Temporal and Spectral Impedance Myography: Visualization of Dynamic Electrical Properties in Forearm Tissue During Wrist Movements.

The recently proposed short-time impedance spectroscopy (short-time IS) measures impedance spectra with high temporal resolution using a nonsinusoidal mode-switching oscillator. With a view to application for muscular disease diagnosis and human-machine interaction, this study presents the temporal and spectral impedance myography using the short-time IS system. We applied the proposed system to the measurement of human forearm impedance and analyzed impedance changes during wrist motion. The forearm's impedance at 40 frequency points was measured by our developed system. The forearm's rapid impedance response during wrist motion was captured with a high temporal resolution of about 0.5 ms, displaying the impedance magnitude and phase angle change as a color map. Furthermore, we experimentally and theoretically demonstrated that difference and differential Cole-Cole plots reduced skin impedance effects and produced a characteristic curve corresponding to wrist motion, even with two-terminal measurement. We anticipate that the IS system and visualization method will be beneficial for myoelectric control in prosthetic hands and noninvasive muscle disease diagnosis.