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

Abstract

<jats:p>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.</jats:p>

Wearable super-resolution muscle–machine interfacing

“…Adapted from Akhlaghi et al (2016) . Copyright 2016, IEEE; (D) the photo of wearable ultrasonic sensor developed by AlMohimeed and Ono (2020) . Reproduced with permission ( AlMohimeed and Ono, 2020 ).…”

Flexible Piezoelectric Sensors for Miniaturized Sonomyography

“…Crystalline and ceramics are common piezoelectric materials but the most commonly used piezoceramic is lead zirconate titanate (PZT) [5] due to its high electromechanical coupling coefficient and its very adequate dielectric and elastic properties for biomedical imaging. Other materials of interest inlude polyvinylidene fluoride (PVDF), shown to have great flexibility and biocompatibility [8], and Aluminium Nitride (AIN) which offers higher sensitivity than PZT [9]. These materials were analysed in different studies (Table 1) to evaluate the optimum configuration for SMG applications.…”

Classifying Muscle States with One-Dimensional Radio-Frequency Signals from Single Element Ultrasound Transducers

“…Another work published in 2020 made use of 1-D SMG signals to measure acoustic nonlinearity parameters and showed that they have the potential to represent skeletal muscles dynamically [ 20 ]. An additional publication from 2020 presented a single element wearable ultrasonic sensor, consisting of a transmitter and receiver, and a corresponding method to measure skeletal muscle contractile parameters [ 21 ].…”