ELECTROIMPEDANCE TOMOGRAPH WITH COMMON-MODE SIGNAL SUPPRESSION

An electroimpedance tomograph with a plurality of electrodes ( 1 ) is provided, which can be placed on the body of a patient and are connected via a selector switch ( 60 ) with a control and evaluating unit ( 20 ). The control and evaluating unit ( 20 ) cooperates with the selector switch ( 60 ) such that two electrodes each are supplied with an alternating current from an AC power source ( 22 ) and the detected analog voltage signals of the other electrodes are processed in order to reconstruct therefrom the impedance distribution of the body in the plane of the electrodes, wherein a symmetrical AC power source is used to reduce common-mode signals. To further suppress interferences due to common-mode signals, provisions are made for the control and evaluating unit ( 20 ) to be set up, furthermore, for detuning the common-mode signal of the alternating current on the body against the ground by means of a common-mode signal measuring electrode ( 4 ) and, based on this, the symmetry of the symmetrical AC power source such that the common-mode signal on the body is minimized, and the corresponding detuning parameters are stored for each electrode pair.