Investigation of effect of trabecular microstructure on ultrasound propagation through cancellous bone using finite‐difference time‐domain simulations

Abstract

Using finite‐difference time‐domain (FDTD) numerical simulations, it was investigated how the trabecular microstructure could affect the propagation of ultrasound waves through cancellous bone. Three‐dimensional (3D) numerical models of cancellous bone were reconstructed from 3D micro‐computed tomography images of bovine femoral bone with oriented trabecular structure. In these models, the trabecular elements were eroded to increase porosity using an image processing technique. Three erosion procedures were given to realize different changes in the trabecular microstructure with increasing porosity. FDTD simulations of the ultrasound pulse waves propagating through the cancellous bone models were performed in two cases of the propagations parallel and perpendicular to the main trabecular orientation, and the porosity dependences of the propagation properties, attenuation and propagation speed, were derived for various trabecular changes. It was demonstrated from the simulated results that the propagation properties in both directions parallel and perpendicular to the trabecular orientation could be affected by the trabecular microstructure. In addition, the effects of the major (or plate‐like) and minor (or rod‐like) trabecular elements on the ultrasound propagation were respectively investigated for both the parallel and perpendicular propagations.