Detection and imaging of electric conductivity and permittivity at low frequency

The authors discuss low-frequency electrical impedance imaging, the process of constructing images of the electrical impedance of a body´s interior based on measurements of voltage and current made at the body´s surface. The electrical impedance accounts for both resistivity and permittivity. It is shown how permittivity can be exploited to improve the performance of an electrical impedance imaging system. It is shown that explicit use of the independent information in the data due to the permittivity will enhance a system´s ability to distinguish objects in the interior of a body. In addition. the results of experiments performed using the Rensselaer ACT 2 system on a saline bath containing various objects are reported. These objects include both living tissue and metal conductors with oxide layers. The system´s ability to distinguish these objects is demonstrated. and gray scale images of both their resistivity and permittivity distributions are given.