Rapid assessment of electrode characteristics for impedance imaging

When a multiplicity of electrodes is applied in one or more rows around a body structure such as the thorax or limb, it is useful to be able to rapidly assess the general status of the electrode-body interface to determine if the skin has been suitably prepared, and that electrode and skin impedance are suitably low. In addition, assessment of the impedance of individual electrodes should precede acquisition of data for image formation. Techniques are presented for assessing the overall skin and electrode impedances relative to the impedance of the body interior and for assessing the integrity of each electrode´s contact impedance. Experimental results are given. It was found that the homogeneous saline phantom has negligible skin impedance and negligible reaction impedance. The intact thigh has a high and variable reactive impedance near the skin, which is made more uniform and somewhat lowered by stripping the stratum corneum. After stripping, the real component of skin impedance has approximately half the impedance of the interior structures.