The feasibility of measuring total body carbon by counting neutron inelastic scatter gamma rays

Abstract

A technique is examined for measuring the mass of carbon of both ambulatory and non-ambulatory subjects. The method is based upon the detection of the 4.43 MeV gamma rays emitted from carbon nuclei when the body is irradiated with fast neutrons. The supine subject is irradiated laterally by a horizontal collimated beam of 14 MeV neutrons and the emitted gamma rays are counted by a shielded NaI(Tl) detector placed underneath the subject. The method has been calibrated for all sizes of subjects from 30 to 90 kg and there appears to be no significant interference from the other bulk elements of the body. Body carbon has been measured in six normal volunteers; body nitrogen was also determined by measuring the 13N induced in each subject in a second irradiation. Body fat was estimated from the measured carbon and nitrogen, and the values compared with those derived from skinfold thicknesses. The technique is proposed as a method of estimating long-term energy expenditure.

Human Body Composition: In Vivo Methods

“…Another example is the simultaneous measurement of body carbon and body hydrogen (by neutron activation) as assays for body fat mass and total body water, respectively (161,178,286). This information is a duplication of that obtained using DXA for fat mass and deuterium dilution for total body water.…”

Development of methods for body composition studies

“…Fast neutrons that interact with matter by inelastic collisions result in prompt nuclear de-excitation with gamma-ray release (n, n γ ) preferentially measured in large volume neutron-tolerant BGO detectors. Total body carbon (which is used as a measure of the body fat content) is derived by measuring the 4.44 MeV photons from 12 C nuclei (Kyere et al 1982) and the total body oxygen by measuring the 6.13 MeV gamma ray from inelastic scattering in oxygen. The carbon/oxygen ratio offers a technique to measure the axial distribution of fat because of the dramatic difference in C/O ratio between fat and fat-free tissues (Kehayias et al 1991, Kehayias andZhuang 1993).…”

Multi-component body composition models: recent advances and future directions

“…The ®rst component in this model, total body water, is quanti®ed using either tritiated water or deuterium dilution. Total body nitrogen is next measured with the technique referred to as prompt gamma neutron activation analysis (Beddoe et al, 1984;Dutton, 1991;Kyere et al, 1982;Mernagh et al, 1977;Pierson et al, 1990;Varstsky et al, 1984). Total body nitrogen is then used to calculate total body protein mass.…”