Effects of Body Size on Potassium-40 Measurement in the Whole Body Counter (Tilt-chair Technique)

Abstract

The precision of ⁴⁰K determination in man by the tilt-chair technique is compromised by geometrical and self absorption factors. In an attempt to improve calibration accuracy simultaneous measurements of ⁴⁰K and total body water (deuterium dilution) were made in 50 subjects of widely varying body size. The results show that neither height nor weight per se affects the observed body ratio of ⁴⁰K/H₂O, and that the principal systematic error concerns the relative fat content of the subject. Correction of the observed ⁴⁰K values for this factor improves the accuracy of the measurement.