In Vivo Measurements of Cortical Thickness and Porosity at the Proximal Third of the Tibia Using Guided Waves: Comparison with Site-Matched Peripheral Quantitative Computed Tomography and Distal High-Resolution Peripheral Quantitative Computed Tomography

The aim of this study was to estimate cortical porosity (Ct.Po) and cortical thickness (Ct.Th) using 500-kHz bi-directional axial transmission (AT). Ct.Th AT and Ct.Po AT were obtained at the tibia in 15 patients from a 2-D transverse isotropic free plate model fitted to measured guided wave dispersion curves. The velocities of the first arriving signal (υ FAS ) and A 0 mode (υ A0 ) were also determined. Site-matched peripheral quantitative computed tomography (pQCT) provided volumetric cortical bone mineral density (Ct.vBMD pQCT ) and Ct.Th pQCT . Good agreement was found between Ct.Th AT and Ct.Th pQCT ( R 2 = 0.62, root mean square error [RMSE] = 0.39 mm). Ct.vBMD pQCT correlated with Ct.Po AT ( R 2 = 0.57), υ FAS ( R 2 = 0.43) and υ A0 ( R 2 = 0.28). Furthermore, a significant correlation was found between AT and distal high-resolution pQCT. The measurement ofcortical parameters at the tibia using guided waves might improve the prediction of bone fractures in a cost-effective and radiation-free manner.