Apparatus is provided, comprising: (a) an elongate member, having a proximal portion and a distal portion； (b) an extracorporeal controller, coupled to the proximal portion of the elongate member, and comprising a user interface and control circuitry； and (c) an effector unit. The effector unit is coupled to the distal portion of the elongate member, defines a longitudinal axis, and has a contracted state and an expanded state. The effector unit comprises a plurality of electrodes, operable by the control circuitry, and disposed circumferentially around the central longitudinal axis of the effector unit； and an ultrasound transducer, operable by the control circuitry. In the expanded state, each electrode is disposed further radially outward from (i) the central longitudinal axis of the effector unit, and (ii) the transducer compared to the contracted state, and the transducer is oriented to direct ultrasound radially outwardly.
