Ultrasonic backscatter and transmission parameters at the os calcis in postmenopausal osteoporosis

Ultrasound technology has emerged as a new tool in the assessment of osteop orosis. Ultrasound parameters usually are measured in transmission; there i s a potential for the analysis of backscattered signals to provide informat ion on bone microarchitecture. The aim of this study was to explore a new t echnological development of the method, adding backscatter coefficient to t ransmission parameters, and to examine the appropriate thresholds to identi fy postmenopausal osteoporotic women. We examined 210 postmenopausal women (including 60 with osteoporotic fractures) and 30 healthy premenopausal con trols. They had lumbar spine and hip bone mineral density (BMD) measurement and quantitative ultrasound (QUS) evaluation at the os calcis, measured in transmission (broadband ultrasound attenuation [BUA], speed of sound [SOS] , ratio of transit time [dt] to BUA [dt/BUA], and "strength" index [STI]) a nd reflexion (broadband ultrasound backscattering [BUB]). The standardized CVs (sCVs) were between 2.27% and 3.40% for QUS measured in transmission an d 4.41% for BUB. The odds ratio (OR) for fracture discrimination adjusted f or age was 2.77 for hip BMD and between 1.6 and 2.9 for QUS. After adjustme nt for hip BMD, ORs were still highly significant for SOS, STI, and dt/BUA. According to hip BMD T score, prevalence of osteoporosis in our population was 39%. To detect the same prevalence, T scores ranged between -0.95 and -1.42 for QUS. QUS parameters have adequate ability to discriminate osteopo rotic patients from controls. The World Health Organization (WHO) threshold for diagnosis of osteoporosis does not apply to this technology. The clini cal utility of BUB at the os calcis, in addition to usual ultrasound parame ters, is not yet proven. However, BUB evaluation, which does not require tw o transducers and may be implemented in conventional reflection mode system s, warrants further studies.