An apparatus and method for heating a treatment region of a subject by providing a substantially constant current across the treatment region is disclosed. The method includes positioning the treatment region between first and second electrodes connected to a generator operable to apply an alternating electric field between the electrodes. The method also includes displacing any air located between the treatment region and the first and second electrodes with one or more flowable materials that allow a substantially constant current to pass between the first and second electrodes and through the treatment region. The method further includes activating the generator to apply the alternating electric field between the first and second electrodes and across the treatment region to thereby heat the treatment region.
