Abstract
An anthropomorphic phantom was used to calibrate a supine geometry sodium iodide total body potassium monitor. Correction factors accommodating variability in subject size were empirically determined. Measurements on 12 males of weight 45 - 96 kg, height 161 - 184 cm and 18 females of weight 48 - 89 kg, height 153 - 175 cm, showed that the 
calibration factor 
was significantly correlated (r = 0.88, p < 0.0001) to subject 
, indicating comparable accuracy to 
-based calibration procedures. Fat-free mass determined from the potassium measurements of 16 subjects correlated significantly with fat-free mass estimated from skinfold thickness (r = 0.98, p < 0.0001), dual-energy x-ray absorptiometry (r = 0.99, p < 0.0001) and bioimpedance analysis (r = 0.98, p < 0.0001). These data, together with the precision (coefficient of variation, CV = 1.5%) and accuracy (CV = 4.5%) of the system, indicate that this calibration procedure represents a relatively low-cost, non-invasive alternative to -based methods of calibrating total body potassium monitors.