Catheterization is carried out by bringing an electrode that is disposed on a distal portion of a catheter into contact with tissue, wherein the electrode has an area that falls within a range of 0.01 - 25 mm 2 . A power generator delivers pulses of radiofrequency power through the electrode to the tissue. While applying the pulses temperatures at the distal portion of the catheter are recorded. A rate of change of the temperatures is calculated and tissue thickness estimated based on the rate of change.
