In vitro ultrasound characterization of human proximal femur microstructure and comparison with micro-CT data

An in vitro investigation based on Quantitative Ultrasound (QUS) has been carried out in this paper on a sample of human femoral head, aiming at microstructure characterization and bone quality assessment. Two QUS parameters, Integrated Reflection Coefficient (IRC) and Apparent Integrated Backscatter (AIB) were measured by accurately analyzing ultrasonic signals backscattered from the target bone when immersed in water and insonified at 2.25 MHz. In particular, US data were acquired from 22 different positions along the maximum section perpendicular to the axial direction (head-neck axis) of the target sample. The obtained data were compared with local structural properties gathered at each considered position from a high-resolution micro-computed tomography (microCT) scan of the same sample. A linear regression analysis showed an appreciable correlation between QUS parameters and some of the micro-structural parameters. As expected, IRC correlated better with cortical bone volume fraction (r = -0.53), and AIB with trabecular bone volume fraction (r = -0.60) and trabecular spacing (r = 0.47). These results are particularly encouraging in view of a possible clinical translation of the proposed approach for early osteoporosis diagnosis.