MXPA06000857A - Method for making a spiral array ultrasound transducer - Google Patents

Abstract

The present invention relates to a method for making an ablation transducer having a plurality of helical elements that can be operated out of phase to orient the acoustical energy beam forward or backward in the longitudinal direction. The transducers includes a cylindrical inner electrode, a cylindrical piezoelectric material disposed over the inner electrode, and a cylindrical outer electrode disposed over the cylindrical piezoelectric material. Spiral grooves are cut through at least the outer electrode separating the transducer into a plurality of functionally discrete helical transducer segments. The helical transducer segments can be operated independent from one another. An array of intertwined helical transducers arranged linearly along a helical axis are also contemplated.

Description

METHOD FOR ELABORATING A ULTRASOUND TRANSDUCER OF SPIRAL DISPOSAL FIELD OF THE INVENTION The present invention relates to a method for making a surgical device. More particularly, it relates to a method for making a tissue separation transducer having a plurality of helical elements that can be operated out of phase to orient the acoustic energy beam forward or backward in the longitudinal direction.

BACKGROUND OF THE INVENTION Many devices and methods of local energy delivery have been developed to treat various conditions of abnormal tissue in the body, and particularly, for the treatment of abnormal tissue along the walls of body space that define various body spaces in the body. For example, various devices have been described with the primary purpose of treating or re-channeling atherosclerotic vessels with localized energy delivery. Various prior devices and methods combine energy delivery assemblies with cardiovascular stent devices in order to deliver energy locally to the tissue with the object of keeping the open state in sick lumens such as blood vessels. Endometriosis, another condition of abnormal wall tissue that is associated with the endometrial cavity and characterized by dangerously proliferative uterine wall tissue along the surface of the endometrial cavity, has also been treated using devices and methods of treatment. local energy delivery. Various other devices and methods have also been described, which use heat sources based on a catheter for the intended purpose of inducing thrombosis and controlling hemorrhages within certain body lumens such as vessels. Detailed examples of local energy delivery devices and related procedures, such as those of the types described above, are described in the following references: U.S. Pat. No. 4,672,962 for Hershenson; the Patent of E.U.A. No. 4,676,258 to InoKuchi et al .; the Patent of E.U.A. No. 4,790,311 for Ruiz; the Patent of E.U.A. No. 4,807,620 to Strul et al .; the Patent of E.U.A. No. 4,998,933 for Eggers et al .; the Patent of E.U.A. No. 5,035,694 for Kasprzyk et al .; the Patent of E.U.A. No. 5,190,540 for Lee; the Patent of E.U.A. No. 5,226,430 to Spears et al .; and the U.S. Patent. No. 5,292,321 for Lee; the Patent of E.U.A. No. 5,449,380 for Chin; the Patent of E.U.A. No. 5,505,730 for Edwards; the Patent of E.U.A. No. 5,558,672 to Edwards et al .; and the U.S. Patent. No. 5,562,720 to Stern et al .; the Patent of E.U.A. No. 4,449,528 to Auth et al .; the Patent of E.U.A. No. 4,522,205 to Taylor et al .; and the U.S. Patent. No. 4,662,368 for Hussein et al .; the Patent of E.U.A. No. 5,078,736 for Behl; and the U.S. Patent. No. 5,178,618 for Kandarpa. Other prior devices and methods electrically couple the fluid to an ablation element during the delivery of local energy for the treatment of abnormal tissues. Some of said devices couple the fluid to the ablation element for the primary purpose of controlling the temperature of the element during the delivery of energy. Said other devices couple the fluid more directly to the tissue-device interface, either as another temperature control mechanism or in certain known applications, such as a vehicle or means for delivery of localized energy. Detailed examples of ablation devices that use fluid to assist in electrically coupling electrodes to tissue are described in the following references: US Pat. No. 5,348,554 for Imran et al .; the Patent of E.U.A. No. 5,423,811 to Imran et al .; the Patent of E.U.A. No. 5,505,730 for Edwards; the Patent of E.U.A. No. 5,545,161 for Imran et al.; the Patent of E.U.A. No. 5,558,672 to Edwards et al .; the Patent of E.U.A. No. 5,569,241 for Edwards; the Patent of E.U.A. No. 5,575,788 to Baker et al .; the Patent of E.U.A. No. 5,658,278 to Imran et al .; the Patent of E.U.A. No. 5,688,267 to Panescu et al .; the Patent of E.U.A. No. 5,697,927 for Imran et al .; the Patent of E.U.A. No. 5,722,403 to McGee et al .; the Patent of E.U.A. No. 5,769,846; and PCT Patent Application Publication No. WO 97/32525 for Pomeranz et al .; and PCT Patent Application Publication No. WO 98/02201 for Pomeranz et al.

Atrial Fibrillation Cardiac arrhythmias and atrial fibrillation in particular persist as a common and dangerous medical condition associated with abnormal cardiac chamber wall tissue, and is often seen in older patients. In patients with cardiac arrhythmia, the abnormal regions of cardiac tissue do not follow the synchronous beat cycle associated with the normally conducting tissue in patients with the rhythm of the cavity. Instead, abnormal regions of cardiac tissue lead aberrantly to adjacent tissue, thereby destabilizing the cardiac cycle in an asynchronous heart rhythm. Such abnormal conduction is known to occur in various regions of the heart, such as, for example, in the region of the sinoatrial node (SA), along the conduction trajectories of the atrioventricular (AV) node and the atrioventricular trunk, or in the heart muscle tissue that forms the walls of the ventricular and atrial cardiac chambers. Arrhythmias, which include atrial arrhythmia, can be of a multiple small wave type that re-enter, characterized by multiple asynchronous electric impulse circuits that are scattered around the ventricular chamber and are often of autonomous propagation. In the alternative or in addition to the multiple small wave type, Cardiac arrhythmias may also have a focal origin, such as when an isolated region of tissue in an atrium triggers autonomously in a repetitive, rapid manner. Cardiac arrhythmias, which include atrial fibrillation, can usually be detected using the global technique of an electrocardiogram (EKG). The most sensitive procedures for generating specific conduction maps along the cardiac chambers have also been described, such as, for example, in the U.S. Patent. No. 4,641, 649 for Walinsky et al., And PCT Patent Application Publication No. WO 96/32897 for Desai. A presence of clinical conditions may be the result of irregular cardiac function and result in hemodynamic abnormalities associated with atrial fibrillation, including heart attack, heart failure, and other thromboembolic events. In fact, atrial fibrillation is considered a significant cause of cerebral attack, in which abnormal hemodynamics in the left atrium produced by fibrillatory wall movement precipitate the formation of thrombi within the atrial chamber. A thromboembolism is ultimately expelled into the left ventricle which in the future pumps the embolism into the cerebral circulation to where the attack occurs. Accordingly, numerous methods have been developed for the treatment of atrial arrhythmias, including pharmacological, surgical and catheter ablation procedures.

Various pharmacological methods intended to remedy or otherwise treat atrial arrhythmias have been described, such as, for example, those methods described in the following references: US Pat. No. 4,673,563 to Berne et al .; the Patent of E.U.A. No. 4,569,801 to Molloy et al .; and the publication "Current management of arrhythmias" (1991) by Hindricks, et al. However, such pharmacological solutions are generally not considered to be effective in their entirety in many cases and it is still considered that in some cases it results in a pro-arrhythmia and is ineffective in the long term. Various surgical methods have also been developed with the intention of treating atrial fibrillation. One example in particular is known as the "labyrinth procedure", as described by Cox, JL, et al., In the document "The surgical treatment of atrial fibrillation." I. Summary "Thoracic and cardiovascular surgery 101 (3), pages 402 to 405 (1991); and also by Cox, J. L. in the publication "The surgical treatment of atrial fibrillation, IV Surgical Technique," Thoracic and cardiovascular surgery 101 (4), pages 584 to 592 (1991). In general, the "labyrinth" procedure is designed to mitigate atrial arrhythmia by restoring effective atrial systole and controlling the cavity node through a previously described pattern of incisions around the tissue wall. In previous reported clinical experiences, the "labyrinth" procedure included surgical incisions in the atrial chambers both right and left. However, the most recent reports predict that the surgical "labyrinth" procedure It can be substantially efficient when performed only in the left atrium. See publication of Sueda et al., "Simple left atrial procedure for chronic atrial fibrillation associated with mitral valve disease" (1996). The "labyrinth procedure" as it was done in the left atrium, includes in a general way the formation of vertical incisions from the two superior pulmonary veins and ending in the region of the mitral valve ring, crossing the region of the inferior pulmonary veins in the route. An additional horizontal line also connects the top ends of the two vertical incisions. Accordingly, the region of the atrial wall delimited by the opening of the pulmonary vein is isolated from the other atrial tissue. During this procedure, the mechanical generation of atrial tissue sections eliminates arrhythmogenic conduction from the boxed region of the pulmonary veins to the rest of the atrium, creating conduction blocks within aberrant electrical conduction trajectories. Other variations or modifications of this specific pattern just described have also been described, all sharing the main purpose of isolating known or suspected regions of arrhythmogenic origin or spread along the atrial wall. Although the "labyrinth" procedure and its variations are reported by Dr. Cox and others have achieved some success in the treatment of patients with atrial arrhythmia, this highly invasive methodology is considered to be prohibitive in most cases. However, these Procedures have provided a guiding principle in which the electrical isolation of the damaged cardiac tissue can successfully prevent atrial arrhythmia, and particularly, atrial fibrillation produced by the arrhythmogenic conduction that starts from the region of the pulmonary veins. The less invasive catheter-based methods for treating atrial fibrillation that have been described implement ablation of cardiac tissue to terminate arrhythmogenic conduction in the atrium. Examples of such catheter-based devices and methods of treatment have generally been aimed at atrial segmentation with ablation catheter devices and methods adapted to form linear or curvilinear lesions in the wall tissue defining the atrial chambers. Some methods described specifically provide specific ablation elements that are linear over a defined length intended to couple the tissue to create the linear lesion. Other described methods provide guided or shapeable guiding sheaths, or sheaths inside sheaths, for the intended purpose of directing the tip of the ablation catheters towards the posterior left atrial wall, such that sequential ablations along of the previously determined trajectory of tissue can create the desired lesion. In addition, various modalities of energy delivery have been described for the formation of atrial wall lesions, and include the use of microwaves, lasers, ultrasound, thermal conduction and most commonly, radiofrequency energies to create driving blocks along the wall of cardiac tissue.

