Development and testing of acoustically-matched hydrogel-based electrodes for simultaneous EMG-ultrasound detection

Area of Science:

• Biomedical Engineering
• Neuroscience
• Musculoskeletal Research

Background:

• Simultaneous muscle imaging and electrical activity recording is challenging.
• Existing methods often require separate devices, limiting concurrent data acquisition.
• Multimodal assessment of muscle function requires integrated sensing technologies.

Purpose of the Study:

• To develop and validate a bipolar electrode (bEMG-US) for simultaneous ultrasound (US) imaging and surface electromyogram (EMG) acquisition.
• To assess the electrical properties and signal quality of the bEMG-US electrode.
• To evaluate the impact of the bEMG-US electrode on ultrasound image quality.

Main Methods:

• Development of a novel bipolar hydrogel electrode (bEMG-US) with integrated sensing regions.
• Assessment of electrode-skin impedance, noise levels, and EMG signal quality (M waves) compared to commercial EMG electrodes.
• Evaluation of ultrasound image quality by comparing anatomical measurements (pennation angle, muscle thickness) with and without the bEMG-US electrode in place.
• Testing conducted on five human subjects during electrically elicited muscle contractions.

Main Results:

• The bEMG-US electrode exhibited higher electrode-skin impedance than conventional EMG electrodes (15.6 kΩ vs. 8.2 kΩ).
• Despite higher impedance, comparable electrode-skin noise levels (1.4 µV vs. 1.3 µV) and EMG M-wave quality were achieved.
• Ultrasound image quality remained comparable, with minimal errors in anatomical variable estimation (pennation angle: 0.37-2.35°, muscle thickness: -0.31-0.1 cm).

Conclusions:

• The developed bEMG-US electrode effectively enables concurrent acquisition of EMG and US signals from the same muscle region.
• This technology provides a negligible impact on the quality of both EMG and US signals.
• The bEMG-US electrode facilitates simultaneous, multimodal evaluation of muscle activation, advancing neuromuscular research and clinical diagnostics.