Non-invasive bone quality assessment using quantitative ultrasound imaging and acoustic parameters

Musculoskeletal complications, i. e., osteoporosis, affect not only bone's mineral density, but also quality. Early diagnosis of such poor bone quality leads to prompt treatment and thus will dramatically reduce the risk of complications. Using a newly developed scanning confocal acoustic diagnostic (SCAD) system, trabecular bone quality was evaluated by quantitative ultrasound on 63 sheep bone samples. The structural and strength properties of bone were confirmed using μCT and mechanical testing in three orthogonal directions. While there are good correlations between broadband ultrasonic attenuation and μCT determined parameters, such as bone volume fraction (BV/TV; R=-0.68), strong correlations exist between ultrasound velocity and bone strength and structural parameters such as bulk modulus (R=0.82), and BV/TV (R=0.93). The correlations between SCAD prediction and bone quantity and quality parameters were improved by using a parameter to combine BUA and UV in a linear regression analysis, yielding R=0.96 (BV/TV) and R=0.82 (bulk modulus). A stratified model was proposed to study the effect of transmission and reflection of ultrasound wave within the trabecular architecture on the relationship between ultrasound and BMD. The results demonstrated that ultrasound velocity in trabecular bone was highly correlated with the bone apparent density (r=0.97). Moreover, a consistent pattern of the frequency dependence of ultrasound attenuation has been observed between simulation using this model and experimental measurement of trabecular bone, in which the peak magnitude of nBUA was observed at approximately 60% of the bone porosity. These results suggest that image-based quantitative ultrasound has demonstrated the potentials to predict not only the bone mass, but also bone's mechanical strength in the region of interests of bone.