Detailed examples of device assemblies and ablation methods for creating lesions along an atrial wall are described in the following U.S. Patent references: U.S. Pat. No. 4,898,591 to Jang et al .; the Patent of E.U.A. No. 5,104,393 to Isner et al .; the Patents of E.U.A. Nos. 5,427,119; 5,487,385 for Avitall; the Patent of E.U.A. No. 5,497,119 to Swartz et al .; Patent of E.U.A. No. 5,545,193 to Fleischman et al .; Patent of E.U.A. No. 5,549,661 to Kordis et al .; the Patent of E.U.A. No. 5,575,810 to Swanson et al .; the Patent of E.U.A. No. 5,564,440 to Swartz et al .; the Patent of E.U.A. No. 5,592,609 to Swanson et al.; the Patent of E.U.A. No. 5,575,766 to Swartz et al .; the Patent of E.U.A. No. 5,582,609 for Swanson; the Patent of E.U.A. No. 5,617,854 for Munsif; the Patent of E.U.A. No. 5,687,723 for Avitall .; the Patent of E.U.A. No. 5,702,438 for Avitall. Other examples of such devices and methods of ablation are described in the following publications of PCT Patent Application Nos .: WO 93/20767 to Stem et al .; WO 94/21165 for Kordis et al .; WO 96/10961 for Fleischman et al .; WO 96/26675 for Klein et al .; and WO 97/37607 for Shaer. Additional examples of such devices and methods of ablation are described in the following published articles: "Physics and engineering of transcatheter tissue ablation". Avitall et al., Journal of American College of Cardiology, Volume 22, No. 3: pages 921 to 932 (1993); and "Right and left atrial radiofrequency catheter therapy of paroxysmal atrial fibrillation", Haissaguerre, et al., Journal of cardiovascular electrophysiology 7 (12) pages 1132 to 1144 (1996). In addition to those known assemblies summarized above, the additional tissue ablation device assemblies have been developed recently for the specific purpose of ensuring firm contact and consistent placement of a linear ablation element along a length of tissue, setting the element at least in a predetermined location along that length, in such a way that it has the purpose of forming a pattern of "labyrinth" type lesion in the left atrium. An example of such assemblies is that described in the U.S. Patent. No. 5,971,983, issued October 26, 1999, which is incorporated herein by reference. The assembly includes an anchor at each of the two ends of a linear ablation element in order to secure those ends to each of the two predetermined locations along the left atrial wall, ie, in two pulmonary veins adjacent, in such a way that the tissue can be separated along the length of the tissue extending between them. In addition to attempting atrial wall segmentation with long linear lesions to treat atrial arrhythmia, another device and method of ablation has also been described, which is intended to utilize expandable limbs, such as balloons to separate cardiac tissue. . Some of these devices have been described mainly for use in the separation of tissue wall regions along the cardiac chambers. Other devices and methods have been described to treat abnormal conduction of the accessory paths on the left side, and in particular those associated with the "Wolf-Parkinson-White" syndrome-several of these descriptions use a balloon to separate from the inside of a region of an associated coronary cavity adjacent to the desired cardiac tissue to be separated. Further detailed examples of devices and methods, such as the types just described, are described in various forms in the following published references: Fram et al., In "Feasibility of RF powered thermal balloon ablation of atrioventricular bypass tracts via the coronary sinus: in vivo canine studies "PACE, Vol. 18, Pages 1518 to 1530 (1995); "Long-term effects of percutaneous laser balloon ablation from canine coronary sinus," Schuger CD et al., Circulation (1992) 86: pages 947-954 and "Percutaneous laser balloon coagulation of accessory pathways," McMath LP et al., Diagn. ther cardiovasc interven 1991; 1425: pages 165 to 171.

Arrhythmias originating from foci in pulmonary veins The various modes of atrial fibrillation have also been observed to be focal in nature, produced by the rapid and repetitive performance of an isolated center within the heart muscle tissue associated with the atrium. These foci can act, either as an activator of the paroxysmal fibrillatory atrium or can even sustain fibrillation. They have suggested various descriptions of focal atrial arrhythmia that often originates from at least one region of tissue along one or more pulmonary veins of the left atrium, and even more particularly, in the superior pulmonary veins. Less invasive percutaneous catheter ablation techniques have been described, which use end electrode catheter designs with the intention of separating and thus treating focal arrhythmias in the pulmonary veins. These ablation procedures are typically characterized by the increased application of electrical energy to the tissue to form focal lesions designed to terminate inadequate arrhythmogenic conduction. An example of a method of focal ablation intended to treat focal arrhythmia that originates from a pulmonary vein is described by Haissaguerre, et al., in the publication "Right and left atrial radiofrequency catheter therapy of paroxysmal atrial fibrillation" in Journal of cardiovascular electrophysiology 7 (12), pages 1132 to 1144 (1996). Haissaguerre, et al., Describe the radiofrequency catheter ablation of paroxysmal, drug-resistant atrial fibrillation using linear atrial lesions supplemented by focal ablation aimed at arrhythmogenic foci in a population of selected patients. The site of arrhythmogenic foci was generally located just inside the superior pulmonary vein, and focal ablations were usually performed using a standard 4 mm tip ablation electrode.

Another method of focal ablation for the treatment of atrial arrhythmias is described by Jais et al., "A focal source of atrial fibrillation treated by discrete radiofrequency ablation", Circulation 95: pages 572 to 576 (1997). Jais, et al., Describe the treatment of patients with paroxysmal arrhythmias that originate from a focal source by separating that source. At the site of arrhythmogenic tissue, both in the right and left atria, various pulses from a discrete source of radiofrequency energy were applied in order to eliminate the fibrillation process. Other assemblies and methods oriented to focal sources of arrhythmia in the pulmonary veins have been described separating the circumferential regions of tissue, either along the pulmonary vein, in the vein orifice along the atrial wall, or surrounding the hole and along the atrial wall. More detailed examples of device assemblies and methods for the treatment of focal arrhythmia such as those just described are described in PCT Patent Application Publication No. WO 99/02096 for Diederich et al., And also in The following US Patents pending and patent applications: the Patent of E.U.A. No. 6,024,740, issued February 15, 2000 to Michael D. Lesh et al., For "Circumferential ablation device assembly"; the Patent of E.U.A. No. 6,012,457, issued January 11, 2000 to Michael D. Lesh, for "Device and method for forming a circumferential conduction block in a pulmonary vein"; the Patent of E.U.A. No. 6,117,101 issued September 12, 2000 to Chris J. Diederich et al., For "circumferential" ablation device assembly "; and US Serial No. 09 / 260,316 for" Device and method for forming a circumferential conduction block in a pulmonary vein "for Michael D. Lesh.Another specific device assembly and method, which has the intention to treat focal atrial fibrillation by separating a circumferential region of tissue between two seals for the purpose of forming a conduction block to isolate an arrhythmogenic focus within a pulmonary vein is described in U.S. Patent No. 5,938,660 and a publication PCT Patent Application No. WO 99/00064.

