Multi-element analysis of the human body using neutron activation.

The calibration described is of the Leeds in vivo neutron activation facility for the simultaneous measurement of total body Na, Cl, P, Ca, N and K. The effects of body size and shape have been incorporated into the calibration using a variable anthropomorphic phantom. The main interfering reactions are considered, and the method by which the results are corrected for these interferences described. The accuracy and precision of the technique have been determined. The procedure is suitable for measuring the critically ill since both irradiation and counting are performed with the patient lying supine. For a whole body dose equivalent of 0.5 mSv nitrogen was measured with a coefficient of variation (CV) of 2.2%; potassium was measured in the same counting period with a CV of 1.6%. Using a dose equivalent of 5 mSv sodium (2.2%), chlorine (1.6%) and phosphorus (2.9%) were also determined; for a 10 mSv dose equivalent calcium was measured with a CV of 3%.