Catheters with Compliant Balloons

Abstract

A catheter 102 includes a catheter shaft 212 having a fluid passageway 420, an ultrasound transducer 214, and a compliant balloon 108 mounted on the catheter shaft 212 and in fluid communication with the fluid passageway 420, the compliant balloon 108 having an interior 504 containing the ultrasound transducer 214. The compliant balloon 108 includes a balloon wall 502 having a working section 1600 radially surrounding the ultrasound transducer 214, a proximal shoulder 510B proximal to the working section 1600, and a distal shoulder 510A distal to the working section 1600. The balloon wall 502 is thicker at the proximal shoulder 510B and the distal shoulder 510A than at the working section 1600.

Description

[Technical field]

[0001] The present application relates generally to minimally invasive devices, systems, and methods for delivering energy to a target anatomical site of a subject, and more particularly to catheter-based intraluminal devices and systems configured to deliver ultrasound energy to treat tissue, such as neural tissue. [Background technology]

[0002] According to the Centers for Disease Control and Prevention (CDC), nearly one in three adults suffers from high blood pressure, also known as hypertension. If left untreated, hypertension can lead to kidney disease, arrhythmia, and heart failure. In recent years, treatment of hypertension has focused on interventional techniques to inactivate the renal nerves surrounding the renal artery. Autonomic nerves tend to follow blood vessels to the organs they innervate. Catheters can reach certain structures that are in the vicinity of the lumen through which the catheter travels, such as the renal nerves. Thus, catheter-based systems can deliver energy from within the lumen to inactivate the renal nerves.

[0003] One approach to deactivating renal nerves uses a radio frequency (RF) generator connected to a catheter with multiple electrodes placed against the intima of the renal artery and used to generate an electric field in the vessel wall and surrounding tissue that resistively heats the tissue to a temperature sufficient to ablate the tissue and the renal nerve passing through it. To treat all of the renal nerves surrounding the renal artery, the RF electrode is repositioned multiple times around the inside of the renal artery. However, the relatively limited electric field generated by the RF electrode may miss some of the renal nerves, resulting in incomplete treatment. Furthermore, to heat the renal nerves, the RF electrode must contact the intima, which poses the risk of damaging or necrosing the intima, which may lead to thrombus formation, fibrosis of the vessel wall, mechanical weakening of the vessel, and possibly vessel disruption.

[0004] Another approach to deactivating renal nerves is the use of high-intensity focused ultrasound (HIFU), which uses vibrational energy to cause frictional heating and destruction of tissue, thereby increasing tissue temperature sufficiently to cause ablation or remodeling.

[0005] U.S. Patent Nos. 9,943,666, 9,981,108, and 10,039,901 to Warnking, 9,700,372, 9,707,034, and 10,368,944 to Schaer, and 10,350,440 and 10,456,605 to Taylor address many of the shortcomings of RF and HIFU systems. An example embodiment of the system includes an ultrasound transducer disposed along the distal end of a catheter designed to be inserted into a blood vessel, for example, a renal artery. The ultrasound transducer can be powered using electrical cabling received within a cabling lumen of the catheter. The ultrasound transducer emits one or more therapeutic doses of unfocused ultrasound energy that heats tissue adjacent to the body lumen in which the transducer is disposed. Such unfocused ultrasound energy can, for example, ablate target nerves surrounding the body lumen, but without damaging non-target tissue, such as the internal lining of the body lumen or unintended organs outside the body lumen. The system can include a balloon attached to the distal end of the catheter, the balloon designed to cool the blood vessel when a cooling fluid is delivered to the balloon. Such a design can create one or more ablation zones sufficient to achieve long-term nerve inactivation at different sites around the circumference of the blood vessel. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] U.S. Patent No. 9,943,666 [Patent Document 2] U.S. Patent No. 9,981,108 [Patent Document 3] U.S. Patent No. 10,039,901 [Patent Document 4] U.S. Patent No. 9,700,372 [Patent Document 5] U.S. Patent No. 9,707,034 [Patent Document 6] U.S. Patent No. 10,368,944 [Patent Document 7] U.S. Patent No. 10,350,440 [Patent Document 8] U.S. Patent No. 10,456,605 Summary of the Invention

[0007] The invention is defined in the independent claims. Further embodiments of the invention are defined in the dependent claims.

[0008] Provided herein is a catheter comprising a catheter shaft having a fluid passageway, an ultrasound transducer, and a compliant balloon mounted on the catheter shaft and in fluid communication with the fluid passageway and having an interior containing the ultrasound transducer. The compliant balloon includes a balloon wall having a working section radially surrounding the ultrasound transducer. The working section has a predetermined straightness when the working section has a first diameter and when the working section has a second diameter at least 2 mm greater than the first diameter.

[0009] A kit is provided herein. The kit includes a first catheter and a second catheter, each of which covers a different, overlapping, inflated diameter range. The first catheter can include a first compliant balloon having a first inflated diameter range when fluid is circulated through the balloon at a flow rate that results in an inflation pressure in the range of 10-30 psi. The second catheter can include a second compliant balloon having a second inflated diameter range when fluid is circulated through the balloon at a flow rate that results in an inflation pressure in the range of 10-30 psi. The first inflated diameter range may overlap with the second diameter range. Thus, the kit can be used to treat vessel sizes over a wide range, e.g., 3-9 mm, by selecting a catheter having an inflated diameter range that corresponds to the target anatomy.

[0010] The above summary does not include an exhaustive list of all aspects of the invention. It is contemplated that the invention may be practiced from any suitable combination of the various aspects summarized above, as well as the various aspects disclosed in the detailed description that follows and as particularly pointed out in the claims. Such combinations have particular advantages not expressly described in the above summary.

