Poster Y6 - Exploration of Audible Sound, Time Delay Spectroscopy for Assessing Bone Health

Introduction: Osteoporosis is a degenerative medical condition that affects an estimated 10 million individuals in the United States and 200 millions globally. It results in the gradual degradation of bone tissue which is associated with a characteristic decrease in bone density (BD). The populations most affected by osteoporosis are postmenopausal women, diabetic patients, and the elderly. Around 1 in 3 women and 1 in 5 men over the age of 50 will experience an osteoporosis fracture in their lifetime. Currently, there are a number of density metric and sonometric devices available for BD monitoring, such as quantitative computed tomography (QCT), dual-energy x-ray absorption (DXA), and ultrasound (QUS). Yet these methods are expensive and not always readily available. In the cases of QCT and DXA, patients may be exposed to small, frequent doses of ionizing radiation. While effective for measuring BD, these methods are not always feasible due to their utility limitations in rural healthcare, making them inaccessibly expensive for facilities/patients who require routine screening. Due to the high demand for these costly and invasive nature devices, the need for a rapid, low-cost, and non-invasive method to monitor BD is continuing to increase. The current study explores audible sound, time delay spectroscopy as a viable option for measuring BD in a safe and effective manner by reducing cost drivers and increasing simplicity.

Materials and

Methods: This work utilizes a previously made prototype containing an off the shelf speaker and microphones, linear actuators, current sensors, 2-channel relays, Arduinos and MyDAQs. The speaker and microphones are used to generate and acquire audible sound signals with their position being controlled by linear actuators and 2-channel relays. The coupling force is controlled by regulating the power supplied to the actuators with LabVIEW being used as the primary software.

Results, Conclusions, and Discussions: The use of audible sound frequencies (20Hz - 20kHz) has the potential to solve many of the limitations associated with current densitometric measurement techniques with the guiding principles established as sound speed and attenuation.  Generally, when a material is exposed to incident acoustic frequencies, there is a measurable change in the speed and amplitude of the sound wave2.  The human calcaneus acts as a standard densitometric region because it is easily accessible, poses minimal soft tissue interaction, and contains greater than 90% trabecular bone which simplifies acoustic interaction with the human body2,3. For the calcaneus, the magnitude of these changes is dependent upon density, porosity, anisotropy, and microstructure2. Clinically, these properties can be used to predict a patient’s risk of fracture and monitor trends in their bone health. Previous work on the project included the development of an initial testable prototype, resulting in data validating the sound based approach. Unfortunately, this initial prototype demonstrated limited sensitivity and suffered from difficulty in setup and use.

In the work proposed here, a second prototype, fully implementing Time-Delay Spectroscopy, will be produced and evaluated. Specifically, the acoustic pathlength between the output microphone and each of the two sound receivers will be optimized according to our design calculations which suggest that a significant difference in pathlength can dramatically increase sensitivity. This will be accomplished by reducing the complexity of the initial prototype, including both hardware components and software elements. Additionally, the soft patient foot interface will be re-envisioned for better sound coupling as well as overall comfort and ease of use.

The results of this prototype development will have both clinical and personal implications. The possible clinical implications span from novel fracture detection and densitometric technology to regulatory health screenings that monitor overall bone health. Perhaps the largest contributions could be made in the field of rural medicine by providing a low-cost alternative to existing densitometric techniques, thus increasing the care that patients receive in care in rural medical facilities. The person implies both personal and professional development.

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