In-vitro study of human proximal femur microstructure: analysis of the relationship between micro-computed tomography data and quantitative ultrasound parameters

The aim of this study was to investigate the relationships between selected quantitative ultrasound (QUS) parameters and human femur microstructure properties, as quantified by micro-computed tomography (micro-CT). The authors employed an innovative custom-designed experimental set-up, which allowed the insonification of each portion of an excised femoral head sample, simultaneously including trabecular region, cortical layer and cartilage in their physiologic morphological configuration. Thirty different, uniformly distributed, regions of interest were analysed for the calculation of apparent integrated backscatter (AIB), integrated reflection coefficient (IRC) and several micro-CT parameters. QUS data acquisitions were performed through both single-element ultrasound transducers at two different frequencies (2.25 and 3.5 MHz) and a clinically available 128-element echographic probe. Obtained results showed that AIB was strongly correlated with trabecular network properties (|r| up to 0.80) and IRC had appreciable linear correlations with cortical bone density (|r| up to 0.57). The agreement between single-element transducers and echographic probe, combined with the innovative approach of considering the entire femoral head in its physiological shape with all its components (cartilage, cortical layer, trabecular region), encourages the clinical translation of the proposed approach as a possible new method for early osteoporosis diagnosis.