Wearable ultrasound system for assessing muscle function during physical activity

Abstract

Conventional ultrasound transducers, which are meant for hand-held operation, are not ideally suited for MSK-US during dynamic physical activity. We have developed a custom wearable ultrasound system for Motion-mode (M-mode) MSK-US, which enables multi-site hands-free sensing of tissue movement during physical activity such as that encountered during rehabilitation exercises. Participants performed a jumping task on a force plate with a sensor attached to their right vastus lateralis (VL). Mean pixel value (MPV) and normalized pixel differences (NPDs) were acquired from the images during the jumping task. Signals were filtered and normalized to root-mean square baseline and percent change was calculated for peaks of jump take-off and landing. The correlation coefficient was calculated to determine a relationship between metrics. Concurrently acquired force-plate data showed that the percent change during take-off and landing was 0.28% ± 0.09 and 0.66% ± 0.17 relative to baseline for each peak, respectively. MPV values changed 0.42% ± 0.29 and 0.81% ± 0.17, and NPD changed 0.41% ± 0.32 and 0.84% ± 0.12 for corresponding peaks. Overall results indicated significant correlation between force data and MSK-US (p < 0.05). Our system can maintain acoustic coupling during complex movements providing real-time feedback and expanding the potential for wearable MSK-US sensors.