
Technical Abstract: Prompt-gamma neutron activation (PGNA) analysis is used for the non-invasive measurement of human body composition. Advancements in portable, compact neutron generator design have made those devices attractive as neutron sources. Two distinct generators are available: D-D with 2.5 MeV and D-T with 14.2 MeV neutrons. To compare the performance of these two units in our present PGNA system, we performed Monte Carlo simulations (MCNP-5; Los Alamos National Laboratory), evaluating the nitrogen reactions produced in tissue-equivalent phantoms and the effects of background interference on the gamma detectors. Monte Carlo response curves showed increased gamma production per unit dose when using the D-D generator, suggesting that it is the more suitable choice for smaller sized subjects. The increased penetration by higher energy neutrons produced by the D-T generator supports its utility when examining larger, especially obese, subjects. A clinical PGNA analysis design incorporating both neutron generator options may be the best choice for a system required to measure a wide range of subject phenotypes.