Abstract: A method and apparatus for use in imaging a body uses electrical impedance tomography (EIT). A plurality of electrodes are provided in electrical contact with the body around the periphery of the body. A first electrical input signal is applied to at least one of the electrodes over a first time period, and a second electrical input signal, which is preferably in inverted form of the first, then applied to the at least one of the electrodes over a subsequent, second time period. The resulting electrical output signal is measured at one or more pairs of the remaining electrodes over the first and second time periods and the difference between the measured signal obtained during the first time period and that obtained during the second time period is calculated to provide a difference signal. The difference signal can stored and used for image reconstruction.