Probing ultrasonic waves through long bones with soft tissues and inversion

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Osteoporosis is one of the most common skeletal disorders characterized by reduced bone mass, micro-structural deterioration, cortical bone thinning, and cancellous bone perforation leading to bone fragility and fracture risks. The prevalence of osteoporotic fractures of the wrists, hips, and spines is a serious public health problem affecting about 200 million people worldwide especially in the aging population. Currently, bone quality is assessed mainly by bone mineral density (BMD) using dual energy x-ray absorptiometry (DEXA). However, clinical studies indicated that BMD values measured in normal and osteoporotic bones showed considerable overlap; therefore, BMD measurements do not provide sufficient information for accurate diagnosis. Osteoporosis still remains one of the most prevalent undiagnosed diseases in the world today. This is due to the failure to consider bone elasticity and trabecular microstructures by radiation-based methods. Recently, quantitative ultrasound (QUS) has gained considerable attention as a promising technology to assess bone quality. Ultrasound is free of ionizing radiation. Quantitative ultrasound (QUS) uses mechanical waves to probe the internal bone structure and is, therefore, sensitive to bone tissue elasticity and architectural structure relevant to bone strength. Both in-vitro and in-vivo studies have shown that ultrasound is capable to penetrate bone and travel within the cortex of long bones in the form of bulk and guided waves. This proposal offers an opportunity to further enhance our fundamental understanding of the physical principles governing the ultrasound interaction with soft tissue/cortex system in an axial transmission acquisition configuration. The knowledge in this area is crucial to provide confidence and justification for successful application of QUS to quantify bone status clinically. Ultrasound phased array system will be used to enhance acquisition efficiency and decrease acquisition time. Innovative multichannel signal processing techniques will be used to enhance signal-to-noise ratio and separate bulk and guided wave energies for further analysis. Bone parameters such as elastic constants will be inverted and correlated with BMD using human subjects. The findings of this research plan will lead to new and better methodologies and technology development for ultrasound characterization of skeleton competence and integrity.