Abstract: A method and apparatus for imaging the interior of a structure, such as a mineral or human body, having regions therein which differentially affect particular characteristics of electrical signals transmitted through the body. The method involves injecting a plurality of electrical signals into the body, measuring at least one characteristic of each such signal at a plurality of locations, comparing the measured characteristic with the corresponding characteristic measured at at least one reference point of the structure and generating comparison signals, iteratively reconstructing the impedance spatial relationships between the regions within the structure by utilizing the comparison signals, and providing an image of the interior of the structure from the reconstruction of such impedance spatial relationships.