[0011] The novel features of the invention are set forth with particularity in the appended claims. The features and advantages of the present invention will be better understood by reference to the following detailed description that sets forth illustrative embodiments, in which the principles of the invention are utilized, and the accompanying drawings of which: [Brief description of the drawings]

[0012] [Figure 1] FIG. 1 is a perspective view of a tissue treatment system according to one embodiment. [Figure 2A] 2 is a side view of selected components of the tissue treatment system of FIG. 1, according to one embodiment. [Figure 2B]2 is a side view of selected components of the tissue treatment system of FIG. 1, according to one embodiment. [Diagram 3] 2 is a perspective view of selected components of the tissue treatment system of FIG. 1 inserted into a body lumen, according to one embodiment. [Figure 4] FIG. 1 illustrates a longitudinal cross-sectional view of a distal region of a tissue treatment system, according to one embodiment. [Diagram 5] FIG. 1 is a side view of a tissue treatment system having a compliant balloon inflated to a first inflated diameter, according to one embodiment. [Figure 6] FIG. 13 is a side view of a tissue treatment system having a compliant balloon inflated to a second inflated diameter, according to one embodiment. [Figure 7] FIG. 13 illustrates a balloon pressure curve for a balloon being inflated with a pressure limiting technique, according to one embodiment. [Figure 8] FIG. 1 illustrates a perspective view of a compliant balloon inflated to a predetermined inflation pressure via an arterial restriction procedure, according to one embodiment. [Figure 9] FIG. 13 illustrates a balloon pressure curve for a compliant balloon being inflated using a hybrid inflation technique, according to one embodiment. [Figure 10] FIG. 13 illustrates balloon pressure curves for two compliant balloons being inflated with a pressure limiting technique, according to one embodiment. [Figure 11] 1 is a flowchart of a method of delivering ultrasonic energy to a vessel wall using a tissue treatment system. [Figure 12] FIG. 1 is a perspective view of a compliant balloon having longitudinal ribs according to one embodiment. [Figure 13] 13 is a cross-sectional view of the compliant balloon of FIG. 12, according to one embodiment. [Figure 14A] FIG. 1 is a pictorial diagram of a tissue treatment system having a centering mechanism, according to one embodiment. [Figure 14B] FIG. 1 is a pictorial diagram of a tissue treatment system having a centering mechanism, according to one embodiment. [Figure 15]FIG. 1 illustrates a side view of a compliant balloon of a tissue treatment system, according to one embodiment. [Figure 16] FIG. 1 is a profile view of a compliant balloon of a tissue treatment system, according to one embodiment. [Figure 17] FIG. 1 is a profile view of a compliant balloon of a tissue treatment system, according to one embodiment. [Figure 18] FIG. 13 illustrates a balloon pressure curve for a compliant balloon being continuously inflated in free space, according to one embodiment. [Figure 19] FIG. 1 is a profile view of a compliant balloon of a tissue treatment system, according to one embodiment. [Figure 20] Balloon pressure curves for a compliant balloon undergoing continuous inflation in free space. [Figure 21] 1A-1D are side views of various compliant balloons according to several embodiments. [Figure 22] 1A-1D are side views of various compliant balloons according to several embodiments. [Figure 23] 1A-1D are side views of various compliant balloons according to several embodiments. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] The embodiments describe a tissue treatment system having a compliant balloon, and a method of using the tissue treatment system. The tissue treatment system may be an acoustic-based tissue treatment system, e.g., an ultrasound-based tissue treatment system, used to deliver unfocused ultrasound energy radially outward to heat and thus treat tissue within a target anatomical region. The unfocused ultrasound energy may be targeted to selected nerve tissue within the anatomical region and heat such tissue in a manner to neuromodulate the nerve tissue, e.g., to completely or partially ablate, necrotize, or stimulate the nerve tissue. The tissue treatment system may thus be used to neuromodulate renal nerves to treat hypertension, chronic kidney disease, atrial fibrillation, or other medical conditions. Alternatively, the tissue treatment system may be used for other applications, such as treating the sympathetic nerves of the hepatic plexus in the common hepatic artery, which are responsible for blood glucose levels, which are important for treating diabetes. Thus, reference to the system as a renal denervation system, or as used for treatment, e.g., neuromodulation, renal nerve tissue is non-limiting.

[0014] In various embodiments, the description refers to figures. However, certain embodiments may be practiced without one or more of these specific details or may be practiced in combination with other known methods and configurations. In the following description, many specific details are set forth, such as specific configurations, dimensions, and processes, to provide a thorough understanding of the embodiments. In other instances, well-known processes and manufacturing techniques have not been described in particular detail so as not to unnecessarily obscure the description. Throughout this specification, references to "one embodiment," "one embodiment," and the like, mean that a particular feature, structure, configuration, or characteristic being described is included in at least one embodiment. Thus, the phrases "one embodiment," "one embodiment," and the like appearing in various places throughout this specification do not necessarily refer to the same embodiment. Moreover, these particular features, structures, configurations, or characteristics may be combined in any suitable manner in one or more embodiments.

[0015] Use of relative terms throughout the description may represent relative positions or directions. For example, "distal" may refer to a first direction along a longitudinal axis of the tissue treatment system. Similarly, "proximal" may refer to a second direction opposite the first direction. However, such terms are provided to establish a relative frame of reference and are not intended to limit the use or orientation of the tissue treatment system to the specific configurations described in the various examples below.

[0016] Some existing catheter-based systems used for renal denervation use a non-compliant balloon to center the transducer within the target vessel and contain a circulating cooling fluid that protects the target vessel from being ablated by the energy delivered by the transducer. A non-compliant balloon inflates to a roughly predetermined diameter over an operating range of inflation pressures. More specifically, a non-compliant balloon has a narrow range of inflation diameters over a range of operating pressures. A non-compliant balloon targets a narrow range of vessel lumen diameters and thus requires different device sizes to treat differently sized patient anatomies. Considering that renal artery size may vary not only from patient to patient, but also between the left and right renal arteries of the same patient, and even along the length of a single renal artery in a patient, a substantial portfolio of device sizes may be required to treat a general patient population. Thus, existing catheter-based systems, including non-compliant balloons, require significant shelf space to stock a portfolio of device sizes. A large product portfolio also brings with it the manufacturing complexities associated with producing a wide range of different device models. Device customers and device manufacturers can benefit from a catheter-based system capable of treating a wide range of vessel lumen diameters used for renal denervation with the same and / or better safety and efficacy profile as existing devices. Described herein is such a catheter-based system.

[0017] In one aspect, a tissue treatment system is provided. The system includes a compliant balloon and a transducer mounted on a catheter shaft. The compliant balloon has a balloon wall shaped to center the catheter shaft and transducer within the target vessel when inflated and attached to the vessel wall. More specifically, the catheter shaft and transducer are properly supported and centered within the target vessel despite the balloon flexibility that allows the compliant balloon to be inflated to attach to a wide range of vessel sizes. The compliant and supportive balloon allows a single device to be used to treat target vessels with variable lumen diameters. Thus, a single device can be adapted to the same patient (left renal artery to right renal artery or along the same renal artery) and variable vessel lumen diameters from patient to patient. The compliant and supportive balloon allows a single device to be used per procedure, thus reducing the number of device exchanges required, which in turn reduces procedure time, reduces complexity, and reduces costs. The compliant balloon tissue treatment system, as described below, can therefore reduce the number of catheters required per procedure and shorten procedure times when compared to existing catheter-based systems used for renal denervation.

