From four point probe to impedance imaging

The need to produce images or representations of inaccessible regions is essential in medicine and industrial processing. Impedance imaging is a developing technique with characteristics which make it a valuable addition to existing methods. The technique has grown from an extension of the principle of the four-point probe measurement of impedance into a range of diverse configurations. Examples of some of these configurations are used to illustrate the principles, characteristics and applications of the technique, and to draw conclusions about its possible future development