The goal of this study is to model the frequency dependence of the ultrasonic backscatter coefficient in cancellous bone. A twofold theoretical approach has been adopted: the analytical theoretical model of Faran for spherical and cylindrical elastic scatterers, and the scattering model for weakly scattering medium in which the backscatter coefficient is related to the autocorrelation function of the propagating medium. The ultrasonic backscatter coefficient was measured in 19 bone specimens (human calcaneae) in the frequency range of 0.4-1.2 MHz. The autocorrelation function was computed from the three-dimensional (3D) microarchitecture measured using synchrotron radiation microtomography. Good agreement was found between the frequency dependence of the experimental (f3.38+/-0.31) and autocorrelation modeled (f3.48+/-0.26) backscatter coefficients. The results based on Faran theory (cylindrical Faran model: f2.89+/-0.06 and spherical Faran model: f3.91+/-0.04) show qualitative agreement with experimental data. The good prediction obtained by modeling the backscatter coefficient using the autocorrelation function of the medium opens interesting prospects for the investigation of the influence of bone microarchitecture on ultrasonic scattering.
Our goal was to correlate muscle fibers orientation with anisotropy of ultrasonic parameters. The ultrasonic attenuation and the backscatter coefficient were measured with a reflection technique in bovine skeletal muscle samples. Frequency dependent attenuation and backscattering measurements were made at two angles of incidence. Ultrasonic waves were propagated both across and along the muscle fibers. Two different transducers (5 and 20 MHz center frequency) were used to explore a wide range of frequencies (2 to 30 MHz). A linear frequency dependence of the attenuation was found over the range 2 to 30 MHz and the slope of attenuation was observed to be highly anisotropic (mean values were 3.1 dB/cm.MHz for propagation along the fibers with the 5 and the 20 MHz transducers and 0.9 dB/cm.MHz and 1.3 dB/cm.MHz for propagation across the fibers respectively with the 5 and the 20 MHz transducers). The backscatter coefficient was found to be anisotropic too. The integrated backscatter coefficient for propagation across the fibers was higher than for propagation along the fibers (the difference was approximately 10 dB ) with the 5 and the 20 MHz transducers. The frequency dependence of the backscatter coefficient was found to be af2.5 for propagation along the fibers and bf1.4 for propagation across the fibers with the 5 MHz transducer (f is the frequency).
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.