The use of body hydrogen as an internal standard in the measurement of nitrogen in vivo by prompt neutron capture gamma-ray analysis

The previously established technique of analysis of neutron capture γ-rays for the determination of nitrogen in-vivo has been modified to make estimates of absolute quantities of nitrogen mass. Hydrogen is used as an internal standard and the nitrogen mass is determined from the observed ratio of nitrogen to hydrogen counts, together with the hydrogen mass, estimated from body parameters. Phantom and cadaver studies indicate that nitrogen mass can be estimated to ±4% or better by this means.