Toward harmonizing ultrasound-based cortical bone characterization: A comparison of attenuation measurement...

Ultrasonic attenuation is used to evaluate the microstructure of bone. However, the field currently lacks a standardized, universally accepted method for performing these measurements in vivo, leading to a proliferation of approaches, each with its own experimental protocols and inherent limitations. This methodological diversity presents a significant challenge in extracting quantitative information about the microstructural characteristics of bone. Preliminary evidence suggests that significant discrepancies exist between different attenuation measurement techniques. In this study, a range of in silico bone maps is employed, where porosities range from 3% to 5% area fraction, and pore diameters range from 30 to 100 μm. Absorption by the solid matrix is also varied from 0 to 4.2 dB/mm. In these numerical bone samples, four attenuation measurement techniques are compared: plane wave through-transmission, pulse-echo, the independent scattering approximation (ISA) method, and the cortical backscatter (CortBS) method. It is demonstrated that the effectiveness of these methods depends critically on the underlying physical mechanisms occurring during wave propagation in the material. For instance, the ISA method neglects the complex influence of absorption and assumes low porosity, and the CortBS method relies on backscattering from pores or other inhomogeneities, suggesting that the accuracy of these methods could depend on the porosity. By evaluating these approaches under controlled and identical conditions, this study aims to clarify their respective strengths and limitations. Ultimately, the goal is to support the uniformization and standardization of ultrasound-based characterization of bone and other porous media.