Ultrasonic tissue therapy device

Abstract

To provide devices and methods for the treatment of tissue through the application of energy. SOLUTION: Apparatus (220 / 20) and methods are described that include a transluminal ablation catheter (40) that includes at least one ultrasound transducer (50 / 52 / 150). The at least one ultrasound transducer is configured for insertion into a cardiac chamber (190) of a subject and configured to (a) ablate tissue by applying ultrasound energy to the tissue of the subject, and (b) image tissue by applying non-ablative ultrasound energy to the tissue of the subject. An expandable cage (30 / 301) is disposed about the at least one ultrasound transducer. The at least one ultrasound transducer is configured to rotate and translate axially back and forth within the expandable cage to generate a three-dimensional image of the tissue. Other applications are also described.

Description

Technical Field

[0001] (Cross - Reference to Related Applications) This application claims the priority of U.S. Provisional Patent Application No. 63 / 153,477, entitled "ULTRASOUND TISSUE TREATMENT APPARATUS AND METHOD" filed by Megel on February 25, 2021, which is incorporated herein by reference.

[0002] Some applications of the present invention generally relate to devices and methods for treating tissue by applying energy, and more specifically, to ablation of heart tissue by applying ultrasonic energy for treating cardiac arrhythmias such as atrial fibrillation.

Background Art

[0003] Atrial fibrillation is a common cardiac arrhythmia associated with the atria. During atrial fibrillation, the atria beat irregularly, losing coordination with the ventricles, thereby interrupting efficient heartbeats. The symptoms of atrial fibrillation often include heart palpitations, shortness of breath, and weakness. A major concern associated with atrial fibrillation is the potential to form blood clots in the atria. These blood clots formed in the heart can circulate to other organs, potentially leading to serious medical conditions such as stroke.

[0004] Atrial fibrillation is generally caused by abnormal electrical activity in the heart. During atrial fibrillation, electrical discharges can occur in parts of the atria that normally do not generate discharges, such as the pulmonary vein ostia of the atria.

[0005] Generally, ablation procedures are used, especially in people prone to developing cardiac arrhythmias, to terminate defective electrical pathways from multiple parts of the heart and return the heart to a normal rhythm. For example, pulmonary vein isolation by ablation is a common medical procedure for treating atrial fibrillation.

Summary of the Invention

[0006] According to some applications of the present invention, a device is provided for use with a lumen, such as a pulmonary vein, that extends from a cardiac chamber, such as the left atrium of the heart. Typically, the device electrically isolates the pulmonary vein by applying ultrasonic energy to ablate the tissue at the pulmonary vein orifice in order to treat cardiac arrhythmias. In some applications, the device comprises a transcatheter ablation catheter comprising at least one ultrasonic transducer. The at least one ultrasonic transducer is coupled to the distal end of the catheter and is configured to be inserted into the cardiac chamber of target and to ablate the tissue at the pulmonary vein orifice by applying ultrasonic energy. The transcatheter ablation catheter further comprises a papillary-shaped expandable cage positioned around the ultrasonic transducer. The papillary shape is typically formed by the diameter of the central part of the expandable cage being larger than the diameter of the distal part of the expandable cage, and the distal part of the expandable cage having a shape and size such that it is inserted into the pulmonary vein orifice and contacts the vein wall to temporarily fix the distal part of the catheter in the pulmonary vein.

[0007] In some applications, the expandable cage comprises multiple struts (e.g., flexible struts) that secure the distal end of the transcatheter ablation catheter within the pulmonary vein by contacting the pulmonary vein wall. In some cases, the struts are referred to herein as “flexible wires.” These two terms are used interchangeably throughout this specification and the claims. Typically, the struts are constructed to form an expandable cage with multiple relatively large gaps between them, allowing for blood flow and transmission of ultrasound energy through the expandable cage. Furthermore, in some applications, at least a portion of the struts of the expandable cage have a shape that defines one or more openings formed in the struts, further facilitating the transmission of ultrasound energy to the tissue. In some applications, the openings are formed along the length of the struts. The openings formed in the struts typically increase the area over which ultrasound energy is transmitted through the expandable cage, allowing more ultrasound energy to reach the target tissue, resulting in increased tissue heating and more effective tissue ablation.

[0008] In some applications, in addition to the expandable cage, the device includes a fluid-filled inflatable element, such as a balloon, positioned around the ultrasonic transducer. Typically, the inflatable element is inflated with a fluid such as water and / or saline. Ultrasonic energy is transmitted through this fluid, but the absorption of ultrasonic energy is negligible. In such applications, the expandable cage is positioned around the inflatable element to position the distal portion of the transcatheter ablation catheter within the lumen as described above.

[0009] Typically, placing a fluid-filled (e.g., water-filled) inflatable element around an ultrasonic transducer partially replaces the blood medium between the ultrasonic transducer and the tissue designated for ablation. Although ultrasonic energy is transmitted through water, it is not largely absorbed by water, so a greater amount of transmitted ultrasonic energy reaches the tissue compared to when the transmitted ultrasonic energy is transmitted only through blood.

[0010] In addition to or instead of applying ablation ultrasound energy, the ultrasound transducer is configured to image the target tissue by applying non-ablation ultrasound energy. Typically, the expandable cage has a shape and size that allows the ultrasound transducer to rotate and move axially back and forth within the expandable cage to generate a three-dimensional image of the tissue. Typically, the expandable cage is kept stationary during the rotation of the transcatheter ablation catheter, which causes the rotation of the ultrasound transducer. In some applications, the device includes a rotational force reduction mechanism to reduce the rotational force applied to the expandable cage during the rotation of the transcatheter ablation catheter.

[0011] Additionally or alternatively, according to some applications of the present invention, the ultrasonic transducer comprises a curved piezoelectric ultrasonic transducer having a shape that defines a convex surface extending outward from the longitudinal axis of the transducer. Typically, providing a curved piezoelectric ultrasonic transducer promotes effective and rapid ablation of tissue because the thermal profile of the tissue is expanded (compared to the case where the piezoelectric ultrasonic transducer is not curved, all other things being equal) thereby heating larger portions of the tissue more effectively.

[0012] Accordingly, according to some applications of the present invention, an apparatus for use with the target tissue is provided. This apparatus is It is a transcatheter ablation catheter, At least one ultrasound transducer, which is inserted into the target cardiac chamber and configured to (a) ablate the target tissue by applying ultrasound energy to the target tissue and (b) image the target tissue by applying non-ablation ultrasound energy to the target tissue, An expandable cage configured to be positioned around at least one ultrasonic transducer, The system includes a transcatheter, and at least one ultrasound transducer is configured to rotate within an expandable cage and translate axially back and forth to generate a three-dimensional image of the tissue.

[0013] In some applications, at least one ultrasound transducer is configured to be inserted into the left atrium near the pulmonary vein orifice and to electrically isolate the pulmonary veins by ablating the tissue at the pulmonary vein orifice.

[0014] In some applications, the tissue includes the tissue of the lumen opening extending from the target cardiac chamber, and the ultrasound transducer is configured to generate a three-dimensional image of the lumen opening tissue by applying non-ablation ultrasound energy to the lumen opening tissue.

[0015] In some applications, the tissue includes the tissue of the lumen opening extending from the target cardiac chamber, and the expandable cage includes multiple struts, at least a portion of which curves outward at at least two positions along the strut, and the portion of which contacts the lumen wall, thereby the cage temporarily secures the distal portion of the transcatheter ablation catheter within the lumen.

[0016] In some applications, the tissue includes the tissue of the lumen opening extending from the cardiac chamber of the subject, the expandable cage has a central and distal portion, the expandable cage has a shape such that the diameter of the central portion is greater than the diameter of the distal portion, thereby defining a papillary structure, and the distal portion has a shape and size such that it is inserted into the lumen opening and contacts the lumen wall to temporarily fix the distal portion within the lumen.

[0017] In some applications, at least one ultrasonic transducer is configured to generate ultrasonic energy at a frequency of 8–20 MHz.

[0018] In some applications, at least one ultrasonic transducer has a shape that defines a convex surface extending outward from the longitudinal axis of the transducer, with a width of 0.5 to 3 mm and a radius of curvature of 0.75 to 5 mm.

[0019] In some applications, the tissue includes the tissue of the lumen opening extending from the target cardiac chamber, and at least some of the struts are conductive struts, which are configured to contact the lumen opening tissue and ablate the lumen opening tissue in contact with the conductive struts by driving an electric current into the lumen opening tissue.

[0020] In some applications, at least a portion of the conductive strut includes an insulating portion and a conductive portion, the conductive portion being configured to contact the tissue at the lumen opening and ablate the tissue at the lumen opening.

[0021] In some applications, at least some of the struts have a shape that defines an opening formed in the strut, through which ultrasonic energy is transmitted from the ultrasonic transducer to the tissue.

[0022] In some applications, each of the struts in some of the multiple struts has a width of 0.5 to 1 mm, and the opening of the strut has a width of 0.25 to 0.5 mm. In some applications, the thickness of the strut is 0.1 to 0.25 mm.

[0023] In some applications, the transcatheter ablation catheter includes an elongated shaft having a proximal end including a handle and a distal end to which at least one ultrasonic transducer is coupled. In some applications, the elongated shaft is configured to be rotatable to rotate the ultrasonic transducer, and the transcatheter ablation catheter includes one or more sensors coupled to the distal end of the elongated shaft and configured to detect the rotational position of the distal end of the elongated shaft.

[0024] In some applications, the elongated shaft is configured to be rotatable to rotate the ultrasonic transducer, the transcatheter ablation catheter further includes a rotational force reduction mechanism configured to reduce the rotational force applied to the expandable cage by the elongated shaft during rotation of the elongated shaft so as to keep the expandable cage in a stationary state during rotation of the ultrasonic transducer.

[0025] In some applications, at least one ultrasonic transducer is configured to apply non-ablation ultrasonic energy to tissue, and at least a part of the non-ablation ultrasonic energy is reflected and received by the ultrasonic transducer, the apparatus further includes a computer processor configured to evaluate parameters of the reflected energy to determine parameters of the ultrasonic energy applied by the ultrasonic transducer to ablate the tissue, at least one ultrasonic transducer is configured to apply ultrasonic energy to the tissue based on the determined parameters.

[0026] In some applications, the apparatus further includes an expandable element configured to be disposed around the ultrasonic transducer. In some applications, the expandable element is configured to be expanded with at least one of water and saline.

[0027] In some applications, at least one ultrasonic transducer a first ultrasonic transducer configured to ablate tissue by transmitting ablation ultrasonic energy toward the target tissue, and The system includes a second ultrasound transducer configured to image tissue by transmitting one or more pulses of pulsed echo ultrasound energy toward a target tissue and receiving reflections of the transmitted pulsed echo ultrasound energy, wherein the second ultrasound transducer is configured to rotate within an expandable cage and to translate axially back and forth to generate a three-dimensional image of the tissue.