[0018] The catheter-based system can have a stable run-to-run compliance curve that provides repeatable, controllable inflation within a range of vessel sizes. The compliance curve of a compliant balloon can change with each inflation. To treat a patient using only one catheter, the catheter-based system described herein includes a compliance curve that does not change significantly between inflations and / or changes in a controlled / known manner. A stable compliance curve allows the system to be inflated multiple times within multiple sites of the vessel and still be sized predictably to ensure good adhesion to the vessel wall and uniform energy delivery. Additionally, a stable compliance curve allows the controller used to control the inflation of the system to be programmed to inflate the balloon based on the stable compliance curve, reducing software complexity.

[0019] Support and centering of the transducer in the vessel can contribute to uniform energy delivery. However, the pressure of the balloon of an ultrasonic ablation catheter can vary as a function of the required flow rate and / or diameter of the vessel being treated. At higher pressures, such as those used in larger diameter vessels, and / or during higher flow conditions, a wider range of compliant balloon materials can more easily center the transducer. However, under lower pressure conditions, such as in smaller vessels, and / or lower flow conditions, the same compliant balloon may not adequately center the transducer. The catheter-based system described below can support and center the ultrasound transducer over a range of operating pressures and within a range of vessel sizes to enable more uniform circumferential ablation around the vessel. More specifically, the catheter-based system can include a balloon that can center the ultrasound transducer both in smaller vessels at lower inflation pressures and in larger vessels at higher inflation pressures.

[0020] Radial access catheters may be less painful to insert, are associated with fewer complications such as bleeding and infection at the access site, and may shorten the total treatment time. The patient may be released the same day as the treatment. The catheter-based systems described below may provide balloons that are compatible with guide sheaths configured to be inserted through the radial vessels of the arm. For example, the balloons of the systems may have a crossover profile that is less than 5 French, less than 0.060 inches, and / or less than 0.058 inches. Additionally, the balloons may have a crossover profile of 4 French.

[0021] The system described below is capable of providing consistent, safe, and effective ultrasonic ablation therapy. To this end, a balloon is described that does not significantly interfere with the sonication of the transducer. In certain embodiments, a balloon is provided that is made of a material and has a selective thickness such that the balloon does not interfere with the energy transmission of the transducer.

[0022] In certain embodiments, a compliant balloon is provided that restricts an artery. In certain artery restriction embodiments, the balloon material is selected such that wrinkles in the balloon do not interfere with sonication. In certain artery restriction embodiments, the balloon material is selected such that the energy profile can be tailored such that the balloon wrinkles in a predictable manner such that wrinkles do not interfere with sonication of the transducer.

[0023] Provided herein is a tissue treatment system including a catheter having a compliant medical balloon configured for use in a wide range of vessel lumen diameters. In one embodiment, the compliant balloon is mounted on a catheter shaft and has an interior portion containing an ultrasound transducer. The compliant balloon can be made of a material and can be constructed such that the balloon can be inflated to adhere to a wide range of body lumens. For example, the compliant balloon can be made of a polyether-based thermoplastic polyurethane and can have a working section with a predetermined linearity over a range of inflated diameters. The range of inflated diameters can include several diameters that differ by at least 2 mm. For example, a first diameter can be in the range of 3.5-6 mm, e.g., 5 mm, and a second diameter can be in the range of 8-9 mm, e.g., 8.5 mm.

[0024] As used herein, inflated diameter refers to the outer diameter of the cross-sectional shape of the balloon passing through the center of the transducer. More specifically, a transverse plane oriented perpendicular to the central axis of the balloon can intersect the balloon at the balloon's outer contour. The outer dimension of that contour, e.g., the outer diameter, represents the inflated diameter of the balloon. In one embodiment, the outer diameter can be measured by inflating the balloon and measuring the outer dimension at the balloon surface radially outward from the transducer. For example, the balloon can be supported in free space and inflated to a given inflation pressure, and a measuring tool, such as a laser caliper, can be used to measure the outer diameter of the inflated balloon.

[0025] The predetermined straightness of the working section of the balloon allows the transducer to be supported and centered within the target vessel. In one embodiment, the predetermined straightness includes a predetermined threshold of cylindricity of the working section, e.g., less than 1 mm. The straightness can be determined with respect to other geometric characteristics, such as the ratio of the radius of curvature of the working section to the length of the compliant balloon, or the ratio of the radius of curvature of the working section at different inflation diameters. The predetermined straightness of the compliant balloon may compare favorably in terms of tissue contact and transducer support when compared to a typical compliant balloon, which tends toward a spherical profile upon inflation.

[0026] Referring to FIG. 1, a perspective view of selected components of a tissue treatment system is shown, according to one embodiment. The tissue treatment system 100 may be a catheter-based system. More specifically, the system may include a catheter 102 that may be delivered intraluminally, e.g., intervascularly, in a target anatomical region of a subject. Once so positioned, a transducer of the system (FIG. 2A) may be positioned within the target anatomical structure, e.g., within a body lumen such as a blood vessel. As described below, the transducer may be an ultrasound transducer that may be positioned within a medical balloon 108. The transducer may be activated to deliver unfocused ultrasound energy radially outward, thereby appropriately heating and thus treating tissue within the target anatomical region. The transducer may be activated at a frequency, time, and energy level appropriate for treating the target tissue.

[0027] The tissue treatment system 100 may include a catheter 102, a controller 104, and a connecting cable 106. In certain embodiments, the tissue treatment system 100 may optionally further include a balloon 108 (or other suitable inflatable member), a reservoir 110, a cartridge 112, and a control mechanism, such as a handheld remote control. In certain embodiments, the controller 104 is connected to the catheter 102 via the cartridge 112 and the connecting cable 106. In certain embodiments, the controller 104 interfaces with the cartridge 112 to provide cooling fluid to the catheter 102 for inflating and deflating the balloon 108.

[0028] In one embodiment, the balloon catheter 102 can include a compliant balloon 108 configured to accommodate a range of target vessel sizes, as described below. The compliant balloon 108 can accommodate differences in vessel lumen diameter along the length of the artery and between the left and right renal arteries. For example, the compliant balloon 108 can be configured to treat vessels having vessel lumen diameters ranging from 3 mm to 9 mm in diameter. The compliant balloon 108 can thus reduce the need to use several different balloon catheters 102 per procedure. The balloon 108 can therefore reduce procedure time and complications.

