actuators employable for oscillating movement of a load . an improved actuator may include at least a first shape memory member that is actuatable to affect at least a portion of the oscillating movement of the load . the actuator may further include a second shape memory member actuatable to affect at least a second portion of the oscillating movement of the load . the utilization of one or more shape memory members facilitates the realization of controllable and reliable oscillating movement of a load in a compact manner . such actuators may be used in imaging catheters having an ultrasound transducer disposed for oscillating movement to scan across an internal region of interest . such imaging catheters may be used in generating three dimensional and / or real - time three dimensional images .