[0028] In some application examples, the transcatheter ablation catheter is used. A first support, configured to support the first ultrasonic transducer and enable the transmission of ablation ultrasonic energy towards the tissue, A second attenuation support is provided to support the second ultrasonic transducer and to provide a higher attenuation level than that provided by the first support, so that the second ultrasonic transducer can receive the reflection of the transmitted pulsed echo ultrasonic energy while the first ultrasonic transducer is transmitting ablation ultrasonic energy toward the tissue. Includes.

[0029] In some application examples, The first support includes an air barrier configured to allow vibration of the first ultrasonic transducer during the transmission of ablation ultrasonic energy toward the tissue. The second damping support includes a mechanical support comprising at least one of a backing layer and a damping element.

[0030] Furthermore, according to some applications of the present invention, a device is provided which is used in conjunction with a target lumen extending from a target cardiac chamber. This device is A transcatheter ablation catheter configured such that its distal portion is positioned within the lumen of the target tube, At least one ultrasound transducer, which is inserted into the target cardiac chamber and configured to ablate the tissue at the lumen orifice by applying ultrasound energy to the tissue at the lumen orifice, An expandable cage, including a strut and configured to be positioned around an ultrasonic transducer, having a central and distal portion, and having a shape such that, when positioned in a configuration not constrained radially, the diameter of the central portion is greater than the diameter of the distal portion, defining a papillary structure, and the distal portion has a shape and size such that it is inserted into the lumen orifice and contacts the lumen wall to temporarily fix the distal portion within the lumen; Includes a transcatheter ablation catheter.

[0031] In some applications, the expandable cage has a shape such that the struts define a papillary structure by defining a convex curvature at the distal part of the expandable cage, then passing through an inflection point and having a concave curvature in the central part.

[0032] In some applications, the central portion of the expandable cage has a maximum diameter up to five times greater than the maximum diameter of the distal portion of the expandable cage.

[0033] In some applications, the device is designed so that when the distal portion is inserted into the lumen, the central portion remains within the cardiac chamber.

[0034] In some applications, at least one ultrasound transducer is configured to be positioned within the left atrium near the pulmonary vein orifice and to electrically isolate the pulmonary veins by ablating the tissue at the pulmonary vein orifice.

[0035] In some applications, the expandable cage is rotationally asymmetric. In some applications, the expandable cage is rotationally symmetric.

[0036] In some applications, the ultrasonic transducer includes a transversely oriented ultrasonic transducer. In some applications, the ultrasonic transducer includes a distally oriented ultrasonic transducer.

[0037] In some applications, the ultrasound transducer is further configured to image the target tissue by applying non-ablation ultrasound energy to the tissue, and the ultrasound transducer is configured to rotate within an expandable cage and translate axially back and forth to generate a three-dimensional image of the tissue.

[0038] In some applications, at least some of the struts of the expandable cage have a shape that defines an opening formed in the strut, through which ultrasonic energy is transmitted from the ultrasonic transducer to the tissue.

[0039] In some applications, each of the struts in some of the multiple struts has a width of 0.5 to 1 mm, and the opening of the strut has a width of 0.25 to 0.5 mm. In some applications, the thickness of the strut is 0.1 to 0.25 mm.

[0040] Furthermore, according to some applications of the present invention, a device is provided which is used in conjunction with a target lumen extending from a target cardiac chamber. This device is It is a transcatheter ablation catheter, At least one ultrasound transducer, which is inserted into the target cardiac chamber and configured to ablate the tissue at the lumen orifice by applying ultrasound energy to the tissue at the lumen orifice, An expandable cage configured to be positioned around an ultrasonic transducer, comprising a plurality of struts, wherein at least a portion of the struts have a shape that defines an opening formed in the struts, through which ultrasonic energy is transmitted from the ultrasonic transducer to the tissue; Includes a transcatheter ablation catheter.

[0041] In some applications, each of the struts in a portion of the strut has a width of 0.5 to 1 mm, and the opening in each of the struts in a portion of the strut has a width of 0.25 to 0.5 mm. In some applications, at least some of the struts have a thickness of 0.1 to 0.25 mm.

[0042] Furthermore, according to some applications of the present invention, a device is provided which is used in conjunction with a target lumen extending from a target cardiac chamber. This device is It is a transcatheter ablation catheter, At least one ultrasound transducer, which is inserted into the target cardiac chamber and configured to image the target tissue, An expandable cage configured to be positioned around an ultrasonic transducer, comprising a plurality of struts, at least a portion of which are conductive struts, and these conductive struts are configured to contact the tissue at the luminal opening and ablate the tissue in contact with the conductive struts by driving an electric current into the tissue; Includes a transcatheter ablation catheter.

[0043] In some applications, at least a portion of the conductive strut includes an insulating portion and a conductive portion, the conductive portion being configured to contact the tissue at the lumen opening and ablate the tissue at the lumen opening.

[0044] In some applications, the expandable cage is configured to drive radio frequency (RF) current into the tissue. In some applications, the expandable cage is configured to drive alternating current (AC) into the tissue. In some applications, the expandable cage is configured to drive direct current (DC) into the tissue.

[0045] In some applications, at least one ultrasound transducer is configured to rotate and translate axially back and forth within an expandable cage to generate a three-dimensional image of the tissue at the luminal orifice.

[0046] In some applications, at least one ultrasonic transducer is configured to ablate the tissue at the lumen opening by applying ultrasonic energy to the tissue at the lumen opening.

[0047] In some applications, at least one ultrasound transducer is configured to be inserted into the left atrium near the pulmonary vein orifice and to electrically isolate the pulmonary veins by ablating the tissue at the pulmonary vein orifice.

[0048] Furthermore, according to some applications of the present invention, a device is provided that is used in conjunction with the target cardiac chamber. This device is It is a transcatheter ablation catheter, At least one ultrasound transducer configured to be inserted into the target cardiac chamber and to ablate the target tissue by applying ultrasound energy, An inflatable element configured to be positioned around an ultrasonic transducer, An expandable cage positioned around an expandable element and configured to temporarily secure a transcardiac ablation catheter within a target cardiac chamber by contacting the target tissue, Includes a transcatheter ablation catheter.

[0049] In some applications, the expandable element is configured to expand with water. In some applications, the expandable element is configured to expand with physiological saline.

[0050] In some applications, at least one ultrasonic transducer is configured to generate ultrasonic energy at a frequency of 8–20 MHz. In some applications, at least one ultrasonic transducer is configured to generate ultrasonic energy at a frequency of 10–12 MHz. In some applications, at least one ultrasonic transducer is configured to generate ultrasonic energy at a frequency of 11 MHz.

[0051] Furthermore, according to some application examples of the present invention, an apparatus is provided. This apparatus is It is a transcatheter ablation catheter, An ultrasonic transducer configured to ablate tissue by transmitting ultrasonic energy to the target tissue, A computer processor, The ultrasound transducer detects signs of blood carbonization, A computer processor configured to block the application of ultrasonic energy from an ultrasonic transducer in response to the signal of detected blood carbonization, Includes a transcatheter ablation catheter.

[0052] In some application examples, The ultrasonic transducer is further configured to transmit one or more pulses of pulsed echo ultrasonic energy towards the tissue and to receive the reflection of the transmitted pulsed echo ultrasonic energy. The computer processor is configured to detect indications of blood carbonization near the ultrasonic transducer by determining the parameters of the reflected pulsed echo ultrasonic energy.

[0053] In some applications, the ultrasonic transducer is configured to transmit ultrasonic energy at power levels of 3 to 50 W to ablate tissue, while the ultrasonic transducer is configured to transmit pulsed echo ultrasonic energy at power levels of less than 2 W.

[0054] In some application examples, The ultrasonic transducer is the first ultrasonic transducer, The transcatheter ablation catheter includes a second ultrasound transducer configured to transmit pulsed echo-ultrasound energy to tissue and to receive the reflected pulsed echo-ultrasound energy. The computer processor is configured to detect indications of blood carbonization near the ultrasonic transducer by determining the parameters of the reflected pulsed echo ultrasonic energy.

[0055] In some applications, the first ultrasonic transducer is configured to transmit ultrasonic energy at a power level of 3 to 50 W to ablate tissue, and the second ultrasonic transducer is configured to transmit pulsed echo ultrasonic energy at a power level of less than 2 W.

[0056] Furthermore, according to some applications of the present invention, a device is provided which is used in conjunction with a target lumen extending from a target cardiac chamber. This device is A transcatheter ablation catheter configured such that its distal portion is positioned within the lumen of the target tube, At least one ultrasound transducer, which is inserted into the target cardiac chamber and configured to ablate the tissue at the lumen orifice by applying ultrasound energy to the tissue at the lumen orifice, An expandable cage configured to be positioned around an ultrasonic transducer, comprising a plurality of struts, wherein at least a portion of the struts curve outward at at least two positions along the struts, and the portion of the struts contacts the wall of the lumen, thereby the cage temporarily securing the distal portion of a transcatheter ablation catheter within the lumen; Includes a transcatheter ablation catheter.

[0057] In some applications, at least one ultrasound transducer is configured to be inserted into the left atrium near the pulmonary vein orifice and to electrically isolate the pulmonary veins by ablating the tissue at the pulmonary vein orifice.

[0058] In some applications, the expandable cage is rotationally asymmetric. In some applications, the expandable cage is rotationally symmetric.

[0059] In some applications, the expandable cage is configured to adjust the distance between the transducer and the tissue by applying pressure and pushing the tissue when it comes into contact with the lumen wall in a curved position.

[0060] In some applications, each of the struts that curves outward at at least two positions has a shape such that the radius of curvature of the first curved portion is 10 to 20 mm and the radius of curvature of the second curved portion is 5 to 10 mm.

[0061] In some applications, at least a portion of the struts are conductive struts, which are configured to contact the tissue at the lumen opening and ablate the tissue at the lumen opening that is in contact with the conductive struts by driving an electric current into the tissue at the lumen opening.

[0062] In some applications, at least a portion of the conductive strut includes an insulating portion and a conductive portion, the conductive portion being configured to contact the tissue at the lumen opening and ablate the tissue at the lumen opening.

[0063] In some applications, the expandable cage is configured to drive radio frequency (RF) current into the tissue. In some applications, the expandable cage is configured to drive alternating current (AC) into the tissue. In some applications, the expandable cage is configured to drive direct current (DC) into the tissue.

[0064] In some applications, at least some of the struts have a shape that defines an opening formed in the strut, through which ultrasonic energy is transmitted from the ultrasonic transducer to the tissue.

