In Vitro Ultrasonic Characterization of Human Femoral Bone using Transmission and Backscatter Measurements : Relationships to Density and Microachitectural parameters

The goal of this study is to clarify the relationship between quantitative ultrasonic measurements (QUS), bone mineral density (BMD) and micro architectural parameters (reflecting morphology, connectivity and anisotropy) measured on human proximal femur. BMD was determined using X-ray quantitative computed tomography (QCT) and micro architecture was investigated using synchrotron radiation micro tomography (μ-CT). 38 specimens removed from fresh cadavers were investigated by first cutting 1-cm thick slices threw the proximal femur. 2-D scans were performed using a pair of 1-MHz focused transducers. Both transmission and backscatter measurements were performed. Up to 660 ROIs were selected for quantitative analysis on both QUS and QCT images. Finally, μ-CT measurements were performed on 40 cylindrical cores of 8-mm. The relationship between nBUA (normalized BUA) and BMD (r=0.83), between SOS and BMD (r=0.86) and between BUB (broadband ultrasonic backscatter) and BMD (r=0.66) were found highly significant (p<10) and comparable to results previously published for the calcaneal bone. BUA and SOS were also found to be significantly correlated with micro architectural parameters except for the degree of anisotropy.