A novel method for broadband ultrasonic attenuation measurement in calcaneal quantitative ultrasound system

Abstract

Quantitative ultrasound (QUS) methods have been introduced in recent years for the assessment of skeletal status in osteoporosis. As an important parameter of QUS, broadband ultrasonic attenuation (BUA) has been clinically validated in terms of prediction of hip fracture risk. However, the short-term reproducibility of BUA has typically been inferior to that of dual-energy X-ray absorptiometry (DXA). Poor precision estimates may reduce the ability to detect longitudinal changes in BUA or the ability of QUS to assess response to therapy. In this paper, a new method for BUA measurement is proposed. In this method, an ultrasound signal covering range of frequencies (broadband) is passed through a patient’s heel to determine the BUA index. The amplitude spectrum of the received signal is then compared to the spectrum of a standard ultrasound bone phantom. The difference between the two spectra is then plotted against frequency, giving a straight line graph, the slope of which is the BUA index dB/MHz. The method eliminates the influence of water, fat and amplitudefrequency error, and improves the precision of BUA measurement, which is validated in 508 women ranging in age from 21 to 80 in vivo. Each subject was examined in two different methods, with foot repositioning before each examination. Precision was evaluated by calculating the coefficient of variation(CV). The CVs for the measurements reduced from 4.45% to 1.5%, which shows that our method effectively improve the precision of BUA measurement.