The fast wave propagation in bovine cancellous bone-experiments and simulation

Cancellous bone is comprised of a complicated network of trabeculae and has strong anisotropy and inhomogeneity. In the cancellous bone, two types of longitudinal waves, fast and slow waves, are observed when the waves propagate parallel to the trabeculae direction. Paying attention to the wave front of observed waves, we have experimentally made clear the effect of anisotropy on the fast wave speeds and shown interesting relation between the mean trabeculae length and wave speeds (Mizuno et. al., IEEE Trans., UFFC, accepted), making use of the microstructural indices of the measured bone. We then compared the experimental results of fast waves with the simulation studies, using the three dimensional X-ray CT data and the Finite-Difference Time-Domain (FDTD) method. In spite of the lack of attenuation effects in the simulation, we can find interesting correlation between the fast wave speeds obtained by experiments and simulation. In addition, the characteristic attenuation behaviors of fast wave were found in both experiments and simulations. Attenuation of fast wave is always higher in the initial state of propagation, regardless of propagation direction and samples.