A New Four-Electrode Focused Impedance Measurement (FIM) System for Physiological Study

A recently developed Focused Impedance Measurement (FIM) system (by the authors' group) uses six electrodes to localize a zone of interest. Because of 3D sensitivity it could give physiological information on large organs like stomach, lungs, etc. using surface electrodes in the frontal plane. This paper presents a modified FIM technique using four electrodes placed at the corners of a square matrix. Firstly current is driven through an adjacent electrode pair while the potential is measured across the opposite pair from which an impedance value is obtained. Then a similar measurement is made at 90 degrees to the above by changing connections to the electrode pairs appropriately. The sum of these two impedance values has a dominant contribution from the…