[0065] In some applications, each of the struts in some of the multiple struts has a width of 0.5 to 1 mm, and the opening of the strut has a width of 0.25 to 0.5 mm. In some applications, the thickness of the strut is 0.1 to 0.25 mm.

[0066] In some applications, the transcatheter ablation catheter includes an elongated shaft comprising a proximal end including a handle and a distal end to which at least one ultrasonic transducer is coupled. In some applications, the device further includes one or more sensors coupled to the distal end of the elongated shaft and configured to detect the rotational position of the distal end of the elongated shaft.

[0067] In some applications, the ultrasonic transducer includes a transversely oriented ultrasonic transducer. In some applications, the ultrasonic transducer includes a distally oriented ultrasonic transducer.

[0068] In some applications, the distal tip of a transcatheter ablation catheter includes an electrode configured to ablate the tissue of the lumen wall.

[0069] In some applications, the ultrasound transducer is further configured to image the tissue by applying non-ablation ultrasound energy to the target tissue, and the ultrasound transducer is configured to rotate within an expandable cage and translate axially back and forth to generate a three-dimensional image of the tissue.

[0070] In some applications, the tissue includes the tissue of the lumen orifice, and the ultrasound transducer is configured to image the lumen orifice tissue by applying non-ablation ultrasound energy to the lumen orifice tissue.

[0071] In some applications, the apparatus further includes one or more acoustic reference markers placed on an expandable cage.

[0072] Furthermore, according to some application examples of the present invention, an apparatus is provided. This apparatus is This includes a transcatheter ablation catheter, and this transcatheter ablation catheter is The device includes a piezoelectric ultrasonic transducer configured to be inserted into the target cardiac chamber, the piezoelectric ultrasonic transducer having a shape that defines a convex surface extending outward from the longitudinal axis of the transducer, and having a width of 0.5 to 3 mm and a radius of curvature of 0.75 to 5 mm.

[0073] In some applications, at least one ultrasound transducer is configured to be positioned within the left atrium near the pulmonary vein orifice and to electrically isolate the pulmonary veins by ablating the tissue at the pulmonary vein orifice.

[0074] In some applications, the ultrasonic transducer has a width of 1 to 2 mm. In some applications, the ultrasonic transducer has a thickness of 0.1 to 0.3 mm. In some applications, the ultrasonic transducer has a length of 2 to 20 mm.

[0075] Furthermore, according to some applications of the present invention, a device is provided which is used in conjunction with a target lumen extending from a target cardiac chamber. This device is It is a transcatheter ablation catheter, An ultrasonic transducer configured to ablate tissue by transmitting ultrasonic energy to the target tissue, A sensor configured to be in a state of operational communication with a transcatheter ablation catheter and to detect changes in blood flow within the lumen, A computer processor, Based on the detected changes in blood flow, the optimal tissue target site for ablation is determined. A computer processor configured to drive an ultrasonic transducer to deliver ultrasonic energy to the optimal tissue target, Includes a transcatheter ablation catheter.

[0076] In some applications, the sensor includes a Doppler ultrasound device. In some applications, the sensor is configured to detect audible signals indicating changes in blood flow within a lumen.

[0077] In some applications, the transcatheter ablation catheter further includes an actuator configured to adjust the position of the ultrasound transducer so that the transmitted ultrasound energy is applied to the optimal tissue target site in response to detected changes in blood flow.

[0078] In some application examples, The optimal tissue target includes the luminal opening. The sensor is configured to detect changes in blood flow between the tubular lumen and the cardiac chamber. The computer processor is configured to drive an ultrasonic transducer to transmit ultrasonic energy to the lumen opening based on detected changes in blood flow between the lumen and the heart chamber.

[0079] In some application examples, The optimal tissue target includes the pulmonary vein opening. The ultrasound transducer is configured to be positioned within the target atrium. The sensor is configured to detect changes in blood flow between the pulmonary veins and the atria. The computer processor is configured to drive an ultrasonic transducer to transmit ultrasonic energy to the pulmonary vein orifice based on detected changes in blood flow between the pulmonary veins and the atria.

[0080] Furthermore, according to some applications of the present invention, a method is provided. This method is The transcatheter ablation catheter, which includes at least one ultrasound transducer, is advanced into the target atrium. Using sensors, the location of the pulmonary veins relative to the atria is determined by detecting changes in blood flow near at least one ultrasound transducer, Depending on the location, the ultrasound transducer is activated to ablate the tissue at the pulmonary vein orifice, Includes.

[0081] In some applications, the use of a sensor includes using Doppler ultrasound. In some applications, the use of a sensor includes using a sensor to detect audible signals indicating changes in blood flow. In some applications, the method further includes adjusting the position of the ultrasound transducer according to the location determination.

[0082] In some application examples, the method further, To generate 3D image data of the atrium using an ultrasound transducer, The image data is used in combination with changes in blood flow detected by sensors to determine the position of the pulmonary veins relative to the atria, Includes.

[0083] Furthermore, according to some applications of the present invention, a method is provided. This method is The procedure involves advancing at least one ultrasound transducer into the target cardiac chamber to ablate the target myocardial tissue, Applying non-ablation ultrasound energy to myocardial tissue so that at least a portion of the non-ablation ultrasound energy is reflected and received by an ultrasound transducer, The parameters of the reflected energy are assessed to determine the parameters of the ultrasound energy applied by the ultrasound transducer to ablate myocardial tissue, Applying ultrasound energy to the myocardial tissue based on the determined parameters, Includes.

[0084] In some applications, assessing the parameters of reflected energy includes determining the energy level of the reflected energy. In some applications, assessing the parameters of reflected energy to determine the parameters of the ultrasonic energy applied by the ultrasonic transducer to ablate myocardial tissue includes assessing the parameters of reflected energy to determine the power level of the ultrasonic energy applied by the ultrasonic transducer to ablate myocardial tissue. In some applications, assessing the parameters of reflected energy includes assessing the parameters of reflected energy to determine whether the ultrasonic transducer is in the desired position and adjusting the position of the ultrasonic transducer accordingly.

[0085] Furthermore, according to some applications of the present invention, a device is provided which is used in conjunction with a target lumen extending from a target cardiac chamber. This device is This includes a transcatheter ablation catheter, and this transcatheter ablation catheter is A long, slender shaft having a proximal and distal portion, The system includes at least one ultrasound transducer coupled to the distal end of a shaft, which is inserted into a target cardiac chamber and configured to ablate tissue by applying ultrasound energy to the tissue at the luminal orifice, The elongated shaft is configured to rotate so as to rotate the ultrasonic transducer. The transcatheter ablation catheter further includes an expandable cage positioned distal to the shaft, the expandable cage configured to surround the ultrasound transducer when the ultrasound transducer is positioned within the target cardiac chamber when the cage is expanded, A rotational force reduction mechanism is configured to reduce the rotational force applied to the expandable cage by the elongated shaft when the elongated shaft rotates, so as to keep the expandable cage stationary while the ultrasonic transducer rotates. Includes.

[0086] Furthermore, according to some application examples of the present invention, an apparatus is provided. This apparatus is It is a transcatheter ablation catheter, A first ultrasonic transducer configured to ablate tissue by transmitting ablation ultrasonic energy towards the target tissue, A second ultrasonic transducer configured to transmit one or more pulses of pulsed echo ultrasonic energy towards tissue and to receive the reflection of the transmitted pulsed echo ultrasonic energy, A first support configured to support a first ultrasonic transducer and to enable the transmission of ablation ultrasonic energy toward the tissue, A second support is provided to support the second ultrasonic transducer, and is configured to provide a higher attenuation level than that provided by the first support, so that the second transducer can receive the reflection of the transmitted pulsed echo ultrasonic energy while the first ultrasonic transducer is transmitting ablation ultrasonic energy toward the tissue. Includes a transcatheter ablation catheter.

[0087] In some application examples, The first support includes an air barrier configured to allow vibration of the first ultrasonic transducer during the transmission of ablation ultrasonic energy toward the tissue. The second support includes a mechanical support comprising at least one of a backing layer and a damping element.

[0088] The present invention will be better understood by reading the following detailed description of embodiments together with the drawings. [Brief explanation of the drawing]

[0089] [Figure 1A] This is a schematic diagram of an apparatus for applying ultrasonic energy to tissue within a target body, according to some application examples of the present invention. [Figure 1B]This is a schematic diagram of an apparatus for applying ultrasonic energy to tissue within a target body, according to some application examples of the present invention. [Figure 1C] This is a schematic diagram of an apparatus for applying ultrasonic energy to tissue within a target body, according to some application examples of the present invention. [Figure 1D] This is a schematic diagram of an expandable cage for a device for applying ultrasonic energy to tissue within a target body, according to some application examples of the present invention. [Figure 1E] This is a schematic diagram of an apparatus for applying ultrasonic energy to tissue positioned within a target body, according to some application examples of the present invention. [Figure 2A] This is a schematic diagram of an apparatus for applying ultrasonic energy to tissue within a target body, according to some application examples of the present invention. [Figure 2B] This graph shows the effect of the distance from the ablation site to the ultrasonic transducer on the absorption of ultrasonic energy by various media through which the ultrasonic energy is transmitted, according to several application examples of the present invention. [Figure 3A] This is a schematic diagram of an apparatus for applying ultrasonic energy to tissue within a target body, according to some application examples of the present invention. [Figure 3B] This figure shows the components of a device for applying ultrasonic energy to tissue within a target body, according to some application examples of the present invention. [Figure 3C] This figure shows the components of a device for applying ultrasonic energy to tissue within a target body, according to some application examples of the present invention. [Figure 4A] This is a schematic diagram of a rotational force reduction mechanism for reducing the rotational force applied to an expandable cage during rotation of an ultrasonic transducer, according to some application examples of the present invention. [Figure 4B] This is a schematic diagram of a rotational force reduction mechanism for reducing the rotational force applied to an expandable cage during rotation of an ultrasonic transducer, according to some application examples of the present invention. [Figure 4C]This is a schematic diagram of a rotational force reduction mechanism for reducing the rotational force applied to an expandable cage during rotation of an ultrasonic transducer, according to some application examples of the present invention. [Figure 4D] This is a schematic diagram of a rotational force reduction mechanism for reducing the rotational force applied to an expandable cage during rotation of an ultrasonic transducer, according to some application examples of the present invention. [Figure 4E] This is a schematic diagram of a rotational force reduction mechanism for reducing the rotational force applied to an expandable cage during rotation of an ultrasonic transducer, according to some application examples of the present invention. [Figure 4F] This is a schematic diagram of a rotational force reduction mechanism for reducing the rotational force applied to an expandable cage during rotation of an ultrasonic transducer, according to some application examples of the present invention. [Figure 5A] This is a schematic diagram of a curved piezoelectric ultrasonic transducer according to some application examples of the present invention. [Figure 5B] This image shows an ultrasonic energy transmission profile using the ultrasonic transducer shown in Figure 5A, according to several application examples of the present invention. [Figure 5C] This image shows an ultrasonic energy transmission profile using the ultrasonic transducer shown in Figure 5A, according to several application examples of the present invention. [Figure 5D] This graph shows the effect of various dimensions of the ultrasonic transducer on the radiation angle of the ultrasonic transducer shown in Figure 5A, according to several application examples of the present invention. [Figure 6] This flowchart shows the steps of a method carried out according to some applications of the present invention. [Modes for carrying out the invention]

[0090] Refer to Figures 1A, 1B, and 1C, which are schematic diagrams of an apparatus for applying ultrasonic energy to tissue within a target body, according to some application examples of the present invention.

