A system for ablating tissue, said system comprising: a steerable elongate flexible shaft having a proximal portion and a distal portion; an ultrasound transducer (68;124;64) coupled with the distal portion of the elongate flexible shaft, wherein the ultrasound transducer (68;124;64) emits a beam of ultrasound energy for ablating target tissue, and wherein the beam of ultrasound energy is adapted to form a continuous lesion (162;172;174) in the target tissue without contact between the ultrasound transducer (68;124;64) and the target tissue; a housing coupled to the distal portion of the steerable elongate flexible shaft, wherein the ultrasound transducer (68;124;64) is disposed adjacent the housing; a barrier disposed between the ultrasound transducer (68;124;64) and adjacent blood or tissue, wherein the barrier permits the beam of ultrasound energy to ablate the target tissue without contact between the ultrasound transducer (68;124;64) and the target tissue, and wherein the barrier comprises a fluid flow through the housing and past the ultrasound transducer (68;124;64) to prevent blood from coagulating thereon; a handle coupled with the proximal portion of the elongate flexible shaft; an actuation mechanism operably coupled with the handle for steering the distal portion of the elongate flexible shaft, and wherein the distal portion of the elongate flexible shaft is movable to form the continuous lesion (162;172;174); and a catheter pod (30;202) having a plurality of actuators for aiding in movement and control of the steerable elongate flexible shaft, the catheter pod (30;202) being releasably coupled with the handle, and wherein the catheter pod (30;202) is electrically and mechanically coupled with the handle. a steerable elongate flexible shaft having a proximal portion and a distal portion; an ultrasound transducer (68;124;64) coupled with the distal portion of the elongate flexible shaft, wherein the ultrasound transducer (68;124;64) emits a beam of ultrasound energy for ablating target tissue, and wherein the beam of ultrasound energy is adapted to form a continuous lesion (162;172;174) in the target tissue without contact between the ultrasound transducer (68;124;64) and the target tissue; a housing coupled to the distal portion of the steerable elongate flexible shaft, wherein the ultrasound transducer (68;124;64) is disposed adjacent the housing; a barrier disposed between the ultrasound transducer (68;124;64) and adjacent blood or tissue, wherein the barrier permits the beam of ultrasound energy to ablate the target tissue without contact between the ultrasound transducer (68;124;64) and the target tissue, and wherein the barrier comprises a fluid flow through the housing and past the ultrasound transducer (68;124;64) to prevent blood from coagulating thereon; a handle coupled with the proximal portion of the elongate flexible shaft; an actuation mechanism operably coupled with the handle for steering the distal portion of the elongate flexible shaft, and wherein the distal portion of the elongate flexible shaft is movable to form the continuous lesion (162;172;174); and a catheter pod (30;202) having a plurality of actuators for aiding in movement and control of the steerable elongate flexible shaft, the catheter pod (30;202) being releasably coupled with the handle, and wherein the catheter pod (30;202) is electrically and mechanically coupled with the handle.