A NOVEL SYSTEM OF ELECTRODES TRANSPARENT TO ULTRASOUND FOR SIMULTANEOUS DETECTION OF MYOELECTRIC ACTIVITY AND B-MODE ULTRASOUND IMAGES OF SKELETAL MUSCLES

Application of two dimensional surface electrode arrays can provide a means of mapping motor unit action potentials on the skin surface above a muscle. The resulting muscle tissue displacement can be quantified, in a single plane, using ultrasound imaging (US). Currently however, it is not possible to simultaneously map spatio-temporal propagation of activation and resulting tissue strain. In this manuscript we eveloped and tested a material that will enable concurrent measurement of 2D surface EMGs with US images. Specific protocols were designed to test the compatibility of this new electrode material both with EMG recording and with US analysis. Key results indicate that, for this new electrode material: i) the electrode-skin impedance is similar to that of arrays of electrodes reported in literature; ii) the reflection of ultrasound at the electrode-skin interface is negligible; iii) the likelihood of observing missing contacts, short-circuits and artefacts in EMGs is not affected by the US probe; iv) movement of tissues sampled by US can be tracked accurately. We therefore conclude this approach will facilitate multi-modal imaging of muscle to provide new spatio-temporal information regarding electromechanical function of muscle. This is relevant to basic physiology-biomechanics of active and passive force transmission through and between muscle, of motor unit spatio-temporal activity patterns, of their variation with architecture and task related function, and of their adaptation with ageing, training-exercise-disuse, neurological disease and injury