An ablation system comprises a catheter including a pulse-echo ultrasonic transducer disposed in a distal portion and arranged to emit and receive an acoustic beam. The transducer emits and receives acoustic pulses to provide transducer detected information regarding the targeted tissue region being ablated. A rotation mechanism rotates at least the distal portion around a longitudinal axis of the catheter. A control and interface system processes the transducer detected information and provides feedback to a user via a user interface and/or the control and interface system to be used to control ablation. The transducer detected information includes a detected lesion depth along a beam emanation direction. The control and interface system includes a lesion depth correction module which converts the detected lesion depth along the beam direction to a corrected lesion depth in a normal direction which is perpendicular to the tissue surface in contact with the ablation element.