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Open AccessArticle

Ultrasound Measurement of Skeletal Muscle Contractile Parameters Using Flexible and Wearable Single-Element Ultrasonic Sensor

by Ibrahim AlMohimeed 1,2 and Yuu Ono 1,*
1
Department of Systems and Computer Engineering, Carleton University, Ottawa, ON K1S 5B6, Canada
2
Department of Medical Equipment Technology, Majmaah University, Majmaah 11952, Saudi Arabia
*
Author to whom correspondence should be addressed.
Sensors 2020, 20(13), 3616; https://doi.org/10.3390/s20133616
Received: 10 May 2020 / Revised: 17 June 2020 / Accepted: 23 June 2020 / Published: 27 June 2020
(This article belongs to the Section Wearables)
Skeletal muscle is considered as a near-constant volume system, and the contractions of the muscle are related to the changes in tissue thickness. Assessment of the skeletal muscle contractile parameters such as maximum contraction thickness ( T h ), contraction time ( T c ), contraction velocity ( V c ), sustain time ( T s ), and half-relaxation ( T r ) provides valuable information for various medical applications. This paper presents a single-element wearable ultrasonic sensor (WUS) and a method to measure the skeletal muscle contractile parameters in A-mode ultrasonic data acquisition. The developed WUS was made of double-layer polyvinylidene fluoride (PVDF) piezoelectric polymer films with a simple and low-cost fabrication process. A flexible, lightweight, thin, and small size WUS would provide a secure attachment to the skin surface without affecting the muscle contraction dynamics of interest. The developed WUS was employed to monitor the contractions of gastrocnemius (GC) muscle of a human subject. The GC muscle contractions were evoked by the electrical muscle stimulation (EMS) at varying EMS frequencies from 2 Hz up to 30 Hz. The tissue thickness changes due to the muscle contractions were measured by utilizing a time-of-flight method in the ultrasonic through-transmission mode. The developed WUS demonstrated the capability to monitor the tissue thickness changes during the unfused and fused tetanic contractions. The tetanic progression level was quantitatively assessed using the parameter of the fusion index (FI) obtained. In addition, the contractile parameters ( T h , T c , V c , T s , and T r ) were successfully extracted from the measured tissue thickness changes. In addition, the unfused and fused tetanus frequencies were estimated from the obtained FI-EMS frequency curve. The WUS and ultrasonic method proposed in this study could be a valuable tool for inexpensive, non-invasive, and continuous monitoring of the skeletal muscle contractile properties. View Full-Text
Keywords: wearable and flexible ultrasonic sensor; single-element ultrasonic sensor; ultrasonic transducer; piezoelectric PVDF film; skeletal muscle monitoring; electrical muscle stimulation; tetanic contraction; fusion index; muscle contractile parameters wearable and flexible ultrasonic sensor; single-element ultrasonic sensor; ultrasonic transducer; piezoelectric PVDF film; skeletal muscle monitoring; electrical muscle stimulation; tetanic contraction; fusion index; muscle contractile parameters
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MDPI and ACS Style

AlMohimeed, I.; Ono, Y. Ultrasound Measurement of Skeletal Muscle Contractile Parameters Using Flexible and Wearable Single-Element Ultrasonic Sensor. Sensors 2020, 20, 3616.

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