[0029] Referring to FIG. 2A, a side view of selected components of the tissue treatment system of FIG. 1 is shown, according to one embodiment. The tissue treatment catheter 102 can include a distal region 202 and a proximal region 204. The catheter 102 can have a length that depends on the treatment application. For example, in certain embodiments, such as those suitable for renal denervation via a femoral access delivery method, the catheter 102 can have a working length (measured from the distal tip of the catheter 102 to the proximal hub 240 of the catheter 102) of 80-90 cm, such as 85 cm, in a femoral access delivery method. In embodiments, such as those suitable for renal denervation via a radial access delivery method, the catheter 102 can have a relatively longer working length. More specifically, the working length can be 150-160 cm, such as 155 cm. Additionally, the total length of the catheter 102 for such applications can be longer, including the length of the cabling that extends to the electrical coupling 206. More specifically, the cabling can have a length from the proximal hub 240 to the electrical coupling 206 of approximately 305 cm.

[0030] The catheter 102 can have a profile suitable for accessing the renal arteries via femoral and radial access sites. For example, the catheter 102 may have a diameter of 4 French to 6 French, e.g., 5 French. This profile is facilitated in part by the catheter shaft 212 having an outer diameter in the range of 0.050 inches to 0.060 inches, e.g., 0.057 inches.

[0031] The distal region 202 of the tissue treatment system 100 may be the portion of the device that is advanced into a target anatomical structure, e.g., a target vessel having a vessel wall, to treat the target vessel. The distal region 202 may include a balloon 108 mounted on a catheter shaft 212. The balloon 108 may be a compliant balloon having characteristics that are described in detail below. For example, the balloon 108 may have a cylindricity that supports and centers the transducer 108 within a range of vessel diameters, thus contributing to uniform energy delivery.

[0032] The catheter shaft 212 may be an elongated tubular structure extending longitudinally from a proximal end to a distal end. The balloon 108 may be mounted on and supported by the catheter shaft 212 at the distal end. Additionally, an ultrasound transducer 214 may also be mounted on the catheter shaft 212 and contained within the balloon 108. The catheter shaft 212 may thus facilitate delivery of cooling fluid to the balloon 108 and electrical energy to the transducer 104.

[0033] The catheter shaft 212 may include one or more lumens (FIG. 4) that may be used as fluid conduits, electrical cabling passageways, guidewire lumens, and / or the like. In one embodiment, the catheter shaft 212 may include a guidewire lumen 213 that is shaped, sized, or otherwise configured to receive a guidewire. In one embodiment, the guidewire lumen 213 is an over-the-wire type guidewire lumen that extends from the distal tip of the catheter 102 through the entire length of the catheter shaft 212 to an exit port 250 of the proximal hub 240 of the catheter 102. As described below, the lumen of the catheter shaft 212 may also carry inflation / cooling fluid from the proximal region 204 to the balloon 108 while the balloon is inflated.

[0034] In one embodiment, the transducer 214 is mounted on the catheter shaft 212 within the interior of the balloon 108 at the distal region 202. The transducer 214 may be an ultrasound transducer 214 used to emit energy towards the vessel wall. For example, the transducer 214 may emit ultrasound energy circumferentially, e.g., 360 degrees around the vessel wall. In one embodiment, electrical cabling 216 extends from the proximal region 204 to the distal region 202 and is connected to the transducer 214 to generate energy for emission to the target tissue.

[0035] The ultrasonic transducer 214 may include a first electrode and a second electrode disposed on either side of a cylindrical piezoelectric material, such as lead zirconate titanate (PZT). To energize the transducer 214, a voltage is applied across the first electrode and the second electrode, the voltage being applied at a frequency selected to cause the piezoelectric material to resonate and generate vibrational energy that is emitted radially outward from the transducer 214. The transducer 214 is designed to provide a generally uniform and predictable emission profile so as not to damage surrounding non-target tissue. Additionally, to reduce heating of the inner lining of the body lumen and to cool the transducer 214, a cooling fluid is circulated through the balloon 108 both before, during, and after activation of the transducer 214. In this manner, the peak temperature achieved by the tissue within the cooling zone remains lower than the temperature of tissue located outside the cooling zone.

[0036] The proximal region 204 may include one or more connectors or couplings. The connectors or couplings may be electrically connected to the transducer 214 via electrical cabling 216. For example, the proximal region 204 may include one or more electrical couplings 206 that connect to a proximal end of the electrical cabling 216. A distal end of the electrical cabling 216 may be connected to the transducer 214.

[0037] The catheter 102 may be coupled to the controller 104 by connecting the electrical coupling 206 to the connecting cable 106. The connecting cable 106 may be removably connected to the controller 104 and / or the catheter 102 via ports on the controller 104 and / or the catheter 102. Thus, the controller 104 may be used with several catheters 102 during a procedure by disconnecting the coupling of a first catheter, replacing the first catheter with a second catheter, and connecting the coupling of the second catheter to the controller 104. For example, in certain embodiments where only one catheter needs to be used during a procedure, the connecting cable 106 may be permanently connected to the controller 104.

[0038] In certain embodiments, the proximal region 204 of the catheter 102 can further include one or more fluid ports. For example, the proximal hub 240 can include a fluid inlet port 208 and a fluid outlet port 210, via which the expandable member, e.g., the balloon 108, can be fluidly coupled to a reservoir 110 (FIG. 1). The reservoir 110 can thus provide cooling fluid to the balloon 108 via these fluid ports. The reservoir 110 can optionally be included with the controller 104, or can be attached to an external housing of the controller 104, for example as shown in FIG. 1. Alternatively, the reservoir 110 can be provided separately.

[0039] Referring to FIG. 2B, a side view of selected components of the tissue treatment system of FIG. 1 is shown, according to one embodiment. In one embodiment, the catheter 102 can have a rapid-exchange guidewire lumen 213. More specifically, the guidewire lumen 213 can extend from the distal tip of the catheter 102 through a partial length of the catheter shaft 212 to an exit port 250 in the distal portion 202 of the catheter 102. For example, the distance from the distal tip to the rapid-exchange port 250 can be in the range of 20-30 cm, e.g., 23 cm. The proximal hub 240 shown in FIG. 2B can be different than the proximal hub 240 shown in FIG. 2A, so long as the exit port 250 can be moved from the proximal portion 204 to the distal portion 202. Other components of the rapid-exchange version of the catheter 102 can be similar to other components of the over-the-wire version of the catheter 102, and thus the description of the components shown in FIG. 2A can be applied to the similarly numbered components shown in FIG. 2B.

