An ultrasonic transducer includes an elongated catheter that carries a phased linear array of ultrasonic transducer elements at a distal end. This array is aligned with the azimuthal axis of the array oriented substantially parallel to a longitudinal axis of the catheter near the distal end. Two sets of steering lines are carried by the catheter and coupled to the catheter near the distal end. The first set of steering lines is effective to steer the distal end in a first plane, and the second set of steering lines is effective to steer the distal end in a second plane, transverse to the first plane.