Simulated axial transmission propagation on cortical bone

Abstract

The ultrasonic axial transmission technique, used to assess cortical shells of long bones, is investigated using numerical simulations. The 3-D finite difference code generates synthetic signals recorded at different distance emitter–receiver for a linear arrangement of transducers placed along the bone axis. Academic modeling of bone based on cylindrical tubular shape made of anisotropic and porous material has been reported [J. Acoust. Soc. Am. 115 (2004)]. The aim of this paper is to refine the model by taking into account more realistic structural and material bone properties. Finite difference modeling was applied to 50 human radius specimens which were examined both by x-ray tomography at different resolutions and by ultrasonic axial transmission technique (1 MHz). The x-ray macroscopic geometry (pixel around 100 μm) of the 50 samples was imported in the code. Material properties are assigned to each bone according to its own microarchitecture examined at a 10 μm scale. Different assumptions of the relationship between bone structural properties and material properties were tested. Simulations were validated by comparison with experimental results. Numerical simulations of transient propagation in bone is a powerful tool to enlighten interaction between ultrasound and bone and consequently to improve ultrasound based devices for clinical use.