Abstract: A cardiac ablation device treats atrial fibrillation by directing and focusing ultrasonic waves into a ring-like ablation region (A). The device desirably is steerable and can be moved between a normal disposition, in which the ablation region lies parallel to the wall of the heart for ablating a loop-like lesion, and a canted disposition, in which the ring-like focal region is tilted relative to the wall of the heart, to ablate only a short, substantially linear lesion. The ablation device desirably includes a balloon reflector structure (18, 1310) and an ultrasonic emitter assembly (23, 1326), and can be steered and positioned without reference to engagement between the device and the pulmonary vein or ostium. A contrast medium (C) can be injected through the ablation device to facilitate imaging, so that the device can be positioned based on observation of the images.

Abstract: A high intensity focused ultrasound applicator includes a frame, ultrasonic emitters mounted on the frame and a bag containing a substantially air-free fluid permanently connected to the frame. The frame, the bag, the fluid within the bag and the emitters constitute a permanently connected unit which can be releasably connected to an ultrasonic actuation apparatus.

Abstract: A compact, high-power ultrasonic emitting transducer has an active element such as a piezoelectric element and structure defining a reflective backing interface such as an air interface behind the rear surface of the active element. A liquid is provided in the resonant unit between the backing interface and the active element.

Abstract: A balloon catheter is provided with a sleeve and a flexible material where, upon inflation of the balloon, the sleeve is slid over a ball joint, preventing the flexible material and tube from moving through a range of motion in order to prevent the tube from kinking and misaligning.

Abstract: A balloon catheter is provided with engagement elements disposed within the balloon so that, upon inflation of the balloon, the engagement elements move in the proximal to distal direction of the catheter so as to abut one another and form a substantially rigid column to maintain alignment of the distal end of the balloon with the proximal end of the balloon and with the catheter.

Abstract: A method of treating cardiac arrhythmias by ablating a portion of the myocardial fibers within a pulmonary vein. Myocardial fibers within a pulmonary vein are located and ablated to block conduction of electrical signals to the heart from ectopic foci within the pulmonary vein. The myocardial fibers are located and selectively ablated so as to avoid having to create a circumferential conduction block around the pulmonary vein or ostium. Devices for locating the myocardial fibers, selectively ablating such fibers, and directing ablative energy, are also disclosed.

Abstract: A catheter carrying a radially-expansible ultrasonic transducer is threaded into the circulatory system and then the transducer is actuated to provide ultrasonic energy in a ring-like zone surrounding a blood vessel. Desirably, the transducer is arranged to focus the ultrasonic energy into a narrow, ring-like focal zone having an extent, in the axial direction along the catheter, less than the axial extent of the transducer. The transducer desirably is expanded after threading so that during application of the ultrasonic energy, the transducer bears on the interior wall of a blood vessel through a balloon covering the transducer. The transducer may include one or more resilient spiral elements carrying a flexible piezoelectric material.

Abstract: A collapsible ultrasonic reflector incorporates a gas-filled reflector balloon, a liquid-filled structural balloon an ultrasonic transducer disposed within the structural balloon. Acoustic energy emitted by the transducer is reflected by a highly reflective interface between the balloons. In a cardiac ablation procedure, the ultrasonic energy is focused into an annular focal region to ablate cardiac tissue extending in an annular path along the wall. Devices for stabilizing the balloon structure and for facilitating collapse and withdrawal of the balloon structure are also disclosed.

Abstract: A treatment catheter (10) carries an elongated ultrasonic emitter (20) extending in the lengthwise direction of the catheter. The array is flexible in all directions transverse to the lengthwise direction. The treatment catheter is inserted into a chamber of the heart and brought to a desired configuration such as a substantially closed loop. The treatment catheter is then biased into engagement with the wall of the heart by an expansible balloon (62) or other expansible structure, which may be carried on a separate stabilizer catheter (60). While the treatment catheter is engaged with the heart wall, the array is actuated to ablate tissue along a path having a shape corresponding to the configuration of the treatment catheter.

Abstract: A tubular anatomical structure in a mammalian subject is occluded by directing ultrasonic energy from outside of the body. For example, a male subject may be sterilized by directing ultrasonic energy through the skin of the scrotum, onto the vas deferens. The focal spot of an ultrasonic transducer may be registered with the structure to be treated by means of guide members on a probe holding the transducer. The procedure is simple and can be entirely non-invasive. Apparatus for performing this and other treatments may be provided as a disposable unit, and the guide members may be arranged to hold a fold of tissue without substantially obstructing the sonic path from the transducer to the fold.

