In vivo measurements of guided waves at the forearm

Because of the recognized importance of cortical bone in osteoporotic fracture risk, efforts have been made to improve its measurement. A step forward towards the ultrasonic characterization of cortical bone has been made recently with reports showing that cortical bone behaves as a waveguide (WG) for ultrasound. Measurements of the guided modes dispersion relationships, together with appropriate waveguide modeling have the potential for providing estimates of strength-related factors such as stiffness (which is largely determined by cortical porosity) and cortical thickness (Ct.Th). Cortical bone is readily accessible for measurements at the radius using the axial transmission (AT). The guided waves spectrum is used to estimate Ct.Th, based on a comparison of measured and model-predicted dispersion curves. The post-processing relies on finding the optimal pairing of measured and predicted dispersion curves from a free transverse isotropic plate model, assuming a parametrization of the elastic tensor. The present work presents the first in vivo ultrasound-based estimate of Ct.Th US in healthy subjects.