Systems and methods for sensing sub-surface temperatures in body tissue

An apparatus for ablating body tissue comprising

• an ablation electrode having a thermal mass, the ablation element having a contact region for contacting a tissue surface, the ablation electrode being adapted to be connected to a source of radio frequency ablation energy to conduct the radio frequency ablation energy for transmission by the ablation electrode into the tissue surface contacting the tissue contact region, the ablation electrode including an interior well in the tissue contact region,
• a tissue temperature sensing assembly carried within the interior well comprising a cap made of a thermal conductive material having a thermal conductivity that is at least 1.0 W/m K, and an insulating barrier made of thermal insulating material in the interior well to substantially thermally isolate the cap from the thermal mass of the ablation electrode, the cap having a distal end enclosing at least two tissue temperature sensing elements in a spaced apart relationship in thermal conductive contact with the thermal conductive material of the cap while being substantially isolated from electrical contact with the cap, the distal end of the cap projecting outside the interior well and beyond the tissue contact region and into thermal conductive contact with tissue at different distances beneath the tissue surface to obtain a profile of tissue temperatures beneath the tissue surface, the thermal conductive material of the cap reaching thermal equilibrium with tissue temperature conditions without dissipation by the thermal mass of the ablation electrode.