ABSOLUTE MEASUREMENTS OF TOTAL-BODY CALCIUM USING PROMPT GAMMA-NEUTRON ANALYSIS AND INTERNAL CHLORINE STANDARDIZATION - RESULTS IN RENAL PATIENTS

Measurement of total-body calcium (TBCa) is important in the study of several medical conditions. Neutron activation analysis (NAA) is suffi ciently precise for serial measurements, but in order to provide singl e, absolute determinations of TBCa, it requires a correction for body habitus. A method is described for the absolute determination of TBCa by comparing the total-body chlorine, obtained by NAA, with that obtai ned by stable bromine dilution. The method is applied to a group of th irty patients who had been treated for chronic renal failure, and sign ificant differences are found between measured values of TBCa and thos e predicted for 'normal' healthy subjects. The overall experimental er ror in the absolute determination of TBCa is estimated to be 8%, for a dose equivalent of 3.1 mSv (based on skin dose, and a quality factor of 10 for neutrons).