Estimation of Bone and Skeletal Weight by Direct Photon Absorptiometry

The direct photon (125I) absorptiometric method for radiologic measurement of bone was used to examine the intercorrelations among determinations at various sites on the human ulna, radius, humerus and femur. The relationships of local mineral content, determined by this scanning method, with the weights of individual bones and of the total skeleton were also examined. Scans on the different bones were highly intercorrelated (r = 0.80 to 0.90), and correlation coefficients were even higher (r = 0.90 to 0.95) for different locations on the same bone. The relative uniformity of local mineral content was not sufficiently high, however, to allow specific extrapolation from single scan sites. Absorptiometric scans were also highly correlated with the weights of the bones on which they were made (r = 0.94) and with the weights of other bones ( = 0.90) or of the total skeleton (r = 0.90). The weights of individual bones or of the entire skeleton were estimated with only a 5 to 10 per cent error; scans at several sites improved the accuracy. In contrast, linear measurements on the bones were only moderately correlated with local mineral content or bone weights.