[0040] Referring to FIG. 3, a perspective view of selected additional components of the tissue treatment system of FIG. 1 inserted into a body lumen is shown, according to one embodiment. The tissue treatment system 100 can be inserted into a body lumen of a subject. For example, the distal region 202 of the catheter 102 of the tissue treatment system 100 can be advanced into a target vessel 302, such as a vessel, such as a renal artery. The target vessel 302 can have a number of nerves 304 in an outer layer, such as an adventitial layer, of the target vessel 302. In one embodiment, the tissue treatment system 100 includes a guidewire support tip 308 having a lumen that connects to a guidewire lumen 213 of the catheter shaft 212. The support tip 308 can receive a guidewire 310, thereby allowing the device to be tracked over the guidewire 310 to the target anatomical structure.

[0041] When the distal region 202 is positioned within the vascular lumen of the target vessel 302, the transducer 214 and the balloon 108 (or another suitable expandable member) are positioned radially inward from the plurality of nerves 304. The transducer 214 may be positioned partially or completely within the balloon 108. The balloon 108 may be filled with an inflation fluid 306, e.g., a cooling fluid, to inflate the balloon 108. When the balloon 108 is inflated with the inflation fluid 306, the balloon 108 may contact the inner surface of the target vessel, e.g., the intima. The inflated balloon 108 may thus have an inflated diameter equal to the lumen diameter 320 of the target vessel 302 and may be attached to the target vessel 302 to center the transducer 214 within the target vessel 302.

[0042] In certain embodiments, the transducer 214 can be programmed to output an acoustic signal when the balloon 108 completely occludes the target lumen. The balloon 108 can center the transducer 214 within the target lumen. In certain embodiments, for example suitable for renal denervation, the balloon 108 can be a compliant balloon 108, described below, that can be inflated in the patient during the procedure at an operating pressure of about 1.4-2 atm using an inflation fluid 306. The balloon 108 is sized for insertion into the target lumen, for example, for insertion into a renal artery, the balloon 108 can be selected to have an inflated size that includes one or more of the following outer diameters: 3.5 mm, 4.2 mm, 5 mm, 6 mm, 7 mm, 8 mm, or 9 mm. The balloon 108 can have a burst strength of greater than 45 psi.

[0043] In some embodiments, when inflated by filling the inflation fluid 306 under the control of the controller 104 in the target vessel 302, the balloon walls of the balloon 108 may be generally parallel to the outer surface of the transducer 214. Optionally, the balloon 108 may be sufficiently inflated to attach to the target vessel. For example, when inflated, the balloon 108 may at least partially contact and thus adhere to the inner wall of the target vessel. In other embodiments, the balloon 108 is configured to not contact the target vessel upon inflation. The balloon 108 may be maintained at a particular size by pushing fluid into the balloon 108, for example, via the inlet port 208, at a particular flow rate, and withdrawing fluid, for example, via the outlet port 210. More particularly, the inflation fluid 306 may be circulated through the balloon 108 to inflate the balloon 108.

[0044] 4, a longitudinal cross-sectional view of a distal region of a tissue treatment system is shown, according to one embodiment. In a particular embodiment, the diameter of the catheter shaft 212 can be about 1.8 mm. As discussed above, the catheter shaft 212 includes one or more lumens that can be used as a fluid conduit, a passage for electrical cabling or a guidewire 310, or the like. For example, the catheter shaft 212 can include a guidewire lumen 213 that is shaped, sized, or otherwise configured to receive the guidewire 310. The catheter shaft 212 can include a cable lumen 401 (running through the same shaft as the guidewire lumen 213) for receiving electrical cabling, and / or a fluid lumen for transporting an expansion / cooling fluid, such as water, sterile water, saline, 5% dextrose (D5W), other liquids or gases, to and from a fluid source, such as a reservoir 110, of the proximal region 204 of the catheter 102 outside the patient. The catheter shaft 212 may include one or more fluid passages 420 for moving fluid into or out of the balloon 108. For example, the fluid passages may include an inlet fluid passage 403 for delivering the inflation fluid 306 from the inlet port 208 to the balloon 108 under the control of the controller 104. Similarly, the fluid passages may include an outlet fluid passage 405 for removing fluid from the balloon 108 to the outlet port 210. The inlet fluid passage 403 and the outlet fluid passage 405 are thus in fluid communication with the balloon 108 to circulate fluid through the balloon 108 at a flow rate selected to inflate the balloon 108. The flow rate also controls the heat transfer between the balloon 108 and the vessel wall 303 to reduce the possibility of overheating of the tissue during treatment. For example, the flow rate may actively cool approximately the first millimeter of tissue to provide for maintaining the integrity of the renal artery wall, for example.

[0045] For example, in a particular embodiment suitable for renal denervation, the guidewire 310 has a diameter of about 0.36 mm and a length of about 180 cm to about 300 cm, and is delivered using a 2.33 mm (7 French) guide catheter 102 having a minimum inner diameter of 2.06 mm and a length of less than about 80 cm. In a particular embodiment, the guidewire 310 is delivered using a 2 mm (6 French) guide catheter 102. In a particular embodiment, the guide catheter 102 has a length of about 55 cm. In a particular embodiment, the guide catheter 102 has a length of about 85 cm, and a hemostatic valve is attached to the hub of the guide to continuously irrigate the guide and reduce the risk of thromboembolism. In a particular embodiment, the guidewire lumen 213 is located in the center of the catheter shaft 212 to center the transducer 214.

[0046] The ultrasound transducer 214 may include a cylindrical tube 402 made of a piezoelectric material, such as lead zirconate titanate (PZT), or the like, with internal and external electrodes 404, 406 along the inner and outer surfaces of the cylindrical tube 402, respectively. In a particular embodiment suitable for renal denervation, for example, the piezoelectric material includes PZT-8 (Navy III). The bare PZT transducer 214 may be plated with layers of copper, nickel, and gold to create electrodes on the inner and outer surfaces of the cylinder. Applying an alternating current across the internal and external electrodes 406 causes the piezoelectric material to vibrate transversely to the longitudinal direction of the cylindrical tube 402, emitting ultrasonic waves in a radial direction.

