3D Sensitivity of 8-Electrode FIM through Experimental Study in a Phantom

Abstract

Focused Impedance Method (FIM) is a relatively new technique developed in the Biomedical Physics Laboratory of Dhaka University which allows improved localization of a zone without much increase in the complexity of measurement. Three versions using 8, 6 and 4 electrodes respectively have been conceived and developed. FIM has potential for characterization of biological tissues at depths non-invasively placing electrodes on the skin surface at appropriate locations, leading to detection or diagnosis of diseases or disorders. The present work is an experimental study of the sensitivity of the 8-electrode FIM system at different depths and lateral positions inside a volume conductor with respect to the electrode-positions using a cubical phantom with saline. An object of different conductivity and of size smaller than the electrode separation was placed inside the phantom at different positions to measure the change of FIM value, called sensitivity in this work. The study verified the focusing effect at the central zone where the sensitivity remained high and almost constant laterally for a certain depth, falling sharply outside. At shallow depths, the sensitivity showed enhanced peaks under the electrodes which however, decreased fast with depth. The sensitivity falls off sharply with depth becoming almost constant at greater depths but with greatly reduced value. The sensitivity at off axis positions from the centre also reduced outside the focused zone. Slightly negative zones of sensitivity were observed at lateral positions far from the center of the electrodes, but the values were negligible. This work will help standardize the application of 8-electrode FIM for determination of impedance of organs inside the human body.

DOI: http://dx.doi.org/10.3329/bjmp.v6i1.19759

Bangladesh Journal of Medical Physics Vol.6 No.1 2013 55-65