[0091] Figure 1A shows an overview of a system 220 for ultrasound tissue therapy, including a control console 27, a handle 25, and a device 20 for applying ultrasound energy to tissue within the target body. Figures 1B to 1C show embodiments of the device 20 having expandable cages of different shapes, which will be described in more detail below.

[0092] The system 220 shown in Figure 1A typically includes a device 20 comprising an ultrasonic transducer 50 (and / or ultrasonic transducers 52 / 150 described below) configured to apply ultrasonic energy to a target tissue. The device 20 typically operates with a control console 27, which includes a computer processor 26 and a display 23.

[0093] For example, the computer processor 26 is configured to detect various parameters related to the application of ultrasonic energy (such as parameters of applied and / or reflected ultrasonic energy) and drive the ultrasonic transducer to transmit ultrasonic energy (for example, by selecting the optimal ultrasonic energy application parameters). This will be described in more detail below. In some applications, the computer processor 26 drives the ultrasonic transducer to rotate and / or move back and forth. This will be described in more detail below. For example, the computer processor can control the movement of the ultrasonic transducer by an actuator (e.g., a motor) housed in the handle 25 (or elsewhere in the system 220). In some applications, the computer processor 26 is configured to control the device 20 in response to user input received via the handle 25 or another user input interface (such as a keyboard 29).

[0094] The computer processor 26 is typically a hardware device programmed by computer program instructions to generate a dedicated computer. For example, when programmed to perform the techniques described herein, the computer processor 26 typically functions as a dedicated ultrasonic energy application computer processor.

[0095] Next, refer to Figure 1B, a schematic diagram of a device 20 for applying ultrasonic energy to the tissue of a target anatomical structure within a subject body, according to some applications of the present invention. The device 20 is typically configured to be used in conjunction with a target lumen extending from a cardiac chamber of the subject. In some applications, the cardiac chamber is the atrium, and the lumen extending from the atrium is the pulmonary vein.

[0096] Typically, the device 20 applies ultrasonic energy to treat cardiac arrhythmias such as atrial fibrillation. According to some applications of the present invention, the ultrasonic energy is applied to myocardial tissue, and in particular to sites within the myocardial tissue that are involved in the induction, maintenance, or propagation of cardiac arrhythmias, such as the pulmonary vein orifice. For this reason, as described above, the device 20 has a shape and size that allows it to be used in conjunction with the pulmonary vein extending from the left atrium of the heart. The device 20 is configured to apply ultrasonic energy to ablate the tissue at the pulmonary vein orifice, resulting in scarring of the tissue at the ablated site. The scarring typically prevents abnormal electrical pulses generated at the pulmonary vein orifice from propagating into the cardiac chambers, thereby electrically isolating the pulmonary vein from the atrium and reducing or preventing cardiac arrhythmias.

[0097] In some applications, the device 20 comprises a transcatheter ablation catheter 40 including an elongated shaft. The elongated shaft has a proximal end including a handle 25 (shown, for example, in Figure 1A) and a distal end to which at least one ultrasonic transducer 50 is coupled. In this context, as used herein and in the claims, “proximal” means the end of the device closer to the user, and “distal” means the end further from the user, beyond the opening into the target body from which the device is first inserted.

[0098] The transcatheter ablation catheter 40 facilitates the minimally invasive procedure of advancing the ultrasound transducer 50 into the target cardiac chamber (e.g., atrium). The ultrasound transducer 50 is typically inserted into the atrium and ablates the tissue at the luminal opening, such as the pulmonary vein opening, by applying ultrasound energy to that tissue. In addition to or instead of applying ablation ultrasound energy, the ultrasound transducer 50 is configured to image the target tissue by applying non-ablation ultrasound energy.

[0099] In some applications, the ultrasound transducer 50 includes a transversely oriented transducer. In other applications, the ultrasound transducer 50 includes a distally oriented ultrasound transducer. In some applications, two or more ultrasound transducers 50 are coupled to the transcatheter ablation catheter 40, at least one of which is a distally oriented ultrasound transducer and at least one is a transversely oriented ultrasound transducer. Furthermore, in some applications, to further assist in tissue damage formation, the distal tip of the transcatheter ablation catheter 40 includes an electrode configured to drive an electric current into the tissue designated for ablation treatment.

[0100] In some applications, the device 20 further includes a fixing element, such as an expandable cage, which has a shape that defines a three-dimensional structure configured to be positioned around the ultrasonic transducer 50 at the distal end of the transcatheter ablation catheter 40. Figure 1B shows an expandable cage 30 having a shape according to some applications of the present invention, and Figures 1A and 1C show an expandable cage 301 having a shape according to other applications of the present invention.

[0101] As shown in Figure 1B, the expandable cage 30 includes a plurality of struts 32 (flexible struts which can be made from elastic metals such as nitinol, stainless steel, nickel-titanium, or a combination thereof). As stated above, in some cases, the struts are referred to as “flexible wires” in this specification. These two terms are used interchangeably throughout this specification and the claims. The expandable cage 30 is configured to position the distal portion of the transcatheter ablation catheter 40 within the lumen of a target vascular tissue extending from a target cardiac chamber, for example, within the lumen of a pulmonary vein extending from the atrium of the heart.

[0102] The expandable cage 30 positions and temporarily fixes the distal portion of the transcatheter ablation catheter 40 within the lumen by the contact of the struts 32 with the lumen wall. Typically, the expandable cage 30 engages with the wall of a lumen, such as a pulmonary vein, but does not obstruct blood flow through the lumen (as shown in the figure, the expandable cage 30 has a shape that allows blood to flow through it).

[0103] The expandable cage 30 is typically delivered in a folded state to a target anatomical site within the body via the transcatheter ablation catheter 40. The struts 32 typically include a shape memory alloy that automatically expands from a folded configuration to an expanded configuration when deployed in a lumen, such as a pulmonary vein. When it is required to withdraw the transcatheter ablation catheter 40 from the body, the struts 32 are folded from the expanded state to a predetermined folded shape by applying a mechanical compressive or tensile force to the handle. The shapes of the expandable cage and parts of the expandable cage as described herein typically mean the shapes that the expandable cage has when it is not radially constrained (for example, when deployed at a target anatomical site).

[0104] In some applications, the expandable cage 30 is rotationally symmetric. In other applications, the expandable cage 30 is rotationally asymmetric.

[0105] In some applications, the expandable cage 30 is configured to position the transducer 50 and / or catheter 40 at the center of the lumen. In other applications, the expandable cage 30 is configured to position the transducer 50 and / or catheter 40 asymmetrically within the lumen, i.e., not at the center of the vascular lumen. For example, the expandable cage 30 can be positioned to aim at a portion of the lumen wall designated for ablation and / or imaging. For example, the expandable cage 30 can be configured to fix the transcatheter ablation catheter 40 so that the ultrasonic transducer 50 transmits ultrasonic energy toward the lumen orifice when the lumen orifice is designated for ablation and / or imaging. In some applications, the expandable cage 30 is configured to maintain radial separation between the ultrasonic transducer 50 and the lumen wall, and to position the transducer 50 at a desired distance from the site designated for imaging or ablation. For example, the expandable cage 30 is configured to adjust the distance between the ultrasound transducer 50 and the tissue designated for ablation and / or imaging by applying pressure to push the tissue when it comes into contact with the lumen wall. In some applications, the expandable cage 30 is configured to maintain the ultrasound transducer 50 at a fixed distance from the tissue during imaging in order to detect injury formation while reducing artifacts associated with tissue movement.

[0106] In some applications, the expandable cage 30 has a papillary structure in which the distal portion 36 of the expandable cage 30 is narrower than the central portion 34 of the expandable cage 30. Having a narrow distal portion 36 typically facilitates insertion of the expandable cage 30 into relatively small or narrow anatomical structures of various diameters, such as vascular lumenes like pulmonary veins. For example, in some applications, only the narrow distal portion 36 of the cage 30 is inserted into the vein, while the rest of the device 20 remains in the atrium. In some applications, this allows the narrow distal portion 36 of the cage 30 to fix the cage 30 to the pulmonary vein.

[0107] Typically, starting from the distal end of the expandable cage 30, the strut first defines a convex curvature (relative to the outside of the expandable cage), then passes through the inflection point 21 and has a concave curvature. The slender distal portion extends from the distal end of the expandable cage to the inflection point.

[0108] In some applications, the maximum diameter D1 at the central portion 34 of the expandable cage 30 is up to five times larger than the maximum diameter D2 at the narrow distal portion 36 of the expandable cage 30, which facilitates the insertion of the narrow distal portion 36 into the pulmonary vein.

[0109] In some applications, the expandable cage 30 is constructed such that at least a portion of the struts 32 curves outward (i.e., curves convexly relative to the outside of the expandable cage) at at least two positions along a single strut, for example, at bending positions 22 and 24. In some applications, the outwardly curved area contacts the lumen wall to secure the transcatheter ablation catheter 40 within the lumen. In some applications, the struts 32 that curve outward at at least two positions (e.g., 22 and 24) have a shape such that the radius of curvature at the first bending position 22 is 10-20 mm and the radius of curvature at the second bending position 24 is 5-10 mm. The radii of curvature at bending positions 22 and 24 are such that the tissue is not generally penetrated or damaged when these portions are biased against the lumen wall.

[0110] As described above, in some applications, the ultrasonic transducer 50 is configured to generate tissue images by applying non-ablation ultrasonic energy to the tissue. In some applications, the ultrasonic transducer 50 generates a three-dimensional image (e.g., of the pulmonary vein orifice) by rotating in the direction indicated by arrow A1 about the longitudinal axis LA of the transcatheter ablation catheter 40, and by translating longitudinally back and forth along the longitudinal axis LA in the direction indicated by arrow A2. According to some applications of the present invention, the dimensions of the expandable cage 30 are such that the transducer 50 can rotate within the cage and translate back and forth in the directions indicated by arrows A1 and A2 when the expandable cage 30 is positioned around the transducer.

