Abstract: A lens for focusing an ultrasound wave having a wavelength, includes a plurality of substantially concentric rings disposed about a central point, at least one of the rings having a substantially triangular cross-section defined by first, second, and third sections, the first section extending from a proximal end radially away from the central point to a distal end, the second section extending from the distal end of, and substantially perpendicular to, the first section and terminating at a peak, and the third section smoothly sloping from the proximal end of the first section to the peak of the second section, and wherein the first, second and third sections have lengths with respect to the wavelength of the ultrasound wave such that (i) phases of the ultrasound wave are substantially additive at a focal point located on an axis perpendicular to the lens that passes through the central point, and (ii) aggregate focused ultrasound energy would not be predicted at the focal point by Snell's law refractio

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: An ultrasonic emitting apparatus (10) for cauterizing and ablating tissue. Ultrasonic waves are focused at an intended region of operation by an elongated waveguide (15), thus reducing damage to adjacent unintended tissue. The waveguide (15) can be inserted into structures of the body through overlying organs. The device may be used, for example, to ablate protruding portions of spinal disks.

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 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 method and apparatus for performing transmyocardial revascularization using ultrasound is disclosed. The apparatus includes a phased array ultrasonic device that includes a plurality of ultrasonic transducer elements which are controlled using a feedback control system so that each ultrasonic transducer element produces an ultrasonic wave of particular power and phase in order to achieve constructive interference at a desired acoustic focus. The constructive interference creates high pressure amplitudes for vaporizing the target tissue at the focus. A method is provided for vaporizing target tissue for which a plurality of ultrasonic transducers are focused so as to provide constructive interference within the target tissue. The ultrasonic beams are launched and produce a rapid rise in tissue temperature that will vaporize the target tissue within the focal zone.

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: 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: A method and apparatus for performing transmyocardial revascularization using ultrasound is disclosed. The apparatus includes a phased array ultrasonic device that includes a plurality of ultrasonic transducer elements which are controlled using a feedback control system so that each ultrasonic transducer element produces an ultrasonic wave of particular power and phase in order to achieve constructive interference at a desired acoustic focus. The constructive interference creates high pressure amplitudes for vaporizing the target tissue at the focus. A method is provided for vaporizing target tissue for which a plurality of ultrasonic transducers are focused so as to provide constructive interference within the target tissue. The ultrasonic beams are launched and produce a rapid rise in tissue temperature that will vaporize the target tissue within the focal zone.

Abstract: Apparatus and methods for ablating tissue surrounding a tubular anatomical structure such as the wall of a blood vessel or prostatic tissue surrounding the urethra. The apparatus includes an ultrasonic emitter such as a cylindrical emitter and an inflatable annular lens balloon surrounding the ultrasonic emitter. The lens balloon is inflated with a liquid having acoustic velocity different than that of the surrounding medium, so as to form an annular refracting surface. The acoustic energy from the emitter is focused into an annular focal region.

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 lens for focusing an ultrasound wave having a wavelength, includes a plurality of substantially concentric rings disposed about a central point, at least one of the rings having a substantially triangular cross-section defined by first, second, and third sections, the first section extending from a proximal end radially away from the central point to a distal end, the second section extending from the distal end of, and substantially perpendicular to, the first section and terminating at a peak, and the third section smoothly sloping from the proximal end of the first section to the peak of the second section, and wherein the first, second and third sections have lengths with respect to the wavelength of the ultrasound wave such that (i) phases of the ultrasound wave are substantially additive at a focal point located on an axis perpendicular to the lens that passes through the central point, and (ii) aggregate focused ultrasound energy would not be predicted at the focal point by Snell's law refraction.

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.