Frequency dependence of ultrasonic backscattering in cancellous bone: Autocorrelation model and experimental results

The goal of this study is to model the frequency dependence of the ultrason ic backscatter coefficient in cancellous bone. A twofold theoretical approa ch has been adopted: the analytical theoretical model of Faran for spherica l and cylindrical elastic scatterers, and the scattering model for weakly s cattering medium in which the backscatter coefficient is related to the aut ocorrelation function of the propagating medium. The ultrasonic backscatter coefficient was measured in 19 bone specimens (human calcaneae) in the fre quency range of 0.4-1.2 MHz. The autocorrelation function was computed from the three-dimensional (3D) microarchitecture measured using synchrotron ra diation microtomography. Crood agreement was found between the frequency de pendence of the experimental (F3.38+/-0.31) and autocor-relation modeled (f (3.48=/-0.26)) backscatter coefficients. The results based on Faran theory (cylindrical Faran model: f(2.89+/-0.06) and spherical Faran model: f(3.91/-0.04)) show qualitative agreement with experimental data. The good predic tion obtained by modeling the backscatter coefficient using the autocorrela tion function of the medium opens interesting prospects for the investigati on of the influence of bone microarchitecture on ultrasonic scattering. (C) 2000 Acolrstical Society of America. [S0001-4966(00)04011-X].