Abstract: Methods and apparatus for treating cardiac arrhythmias by ablating myocardial fibers within a pulmonary vein through use of a catheter. For example, the ablative element of the catheter is rotated around an axis to ablate a partial or complete loop of tissue within the pulmonary vein so as to block the transmission into the cardiac tissue of electrical signals originating or propagating from myocardial fibers within a pulmonary vein. In other examples, signals from the catheter are monitored to determine whether the ablative element is in contact with the wall of the pulmonary vein. Additional apparatus allow precise angular positioning of the ablative element within the lumen of the pulmonary vein. Apparatus and methods for detecting the properties of the tissue within the pulmonary vein, locating myocardial fibers, selectively ablating such fibers, and determining if such fibers are ablated are also disclosed.

Abstract: A collapsible ultrasonic reflector incorporates a gas-filled reflector balloon, a liquid-filled structural balloon an ultrasonic transducer disposed within the structural balloon. Acoustic energy emitted by the transducer is reflected by a highly reflective interface between the balloons. In a cardiac ablation procedure, the ultrasonic energy is focused into an annular focal region to ablate cardiac tissue extending in an annular path along the wall. Devices for stabilizing the balloon structure and for facilitating collapse and withdrawal of the balloon structure are also disclosed.

Abstract: Magnetic resonance information acquired by a movable magnetic resonance instrument is used to monitor hyperthermia treatments such as tissue ablation. The instrument may include both the magnetic resonance equipment and an energy applicator such as a high intensity focused ultrasound unit. The treatment can be conducted under automatic control after the operator marks a treatment volume on an image of the subject, such as a magnetic resonance image acquired using the movable magnetic resonance instrument. The automatic treatment can be based on interpolation of tissue response curves at plural test points near the treatment volume. The system can also provide automatic supervisory control during manual operation, to prevent application of heat to sensitive anatomical structures.

Abstract: High intensity focused ultrasound heating is provided by applying therapeutic ultrasonic waves using an array of transducers. Cavitation is detected by using some or all of the transducers in the array to detect ultrasonic waves emanating from or reflected from the patient's body or the interface. A feedback signal is generated based on such detection. If the feedback signal indicates the presence of cavitation, the therapeutic ultrasonic waves are terminated or altered. Obstacles to ultrasound transmission, such as bony structures or bubbles at the interface between the transducer array and the patient can be detected using the same transducers.

Abstract: An apparatus and method for applying sonic energy within the body of the living subject. A probe for applying sonic energy within the body of a subject comprises a probe body having a proximal and a distal end adapted for insertion into the body of a subject, a spatially-distributed sonic transducer disposed adjacent to the distal end of the probe body and a device for moving one portion of the spatially-distributed transducer relative to another portion of the transducer while the distal end of the probe is disposed within the body of the subject.

Abstract: An electrical appliance such as an ultrasonic energy applicator used in conjunction with magnetic resonance apparatus is controlled so that the appliance is active only while the magnetic resonance signals from the subject are not being received. Alternatively, magnetic resonance signals received while the appliance is operating can be rejected and the magnetic resonance cycles used to acquire such signals can be repeated. RF noise from the appliance does not affect the signals which are accepted and used to form an image.

Abstract: A multi-layer piezoelectric transducer includes a first polymeric layer of piezoelectric material having spaced apart first and second surfaces and a second polymeric layer of piezoelectric material having spaced apart first and second surfaces. A first ground layer overlies the first surface of the first polymeric layer and a second ground layer overlies the first surface of the second polymeric layer. A signal layer is sandwiched between the second surfaces of the first and second polymeric layers.

Abstract: An apparatus and method for applying sonic energy within the body of the living subject. A probe for applying sonic energy within the body of a subject includes a probe body having a proximal and a distal end adapted for insertion into the body of a subject, a spatially-distributed sonic transducer disposed adjacent to the distal end of the probe body and a device for moving one portion of the spatially-distributed transducer relative to another portion of the transducer while the distal end of the probe is disposed within the body of the subject.

Abstract: Magnetic resonance information acquired by a movable magnetic resonance instrument is used to monitor hyperthermia treatments such as tissue ablation. The instrument may include both the magnetic resonance equipment and an energy applicator such as a high intensity focused ultrasound unit. The treatment can be conducted under automatic control after the operator marks a treatment volume on an image of the subject, such as a magnetic resonance image acquired using the movable magnetic resonance instrument. The automatic treatment can be based on interpolation of tissue response curves at plural test points near the treatment volume. The system can also provide automatic supervisory control during manual operation, to prevent application of heat to sensitive anatomical structures.

Abstract: A single-sided magnet for magnetic resonance imaging has a main field assembly including numerous small outer field coils arrayed around a main axis. The main field assembly may also include a central field coil coaxial with the main axis inside the array of outer field coils, as well as shim coils, also coaxial with the main axis.