1988 Volume 25 Issue 6 Pages 591-596
Measurements of bone phantoms and human subjects were performed in order to aseess the precision of dual photon absorptiometry (DPA) and single photon absorptiometry (SPA), as well as the relation between the results of the two method. SPA measurements were done with a Norland Bone Mineral Analyzer (Model 278) using 125-I, and DPA measurements were done with a Lunar Bone Densitometer (Model DP-4) using 153-Gd. The coefficient of variation (CV) of SPA and DPA in the measurement of bone phantoms was 2.8% and 0.2%, respectively. Thus, the precision error of DPA was less than one tenth that of SPA. The reproducibility of DPA measurements in vivo was examined in 3 subjects. The total body and regional bone mineral density (BMD) of each subjects was measured twice within one month. The precision for the total body BMD was 0.5% while regional densities and CV values from about 1 to 2% depending on the site. Subsequently, we examined the association between the bone mineral density of the radius shaft measured by SPA and the BMD of various skeletal regions measured by DPA in 33 subjects (7 males and 26 females). The BMD of radius shaft correlated well with BMD of anatomical regions containing predominantly compact bone measured by DPA (radius BMD vs arm BMD; r=0.93, radius BMD vs leg BMD; r=0.92). In contrast, there was a lower correlation between radius BMD and BMD of trabecular bone (radius BMD vs pelvis BMD; r=0.85, radius BMD vs spine BMD; r=0.87). In conclusion, DPA is a much more accurate tool for the measurement of bone mineral density than SPA. Local measurements of BMD on the radius shaft correlated well with predominantly cortical regions in the peripheral skeleton measured by DPA, but not as well to the axial skeleton, which is more trabecular in composition.
