A form of resistivity surveying applied to human bodies. A number of electrodes are attached to the body and then electrical signals are applied, usually at high frequency, and the resulting impedance values are measured. From these data, images of sections through the body interior can be constructed. While the resolution is lower than with computed tomography, EIT is the only way to determine internal electrical properties of organs. Not yet widely used, it is most promising as a means for observing and monitoring lung function.