An ablation catheter comprises: an elongated catheter body extending along a longitudinal axis at least one ablation element disposed in a distal portion which is adjacent the distal end of the catheter body to ablate a targeted tissue region outside the catheter body a single pulse-echo ultrasonic transducer disposed in the distal portion and arranged to emit and receive an acoustic beam along a centroid in a beam direction, at a transducer angle of about 30-60 degrees relative to a distal direction of the longitudinal axis at a location of intersection between the longitudinal axis and the beam direction of the centroid of the acoustic beam and a mechanism to manipulate the distal portion in movement including rotation of at least the distal portion around the longitudinal axis. The single ultrasonic transducer emits and receives acoustic pulses to provide lesion information in the targeted tissue region being ablated.
