Ablation apparatus such as a catheter ( 10 ) carrying an ultrasonic ablation device ( 20 ) including an ablation transducer ( 42 ) and a balloon reflector structure ( 22, 24 ) for directing ultrasonic energy from the ablation transducer into a ring-like ablation region (A) is provided with an imaging ultrasonic transducer ( 86 ) mounted on an imaging probe ( 80 ) which may be inserted into or through a passageway ( 18, 65 ) extending through the catheter and into or through the ablation device to image the ablation region or neighboring regions. Alternatively, the imaging transducer ( 102, 202 ) may be mounted within the balloon reflector structure or distal to this structure.