BRIEF DESCRIPTION OF THE INVENTION The present invention relates to a method for making a tissue ablation device and transducer assembly having a plurality of helical elements that can be operated out of phase to orient the acoustic energy beam forward and backward in the longitudinal direction . In one embodiment of the present invention, the method for making a piezoelectric transducer comprises first providing a shutter of ceramic material, and machining the shutter in a tubular configuration. The ceramic tube is covered with a metal layer. The metal-coated ceramic tube is then machined to form an inner electrode and a series of external electrodes interlocked in helical form, where each outer electrode is associated with a transducer segment. The ceramic material is transformed into a piezoelectric crystal, thereby forming a transducer with a series of individual interlaced helical transducer segments. In another embodiment of the present invention, a method for making a piezoelectric transducer, having a plurality of transducer segments, from a ceramic PZT tube comprises coating the inside and outside of the ceramic tube with a metal layer. In the relevant part, this step forms an inner electrode and an outer electrode. At least the outer electrode is then etched to form a plurality of intertwined helical transducer segments. In yet another embodiment of the present invention, a method for making an ultrasound transducer with a helical phase arrangement comprises providing a cylindrical piezoelectric transducer having a piezoelectric material disposed between a cylindrical inner electrode and a cylindrical outer electrode. The slots are then machined through at least the electrode exterior to the transducer segment within a plurality of functionally discrete interleaved helical transducer segments.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1A is a perspective representation showing an example of a circular ablation trajectory. Figure 1B is a perspective representation showing an example of an elliptical ablation path. Figure 1C is a perspective representation showing an example of an irregular ablation trajectory. Figure 1D is a perspective representation showing an example of a step ablation path. Figure 2A is a perspective view showing an ablation catheter connected in a way that can operate to an ablation control system and a position perception system according to an embodiment of the present invention. A member that can expand from the catheter is illustrated in an expanded state. Figure 2B is a perspective view showing the details of an ablation member in the expanded state at a distal end of the ablation catheter of Figure 2A, according to an embodiment of the present invention. Figure 3A is a cross-sectional view showing the construction of a typical cylindrical ultrasonic transducer of the prior art having inner and outer electrodes.

Figure 3B is a perspective view of a typical prior art ultrasound transducer in isolation, showing the electrical conductors coupled to the transducer. Figure 3C is a perspective view of a prior art ultrasound transducer with individually driven sectors. Figure 3D is a side view of a prior art ablation catheter showing the radial acoustic energy ray paths colliding when the ablation device is placed in a lumen of the body, such as a pulmonary vein. Figure 3E, is a side view of a prior art ablation catheter showing the radial acoustic energy ray paths colliding when the ablation device is placed at the junction between a body lumen and a body cavity, such as a pulmonary vein cavity. Figure 4A is a perspective view showing the construction of a transducer sectioned in a spiral arrangement of ultrasonic transducer segments according to an embodiment of the present invention. Figure 4B is a side view showing the construction of a transducer sectioned in a spiral arrangement of ultrasonic transducer segments according to an embodiment of the present invention.

Figure 4C is an end view showing the construction of a transducer sectioned into a spiral arrangement of ultrasonic transducer segments according to an embodiment of the present invention. Figure 5A is a sectional view showing the construction of a segmented transducer by interlacing individual helical elements essentially in an array of functionally discrete transducer segments according to one embodiment of the present invention. Figure 5B is a cross-sectional view showing the construction of a segmented transducer by individual helical elements interleaved essentially in an array of functionally discrete transducer segments according to one embodiment of the present invention. Figure 6A is a sectional view showing the construction of a transducer having grooves extending through the outer electrode and into the cylindrical piezoelectric material according to one embodiment of the present invention. Figure 6B is a cross-sectional view showing the construction of a transducer having grooves extending through the outer electrode and into the cylindrical piezoelectric material according to one embodiment of the present invention.

Figure 7A is a schematic representation illustrating a fixed phase delay for sinusoidal input signals that drive an array of transducer segments according to one embodiment of the present invention. Figure 7B, is a schematic representation illustrating the resulting cumulative acoustic energy beams emanating from each of the plurality of transducer elements when driven at different frequencies in accordance with one embodiment of the present invention. Figure 7C is a side view of an ablation catheter showing the acoustic energy beam paths projected at an angle relative to the longitudinal axis of the transducer when the ablation device is placed at the junction between a body lumen and a body cavity , such as a pulmonary vein cavity. Figure 8 is a flow chart illustrating the method for making a transducer having a plurality of helical transducer elements according to one embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION Definitions of the terms The following terms will have the following meanings through the specification.

The term "body space" including derivatives thereof, is intended in the present description to mean any cavity or lumen within the body that is defined at least in part by a tissue wall. For example, the cardiac chambers, the uterus, the regions of the gastrointestinal tract, and the venous artery or vessels are all considered as illustrative examples of the body spaces within the intended meaning. The term "circumference" or "circumferential", which includes derivatives thereof, as used in the present description, includes a continuous path or line forming an outer boundary or perimeter surrounding and therefore defining a region of space included. Such as a continuous path that starts at a position along the outer boundary or perimeter, and moves along the outer boundary or perimeter until the original starting position is completed to include the region of defined space. The related term "circumscribe" which includes derivatives thereof, as used in the present description, includes a surface to be included, surrounded, or encompassed by a region of defined space. Therefore, a continuous line, which is traced around a region of space and which starts and ends substantially in the same position, "circumscribes" the region of space and has a "circumference" which includes the distance that travels the line as it moves along the path that circumscribes the space.

Still further a circumferential path or element may include one or more of various shapes, and may be, for example, circular, rectangular, ovular, elliptical, or otherwise even planar. A circumferential path may also be three-dimensional, such as, for example, two semicircular paths of opposite orientation in two different parallel or off-axis planes that are connected to their ends by joining segments of the line between the planes. For the purpose of further illustration and example, Figures 1A and 1D show circumferential trajectories 160, 162, 164 and 166, respectively. Each path 160, 162, 164, 166, is moved along a portion of a body space, for example, a wall of the pulmonary vein, and circumscribes a region of defined space, shown with numbers 161, 163, 165 and 167, respectively, each region of circumscribed space is a portion of the body space. However, the circumferential trajectory does not necessarily have to be transferred along a tubular structure as shown, and other geometric structures are also contemplated, such as along the atrial wall in the atrium of the heart. The term "crosscutting" which includes derivatives thereof, as used in the present disclosure, includes a form for dividing or separating a region of space in isolated regions. Therefore, each of the regions circumscribed by the circumferential trajectories shown in Figures 1A-1 D transversally cuts the body space respective, for example, the pulmonary vein, which includes its lumen and its wall, to the extent that the respective body space is divided into a first longitudinal region located on one side of the cross-sectional region, shown for example in the region "X" in Figure 1A, and a second longitudinal region on the other side of the plane that is cut transversely, shown for example, in the "Y" region, also in Figure 1A. Similarly, a circumferential path along other structures, such as the atrial wall around the pulmonary vein orifice, will cut transversely the pulmonary vein of the atrium. Therefore, a "circumferential driving block" according to the present invention is formed along a region of the tissue that follows a circumferential path, which circumscribes the region of the tissue and which transversally cuts the region of the tissue relative to the electrical conduction to along the circumferential path. By way of example, the transverse circumferential conduction block thus isolates the electrical conduction between the left atrium and a pulmonary vein. The terms "perform ablation" or "ablation", which include derivatives thereof, are intended in the following to include substantial alteration of the mechanical, electrical, chemical or other structural nature of tissue. In the context of ablation applications shown and described with reference to the variations of the illustrative device that follows, "ablation" is intended to include sufficient alterations of the tissue properties for the conduction of the ablation. block substantially the electrical signals from or through the separated cardiac tissue. The term "element" within the context of "ablation element" in the present disclosure, is intended to include a discrete element, such as an ultrasonic transducer, or a plurality of discrete elements, such as a plurality of separate ultrasonic transducers, which are placed in such a way that they collectively separate a region of the tissue. Accordingly, an "ablation element" according to the defined terms may include a variety of specific structures adapted to separate a defined region from the tissue. For example, an ablation element suitable for use in the present invention can be formed, according to the teachings of the modalities mentioned below, from a type of "energy emission" of the structure, which is adapted for the emission of sufficient energy to separate the tissue when it is coupled to and energized by means of an energy source. A particular "energy emission" ablation element suitable for use in the present invention may therefore include, for example, an ultrasonic element such as an ultrasonic crystal element, which is adapted to emit sufficient ultrasonic sound waves to separate the tissue when it is coupled to a suitable source of stimulation.

