Precision and Accuracy of Bone Mineral Determination by Direct Photon Absorptiometry

Bone mineral was determined using a radiologic absorptiometric method. The attenuation of a low-energy beam from a well-collimated radionuclide source (125I or 241Am) was measured using a collimated scintillation detectorpulse height analyzer system. The absorption of the photon beam by bone, as shown by this scanning method, was highly correlated with the weight of standard sections on excised bones (r = 0.97 to 0.99). Even scans on tissue covered cadaver forearms were highly correlated (r = 0.96) with the weight of underlying bone components and single scans on human ulnae were highly correlated (r= 0.96) with total ulna weight. The precision (2%) and accuracy (4 to 7%error) were the highest ever demonstrated for a radiologic method of bone determination and the large inaccuracies (more than 20 to 30% error) of older methods, which used photodensitometry of radiographs, were eliminated by the present method. Improved techniques allow even higher precision (1 to 2%) and accuracy (2 to 4%); therefore, the radionuclide absorption method is potentially useful for diagnostic, clinical and normative evaluation of appendicular skeletal mineralization where older photodensitometric methods cannot be used.