EFFECTS OF BODY SIZE ON POTASSIUM-40 MEASUREMENT IN WHOLE BODY COUNTER (TILT-CHAIR TECHNIQUE)

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. © 1968 Health Physics Society.