[0047] Additionally, the transducer 214 is generally supported via a backing member or post 408. In a particular embodiment, the backing member 408 comprises stainless steel coated with nickel and gold, with nickel used as a bond between the stainless steel and the gold plating. For example, in a particular embodiment suitable for renal denervation, the transducer 214 has an outer diameter of about 1.5 mm, an inner diameter of about 1 mm, and a length ranging from 3 to 9 mm, such as 6 mm. The backing member 408 can be deployed from the distal end of the catheter shaft 212 to the support tip 308. For example, the distal end of the backing member 408 can be positioned within an adjacent opening in the support tip 308, and the proximal end of the backing member 408 can be movably coupled to the distal end of the catheter shaft 212 via electrical cabling. In other embodiments, a gap 410 exists between the distal end of the catheter shaft 212 and the backing member 408 supporting the transducer 214 and / or a gap exists between the backing member 408 and the support tip 308.

[0048] To allow cooling along both the inner and outer electrodes 406 by the liquid, the backing member 408 may include one or more standoff assemblies 412. The standoff assemblies may define one or more annular openings 414 through which cooling fluid may enter the space between the backing member 408 and the inner electrode 404. The backing member 408 may act as a fluid barrier between the inflation / cooling fluid circulating within the balloon 108 and the lumen of the backing member 408 that receives the guidewire 310. The standoff assemblies of the backing member 408 may be located along each end of the ultrasonic transducer 214 (separated by a main post body 416) and may couple the cylindrical tube 402 of the ultrasonic transducer 214 to the backing member 408. The standoff assemblies 412 may have a number of lugs, ribs, or attachment points that engage the inner electrode 404 of the transducer 214. In a particular embodiment, the attachment point is soldered to the inner electrode 404 of the transducer 214. The number, size and arrangement of the ribs can be varied as desired or required. For example, a total of three ribs are spaced approximately equally apart from one another at 120 degree angles to define an annular opening 414 through which fluids and blood can enter the interior space of the cylindrical tube 402 between the inner electrode 404 and the backing member 408 disposed along the inner surface of the cylindrical tube 402. In a particular embodiment, the maximum outer diameter of the standoff assembly is about 1 mm, the outer diameter of the main post body 416 is about 0.76 mm, and the inner diameter of the backing member 408 is about 0.56 mm.

[0049] The standoff assembly can be electrically conductive to electrically couple the inner electrode 404 of the ultrasonic transducer 214 to the backing member 408. One or more conductors of the electrical cabling can be electrically coupled to the backing member 408. Thus, when the controller 104 is activated, electrical current can be delivered from the electrical cabling to the inner electrode 404 of the ultrasonic transducer 214 through the backing member 408 and the standoff assembly, which advantageously eliminates the need to directly couple the electrical cabling to the inner electrode 404 of the transducer 214.

[0050] In one embodiment, the backing member 408 can have an isolation tube (not shown) disposed along its interior surface to prevent or reduce the possibility of electrical conduction between the guidewire 310 and the backing member 408. The isolation tube can be formed of a non-conductive material, for example a polymer such as polyimide. The isolation tube can be deployed from the distal end of the catheter shaft 212 through a lumen of the backing member 408 within the transducer 214 to the support tip 308. The transducer 214 can be mounted on the isolation tube and / or electrical cabling. In this manner, the transducer 214 can be offset distally from the distal end of the catheter shaft 212 by a gap 410.

[0051] The catheter 102 may also include a lumen 418 extending proximally through the catheter 102 from the distal end of the catheter shaft 212. The lumen 418 may be sized and shaped to receive at least a portion of the backing member 408, the electrically insulating isolation tube, and / or the ultrasound transducer 214. Thus, during delivery of the catheter 102 to the anatomical region to be treated, the backing member 408, the isolation tube, and / or the ultrasound transducer 214 may be retracted into the lumen 418 of the catheter 102, for example by retracting the electrical cabling, thereby providing the catheter 102 with sufficient stiffness so that the catheter 102 may be delivered in a safe manner.

[0052] Referring to FIG. 5, a side view of a tissue treatment system having a compliant balloon inflated to a first inflated diameter is shown, according to one embodiment. In certain embodiments, the balloon 108 is compliant and configured to be utilized for a wide range of lumen, vessel, or artery sizes. For example, the balloon 108 may accommodate arteries with inner diameters between 3 mm and 8 mm. Thus, use of the compliant balloon 108 may advantageously reduce procedure time by using only one catheter 102 during the procedure, for example, from about 1 hour to about 15 minutes for a renal denervation procedure. In certain embodiments, use of the compliant balloon advantageously reduces complications, thereby advantageously reducing the complication rate of the procedure.

[0053] In certain embodiments, the tissue treatment system 100 is configured to measure the size of a lumen, vessel, or artery, and the balloon 108 is configured to accommodate a wide range of lumen sizes, e.g., 3-9 mm renal or accessory arteries, so that the controller 104 can be programmed to automatically inflate the balloon 108 to the appropriate diameter. Such automation advantageously provides an improvement in procedural complexity and reduces the risk of user error. In certain embodiments, with a tissue treatment system 100 having a compliant balloon 108, there is no need for a user to select a balloon size and / or exchange catheters to accommodate multiple size balloons during a single procedure.

[0054] The compliant medical balloon 108 can include a balloon wall 502 that can have a generally annular cross-section at any longitudinal location. More specifically, the balloon wall 502 can have an exterior surface that expands to contact the target tissue, and an interior surface that defines an interior 504 of the balloon 108. As discussed above, the transducer 214 can be directly mounted on the catheter shaft 212 or can be indirectly mounted (e.g., via electrical cabling).

[0055] The transducer 214 can be disposed within an interior 504 of the balloon 108. More specifically, the balloon 108 can have a balloon body 506 that can radially surround the transducer 214. For example, the balloon body 506 can be a generally cylindrical portion of the balloon wall 502 that extends radially around the transducer 214 relative to a longitudinal axis of the catheter shaft 212. The balloon body 506 can extend longitudinally between a number of corners 508. For example, a distal corner 508A can define a distal extent of the balloon body 506, and a proximal corner 508B can define a proximal extent of the balloon body 506. In one embodiment, the distance between the corners 508 that define the length of the balloon body 506 can be equal to or greater than the length of the transducer 214. More specifically, the length of the balloon body can be, at a minimum, the length of the transducer 214. Thus, the transducer 214 can be positioned such that a proximal end of the transducer 214 is distal to a proximal corner 508B of the balloon 108 and a distal end of the transducer 214 is proximal to a distal corner 508A of the balloon 108. The corners 508 can transition the balloon body 506 into a number of shoulders 510. Furthermore, in addition to the transition of the balloon 108 sections, the shape of the corners 508 can have a primary impact on the ability of the balloon 108 to center the transducer 214 within the target vessel 302.

