New tetrapolar method using magnetic field for local impedance measurement

The tetrapolar circuit method has been used to detect physiological events as changes in electrical impedance. However, it is still difficult to obtain more meaningful information of local events because of the expanse of current distribution. In order to measure the local impedance change in living tissue, the authors propose a tetrapolar circuit method using a magnetic field. In this method, an eddy current generated in the living tissue by the magnetic field is used in addition to the constant current. The current distribution can be restricted to a local area by combining the eddy current with the constant current. The effectiveness of this method was confirmed by in-vivo measurement of pulsatile waveforms due to the arterial blood flow in the forearm.<>