MODALITIES OF THE INVENTION Next, ablation devices of a medical device system are described. The disclosed devices may include a position monitoring system that allows a physician to accurately position a distal end of the medical device within a body space using the feedback information provided by the system. Said feedback information is indicative of the position of the distal end of the medical device within the body space. The following devices of the position monitoring system are particularly well suited for applications involving the placement of an ablation member in an area where a pulmonary vein extends from the left atrium and relative to an objective circumferential region of tissue within the area , and therefore, these devices are described in this context. However, various aspects of the present invention can be readily adapted by those skilled in the art for applications involving the placement of medical articles within other body spaces. In the context of illustrative application, catheter-based cardiac arrhythmia therapies generally involve introducing an ablation catheter into the cardiac chamber, such as in a percutaneous transluminal procedure, wherein an ablation element in the portion of distal end of the catheter is placed in or adjacent to the conductive tissue damaged. The ablation element is used to separate the target tissue, thereby creating a lesion. Figure 2A shows an exemplary ablation catheter assembly 100 operably connected through an electrical connector 112 to an ablation control system 118. The catheter assembly 100 includes an elongate delivery member 102 with a proximal end portion 104 and a distal end portion 106. The distal end portion 106 supports an ablation member 128 that includes an ablation element 120 and an anchor mechanism 108. In a preferred embodiment (illustrated in Figure 2A ), the anchor mechanism 108 is a member that can be expanded. The expandable member may also include a sensor 108 that is explained below. Delivery member 102 desirably includes a plurality of lumens (some of which are illustrated in Figure 2B). Various cables and electrical conductors are routed to the distal end portion 106, through at least some of these lumens. In a preferred device, these lumens generally run the length of the delivery member 102; however, for some applications, the lumens may be shorter. In one example, a guide wire 110 travels through a lumen in the delivery member 102 from the proximal end portion 104 to the far end portion. The distal end portion 104 is also connected through a tube 113 to a threaded connector 114. By introducing fluid into the tube 113 through a thread connector 114, a physician can inflate the expandable member 108, as is known in the art. In some modes of the catheter assembly, as seen in Figure 2B, the delivery member 102 includes a distal port 121, which is distal to an ablation member 128. In addition, there is a proximal port 122, which is provided next to the ablation member 128. The proximal port 122 is connected to a proximal port lumen 123, and the distal port 121 is connected to a distal port lumen 124. The distal port 121 allows the physician to introduce fluids into the patient, take fluid samples from the patient, and take the fluid pressure reading on the distal side of the ablation member 128. Similarly, the proximal port 122 allows the physician to introduce fluids into a patient, take patient fluid samples and take the reading of fluid pressure on the proximal side of ablation member 128. These ports 121, 122 and lumens 123 and 124 are particularly useful when pressure or X-ray placement techniques are employed, such as the It is explained later; however, the catheter assembly 100 need not include such ports and lumens when only one A-mode or Doppler monitoring system is used with the catheter assembly. In the illustrated device, the delivery member 102 also includes a guidewire lumen 125 that is sized to track the guidewire 110. The lumen 125 terminates in a distal port 127 located on the distal end 106 of the delivery member 102.

When constructed for use in transeptal left atrial ablation procedures, the delivery member 102 desirably has an outer diameter provided within the range of from about 1.65 mm to about 3.3 mm, and more preferably, from about 2.31 mm to about 2.97 mm. . The guidewire lumen 125 is preferably adapted to slidably receive the guidewires which are within the range of about 0.0254 centimeters to about 0.965 centimeters in diameter, and is preferably adapted to be used with guidewires which are within the range from about 0.045 centimeters to about 0.088 centimeters in diameter. Where a 0.088 cm guidewire is to be used, the guidewire lumen 125 preferably has an inside diameter of 0.1016 centimeters. Further, wherein the delivery member 102 includes an inflation lumen 130 for use with an inflatable balloon (a preferred form of the expandable member 108), the inflation lumen 130 preferably has an inner diameter of approximately 0.0508 centimeters in order to allow fast deflation times, although this may vary based on the viscosity of the inflation medium used, the length of the lumen 130, and other dynamic factors that are related to the flow and pressure of the fluid. In addition to providing the required lumens and support for the ablation member 128, the delivery member 102 for the application illustrative is also adapted to be introduced into the left atrium, such that the distal end portion 106 can be placed within the pulmonary vein cavity in a percutaneous transluminal procedure, and even more preferably in a transseptal procedure as described above. otherwise stated in the present description. Accordingly, the distal end portion 106 is preferably flexible and adapted to track over and along a guidewire seated within the objective pulmonary vein. In a further construction, the proximal end portion 104 is adapted to be at least 30% stiffer than the distal end portion 106. In accordance with this relationship, the proximal end portion 104 can be suitably adapted to providing the transmission thrust to the distal end portion 106 while the distal end portion 106 is suitably adapted to be tracked through the curved anatomy during in vivo delivery of the distal end portion 106 of the device within the desired ablation region. However, the specific device constructions just described, other delivery mechanisms for the delivery of the ablation member 128 for the desired ablation region are also contemplated. For example, although the variation of Figure 2A is shown as a "over the wire" catheter construction, other guide wire tracking designs are suitable substitutes, such as, for example, catheter devices which are known as variations of "exchange rapid "or" monorail ", wherein the guidewire is housed only coaxially within a lumen of the catheter in the distal region of the catheter.In another example, a bent tip design may also be a suitable substitute for select independently a desired pulmonary vein and direct the transducer assembly within the desired location for ablation.In addition to this last variation, the guidewire lumen and the variation guidewire shown in Figure 2A can be replaced with a "pulling cable" lumen and the associated fixed pull cable, it is adapted to bend the tip of the catheter by applying tension along the rigid transitions along the length of the catheter.Although additional to this variation of the cable for pulling, acceptable pull wires may have a diameter in the range from about 0.0203 centimeters to about 0.0508 centimeters, and may further include a tapered, such as, for example, an outer diameter tapered from about 0.0508 centimeters to about 0.0203 centimeters. As discussed above, the distal end portion 106 of the delivery member supports an ablation member 128. The ablation member 128 includes an expandable member 108 and an ablation member 120. The expandable member 108 cooperates with the ablation element 120 to position and anchor the ablation element 120 relative to a circumferential region of tissue. The tissue regions selected as the target for ablation may include, for example, a location where a pulmonary vein extends from the left atrium, including the posterior atrial wall of the left atrium, the pulmonary vein cavity, or the pulmonary vein. In the illustrated device, the expandable member 108 is a balloon that can be inflated. The balloon has a diameter in the collapsed state approximately equal to the outer diameter of the distal end portion of the delivery member 106. The balloon 108 can be expanded to a diameter which generally coincides with the diameter of the circumferential region of the tissue and which is it can expand to a plurality of expanded positions for the purpose of working with the pulmonary vein cavity and / or pulmonary veins of various sizes. However, it should be understood that the ablation catheter assembly may also include other types of expandable members, such as, for example, baskets, boxes and similar expandable structures. The expandable balloon 108 may be constructed from a variety of known materials, although the balloon is preferably adapted to conform to the contour of a pulmonary vein cavity and / or pulmonary vein lumen wall. For this purpose, the material of the balloon can be of a highly docile variety, such that the material extends from the application of pressure and takes the shape of the lumen or body space when it is inflated in its entirety. Suitable balloon materials include elastomers, such as, by example, but not limited to silicone, latex or low durometer polyurethane (for example, with a durometer of approximately 80 A). In addition, or alternatively to construct the balloon of highly docile material, the balloon can be formed to have an inflated shape in its entirety previously defined (i.e., previously formed) to generally coincide with the anatomical shape of the body lumen in which will be inflated the balloon. For example, the balloon may have a tapered shape distally to generally coincide with the shape of a pulmonary vein cavity, and / or may include a bulbous proximal end to generally coincide with a transition region of the posterior part of the balloon. atrium adjacent to the pulmonary vein cavity. In this way, the desired settlement within the irregular geometry of a pulmonary vein or vein cavity can be achieved with both balloon variations both docile and non-compliant. However, the alternatives which may be acceptable as those just described, the balloon is preferably constructed to exhibit at least 300% expansion at 3 atmospheres of pressure, and more preferably, to exhibit at least 400% of expansion to that pressure. The term "expansion" in the present description is intended to mean the outer diameter of the balloon after pressurization divided by the inner diameter of the balloon before pressurization, wherein the inner diameter of the balloon before pressurization is taken after that the balloon was substantially filled with the fluid in a tension configuration. In other words, "expansion" in the present description is intended to relate the change in diameter that can be attributed to the docility of the material in a stress / strain relationship. In a more detailed construction, which is considered to be suitable for use in most conduction block procedures in the region of the pulmonary veins, the balloon is adapted to expand under a normal pressure range, such that its diameter The exterior can be adjusted from a radially collapsed position of approximately 5 millimeters to a radially expanded position of approximately 2.5 centimeters (or approximately 500% expansion). The ablation element 120 cooperates with the expandable member 108, such that the ablation element 120 is maintained in a generally fixed position relative to the target circumferential region of tissue. The ablation element may be located outside or within the expandable member, or it may be located at least partially outside the expandable member. The ablation element, in some forms, also includes a portion of the expandable member. For example, the ablation catheter assembly in Figures 2A and 2B includes an ultrasonic transducer located within the expandable member 108. In a device, the ultrasonic transducer stimulates a portion of the expandable member 108 during ablation. . The specific construction of the transducer ultrasonic and the associated construction of the axis of the delivery member supporting the transducer is described below. Figure 2B shows the details of the distal end portion 106 of the catheter assembly 100, and in particular, shows the ablation element 120 located circumferentially about an axial centerline of the delivery member 102. A plurality of cables 129 connects the ablation element 120 to a connector 112 at the proximal end of the catheter (shown in Figure 2A). The connector 112 is coupled to a corresponding cable of the ablation control system 118. If the ablation element 120 includes more than one electrode, the conductor can be connected to all the electrodes or energy sources, or separate conductors can be used as such. way that allow independent control of each electrode or power source under some operating modes. In Figure 3A, a cross-sectional view shows the construction of a typical single cylindrical ultrasonic transducer 300 having a cylindrical inner electrode 302, a cylindrical outer electrode 304, and a cylindrical piezoelectric material 303 between the electrodes. The piezoelectric material 303 is a suitable material, such as, for example, quartz, PZT, and the like, which exhibit a change in the physical dimension in response to a printed voltage. The piezoelectric material 303 is oriented such that when a voltage is printed between the electrodes 302 and 304, the thickness of the piezoelectric material 303 changes slightly. When the polarity of the printed voltage is alternated at a frequency ultrasonic F, the piezoelectric material 303 will vibrate at the ultrasonic frequency F. The vibrations of the piezoelectric material 303 produce ultrasonic sound waves. Because the electrodes are symmetrical in cylindrical form, the piezoelectric material 303 will vibrate radially, with cylindrical symmetry. Conversely, when an ultrasonic wave hits the piezoelectric material 303, the ultrasonic wave will produce vibrations in the piezoelectric material. These vibrations will generate a voltage between the electrodes 302 and 304. Accordingly, the transducer is a reciprocal device that can both transmit and receive ultrasonic waves. A detailed construction for a cylindrical ultrasound transducer is shown in Figures 3B and 3C. The length of the transducer 300 or the transducer assembly (for example, disposition of multiple elements of the transducer elements) are desirably selected for a given clinical application. In connection with the formation of circumferential condition blocks in cardiac wall or pulmonary vein tissue, the length of the transducer may be in the range of about 2032 micrometers to more than about 10033 micrometers, and preferably equals about 5080 micrometers to 7493 micrometers. A transducer dimensioned in this way is considered to form a lesion of a sufficient width to guarantee the integrity of the conductive block formed without ablation of undue tissue. However, for other applications, the length can be significantly longer.