[0111] In some applications, the expandable cage 30 is further configured to electrically stimulate and / or detect electrical signals from the anatomical structure in which the device 20 is positioned. In some such applications, the expandable cage 30 includes one or more electrodes 60 (shown in Figure 3A) configured to record electrical activity before, during, or after ablation in order to monitor the ablation procedure and damage formation. In some applications, ablation treatment parameters (e.g., duration of energy application and / or level of energy applied to the tissue) are adjusted based on monitoring by one or more electrodes 60.

[0112] Additionally or alternatively, at least some of the struts 32 forming the expandable cage 30 include conductive struts, such as flexible metal wires, which are configured to contact the tissue of the lumen wall (e.g., the lumen opening) and ablate the tissue in contact with the conductive struts / wires by driving an electric current into the tissue. Typically, in such applications, the ultrasound transducer 50 is used primarily to image the tissue.

[0113] In some such applications, at least a portion of the conductive strut includes both a conductive portion and an electrically insulated portion. Typically, the insulated portion of the strut is coated with an insulating material, while the conductive portion is exposed. Typically, the position of the strut 32 in contact with the tissue is conductive and designed to drive an electric current into the tissue to ablate it (e.g., the curved positions 22 and 24 shown in Figure 1B, which are typically biased against the lumen wall).

[0114] According to some applications of the present invention, the expandable cage 30 drives a radio frequency (RF) current into the tissue via the conductive portion of the strut 32. Additionally or alternatively, the expandable cage 30 drives alternating current and / or direct current (DC) into the tissue via the conductive portion of the strut 32.

[0115] Next, we refer to Figure 1C, a schematic diagram of the apparatus 20 according to some applications of the present invention. As shown in Figure 1C, in some applications, the apparatus 20 comprises an expandable cage 301, and the struts 32 have a shape that defines the spherical shape of the expandable cage 301. Generally, the expandable cage 301 does not have the narrowing of the distal portion 36 that gives the papillary shape of the expandable cage 30 (shown in Figure 1B). The expandable cage 301 is substantially the same as the expandable cage 30, except that the narrow distal portion 36 extends from the distal end of the expandable cage to an inflection point 21 (which does not exist in the expandable cage 301).

[0116] Referring again to Figure 1A, it should be noted that the shape of the expandable cage shown in Figure 1A is illustrated as an example, not an limitation. Furthermore, any other suitable shape of the expandable cage may be used, including the expandable cage 30 having the shape shown in Figure 1B, an elliptical expandable cage (not shown), or any other arbitrary shape of expandable cage, with necessary modifications. Additionally, it should be noted that the additional embodiments of the present invention described herein with reference to Figures 1D to 6 are applicable to either the shape of the expandable cage 30 or the expandable cage 301.

[0117] Next, we refer to Figure 1D, a schematic diagram of an expandable cage 30 according to some applications of the present invention. As shown in Figure 1B, the expandable cage 30 has a shape that defines several relatively large gaps 90, and the struts 32 are constructed to form the expandable cage 30 so that ultrasonic energy is transmitted from the ultrasonic transducer 50 to the tissue designated for ablation and / or imaging through these gaps 90. Furthermore, in some applications, in order to further facilitate the transmission of ultrasonic energy to the tissue, at least a portion of the struts 32 of the expandable cage 30 has a shape that defines one or more openings 94 formed in the struts (the openings 94 are shown in Figure 1D). The openings formed in the struts 32 typically increase the area over which ultrasonic energy is transmitted through the expandable cage 30, allowing more ultrasonic energy to reach the target tissue, resulting in increased tissue heating and more effective tissue ablation.

[0118] The width of the struts 32 is typically narrow enough to allow for the formation of gaps 90 between the struts 32, and at the same time wide enough to provide the necessary fixation and stabilization of the distal portion of the transcatheter ablation catheter 40 within the lumen. Therefore, providing an opening 94 in the struts 32 improves the transmission of ultrasonic energy to the tissue via the expandable cage 30 while adequately fixing the catheter 40 within the lumen. Typically, the width W1 of a single strut 32 is 0.5 to 1 mm, for example, 0.7 mm. The width W2 of the strut opening is 0.25 to 0.5 mm, for example, 0.35 mm. In some applications, the opening 94 extends along the entire length of the strut 32. Alternatively, in some applications, the opening 94 extends along a portion of the length of the strut 32.

[0119] Refer to Figures 1B to 1D. Typically, according to some applications of the present invention, the thickness of each or part of the struts 32 is less than the value of the ultrasonic wavelength for the ultrasonic frequency generated by the ultrasonic transducer 50. When the thickness of the struts 32 is less than the value of the ultrasonic wavelength (when propagating in blood) for the frequency used, interference with the propagation of ultrasound (e.g., interference by the struts) is reduced, so that more energy reaches the tissue.

[0120] According to some applications of the present invention, in order to achieve effective heating and ablation of tissue, ultrasonic energy is applied at a frequency of 8 to 20 MHz, e.g., 10 to 12 MHz, e.g., 11 MHz. Generally, since the ultrasonic wavelength decreases as the frequency increases, when the ultrasonic transducer 50 is operated at a frequency of, for example, 8 to 20 MHz, e.g., 10 to 12 MHz, e.g., 11 MHz, the struts 32 have a thickness of approximately 0.1 to 0.25 mm (e.g., 0.14 to 0.2 mm) to facilitate the propagation of ultrasound through the cage 30.

[0121] Next, we refer to Figure 1E, a schematic diagram of a device 20 positioned within a target body according to several application examples of the present invention.

[0122] In some applications, the device 20 is advanced into the left atrium 190 and positioned adjacent to or within the pulmonary vein orifice. In some applications, a transseptal approach is used to advance the device 20 into the left atrium 190 (illustrated in Figure 1E). Alternatively, a transapical approach may be used to advance the device 20 into the left atrium 190 via the left ventricular apex and mitral valve (approach not shown). Further alternatives include advancing the device 20 into the left atrium 190 via the aorta, left ventricle, and mitral valve (approach not shown).

[0123] Typically, the device 20 is advanced into the left atrium 190 by an expandable cage 30 in a folded state. The struts 32 expand from a folded configuration to an expanded configuration within the left atrium of the heart, making the device 20 operational. The device 20 is positioned adjacent to the orifice of the pulmonary vein 160 and the tissue of the atrial wall 170, so that a portion of the cage 30 (typically a portion of the central part 34) is fixed to the wall 170. The distal portion 36 of the cage 30 is typically advanced into the pulmonary vein 160 to optimally position the ultrasound transducer 50 against the tissue designated for ablation (typically the orifice of the pulmonary vein). Additionally or alternatively, the distal portion 36 of the expandable cage 30 is advanced into the pulmonary vein 160 to fix and maintain the device 20 in place during the application of ultrasound energy by applying pressure to the wall of the pulmonary vein.

[0124] Figure 1E shows an ultrasonic transducer 50 positioned outside the pulmonary vein, but it should be noted that the device 20 may also be configured so that the ultrasonic transducer advances into the pulmonary vein when the distal portion 36 of the cage 30 is advanced into the pulmonary vein, by positioning the ultrasonic transducer further distally along the catheter 40.

[0125] Furthermore, it should be noted that the scope of the present invention includes the use of the apparatus and methods described herein in anatomical locations other than the left atrium and pulmonary veins.

[0126] Next, refer to Figure 2A, a schematic diagram of a device 20 for applying ultrasonic energy to tissue within a target body, according to some application examples of the present invention. Also refer to Figure 2B. Figure 2B is a graph showing the absorption of ultrasonic energy by blood (indicated by line 106) and myocardial tissue (indicated by line 105) when ultrasonic energy of relatively high frequencies (e.g., 8-20 MHz, e.g., 10-12 MHz, e.g., 11 MHz, e.g., 11.2 MHz) is applied, and the distance (in millimeters) from the tissue site designated for ablation (e.g., pulmonary vein) to the ultrasonic transducer is gradually increased.

[0127] As shown in Figure 2A, in some applications, the device 20 includes, in addition to the expandable cage 30, a fluid-filled inflatable element 100, such as a balloon, configured to be positioned around the ultrasonic transducer 50. Typically, the inflatable element 100 is inflated with a fluid such as water (e.g., distilled water) and / or saline solution and / or any liquid having an acoustic attenuation coefficient similar to that of saline solution. Ultrasonic energy is transmitted through this fluid, but the absorption of ultrasonic energy is negligible. In such applications, as described above, the expandable cage 30 is positioned around the inflatable element 100 to position the distal portion of the transcatheter ablation catheter 40 within the lumen.

[0128] Typically, when the expandable cage 30 is present but the expandable element 100 is absent (as shown in Figures 1B to 1C), the primary medium through which the ultrasonic energy emitted from the ultrasonic transducer 50 is transmitted to the tissue is blood. This is because the expandable cage 30 has a shape that allows blood flow through vascular lumen (e.g., pulmonary veins). When ultrasonic energy from the transducer 50 is transmitted to the tissue via the blood, some of the energy is absorbed by the blood, thus reducing the amount of ultrasonic energy that reaches the tissue. This is especially true when using relatively high frequencies (e.g., 8-20 MHz, e.g., 10-12 MHz, e.g., 11 MHz) to perform effective tissue ablation according to some applications of the present invention, compared to using low frequencies such as 6 MHz.

[0129] Typically, as shown in Figure 2B, the greater the distance between the piezoelectric element (PZT) of the ultrasound transducer 50 and the tissue designated for ablation / imaging (pulmonary veins (PV)), the more ultrasound energy is absorbed by the blood in the vessels (and therefore less energy reaches the tissue). For example, if the ultrasound transducer 50 is positioned at a distance of approximately 10 mm from the tissue designated for ablation, only a portion of the transmitted ultrasound energy (e.g., about 50%) reaches the tissue. In such cases, the tissue may not be heated sufficiently to achieve ablation.

[0130] Typically, as shown in Figure 2B, the absorption of ultrasound energy by blood (line 106) increases as the distance the ultrasound travels increases, and correspondingly, the absorption of ultrasound energy by myocardial tissue decreases (line 105).

[0131] As shown in Figure 2A, by placing a fluid-filled (e.g., water-filled) inflatable element 100 around the ultrasonic transducer 50, the blood medium between the ultrasonic transducer 50 and the tissue designated for ablation is partially replaced. As described above (and also shown in Figure 2B), although ultrasonic energy is transmitted through water, it is not substantially absorbed by water, so a greater amount of transmitted ultrasonic energy reaches the tissue compared to when the transmitted ultrasonic energy is transmitted only through blood.

