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Comparison of speed of sound and ultrasound attenuation in the os calcis to bone density of the radius, femur and lumbar spine.

Broadband ultrasonic attenuation (BUA) between 0.1 and 0.6 MHz and speed of sound (SOS) were measured on the os calcis in normal women (n = 40), and women who had mild osteoporosis (n = 36). Comparisons were made between the ultrasonic properties and bone mineral densities (BMD) obtained using photon absorptiometry on the lumbar spine, proximal femur and radius shaft. In the osteoporotic women, whose spine BMD was significantly reduced, BUA and SOS were lower, to about the same degree of significance as radius BMD; ROC analysis demonstrated that for discrimination of spinal osteopenia, the area under the ROC curve was similar for radius BMD, SOS, and BUA. There was a modest correlation (r about 0.65) between either SOS or BUA on the os calcis and BMDs of the spine and radius. Correlations of the SOS and BUA with femoral neck BMD were lower (r about 0.4 to 0.5). The standard error of estimate for both spine and femoral neck BMD was too high (about 0.14 g cm-2) for os calcis measurements to be substituted clinically for densitometry at these fracture sites.