THE ROLE OF QUANTITATIVE ULTRASOUND IN THE ASSESSMENT OF BONE - A REVIEW

Quantitative ultrasound (QUS) bone measurement is a promising, relativ ely new technique for the diagnosis of osteoporosis. Unlike to the mor e established method of bone densitometry [measurement of bone mineral density (BMD) e.g. using dual X-ray absorptiometry (DEXA)], QUS does not use ionizing radiation. It is cheaper, takes up less space and is easier to use than densitometry techniques. The two QUS parameters cur rently measured are broadband ultrasound attenuation (BUA) and speed o f sound (SOS). The reported age-related changes for healthy women rang e from -0.27% to -1.62% per year for BUA and from -0.06% to -0.19% per year for SOS. Precision ranges from 1.0 to 3.8% (CV) for BUA and from 0.19 to 0.30% (CV) for SOS. The new method of imaging ultrasound has improved the precision of QUS measurements. QUS is significantly corre lated with BMD. Studies with the latest equipment have shown r-values between 0.6 and 0.9 in site-specific measurements, and QUS is thus bel ieved to reflect mainly BMD. However, other studies indicate that QUS measures something other than the actual mineral content of bone, name ly bone quality, e.g. in vitro studies have shown that QUS reflects tr abecular orientation independently of BMD. In both cross-sectional and prospective studies, QUS seems to be as good a predictor of osteoporo tic fractures as BMD. In two large prospective studies, QUS also predi cted fracture risk independently of BMD. QUS has just begun to be used systematically for monitoring the response to anti-osteoporotic treat ments in prospective trials. In the studies performed, QUS has been fo und to be useful in the follow-up of patients. QUS is thus a promising new technique for bone assessment.