[0132] For example, the inflatable element 100 is expanded with water to occupy up to 50% (e.g., 30-40%) of the distance between the transducer 50 and the tissue designated for ablation, thereby reducing the amount of ultrasonic energy that might have been absorbed by the blood in the lumen if the inflatable element 100 were not present. Typically, providing the inflatable element 100 allows the ultrasonic transducer 50 to operate at a lower power level and for a shorter duration compared to when the transmitted ultrasonic energy is transmitted only through the blood.

[0133] Advantageously, since the inflatable element 100 is used in addition to the expandable cage 30 (and therefore not used for positioning the ablation catheter 40 in the lumen), the inflatable element 100 can be inflated to any desired degree based on, for example, the anatomical site where the ultrasonic transducer is inserted and / or the operating parameters of the ultrasonic transducer 50. In some applications, the inflatable element 100 is inflated with water to a diameter of 6-9 mm, for example, 8 mm.

[0134] Next, refer to Figure 3A, which is a schematic diagram of a device 20 for applying ultrasonic energy to tissue within a target body, according to some applications of the present invention. Also refer to Figures 3B and 3C, which show additional components of the device 20, according to some applications of the present invention.

[0135] In some applications of the present invention, in addition to applying ultrasonic energy for ablation purposes, the ultrasonic transducer 50 is configured to perform acoustic sensing by transmitting one or more pulses of pulsed echo ultrasonic energy toward a designated tissue site and receiving the reflection of the transmitted pulsed echo ultrasonic energy. Generally, the parameters of the reflected pulsed echo ultrasonic energy can indicate the ultrasonic energy applied to the tissue and the effect of the ultrasonic energy on the tissue. As described above, in some applications, the apparatus 20 comprises a control console 27 and a computer processor 26 (shown, for example, in Figure 1A), which are configured to determine the parameters of the reflected pulsed echo ultrasonic energy and detect the effect or indication of the applied ultrasonic energy.

[0136] In some applications, a second ultrasonic transducer 52 is coupled to the transcatheter ablation catheter 40 in addition to the first ultrasonic transducer 50. In some such applications, the first ultrasonic transducer 50 is configured to ablate tissue by transmitting ablation ultrasonic energy towards the tissue in the lumen, and the second ultrasonic transducer 52 is configured to transmit pulsed echo ultrasonic energy to the tissue and to receive the reflection of the transmitted pulsed echo ultrasonic energy. For example, the first ultrasonic transducer 50 is configured to ablate tissue by transmitting ultrasonic energy at a power level greater than 3W, e.g., 3W to 50W, e.g., 6 to 35W, and the second ultrasonic transducer 52 is configured to transmit pulsed echo ultrasonic energy at a power level of up to 2W (e.g., less than 2W).

[0137] Typically, the ultrasonic transducer 50 is suspended above a first support including an air barrier (shown as reference no. 80 in Figure 5A), allowing for nearly free vibration of the ultrasonic transducer 50 with relatively low attenuation when ablation energy is applied to the tissue. This usually enables effective transmission of the ablation energy to the tissue. In contrast, the pulsed echo ultrasonic transducer 52, which detects the return signal (reflection) of the transmitted pulsed echo ultrasonic energy, does not, as a transducer 52, generally self-vibrate while detecting the reflected signal.

[0138] As shown in Figure 3A, transducers 50 and 52 are positioned adjacent to each other on the ablation catheter 40 (and are usually assembled within a single housing), so it is necessary to prevent mechanical vibrations of transducer 50 from reaching transducer 52. This is because vibrations of transducer 52 are likely to reduce the effectiveness of detecting reflected signals (especially signals reflected from very close to the transducer, e.g., from a distance of 1 mm).

[0139] Typically, the ultrasonic transducer 50 is suspended above an air barrier and, when ablation energy is applied to the tissue, is allowed to vibrate almost freely with relatively low attenuation, whereas the pulsed echo ultrasonic transducer 52 is supported with relatively high attenuation by a backing layer 120 (Figure 3B) and / or attenuation elements 140, such as an attenuation ring (Figure 3C). This allows both transducers to be positioned adjacent to each other, enabling sensing by the ultrasonic transducer 52 and ablation energy transmission by the ultrasonic transducer 50. Typically, the backing layer 120 is surrounded by attenuation elements 140, which include a soft material and / or high density (low hardness Pebax® or Pebax® and / or tungsten) intended to isolate the mechanical vibrations of the ultrasonic transducer 50 from reaching the ultrasonic transducer 52. Note that in Figure 3C, the attenuation element 140 is shown as having a round shape, not as an example but as an illustration. The attenuation element 140 typically has a shape corresponding to the shape of the ultrasonic transducer 52 (for example, it may have a rectangular or square shape).

[0140] As described above, in some applications, reflected ultrasound energy can indicate the ultrasound energy applied to the tissue and its effect on the tissue, and can function as an input for changing the operating parameters of the ultrasound transducer. For example, the power, duty cycle, or any other parameter of the ablation is adjusted in response to the detected reflected ultrasound energy. In some applications, reflected ultrasound energy is used to assess the outcome of post-treatment care after ablation and / or to assess the progression of damage formation during ablation.

[0141] In some applications, the computer processor 26 is configured to detect indications of blood carbonization near the ultrasonic transducers 50 and / or 52 by determining the parameters of the reflected pulsed echo ultrasonic energy, and to block the application of ultrasonic energy from the ultrasonic transducers in response to the detected indications of blood carbonization. Typically, blood carbonization interferes with the transmission of ultrasound, and since the distance between the transducer and the tissue is known, indications of blood carbonization and their location can be derived from the parameters of the reflected ultrasonic energy.

[0142] Refer again to Figures 1A to 3A, which show an apparatus 20 according to some applications of the present invention. As described above, the transcatheter ablation catheter 40 has an elongated shaft, which includes a handle 25 at the proximal end of the elongated shaft and at least one ultrasonic transducer 50 at the distal end of the elongated shaft.

[0143] Typically, the ultrasonic transducer 50 is rotatable with respect to the longitudinal axis LA of the ablation catheter 40 in the direction indicated by arrow A1 in Figure 1B. The rotation of the ultrasonic transducer 50 (and / or transducer 52) generally facilitates various functions and operating characteristics of the device 20.

[0144] For example, the ultrasound transducer 50 (and / or transducer 52) rotates to generate images of the tissue. The images can be two-dimensional and / or three-dimensional. The generated images can be displayed on the display 23 shown in Figure 1A. To generate a three-dimensional image, the ultrasound transducer 50 (and / or transducer 52) rotates (indicated by arrow A1 in Figure 1A) and translates back and forth along the longitudinal axis along axis LA (indicated by arrow A2 in Figure 1A). In some applications, the transducer 50 (and / or transducer 52) performs continuous imaging of the anatomical structure in which the transducer 50 (and / or transducer 52) is positioned (e.g., the cardiac chambers and the openings of tubular lumens extending from these cardiac chambers). Typically, generating three-dimensional images of the anatomical structure makes it possible to identify the optimal location and optimal plane within the tissue to be ablated. Usually, the transducer 50 (and / or transducer 52) also performs imaging near the anatomical structure designated for ablation. For example, imaging can be used to identify the position of the esophagus relative to the device 20 in order to mitigate potential esophageal damage caused by ablation procedures performed on the heart.

[0145] Additionally or alternatively, the ultrasound transducer 50 rotates to target the tissue site designated for ablation / imaging. Further additional or alternatively, the ultrasound transducer 50 can rotate while continuously transmitting ablation ultrasound energy to generate a continuous circular injury surrounding a vascular lumen (e.g., a pulmonary vein orifice).

[0146] Typically, the rotation of the ultrasonic transducer 50 (and / or transducer 52) is caused by the rotation of the elongated shaft of the ablation catheter 40 to which the ultrasonic transducer 50 (and / or transducer 52) is coupled. The rotation of the elongated shaft of the ablation catheter 40 is caused by the rotation of an actuator (e.g., a knob or motor) at the proximal end of the elongated shaft (e.g., the handle 25 shown in Figure 1A). The rotational motion is transmitted from the proximal end along the elongated shaft to the distal end of the shaft to which the ultrasonic transducer 50 (and / or transducer 52) is coupled, causing the ultrasonic transducer 50 (and / or transducer 52) to rotate.

[0147] Generally, it is advantageous to determine the rotation and longitudinal position of the ultrasonic transducer 50 and / or transducer 52. For example, monitoring the rotation angle of the ultrasonic transducer 50 (and / or transducer 52) usually facilitates the generation of smooth two-dimensional and three-dimensional images. Since rotational motion is generated at the proximal end of the elongated shaft (e.g., the handle), the rotation angle of the ultrasonic transducer 50 (and / or transducer 52) can be assessed by measuring the rotation angle of the handle. However, not all rotational motion occurring at the proximal end of the elongated shaft is always transmitted along the shaft to the distal end. Furthermore, there may be a time lag between the rotational positions of the proximal and distal ends of the elongated shaft. Therefore, if it is desirable to accurately measure the rotational position of the ultrasonic transducer 50 (and / or, for example, the position of transducer 52 in order to determine the rotation angle of ultrasonic transducer 50 and / or transducer 52), measuring the rotational angle of the proximal part of the elongated shaft where the rotation begins (e.g., the handle) may not be sufficient.

[0148] According to some applications of the present invention, the apparatus 20 includes a mechanism configured to determine the rotational position of the distal end of an elongated shaft, separately from the rotational position of the proximal end of the elongated shaft, thereby determining the rotational position of the ultrasonic transducer 50 (and / or transducer 52).

[0149] Therefore, in some application examples, the device 20 includes a distal rotation detection sensor 28 (circularly shown in Figure 4A).

[0150] For example, a gyroscope is coupled to the ultrasonic transducer 50 (and / or transducer 52). The gyroscope is typically configured to measure the rotation angle of the distal end of an elongated shaft, thereby determining the rotation angle of the ultrasonic transducer 50 (and / or transducer 52).

[0151] Additionally or alternatively, the rotational position of the distal end of the elongated shaft can be determined using image guidance techniques. As an image guidance technique, for example, a reference marker (not shown) coupled to the expandable cage 30 and reflecting the ultrasonic energy emitted by the ultrasonic transducer 50 (and / or transducer 52) is used. As described below, the expandable cage 30 typically remains stationary during the rotation of the distal end of the elongated shaft and the ultrasonic transducer 50 (and / or transducer 52). Therefore, in some applications, the rotational position of the ultrasonic transducer 50 (and / or transducer 52) relative to the stationary cage is identified by identifying the position of the reference marker in the ultrasonic image generated using the ultrasonic transducer 50 (and / or transducer 52), thereby deriving the rotational position of the ultrasonic transducer 50 (and / or transducer 52) relative to the expandable cage 30.

