Focused impedance measurement (FIM). A new technique with improved zone localization.

Abstract: Conventional four-electrode impedance measurements (FEIM) cannot localize a zone of interest in a volume conductor. On the other hand, the recently developed electrical impedance tomography (EIT) system offers an image with reasonable resolution, but is complex and needs many electrodes. By placing two FEIM systems perpendicular to each other over a common zone at the center and combining the two results, it is possible to obtain enhanced sensitivity over this central zone. This is the basis of the proposed new method of focused impedance measurement (FIM). Sensitivity maps in both 2D and 3D show the desired improvement. A comparison of stomach-emptying studies also indicates the improvement achieved. This new method may be useful for impedance measurements of large organs like stomach, heart, and lungs. Being much simpler in comparison to EIT, multifrequency systems can be simply built for FIM. Besides, FIM may have utility in other fields like geology where impedance measurements are performed.