Similarly, the outer diameter of the transducer is desirably selected to count delivery through a particular access path (e.g., percutaneously and transeptally), for proper placement and location within a particular body space. , and to achieve a desired ablation effect. In the particular application within or proximal to the pulmonary vein cavity, the transducer 300 preferably has an outside diameter in the range of about 1778 micrometers to over 2540 micrometers. It has been observed that a transducer with an outer diameter of approximately 2032 microns generates sound power levels approaching 20 Watts per centimeter of radiator or greater within the myocardium or vascular tissue, which is considered sufficient for ablation of the occupied tissue by the outer balloon to achieve up to approximately 3.5 centimeters of outside diameter of the balloon. For applications in other body spaces, the transducer 300 may have an outer diameter in the range of about 1016 micrometers to greater than 3048 to 4064 micrometers (e.g., as large as 400 to 800 mil for applications in some body spaces). The central glass layer 303 of the transducer 300 has a thickness selected to produce a desired operating frequency. The frequency of operation will vary, of course, depending on clinical needs, such as the outer diameter that can be tolerated for the ablation and the heating depth, as well as the size of the transducer as limited by the delivery path and the size of the target site. As described in more detail below, the transducer 300 in the illustrated application preferably operates within the range of about 5 MHz to about 20 MHz, and more preferably within the range of about 7 MHz to about 10 MHz. Therefore, for example, the transducer may have a thickness of about 304.80 micrometers at an operating frequency of about 7 MHz (ie, a thickness generally equal to 1/2 wavelength associated with the desired operating frequency). The transducer 300 is vibrated through the wall thickness and to radiate the acoustic energy collimated in the radial direction. For this purpose, the distal ends of the electrical conductors 336, 337 are electrically coupled to the outer and inner tubular members or electrodes 304, 302, respectively, of the transducer 300, such as, for example, by welding the conductors to metal coatings or by resistance welding. In the illustrated device, the electrical conductors are of silver cables of 101.60-203.20 micrometers (0.0101 to 0.0202 centimeters in diameter) or the like. The proximal ends of these conductors are adapted to be coupled to an ultrasonic driver or trigger 340, which is schematically illustrated in Figure 3B.

The transducer 300 may also be divided into sectors by grooves etched or notched in the outer transducer electrode 304 and part of the central piezoelectric crystal layer 303 along the lines parallel to the longitudinal axis L of the transducer 300, as it is illustrated in Figure 3C. The division into sectors substantially electrically insulates the outer transducer electrode 304, in effect creating separate transducers. A separate electrical conductor is connected to each sector in order to couple the sector to a dedicated power control that individually stimulates the corresponding transducer sector. By controlling the driving power and the operating frequency for each individual sector, the ultrasonic booster 340 can improve the uniformity of the acoustic energy beam around the transducer 300, as well as the degree of heating (i.e., injury control) in the angular dimension can vary. However, in this configuration, the acoustic energy remains highly collimated in the radial direction, and does not allow the acoustic beam to be projected forward or backward. Figures 3D and 3E illustrate the trajectories of collimated radial acoustic energy beam 320 when the ablation device is placed in a pulmonary vein 325 and a pulmonary vein cavity 330, respectively. The present invention utilizes a tissue ablation element and a device assembly with the ability to create a circular energy beam that can be phased in the longitudinal direction, orienting the beam forward or backward. In one embodiment of the present invention, the ablation element is a thin-walled ultrasonic transducer divided into sections into a small number of helical transducer segments interleaved with many turns to form a spiral arrangement. Figures 4A through 4C are side and end perspective views, respectively, showing the construction of a spiral arrangement of transducer segments according to one embodiment of the present invention. The arrangement is made from a piezoelectric transducer in the form of a single tube 400 having a longitudinal axis 410. The transducer 400 comprises a piezoelectric crystal 403 between an inner electrode 402 and an outer electrode 404. The transducer 400 is approximately 8255 micrometers long with an outer diameter of approximately 2540 micrometers, and a wall thickness of approximately 457.20 micrometers. The outer electrode 404 is segmented by grooves etched into a small number of interlocking individual helical elements 405 having a plurality of turns. Each individual element 405 is substantially electrically isolated from the other elements, allowing the segmented elements to operate independently with minimal interference. This configuration actually forms essentially an arrangement of discrete transducers with functionally helical shape arranged linearly along the longitudinal axis 410. Subsequently, these obvious functionally discrete transducers will be referred to as transducer segments. When operated out of phase, the helical phase disposition configuration allows the transducer 400 to achieve phase coherence equal to many more transducers by individual series-shaped axially placed phases along the longitudinal axis 410. With the purpose for example, the illustrated embodiment shows a transducer 400 having an outer electrode 404 divided into sectors into five (5) elements 405 (405a to 405e) corresponding to five (5) discrete transducer segments 400a to 400e. Each transducer segment 400a through 400e comprises twenty (20) turns, providing the phase coherence of approximately one hundred (100) separate phase transducers arranged in series fashion along the longitudinal axis 410. The number of elements 405, segments of transducer (400a to 400e), and the illustrated turns are exemplary. One skilled in the art will understand that other configurations are contemplated by the present invention having more or fewer helical elements 405. Various factors, including the desired application, may contribute to these other configurations. Each individual helical element 405 has an extended element pad 406 (406a to 406e) which serves as a connection point for the lead wires (not shown) used to energize the individual transducer segments (400a to 400e, respectively). Each One of these element pads 406 is substantially electrically isolated from each other to limit the interference between the individual elements 405. In addition, a ground-connected pad 407 is attached to the inner electrode 402 and provides a connection point for a power cable. ground connection. The illustrated embodiment has six (6) pads (five pad elements 406a-406e and a grounding pad 407). Each pad is equally spaced around the circumference of transducer 400, approximately sixty (60) degrees from each other. However, this configuration should not be understood as limiting the scope of the present invention. Instead, it is only necessary that each element pad 406 be substantially electrically isolated from each other to minimize interference and superposition of sounds between the elements 405., regardless of the configuration. In a preferred embodiment, the connection of the conductor and grounding cables is achieved by welding cables directly to the element and grounding pads 406, 407, respectively. When an electrical potential is printed through a particular end pad 406, associated with a particular element 405 and the grounding pad 407, the segment (400a to 400e) associated with the particular end pad 406 is energized.