[0152] Additionally or alternatively, one or more sensors of any other type can be used to determine the rotational position of the distal end of the elongated shaft, on the expandable cage 30, and / or on the ultrasonic transducer 50. For example, a first magnetic coil may be coupled to the distal end of the shaft and / or the ultrasonic transducer 50 (and / or transducer 52) so that the rotational position of the first magnetic coil changes as the rotational position of the ultrasonic transducer 50 (and / or transducer 52) changes. A second magnetic coil may be coupled to the cage so that the rotational position of the second magnetic coil remains constant even as the ultrasonic transducer 50 (and / or transducer 52) rotates. Additionally or alternatively, a second magnetic coil may be coupled to the distal end of the shaft so that the rotational position of the second magnetic coil remains constant even as the ultrasonic transducer 50 (and / or transducer 52) rotates. The rotational position of the ultrasonic transducer 50 (and / or transducer 52) is derived by measuring the change in magnetic flux between the first and second coils.

[0153] As described above, both the expandable cage 30 and the ultrasonic transducer 50 are located at the distal end of the elongated shaft of the transcatheter ablation catheter 40. The expandable cage 30 is coupled to the shaft, but during rotation of the distal part of the shaft and the ultrasonic transducer 50, the expandable cage 30 expands and remains stationary. (Since there is limited space for the expandable cage 30 to rotate within the lumen, it is usually not possible for the expandable cage 30 to rotate. Therefore, any attempt to rotate the expandable cage 30 is likely to prevent the rotation of the ultrasonic transducer 50.) In order to keep the expandable cage 30 stationary during rotation of the elongated shaft, in some applications, the device 20 is equipped with a rotational force reduction mechanism to reduce the rotational force applied to the expandable cage 30 by the elongated shaft during rotation, thereby keeping the expandable cage 30 stationary during rotation of the ultrasonic transducer 50.

[0154] Next, refer to Figures 4A to 4F, schematic diagrams of the components of a rotational force reduction mechanism 200 configured to reduce the rotational force applied to the expandable cage 30 by the elongated shaft 42 when the elongated shaft of the transcatheter ablation catheter 40 rotates. The components of the rotational force reduction mechanism 200 are typically located distal to the elongated shaft 42 and, like a swivel mechanism, allow rotation of the ultrasonic transducer 50 while keeping the expandable cage 30 stationary. In some such applications, the elongated shaft 42 includes an inner elongated shaft 42I and an outer elongated shaft 42O. Typically, the proximal end of the expandable cage 30 is coupled to the outer elongated shaft 42O. More typically, the ultrasonic transducer 50 is positioned on an inner elongated shaft 42I, and rotation is transmitted to the ultrasonic transducer via the rotation of the inner elongated shaft 42I within the outer elongated shaft 42O (i.e., the inner elongated shaft 42I rotates within the outer elongated shaft 42O, while the outer elongated shaft remains rotationally stationary).

[0155] In some applications, the rotational force reduction mechanism 200 includes a swivel bearing 44, a bearing stopper 46, and a distal end cover 45 (Figures 4B, 4C, 4D, 4E, and 4F). Typically, the swivel bearing includes a narrow proximal portion 44A and a wider distal portion 44B with a larger diameter than the proximal portion. The swivel bearing 44 is typically coupled to the distal end of an inner elongated shaft 42I (Figure 4B) and rotates together with the elongated shaft 42. The bearing stopper 46 is positioned to surround the narrow proximal portion of the swivel bearing 44, with the wider distal portion of the swivel bearing positioned distal to the bearing stopper. The diameter of the distal wide portion of the swivel bearing is typically larger than the lumen defined by the bearing stopper, so that the distal wide portion of the swivel bearing prevents the swivel bearing from being pulled proximal to the bearing stopper. The distal tip cover 45 typically covers the distal wide portion 44B of the swivel bearing. The bearing stopper and distal tip cover are configured to allow continuous and smooth rotation of the swivel bearing while being held in a rotationally stationary state (thus allowing continuous and smooth rotation of the elongated shaft).

[0156] Typically, the expandable cage 30 is prevented from rotating by (a) the proximal end of the cage being connected to an outer elongated shaft 42O, and (b) the cage itself being in contact with the target tissue, as described above. The distal end of the cage (e.g., the distal ring 48 of the cage) is typically connected to a bearing stopper 46, thereby applying a torsional force to the bearing stopper that prevents its rotation. The bearing stopper is typically designed so that a swivel bearing 44 can rotate freely within the bearing stopper, allowing the inner elongated shaft 42I to continue rotating, and also separating the rotational motion of the inner elongated shaft from the cage, preventing torsional forces from being applied to the cage 30.

[0157] The swivel bearing 44 typically allows the rotation of the elongated shaft 42 while enabling the expansion and folding of the expandable cage 30 at the distal end of the elongated shaft 42. As described above, typically the proximal end of the expandable cage 30 is coupled to the outer elongated shaft 42O. More typically, to expand the cage radially, the distal end of the cage is pulled proximally toward the proximal end of the cage by pulling the distal end of the inner elongated shaft 42I toward the outer elongated shaft 42O. The wide distal section 44B typically transmits the proximal motion of the distal end of the inner elongated shaft to the bearing stopper, which then transmits the proximal motion to the distal end of the cage, thereby pulling the distal end of the cage toward the proximal end, shortening the cage axially and expanding it radially. Typically, to contract the cage radially, the distal end of the inner elongated shaft 42I is pushed distally away from the outer elongated shaft 42O, thereby pushing the distal end of the cage distally away from the proximal end of the cage. The wide distal section 44B typically transmits the distal motion of the distal end of the inner elongated shaft to the distal tip cover 45, which then transmits the distal motion to the bearing stopper and the distal end of the cage, thereby pushing the distal end of the cage away from the proximal end of the cage, lengthening the cage axially and contracting it radially.

[0158] Therefore, the rotational force reduction mechanism 200 is configured, on the one hand, to couple the axial motion of the inner elongated shaft 42I with the axial motion of the distal end of the cage 30, and on the other hand, to separate the rotational motion of the inner elongated shaft 42I from the rotational motion of the distal end of the cage 30.

[0159] Figure 4F is a cross-sectional view of the components of the rotational force reduction mechanism 200 assembled with the device 20 to prevent the rotation of the expandable cage 30 while the ultrasonic transducer 50 is rotating, as described above with reference to Figures 4A to 4E.

[0160] Next, we refer to Figures 5A, 5B, and 5C, which are schematic diagrams of a curved piezoelectric ultrasonic transducer 150 and its ultrasonic energy transmission profile according to some applications of the present invention. We also refer to Figure 5D, which is a graph showing the effect of various radii of curvature and lengths of the piezoelectric ultrasonic transducer 150 on the radiation angle of the piezoelectric ultrasonic transducer 150, according to some applications of the present invention.

[0161] As shown in Figure 5A, in some applications, the ultrasonic transducer 50 includes a curved piezoelectric ultrasonic transducer 150. Figure 5A shows a cross-section of the curved piezoelectric ultrasonic transducer 150, suspended above the air barrier 80 and located within the transducer housing encapsulation layer 154, near the cooling channel 156.

[0162] The piezoelectric ultrasonic transducer 150 has a shape that defines a convex surface 152 that faces outward from the longitudinal axis of the transducer, with a radius of curvature of this convex surface of 0.75 to 5 mm. Typically, the piezoelectric ultrasonic transducer 150 is configured to ablate tissue (e.g., vein ostia) by applying ultrasonic energy to the tissue (e.g., vein ostia) from the convex surface. Typically, the curvature of the transducer 150 expands the area affected by ultrasonic energy (compared to using a flat transducer), enabling faster and / or more efficient ablation procedures.

[0163] In some applications, the width of the ultrasonic transducer 150 is 0.5 to 3 mm (e.g., 1 to 2 mm), and the thickness is 0.1 to 0.3 mm. In some applications, the radius of curvature of the piezoelectric ultrasonic transducer 150 is 0.75 to 5 mm, e.g., 1 to 3 mm, e.g., 1.5 to 2 mm.

[0164] Figures 5B and 5C show the thermal profile (Figure 5B) and pressure profile (Figure 5C) in a pulmonary vein when ablation is performed using a curved piezoelectric ultrasonic transducer 150 according to several applications of the present invention. Typically, providing a curved piezoelectric ultrasonic transducer 150 allows for an enlargement of the tissue's thermal profile, enabling more effective heating of larger portions of the tissue, thereby facilitating effective and rapid tissue ablation. In some examples, using a curved piezoelectric ultrasonic transducer 150 results in at least twice the heated tissue area compared to using a flat piezoelectric ultrasonic transducer of the same width, length, and thickness with the same power parameters. As shown in Figure 5B, providing a piezoelectric ultrasonic transducer 150 with a radius of curvature of 2 mm and a width of 1.5 mm resulted in a radiation angle of 28 degrees and a generally uniform tissue thermal profile, generally without the appearance of side lobes (indicating generally homogeneous damage).

[0165] The graph in Figure 5D shows the effect of the radius of curvature and surface width of the piezoelectric ultrasonic transducer 150 on the emission angle of the piezoelectric ultrasonic transducer 150, according to several application examples of the present invention. In Figure 5D, line 101 shows the effect of the radius of curvature on the emission angle using a piezoelectric ultrasonic transducer with a surface width of 1 mm. Line 102 shows the effect of the radius of curvature on the emission angle using a piezoelectric ultrasonic transducer with a surface width of 1.5 mm. Line 103 shows the effect of the radius of curvature on the emission angle using a piezoelectric ultrasonic transducer with a surface width of 2 mm. As shown in the figure, by providing an ultrasonic transducer 150 with a radius of curvature of 1.5 to 2 mm and a surface width of 1.5 mm, an emission angle of 28 degrees was obtained (shown by line 102).

[0166] Refer again to Figures 1A through 5A, and also to Figure 6. In some applications, a sensor in a state of operational communication with the transcatheter ablation catheter 40 (e.g., coupled to the catheter 40) is used to detect changes in blood flow between the lumen extending from the target cardiac chamber and the cardiac chamber (e.g., changes in blood flow between the pulmonary veins and the atria) to indicate the connection point between the lumen and the cardiac chamber, thereby indicating the location of the lumen orifice. Typically, changes in blood flow can be detected when blood passes through the lumen orifice into the cardiac chamber (e.g., between the pulmonary vein orifice and the atria). Based on the detected changes in blood flow, the computer processor 26 is configured to determine the optimal tissue target site for ablation (e.g., the lumen orifice) and to drive the ultrasonic transducers 50 and / or 150 to transmit ultrasonic energy to that optimal tissue target.

