Abstract: A catheter for insertion into a body cavity, comprises a tubular shaft formed with a passageway extending longitudinally therethrough closed at one end and open at the opposite end and a probe removably received within the passageway through its open end. The probe includes a temperature sensor for sensing the heat produced by a heating applicator applied to an adjacent area of the body. The heating applicator includes a microwave antenna producing an electromagnetic field for heating the body tissue adjacent to the body cavity, and the sensor including an electromagnetic field detector for detecting the peak of the electromagnetic field produced by the applicator antenna.