Detection and Localization of objects within a volume conductor using electrical impedance measurements: phantom study

A uniform volume conductor has symmetrical distribution of electrical impedance. Electrical impedance will change in the presence of a substance (conductor or insulator or any biological tissue) whose dielectric properties differ from that uniform volume conductor. This impedance change could be measured by surface electrodes. Electrical impedance tomography (EIT) is a technique by which impedance measurements on surface of an object are reconstructed into impedance images. It is fast, inexpensive and non-invasive but has relatively low spatial resolution. This paper describes a simple but effective method of detection and localization of objects within a volume conductor using electrical impedance measurements. Sixteen electrodes were placed equidistantly on the surface of a cylindrical tank filled with saline and electrical transfer impedances from 6 pair of electrodes were measured. Similar impedance profiles were also measured by placing in homogeneity (iron rod and glass sphere) at an arbitrary position. Absolute impedance variation from the uniform volume conductor impedance for both objects is calculated and plotted. For both cases, the absolute impedance variation showed maximum value for the electrode near the object which confirms that detection and localization of objects within volume conductor is possible by the proposed method. With the data recorded EIT image can be constructed in future.