Total body bone mineral in vivo by dual photon absorptiometry. II. Accuracy

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Abstract
The accuracy of total body mineral (TBBM) measured by dual photon absorptiometry (1 Ci 153Gd source, 44 and 100 KeV) was investigated using skeletons, soft tissue equivalent materials and whole cadaver extremities. The accuracy was assessed on 5 skeletons (r = 0.99, SEE [standard error of the estimate] = 1.5%). The influence of the soft tissue composition on the TBBM measurement was investigated in the same 5 skeletons. They were scanned in a 16 cm thickness of ethanol solutions of different concentration (0, 20, 40, 60, 80, 100% ethanol) and only a 2% difference (non-significant) was found between measuring 100% ethanol and 100% water. Seven whole cadaver extremities were scanned before and after removal of the soft tissues (r = 0.995, SEE = 6.3%). The slope was not different from 1 and the intercept not different from 0. Equipment at the University of Wisconsin, Madison, and at Glostrup Hospital, Denmark, was compared by measuring the same healthy subjects and skeletons on both scanners. The Glostrup and Madison TBBM values correlated well (r = 0.99, SEE = 5.8%) and the intercept (345 Glostrup arbitrary units) was not significantly different from zero (P > 0.05). The TBBM results were calibrated into total body calcium (TBCa) and no significant difference was found between Glostrup and Madison TBCa values (P > 0.20).