A method of assessing a tissue ablation treatment, including positioning a medical device adjacent a target tissue; measuring a first impedance magnitude a first frequency with the medical device; measuring a first impedance phase at a second frequency with the medical device; ablating at least a portion of the target tissue with the medical device; measuring at second impedance magnitude at a third frequency with the medical device; measuring a second impedance phase at a fourth frequency with the medical device; comparing at least one of (i) the first and second impedance magnitudes and (ii) the first and second impedance phases; and providing an indication of the efficacy of the ablation treatment based at least in part on the comparison.