Scattering of ultrasound in cancellous bone: predictions from a theoretical model

An understanding of the interaction between acoustic waves and cancellous b one is needed in order to realize the full clinical potential of ultrasonic bone measurements. Scattering is likely to be of central importance but ha s received little attention to date. In this study, we adopted a theoretica l model from the literature in which scattering was assumed to be proportio nal to the mean fluctuation in sound speed, and bone was considered to be a random continuum containing identical scatterers. The model required knowl edge only of sound speeds in bone and marrow, porosity, and scatter size. P redicted attenuation, broadband ultrasonic attenuation (BUA) and backscatte r coefficient were obtained for a range of porosities and scatterer sizes, and were found to be comparable to published values for cancellous bone. Tr ends in predicted BUA with porosity agreed with previous experimental obser vations. All three predicted acoustic parameters showed a non-linear depend ence on scatterer size which was independent of porosity. These data confir m the value of the scattering approach and provide the first quantitative p redictions of the independent influence of structure and porosity on bone a coustic properties. (C) 2000 Published by Elsevier Science Ltd. All rights reserved.