[0167] In some applications, the sensor includes a Doppler ultrasound device for detecting blood flow and changes in blood flow patterns. Additionally or alternatively, the transcatheter ablation catheter 40 further includes actuators configured to adjust the position of ultrasound transducers 50 and / or 150 so that the transmitted ultrasound energy is applied to the optimal tissue target site in response to the detected changes in blood flow.

[0168] Refer to Figure 6, a flowchart illustrating the steps of a method performed in response to the detection of changes in blood flow, according to some applications of the present invention. In some applications, an ultrasonic transducer 50 and / or 150 is advanced into the target atrium (step 310), changes in blood flow are detected near the ultrasonic transducer to determine the position of the pulmonary veins relative to the atrium (step 320), and in accordance with this position determination, the ultrasonic transducer 50 and / or 150 is activated to ablate the tissue at the pulmonary vein orifice (step 340). Optionally, before activating the ultrasonic transducer (step 340), the position of the ultrasonic transducer 50 and / or 150 is adjusted in accordance with the position determination (step 330).

[0169] In some applications, to confirm the position of the pulmonary vein orifice relative to the atrium, positional data derived from blood flow changes detected by Doppler ultrasound is used in combination with 3D image data of the atrium and pulmonary vein orifice.

[0170] According to some applications of the present invention, changes in the blood flow pattern between the atrium and pulmonary veins can be detected using any type of sound indication, and the location of the pulmonary vein orifice, which is typically the desired ablation site, can be indicated. For example, any one of the ultrasonic transducers 50, 52, and / or 150 described herein can be used to detect changes in the blood flow pattern between the atrium and pulmonary veins.

[0171] Refer again to Figures 1A to 6. As described above, the apparatus 20 is configured to perform acoustic sensing in addition to tissue ablation and imaging of myocardial tissue.

[0172] For example, before transmitting ultrasonic energy for the purpose of ablation, the device 20 is configured to use acoustic sensing to assess whether the ultrasonic transducer 50 is optimally positioned relative to the target tissue designated for ablation, and to apply ablation energy to the tissue accordingly, or to adjust the position of the ultrasonic transducer 50 and / or adjust the energy level applied to the tissue.

[0173] In some applications, the device 20 (in particular, the ultrasonic transducers 50 / 52 / 150 of the device 20) is configured to transmit low-intensity non-ablation ultrasonic energy to verify the proper positioning of the ultrasonic transducers. In some applications, the device 20 assesses the proper positioning of the ultrasonic transducers 50 / 52 / 150 relative to the target tissue by assessing the parameters of the ultrasonic echoes received by the transducers. For example, the device 20 assesses the proper positioning of the ultrasonic transducers 50 / 52 / 150 relative to the target tissue by measuring the amplitude (i.e., the energy level of the echoes) of the ultrasonic echoes received by the transducers. If the ultrasonic transducer 50 / 52 / 150 is mispositioned relative to the tissue, the echo amplitude will be small (this is because the angle formation of the sound field relative to the tissue creates a large contact area, resulting in a low energy density, causing the delivered energy to disperse and not be properly directed). If the ultrasonic transducer 50 / 52 / 150 is properly positioned relative to the target tissue, the echo amplitude will increase. Typically, upon assessment that the ultrasonic transducer 50 / 52 / 150 is in the desired position, the ultrasonic transducer is activated to ablate the tissue. Alternatively, the energy level applied to the tissue can be adjusted to compensate for the suboptimal positioning of the ultrasonic transducer 50 / 52 / 150. Further alternatively, the position of the ultrasonic transducer 50 / 52 / 150 can be adjusted to more appropriately target the tissue.

[0174] Additionally, or alternatively, when ablation energy is applied to create damage in tissue, the ablation can be monitored by measuring the amplitude of the return ultrasound echoes received by the transducer from the target tissue. Since ultrasound energy is not transmitted through the damage, an increase in the return ultrasound indicates appropriately shaped damage in the tissue.

[0175] Additionally or alternatively, measurements of the amplitude (or other parameters) of ultrasound echoes returning from various tissue depths are used to compare and assess changes along tissue depth (e.g., injury formation). In some applications, a graphical representation of the returned ultrasound echoes is displayed. For example, a graphical representation (e.g., with a resolution of 0.1–0.3 mm) can be presented, with color pixels assigned to each depth interval indicating the degree of ablation performed at each interval.

[0176] Refer to Figures 1A to 6. According to some applications of the present invention, the device 20 can be used to treat cardiac arrhythmias other than atrial fibrillation. For example, the device 20 is used to treat conditions such as ventricular tachycardia. In such applications, the device 20 is advanced into the target ventricle, and damage is generated by ablating the ventricular tissue by applying ultrasonic energy according to the applications of the present invention.

[0177] Furthermore, it should be noted that the application of ultrasound energy to the myocardial region is not limited to vascular orifices, but can be applied to any region of the heart involved in inducing or maintaining cardiac arrhythmias.

[0178] Furthermore, while much of the description herein relates to cardiac tissue, and in particular to the left atrium and the pulmonary veins extending from the left atrium, it should be noted that the scope of the invention includes the use of the devices and methods described herein for other lumens within the body ("lumen" generally means an internal open space, i.e., cavity, within an organ of the subject, which may be a tubular organ but is not necessarily so). For example, the devices and methods described herein may be used, with necessary modifications, for the arteries, veins, intestines, heart, sacs, sinuses, stomach, lungs, pulmonary vascular system, airways, or genitourinary tract of the subject.

[0179] It should be noted that the apparatus and methods described herein may, with necessary modifications, be used to treat other tissues of the target for the treatment of renal denervation, targeted lung denervation, pulmonary hypertension denervation, visceral nerve denervation, carotid body denervation, malignant lung nodule ablation, hypertrophic cardiomyopathy ablation, and / or hepatic artery denervation.

[0180] In some applications, the ultrasonic energy application techniques described herein are performed in combination with other types of ablation, such as pulsed field ablation (PFA) and / or radio frequency (RF) ablation. In some applications, other suitable energy sources (e.g., RF energy, laser energy, cryogenic energy, and / or electromagnetic energy such as ultraviolet and / or infrared) are used instead of or in addition to ultrasonic ablation.

[0181] Those skilled in the art will recognize that the present invention is not limited to what is specifically illustrated and described above. The scope of the present invention includes both combinations and subcombinations of the various features described above, as well as modifications and changes that are not in the prior art and that would be conjured by those skilled in the art when reading the foregoing description.

Claims

1. A device used in conjunction with the target organization, It is a transcatheter ablation catheter, At least one ultrasonic transducer configured to be inserted into the cardiac chamber of the subject, An elongated shaft comprising a proximal portion and a distal portion to which the at least one ultrasonic transducer is coupled, wherein the elongated shaft is configured to be rotatable so as to rotate the ultrasonic transducer, A computer processor configured to drive at least one ultrasonic transducer to (a) ablate the target tissue by applying ultrasonic energy to the target tissue, and (b) image the target tissue by applying non-ablation ultrasonic energy to the target tissue, An expandable cage positioned around the at least one ultrasonic transducer and configured to temporarily secure the transcatheter ablation catheter within the cardiac chamber by contacting the target tissue, Equipped with a transcatheter ablation catheter, The computer processor is configured to rotate within the expandable cage and translate back and forth in the axial direction to drive the at least one ultrasonic transducer via the elongated shaft to generate a three-dimensional image of the tissue, The transcatheter ablation apparatus further comprises a rotational force reduction mechanism configured to reduce the rotational force applied to the expandable cage by the elongated shaft when the elongated shaft rotates, and is configured to keep the expandable cage stationary while the ultrasonic transducer rotates.

2. The apparatus according to claim 1, wherein the at least one ultrasonic transducer is configured to be inserted into the left atrium near the pulmonary vein orifice and to electrically isolate the pulmonary vein orifice by ablating the tissue of the pulmonary vein orifice.

3. The apparatus according to claim 1, wherein the tissue includes the tissue of the opening of a lumen extending from the cardiac chamber of the subject, and the ultrasonic transducer is configured to generate a three-dimensional image of the tissue of the opening of the lumen by applying non-ablation ultrasonic energy to the tissue of the opening of the lumen.

4. The apparatus according to claim 1, wherein the at least one ultrasonic transducer is configured to generate ultrasonic energy at a frequency of 8 to 20 MHz.

5. The apparatus according to claim 1, wherein the at least one ultrasonic transducer has a shape that defines a convex surface extending outward from the longitudinal axis of the at least one ultrasonic transducer, and has a width of 0.5 to 3 mm and a radius of curvature of 0.75 to 5 mm.

6. The apparatus according to any one of claims 1 to 5, wherein the transcatheter ablation catheter includes a handle provided at the proximal end of the elongated shaft.

7. The apparatus according to claim 6, wherein the elongated shaft is configured to be rotatable so as to rotate the ultrasonic transducer, and the transcatheter ablation catheter comprises one or more sensors coupled to the distal end of the elongated shaft and configured to detect the rotational position of the distal end of the elongated shaft.

8. The at least one ultrasonic transducer is configured to apply the non-ablation ultrasonic energy to the tissue, and at least a portion of the non-ablation ultrasonic energy is reflected and received by the ultrasonic transducer. The computer processor is configured to assess the parameters of the reflected energy and determine the parameters of the ultrasonic energy applied by the ultrasonic transducer to ablate the tissue. The apparatus according to any one of claims 1 to 5, wherein the at least one ultrasonic transducer is configured to apply the ultrasonic energy to the tissue based on the determined parameters.

9. The at least one ultrasonic transducer is A first ultrasonic transducer configured to ablate the tissue by transmitting ablation ultrasonic energy to the target tissue, The apparatus according to any one of claims 1 to 5, comprising: a second ultrasonic transducer configured to image the tissue by transmitting one or more pulses of pulsed echo ultrasonic energy to the target tissue and receiving the reflection of the transmitted pulsed echo ultrasonic energy, wherein the second ultrasonic transducer is configured to rotate within the expandable cage and to translate back and forth in the axial direction to generate a three-dimensional image of the tissue.

10. The aforementioned transcatheter ablation catheter is A first support, configured to support the first ultrasonic transducer and to enable the transmission of the ablation ultrasonic energy to the tissue, A second attenuation support is provided to support the second ultrasonic transducer and to provide a higher attenuation level than that provided by the first support, so that the second ultrasonic transducer can receive the reflection of the transmitted pulsed echo ultrasonic energy while the first ultrasonic transducer is transmitting the ablation ultrasonic energy toward the tissue, The apparatus according to claim 9, comprising:

11. The first support includes an air barrier configured to allow vibration of the first ultrasonic transducer during the transmission of the ablation ultrasonic energy toward the tissue. The apparatus according to claim 10, wherein the second damping support includes a mechanical support comprising at least one of a backing layer and a damping element.

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