[0056] In one embodiment, the plurality of shoulders 510 includes a distal shoulder 510A (distal to the balloon body 506) that connects the balloon body 506 to a distal attachment section 512A of the balloon wall 502. Similarly, a proximal shoulder 510B (proximal to the balloon body 506) can connect the balloon body 506 to a proximal attachment section 514B of the balloon wall 502. Thus, the shoulder 510 transitions the portion of the balloon wall 502 that connects the balloon 108 to the catheter shaft 212 with the portion of the balloon wall 502 that interacts with the target tissue during inflation.

[0057] The transducer 214 may be mounted on the isolation tube and / or backing member. In this case, the proximal mounting section 514B may be mounted on the catheter shaft 212 proximal to the transducer, while the distal mounting section 514A may be mounted on the transducer, backing member 408, or support tip 308. The mounting sections may be connected to the catheter shaft 212 via thermal, adhesive, or mechanical bonds that hermetically seal the balloon 108 to the catheter shaft 212. The interior 504 of the balloon 108 between the attachment points may thus surround the transducer 214 and provide space for inflation / cooling fluid to circulate around the transducer 214 during treatment.

[0058] It will be appreciated that unlike a compliant balloon 108 that functions primarily to occlude a target anatomical structure, the balloon 108 of the tissue treatment system 100 functions to center the transducer 214 within the target vessel 302. However, the flexibility of the balloon 108 required to achieve the inflation methodology described below may cause the transducer 214 to be off-centered within the vessel lumen if certain characteristics are not realized in the balloon 108. More specifically, the shape and material of the balloon 108 may be provided as described below to provide a compliant balloon 108 that also adequately supports centering of the transducer 214 within the target vessel 302 during use.

[0059] The shape of the balloon 108 may contribute to optimal centering of the transducer 214 within the target vessel 302. In one embodiment, the balloon body 506 and the shoulders 510 meet at a rounded corner 508. Rather than the transition between the shoulders 510 and the balloon body 506 being sharp, i.e., angular, the transition is smooth and has an arcuate contour, so that the corners 508 may be considered rounded. This contour may be described as having a full radius, as opposed to a discrete radius change evident in medical balloons typically used for angioplasty procedures, for example. In comparison to balloon shapes with sharp corners, the rounded corners 508 of the balloon 108 have been found to keep the catheter shaft 212 (and the transducer 214 mounted on the catheter shaft 212) centered within the target vessel 302 when the balloon 108 is inflated within the target vessel 302.

[0060] The material of the balloon 108 may contribute to optimal centering of the transducer 214 within the target vessel 302. For example, in certain embodiments suitable for renal denervation, the balloon 108 may comprise nylon, polyether block amide (PEBAX®), or other suitable polymers. In one embodiment, the balloon wall 502 is formed from an elastomeric material. For example, the elastomeric material may include a urethane material, such as thermoplastic polyurethane (TPU). The TPU may be a polyether-based TPU, such as Pellethane®. Alternatively, the balloon wall 502 may be formed from another medical grade polyether-based TPU, such as Isothane®.

[0061] Isothane® is a urethane material with tightly controlled material specifications. In comparison to other types of urethanes, Isothane® can be particularly useful in that it has less variation in material properties between lots of material. More specifically, between lots, Isothane® can have less gel and a more consistent block chain compared to other materials. Thus, in one embodiment, the raw material used to form the balloon 108 is Isothane®.

[0062] The stiffness of the balloon material may contribute to the compliance of the balloon 108, e.g., the ability of the balloon to inflate and conform to different vessel lumen diameters. Stiffness may also contribute to the ability of the balloon 108 to support and center the transducer 214. Thus, the material used to form the balloon wall 502 may have a Shore durometer between about 95A and about 55D. More specifically, the balloon wall material may have a Shore D durometer in the range of 50-60. For example, the balloon 108 may be formed from Pellethane® having a Shore D durometer of 55, or Isothane® having a Shore durometer of 5095A, 7195A, or 5055D. In one particular embodiment, it has been found that a balloon wall 502 formed from Isothane® having a Shore D durometer of 55 may provide superior results that balance the performance goals of compliant inflation and support strength.

[0063] While non-compliant balloon inflation is limited by the balloon itself, i.e., the balloon diameter is generally fixed when inflated at different pressures within the expected operating range, and therefore can accommodate a limited range of vessel sizes, compliant balloon inflation can use multiple inflation methods that allow the compliant balloon to accommodate a wider range of vessel sizes. The compliant medical balloon 108 of the tissue treatment system 100 described above can be applied to the target vessel 302 using any of several inflation methodologies. Such methodologies can be referred to as a "pressure limiting approach," an "arterial limiting approach," and a "hybrid approach."

[0064] The pressure limiting approach involves using a specific inflation pressure to obtain a specific balloon diameter to obtain adhesion for various vessel sizes. The arterial limiting approach involves the use of a fixed inflation pressure that is used regardless of arterial diameter. The hybrid approach is a combination of the arterial limiting approach and the pressure limiting approach. The hybrid approach involves the use of a fixed inflation pressure to obtain adhesion for smaller arterial diameters, but the use of an alternative (higher) inflation pressure to obtain adhesion for larger arterial diameters. The strength of the artery essentially determines the size of the balloon 108 at low pressures, and at higher pressures, the balloon pressure determines the size of the balloon 108. These inflation paradigms are described in more detail below.

[0065] Continuing with reference to FIG. 5, the balloon is shown in a first state, and more specifically, a first inflated diameter. The inflated diameter may be an exterior dimension of the balloon body 506. In one embodiment, the balloon wall 502 has a shape and stiffness (as described herein) such that when the compliant balloon 108 is inflated to a first inflation pressure of 10 psi, the balloon body 506 of the balloon wall 502 has a cylindrical profile and a first inflated diameter of between 3.5 mm and 6 mm. The inflation pressure may correspond to a flow rate of fluid circulating through the interior 504 of the balloon 108 between the inlet fluid passageway 403 and the outlet fluid passageway 405. For example, the fluid may be circulated at a flow rate of between 15 and 35 mL / min (e.g., between 25 and 35 mL / min) to inflate the balloon 108 to an inflation pressure of 10 psi, resulting in a first inflated diameter of between 3 and 6 mm (e.g., between 3.5 and 6 mm). The balloon body 506 of the balloon 108 may have a first inflated diameter of 3.5 mm at a first inflation pressure of 10 psi and a flow rate of 30 mL / min.

