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

We investigated the accuracy of total body mineral (TBBM) measured by dual photon absorptiometry (1 Ci 153Gd source, 44 and 100 KeV) using skeletons, soft tissue equivalent materials and whole cadaver extremities. The accuracy was assessed on five skeletons (r = 0.99, SEE = 1.5%). The influence of the soft tissue composition on the TBBM measurement was investigated in the same five 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. Furthermore, 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 one and the intercept not different from zero. 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 greater than 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 greater than 0.20).