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 (v(FAS)) and A(0) mode (v(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), v(FAS) ( R-2 = 0.43) and v(A0) (R-2 = 0.28). Furthermore, a significant correlation was found between AT and distal high-resolution pQCT. The measurement of cortical parameters at the tibia using guided waves might improve the prediction of bone fractures in a cost-effective and radiation-free manner. (C) 2019 The Author(s). Published by Elsevier Inc. on behalf of World Federation for Ultrasound in Medicine & Biology.