Theoretical and experimental study of the ultrasonic attenuation in bovine cancellous bone

In this study a theoretical approach for the estimation of ultrasonic attenuation is proposed. The approach combines two models which take into account both absorption and scattering. Attenuation due to absorption is studied by using the Biot's analytical model whereas that due to scattering is described by means of a generalized weak scattering model which is formulated for binary mixtures. The scattering model takes account of the density fluctuation of the porous medium in addition to the propagation velocity fluctuation. For the calculation of the attenuation coefficient due to absorption, experimental values have been used to link size of pores to porosity. The theoretical results have been compared with experimental data obtained on bovine cancellous bone samples filled with water. Using an immersion acoustic transmission method, the ultrasonic attenuation has been measured at a frequency range between 0.1 and 1.0 MHz for 12 bovine cancellous bone samples with a porosity range between 40% and 70%. The prediction of attenuation with this model appears to correspond more closely to its experimentally observed behavior. This study indicates that scattering is the predominant mechanism which is responsible for attenuation in trabecular bone. Furthermore, it shows that the density fluctuations contribute significantly to the phenomenon of attenuation and cannot thus be neglected.