Current Density Impedance Imaging

Current density impedance imaging (CDII) is a new impedance imaging technique that can noninvasively measure the conductivity distribution inside a medium. It utilizes current density vector measurements which can be made using a magnetic resonance imager (MRI) (Scott et al., 1991). CDII is based on a simple mathematical expression for nablasigma/sigma = nabla ln sigma, the gradient of the logarithm of the conductivity sigma, at each point in a region where two current density vectors J₁ and J₂ have been measured and J₁ x J₂ ne 0. From the calculated nabla In sigma and a priori knowledge of the conductivity at the boundary, the logarithm of the conductivity In sigma is integrated by two different methods to produce an image of the conductivity sigma in the region of interest. The CDII technique was tested on three different conductivity phantoms. Much emphasis has been placed on the experimental validation of CDII results against direct bench measurements by commercial LCR meters before and after CDII was performed.