As described above, the transducer 400 is divided into sections into a small number of interlocking individual helical transducer segments (400a to 400e) that are substantially electrically isolated from each other by grooves etched through at least the electrode External 404. This transducer design is sensitive to material defects, because any fracture or imperfection could disconnect a complete segment. Also, any discontinuous slot could cause a short circuit of two segments. To minimize these potential problems, a suitable raw material for the transducer could include a high density fine grain PZT ceramic material having a porosity of less than 1 thousand. When manufacturing the transducer, the plug of raw PZT ceramic material, originally has the shape of a block or hub, and can be transformed into a tubular configuration using the known machining methods. Figure 8 is a flow diagram illustrating the steps of the method for making a transducer 400 having a plurality of transducer segments 400a to 400e according to one embodiment of the present invention. In a preferred embodiment, the ceramic material shutter PZT (step 800) and the machined and machined center that uses a computer numerical control machine (CNC machine) in a tubular configuration, as shown in step 805. The machine-worked pipe shall have an inner diameter of approximately 2540 micrometers and an outer diameter of approximately 3048 micrometers, which provides a wall thickness of approximately 254 micrometers. The overall length of the PZT ceramic cylinder is also machined at approximately 8255 micrometers. The concentricity must be below 1 thousand at each end of the tube. This tubular PZT ceramic material forms what will ultimately become the piezoelectric material 403. In a preferred embodiment, a quadruple YAG laser beam of approximately 700 nanometers wavelength, hooked to a rotating mandrel CAD / CAM machine, is Used to tighten the PZT ceramic material shutter in the tubular configuration. The outer surface of the PZT cylinder 403 is then polished using the methods known in the art as shown in step 810. An acceptable method for polishing the PZT 403 cylinder involves mounting the cylinder 403 on a rolling mandrel and rolling the mandrel to a high speed, at which time, the cylinder 403 is in contact with a very fine abrasive material, such as paper or sandpaper. It has been found that rotation speeds of about 30,000 RPM or more are acceptable. The finished polishing creates a very fine smooth surface that facilitates the subsequent metallic deposition that forms the electrodes. In addition, the polished surface reduces the possibility of fractures or defects in the surface of the metal electrode, resulting in a very uniform and smooth metallic layer. The uniform metal layer allows the engraving to etching or the subsequent notching of very fine patterns or grooves. In a preferred embodiment, a polished mirror finish of 10 microns or less will allow the etching process with laser beam to produce notches of 30 to 50 microns. The tubular ceramic material PZT 403 is then coated with one or more metallic layers to form the inner and outer electrodes 402, 404, respectively, as shown in step 815. In a preferred embodiment, the ceramic material PZT 403 is first splashed with gold and then nickel plated. The splashing procedure involves placing the ceramic PZT 403 tube in a vacuum chamber, and bombarding the tube with gold ions produced by the use of high temperatures and strong static electric fields between a cathode and an anode. In an embodiment of the present invention, the splashing procedure involves placing the ceramic PZT tube 403 in a vacuum chamber equipped with a cathode and an anode. The cathode, usually consists of a metal lens made of the same metal to be deposited (splashed) on the ceramic PZT tube 403. All the remaining air in the vacuum chamber is evacuated, and the chamber is again filled with a gas of low pressure, such as argon. A high voltage is printed between the cathode and the anode, ionizing the gas and creating what is known as the dark space of Crookes near the cathode. In the illustrated embodiment, it is desired to splash gold on the PZT 403 tube. Therefore, the objective is a cathode of gold. Almost all potential high voltage supplies appear through dark space. The electric field accelerates the argon atoms, which bombard the gold target. There is an exchange of momentum, and an atom is expelled from the target material (in this form a gold atom) and is deposited on the ceramic PZT tube 403, where it adheres and forms a metallic gold film. The PZT 403 tube is rotated and pulled during the procedure to ensure adequate gold coating from all directions. Once the gold splash has been completed, the coated PZT tube 403 is plated using a plating process. In a preferred embodiment, the coated PZT tube 403 is nickel plated by submerging tube 403 in a nickel and acid solution. Using a small electric current, the nickel is extracted from the solution and deposited on the exposed surfaces of the tube. When the patterns, such as the spiral notches forming the helical elements 405, are etched or have notches on the surface of the transducer, the transducer becomes extremely brittle. To reduce transducer fatigue and failure during the machining process, the transducer assembly 400 is mounted on a mandrel prior to machining the notches, as shown in step 820. The mandrel provides additional structural support up to that a matching layer, described below, is placed on the transducer assembly 400.

The metal coated tube is then machined to form the inner and outer electrodes, 402, 404, respectively, as shown in step 825. In a preferred embodiment, the method of machining to form the electrodes 402, 404 comprises the etching by laser of the metallic coating. The combination of these materials (402, 403, 404) forms the transducer 400. Both metallic coating processes are well known in the art and can use metals other than gold and nickel in the process. In addition, the splashing process can be eliminated when the ultrasound transducers are manufactured. However, the splashing process results in a stronger adhesion of the metal to the ceramic PZT material, and therefore, is the preferred method. The segmentation of the transducer 400 can be achieved by etching or notching spiral grooves in at least the outer electrode 404 of the transducer 400, separating the transducer 400 in the discrete transducer segments in operation (400a to 400e) as shown in FIG. Step 830. The slots can be made using various different methods known in the art, such as, for example, etching using a diamond wheel or laser. A particular laser-machining method that can be adapted to cut the helical grooves is described by Corbett, Scott et al., In the document "Laser machining of high density two-dimensional ultrasound arrays "(2002), which is incorporated as a reference in its entirety in the present description.This method uses a YAG laser that emits a wavelength of 355 nm to essentially record or evaporate the material and create the 405 elements. Machining methods with the ability to achieve the desired configuration, such as those used for laser-etched stents and other medical devices, can be used and are known in the art In a preferred embodiment, an Nd-YAG laser is Coupled with a precise CNC system within a few microns to cut the pattern The helical grooves engraved with etching or with laser notches are approximately 76.20 micrometers deep and 50.8 micrometers wide The element end pads 406 and the pad ground connection 407, as well as the end notches that disconnect the inner electrode 402 from the outer electrode 404 are formed in a similar manner using the laser beam and the CNC machine. The helical elements 405 are then cut out and the transducer 400 is grouped in thickness mode, as shown in steps 835, 840, respectively. Provoking a short circuit or creating a "short circuit" is well known in the art with respect to the design of the ultrasonic transducer, and involves the elaboration of a comparatively low temporary resistance connection between the points at which the resistance is usually much greater. In the illustrated mode, a wire is used to make contact and create a short circuit in all the transducer segments 400a to 400e (ie, a short circuit of the desired helical elements 405 and the inner electrode 402). The grouping is known in the art and refers to the method for orienting the molecules of the PZT ceramic material, essentially transforming the PZT ceramic material into a piezoelectric crystal. The grouping is achieved by heating the PZT ceramic material beyond its Kerrie point and applying a strong electric field. In one embodiment of the present invention, the ceramic material PZT is heated to approximately a temperature of 500 degrees C while an electric field of approximately 500 volts DC is applied. There is no need to group each transducer segment (400a to 400e) separately. Instead, it may be sufficient to short circuit all five segments and apply the voltage between the five elements of the transducer 405a to 405e and the grounding electrode 402, together. A multiple coaxial cable is then attached to the transducer 400 as shown in step 845. In the illustrated embodiment, the multiple coaxial cable includes six (6) cables, one for each segment of the transducer (400a to 400e), ie, each one of the element pads 406 and a grounding conductor. In a preferred embodiment, the cables are attached to the pads of the element 406 and the grounding pad 407 by welding. A matching layer is then placed on the transducer 400, which contributes to the force and operating capacity of the transducer assembly 400, as shown in step 850. As described above, the matching layer provides mechanical force to the transducer 400 lost during the etching operation. A ceramic PZT tube with fine notches etched into the surface, such as those provided in the preferred embodiment of the present invention, could fracture and / or fail without an outer coating holding the material together. The matching layer also increases the bandwidth of each transducer segment (400a to 400e), and consequently, the overall bandwidth of the transducer (400). As described in more detail below, this feature provides a higher frequency operating range for each segment of the transducer 400a to 400e. To project the acoustic energy beam forward or backward relative to the longitudinal axis of the transducer 400 which requires the transducer segments 400a to 400e to be operated out of phase with each other. Any desired change to be made for the acoustic energy beam angle is proportionally related to the frequency. Accordingly, the higher the bandwidth of the transducer segments 400a to 400e, the greater the spectrum of the transducer (wider angle) 400 can be projected the acoustic energy beam. The matching layer also provides electrical insulation between the elements of the transducer 405. In a design arrangement, the matching layer is formed from a polymer laminated on the elements of the transducer 405, allowing the notches to separate the transducer elements 405 filled with air. This configuration provides acoustic separation between the transducer segments 400a to 400e and guarantees a uniform thickness of the matching layer. However, when the transducer 400 is used for high intensity ultrasound applications, the printed voltage between the adjacent transducer segments 400a to 400e may be relatively high. This high voltage is coupled with the relatively long distance, so that the adjacent transducer elements 405 traveling in parallel increase the risk of current leakage between the adjacent transducer segments 400a to 400e. However, notches filled with air provide little or no resistance to this leak. Therefore, in another more preferred embodiment, the transducer 400 is coated with a matching layer, preferably a polymer of low viscosity, which twists inside and fills the notches separating the elements of the transducer 405. The matching layer will also cover the transducer 400 with a thin polymeric layer, approximately 50.8 micrometers thick. The polymers used in the matching layer should have a low viscosity, good adhesion to metallic and ceramic material, low coefficient of expansion and reasonably high dielectric strength. An example of a polymer having such characteristics is an epoxy adhesive. Apart from the rolling process, the matching layer can be coated on the transducer 400 by other methods known in the art, including spray coating with an air or airless sprayer, dip coating, chemical vapor deposition, plasma coating, co-extrusion coating, spin coating and insert molding. Figures 5A and 5B are sectional and sectional approach views, respectively showing the construction of a transducer 500 segmented by the individual interlaced helical elements 505 (505a to 505e) essentially in an array of functionally discrete transducer segments 500a to 500e according to one embodiment of the present invention. The transducer 500 has an inner electrode 502 as a common electrode, and a cylindrical piezoelectric material 503 as a common element. The outer electrode 504 is segmented by spiral notches 510 into 5 individual helical electrodes 505 (505a to 505 e) arranged helically around the surface of the outer transducer 500. The helical electrodes 505a through 505e are substantially electrically isolated from each other and correspond to the arrangement of the five helical transducer segments 500a to 500e. When the AC voltage is printed between the inner electrode 502 and one selected from the five outer electrode elements 504 (505a-505e), the piezoelectric material vibrates in the region between the inner electrode 502 and the selected outer electrode element 505. For example , a printed AC voltage between the inner electrode 502 and the outer electrode element 505a will cause the region between the electrode 502 and the 505a electrode vibrate. However, the piezoelectric material 503 is a single piece of a non-sectioned material as shown in Figures 5A and 5B, so that the printed voltage and the subsequent vibration between the inner electrode 502 and the outer electrode element 505a will produce some vibration in the regions between the inner electrode 502 and the outer electrode elements 505b and 505e adjacent the electrode element 505a. This coupling of signals is sometimes referred to as superposition of sounds. Excessive overlapping of sounds between the electrodes may be undesirable for some applications in particular. To reduce such coupling between the adjacent electrodes, the elements may be partially insulated from each other. Figures 6A and 6B are sectional and sectional approach views respectively showing the construction of a transducer 600 having extended notches within the cylindrical piezoelectric material 603 according to one embodiment of the present invention. Extending the notches within the piezoelectric material 603, the piezoelectric material 603 will be divided into zones, partially isolating the signals and subsequently reducing the superposition of sounds. In a manner similar to that described above, the transducer 600 is constructed having interlocking individual helical elements 605 that divide the transducer 600 into sections in an array of functionally spiral transducer segments 600a to 600e. The transducer 600 has an inner electrode 602 as a common electrode and a cylindrical piezoelectric material 603 at least partially as a common element. The outer electrode 604 is separated by the spiral notches 610 within five individual helical electrode elements 605 (605a to 605e) arranged helically about the surface of the external transducer 600. These helical elements 605a to 605e correspond directly to the segments of the 600a to 600e transducer. However, unlike the transducer 500 illustrated in Figures 5A and 5B, these spiral notches 610 extend radially completely through the outer electrode and into at least a portion of the cylindrical piezoelectric material 603. The notches in the material piezoelectric 603 will tend to physically separate the piezoelectric material 603 into zones (five zones in the illustrated embodiment) that directly correspond to the five helical electrode elements 605a to 605e. The coupling between the electrodes can be further reduced by extending the spiral notches all the way through the piezoelectric material (not shown), thus producing separate pieces of piezoelectric material, and therefore, completely separate the transducers. The transducers 500, 600 can be operated in at least two ways. In a first form, the five transducer segments (simulate five helical transducers) that are driven with identical signals. This mode will create a ray of unique radial acoustic energy that has a radial thickness similar to that which exists in the designs of unique transducers. In a second form, the five individual segments are driven as a standard phased arrangement by signals that have a fixed phase delay between the segments. Because the segments are arranged to simulate five helical transducers, the phased arrangement allows the resulting energy beam to be directed forward and backward. A phase delay is a representation of the time delay in seconds experienced by each sinusoidal component of the input signal. The phase of a periodic phenomenon, that is, the sinusoidal input signal, can also be expressed or specified by an angular measurement, with a period that normally covers 360 ° (2p radians). When each transducer element is driven at the same frequency, the phase delay will be directly related to the phase change or the change in the phase angle between each sinusoidal component of the input signal. In Figure 7A, a schematic representation is shown illustrating a fixed phase delay (phase change) for a plurality of sinusoidal input signals 720 (720a to 720e) which drives an array of transducer segments 700a to 700e. This design uses a 700 transducer segmented into 5 interleaved helical transducer segments 700a to 700e by five helical elements 705a through 705e. The transducer segments 700a to 700e are driven through a five-generator channels with five drivers. One advantage of the polished configuration is that it generates a coherent phased sound energy beam that simulates more than fifty individual elements. In the illustrated scheme, the reference numbers are used to show the association between the fixed phase input signals 720a to 720e, the transducer elements 705a to 705e, and the transducer signals 700a to 700e. For example, transducer element 705a produces a sinusoidal ultrasonic sound wave 720a. When an alternating sinusoidal input current 720a to 720e is printed between a particular element 705 of the outer electrode 704 and the inner electrode 702, the thickness of the piezoelectric material 703 associated with the determined transducer segment 700 (700a to 700e) will vibrate at the frequency alternating The repetitive cyclic design illustrated in Figure 7A produces an arrangement that has the same signal in every fifty element. Accordingly, the total cumulative phase change over the five transducer segments 700a to 700e is equal to a total of 360 degrees. Using a fixed phase delay, the optimum phase change between the adjacent transducer segments (700a to 700e) is therefore 72 degrees. As can be seen from the illustrated embodiment, the input signal 720a is 72 degrees out of phase from the input signal 720b. Similarly, the input signal 720b is 72 degrees out of phase of the input signal 720c, and continues in this manner. This configuration maximizes transducer efficiency and provides a coherent energy beam. Typically, a cylindrical ultrasound transducer will produce a highly collimated acoustic energy beam that emanates from the transducer in a direction substantially normal to the longitudinal axis of the transducer. Similarly, a transducer having a plurality of helical segments arranged in series along a longitudinal axis could produce a highly collimated acoustic energy beam normal to the longitudinal axis of the transducer when the individual transducer segments are driven in phase with respect to each other. However, when the helical segments are driven out of phase with each other, as illustrated in Figure 7A, the resulting cumulative acoustic energy beam emanates from the transducer 700 at an angle relative to the longitudinal axis. Varying the phase delay of the 720 input signal, the beam angle of acoustic energy will change. The implication is that for a different acoustic energy beam angle, a different phase delay could be used. One method for varying the phase delay is to vary the frequency at which the transducer segments are driven while maintaining the phase change (angle) between the input signals adjacent to them. Figure 7B is a schematic representation illustrating the resulting cumulative acoustic energy beams (750, 751, 752) emanating from each of the plurality of transducer elements 705a when driven to different frequencies. The relationship between the angle of the acoustic energy beam and the driving frequency can be defined using the following formulas: Y ? = * COS (a) where: -? is the wavelength of the input signal; - V is the speed of sound in water (1550 m / sec) - f is the frequency at which the elements of the transducer are driven; - L is the increase of threading or separation, which is defined as the linear distance traveled by the helical groove that separates the transducer into helical transducer segments when a complete revolution is made; and - a is the angle between the acoustic energy beam and the longitudinal axis of the transducer. In a preferred embodiment, the thread increment L is 0.000508 m. For the purpose of exemplifying, it is assumed that it is desired to project the acoustic energy beam at an angle of 45 ° (degrees) from the longitudinal axis (represented as beam 751 in Figure 7B). Resolving the above equations simultaneously, the arrangement of the transducers 705 could have to be driven at a frequency of 4.3 MHz. In another example, it is assumed that it is desired to project the acoustics of the beam of energy at an angle of 60 ° from the longitudinal axis (represented as ray 750 in Figure 7B). Again, by solving the equations simultaneously, the arrangement of the transducers 705 could have to be driven at a frequency of 6.2 MHz. Similarly, by driving the elements of the transducer 705 an acoustic energy angle 752 could be projected to a 30 ° angle from the longitudinal axis. Figure 7C is a side view of an ablation catheter showing the acoustic energy ray paths 751 projected at an angle relative to the longitudinal axis of the transducer when the ablation device is placed at the junction between a body lumen and a cavity body, such as a pulmonary vein orifice 330. As noted above, a beam of acoustic energy can be projected at a 90 ° angle (ie, perpendicular) to the longitudinal axis with any frequency in the transducer bandwidth driving all the elements that comprise the transducer in phase with each other. In addition, the illustrative arrangement of the transducer elements may also be driven with phase delays that are not fixed, or may not add up to 360 ° as described above. Several factors could be considered when selecting a generator to produce the acoustic energy beam. The generator must have at least one channel for each electrode element (ie, for each transducer segment). Using the illustrated mode as an example, the generator could be, as a minimum, a Five-channel signal generator with an amplifier output stage with the ability to block the operation. A linear RF amplifier must be provided for each matched channel to drive a load of 50 Ohms up to 20 Watts per channel. The amplifiers must have a bandwidth of up to 12 MHz and must have an identical gain and phase change through the channels. The generator should preferably have direction couplers, bypass resistors to dissipate the reflected energy and perceive the circuits for the reflected magnitude and power phase. Preferably, the signal generator must be a computer that drives the signal generator with the ability to generate highly coherent continuous sine wave signals with precise phase delay between the channels. The computer must have the ability to obtain the desired angle as an input, and calculate the frequency and phase for each of the five channels. Other desirable data inputs for the computer should include the desirable output power, the direct and reflected power of each channel, and the target tissue temperature. If the transducer will also be used for the generation of images, appropriate considerations should be taken in the design of the generator, such as the ability to generate short-circuit currents of acoustic energy with precise timing. The above invention variously shows the assemblies of the circumferential ablation device that incorporate ultrasound transducers to separate a circumferential region of tissue. Sayings Ultrasound ablation assemblies are considered to be particularly amenable to use with the placement of monitoring assemblies that incorporate ablation transducer perception capabilities themselves, such as, but not limited to, a mode perception system. " TO". However, it is further contemplated that particular ablation devices may also be combined with other position monitoring assemblies and related sensors. Additionally, said ultrasound ablation assemblies can also be combined with the various ablation monitoring assemblies, such as monitoring assemblies and temperature sensors. As is common for each of the following devices, a source of acoustic energy is provided with a delivery device that may also include an anchoring mechanism. In one mode, the anchoring device comprises an expandable member that also places the source of acoustic energy within the body; however, other anchoring and positioning devices may also be used, such as, for example, a basket mechanism. In a more specific form, the source of acoustic energy is located within the expandable member and the expandable member is adapted to engage a circumferential trajectory of tissue, either around or along a pulmonary vein in the region of its orifice along a left atrial wall. The acoustic energy sources of the prior art are in turn acoustically coupled to the wall of the expandable member and, therefore, to the circumferential region of tissue coupled by the wall of the expandable member by emitting an ultrasound signal collimated circumferentially and longitudinally, when activated by an acoustic energy driver. The use of acoustic energy, and particularly, ultrasonic energy, offers the advantage of simultaneously applying a dose of sufficient energy to separate a relatively long surface area within or near the heart for a desired heating position without exposing the heart to a large amount of current. For example, an ultrasonic transducer may form a lesion, which is approximately 1.5 mm wide, approximately a lumen with a diameter of 2.5 mm, such as a pulmonary vein and of sufficient depth to form an effective driver block. It is considered that an effective driving block can be formed by producing a lesion within the tissue that is transmural or substantially transmural. Depending on the patient, as well as the location within the pulmonary vein orifice, the lesion may have a depth of 1 millimeter to 10 millimeters. It has been observed that the ultrasonic transducer can be energized to provide a lesion having these parameters, such that they form an effective driving block between the pulmonary vein and the posterior wall of the left atrium. Although the particular detailed description of the present disclosure has been provided for particular embodiments and variations in accordance with the present invention, it should be further understood that the various modifications and improvements can be made by a person ordinarily skilled in the art according to this description and without departing from the broad scope of the present invention. Additionally, a circumferential ablation device assembly constructed with an ultrasound ablation element mounted in accordance with the present invention can be used in combination with other linear ablation methods and assemblies, and various components or steps related to said assemblies or methods, respectively, in order to form a circumferential conduction block in an accessory fashion to the formation of long linear lesions, such as in a less invasive "labyrinth" type procedure. In addition, a person skilled in the art can take other obvious or insubstantial modifications or improvements to the specific embodiments shown in the present description and described based on this description without departing from the scope of the present invention as defined by the Claims which are found therein. continuation.

Claims (19)

NOVELTY OF THE INVENTION CLAIMS

1. - A method for making a piezoelectric transducer having a plurality of individual intertwined helical transducer segments, comprising: machining a shutter of ceramic material in a tubular configuration to form a ceramic tube; Cover the ceramic tube with a metal layer; machining the metal-coated ceramic tube to form an inner electrode and a plurality of helically interlocked outer electrodes, wherein each outer electrode is associated with a functionally discrete transducer segment; transform the ceramic material that forms the ceramic tube into a piezoelectric crystal.

2. The method according to claim 1, further characterized in that the step of machining the obturator comprises piercing the center and rotating the obturator using a CNC machine.

3. The method according to claim 2, further characterized in that the step of drilling the center and rotating the shutter comprises using a YAG laser beam quadruple in approximately the wavelength of 700 nanometers, attached to a CAD / CAM machine of rotating mandrel.

4. The method according to claim 1, further characterized in that the step of coating the tubular ceramic material with a metal layer comprises cladding the tubular ceramic material using a metal plating process.

5. The method according to claim 1, further characterized in that the step of coating the tubular ceramic material with a metal layer comprises splashing the ceramic tube with metal using a splashing process.

6. The method according to claim 1, further characterized in that the step of machining comprises laser etching the metal coating on the metal tube to form the inner and outer electrodes.

7. The method according to claim 1, further characterized in that the step of machining comprises laser etching the metal coating on the ceramic tube to form helical grooves that segment the transducer within the transducer segments functionally discrete.

8. The method according to claim 1, further characterized in that the step of transforming the ceramic material forming the ceramic tube into a piezoelectric crystal comprises generating a short circuit of the transducer segments.

9. The method according to claim 8, further characterized in that the step of generating the short circuit of the Transducer segments comprise the creation of a comparatively low temporary resistance connection between the transducer segments.

10. The method according to claim 1, further characterized in that the step of transforming the ceramic material forming the ceramic tube into a piezoelectric crystal comprises grouping the ceramic tube.

11. The method according to claim 10, further characterized in that the step of grouping the ceramic tube comprises: heating the ceramic tube beyond its Kerrie point; and apply an electric field.

12. The method according to claim 1, further characterized in that it further comprises the step of polishing the outer surface of the ceramic tube before coating the ceramic tube with a metallic layer.

13. The method according to claim 12, further characterized in that the step of polishing the outer surface of the ceramic tube comprises: mounting the ceramic tube to a rotating mandrel; turn the mandrel to a high speed index; and contacting the rotating ceramic tube with a fine abrasive material.

14. The method according to claim 1, further characterized in that it further comprises the step of mounting the ceramic tube to a mandrel to add support during machining.

15. - The method according to claim 1, further characterized in that it further comprises the step of applying a matching layer on the segmented transducer.

16. The method according to claim 15, further characterized in that the step of applying a matching layer comprises laminating the matching layer on the transducer.

17. The method according to claim 15, further characterized in that the step of applying a matching layer comprises coating the transducer with a polymer using a process selected from the group consisting of spray coating, dip coating, chemical deposition of steam, plasma coating, co-extrusion coating, rotating coating and insert molding.

18. A method for manufacturing a piezoelectric transducer, having a plurality of intertwined helical transducer segments, from a ceramic tube PZT, comprising: coating the inside and outside of the ceramic tube with a metal layer to form a inner electrode and an outer electrode; and etching at least the outer electrode to form a plurality of intertwined helical transducer segments.

19. A method for producing an ultrasound transducer with a helical phase arrangement, comprising: providing a cylindrical piezoelectric transducer having a piezoelectric material disposed between a cylindrical inner electrode and a cylindrical outer electrode; machine notches through at least the electrode exterior to the transducer segment in a plurality of functionally discrete intertwined helical transducer segments.