[0066] In a particular embodiment used for the pressure limiting technique, a single balloon 108 can have an inflated diameter that is directly related to the pressure of the balloon 108. More specifically, the outer diameter of the balloon 108 is directly related to the pressure of the balloon 108. According to this embodiment, the higher the pressure, the larger the balloon 108. It is contemplated that the balloon 108 can have an inflation range of 3.5-9 mm. More specifically, the balloon 108, when inflated to the state shown in FIG. 5, can have a nominal size of 3.5 mm, but the higher the inflation pressure, the larger the inflated diameter can be.

[0067] 6, a side view of a tissue treatment system having a compliant balloon inflated to a second inflated diameter is shown, according to one embodiment. When the medical balloon 108 is inflated to a second inflated diameter, for example 8 mm, the balloon wall 502 can have essentially the same sections as described above. More specifically, the medical balloon 108 can include an attachment section 512, a shoulder 510, and a balloon body 506. A corner 508 where the balloon body 506 transitions to the shoulder 510 can be rounded. In one embodiment, the arcuate corner 508 can have the same radius as the balloon body 506 and the shoulder 510 such that the balloon wall 502 has a single arcuate profile of the same radius between the distal attachment section 512 and the proximal attachment section 514. As in FIG. 5, the balloon body 506 can be longer than the transducer 214 mounted on the catheter shaft 212 and can surround the transducer 214.

[0068] The shoulder 510 can be rounded, but the balloon 108 can instead have an angled shoulder. More specifically, the angled shoulder described in connection with Figures 21-23 can be incorporated into the balloon design. The angled corner, when combined with other features described in connection with Figures 21-23, is shown to center and support the transducer.

[0069] In one embodiment, the balloon wall 502 has a shape and stiffness (as described herein) such that when the compliant balloon 108 is inflated to a second inflation pressure of 30 psi, the balloon body 506 of the balloon wall 502 has a cylindrical profile and a second inflated diameter of 8 mm to 9 mm. The inflation pressure may correspond to a flow rate of fluid circulating through the interior 504 of the balloon 108 between the inlet fluid passageway 403 and the outlet fluid passageway 405. For example, the fluid may be circulated at a flow rate of 35-50 mL / min (e.g., 40-45 mL / min) to inflate the balloon 108 to an inflation pressure of 30 psi, resulting in a first inflated diameter of 8-9 mm. For example, the balloon body 506 of the balloon 108 may have a second inflated diameter of 8 mm at a second inflation pressure of 30 psi and a flow rate of 40-45 mL / min.

[0070] Referring to FIG. 7, a diagram of a balloon pressure curve for a balloon being inflated with a pressure limiting technique is shown, according to one embodiment. With the pressure limiting technique, the balloon 108 can have a pressure curve that approximates an ideal inflation curve 702. The ideal inflation curve 702 can evolve linearly from a first inflation diameter of 3.5 mm at a first inflation pressure of 10 psi to a second inflation diameter of 8 mm at a second inflation pressure of 30 psi. Thus, the balloon 108 can accommodate vessel lumen diameters of 3.5 to 8 mm for the same or several vessels. More specifically, the inflation diameter 704 of the balloon 108 corresponds to the inflation pressure 706 of the balloon 108.

[0071] The balloon 108 can be inflated by circulating an inflation fluid 306 through the balloon 108. More specifically, circulating the inflation fluid 306 through the balloon 108 generates an inflation pressure that inflates the balloon 108 to an inflated diameter. The inflation pressure can be proportional to a flow rate. Thus, the inflation fluid 306 can be circulated through the balloon 108 to inflate the balloon 108 to a desired size based on the lumen diameter 320 of the target vessel 302. For example, the flow rate associated with the second inflation pressure (and second inflated diameter) can be greater than the flow rate associated with the first inflation pressure (and first inflated diameter). Illustratively, the inflation fluid 306 can be circulated through the balloon 108 at a flow rate of 25-45 mL / min to achieve an inflated diameter 704 along the ideal inflation curve 702. In one example, when the inflation fluid 306 is sterile water, a flow rate of 30 mL / min can be used to achieve an inflation pressure of 10 psi associated with an inflated diameter of 3.5 mm. If the inflation fluid 306 is sterile water, a flow rate of 40-45 mL / min can be used to achieve an inflation pressure of 30 psi associated with an 8 mm inflation diameter. In another example, if the inflation fluid 306 is D5W, a flow rate of 27 mL / min can be used to achieve an inflation pressure of 10 psi associated with a 3.5 mm inflation diameter. If the inflation fluid 306 is D5W, a flow rate of 40 mL / min can be used to achieve an inflation pressure of 30 psi associated with an 8 mm inflation diameter. Thus, the pressure limiting technique can utilize a flow rate of at least 30 mL / min to achieve an inflation pressure of 10-30 psi. Flow rates of 30 mL / min or greater have been found to circulate the fluid sufficiently to adequately cool the tissue during renal denervation.

[0072] In one embodiment, the balloon 108 approximates the idealized inflation curve 702 over several inflation cycles. For example, the balloon 108 may be inflated to a first inflated diameter (or a second inflated diameter) at a first time 708 when the tissue treatment system 100 is introduced into the renal artery. The balloon 108 may be inflated at one or more additional times, such as a fifth time 710, to treat different regions along the length of the renal artery. Using the materials described above, it has been found that the inflation curves for the balloon 108 during each inflation cycle approximate each other and approximate the idealized curve. For example, if the balloon 108 is formed from Isothane® 55D, the inflated diameter when the balloon 108 is inflated at the first time 708 is within 10% of the inflated diameter when the balloon 108 is inflated at the fifth time. On the other hand, balloons formed from other materials not contemplated above may exhibit less consistent inflation curves over several cycles. For example, a balloon formed from other materials not contemplated above may exhibit an inflated diameter 704 at an Nth time 712 that differs by 10% or more from the inflated diameter 704 at a first time 708. Thus, the balloons 108 described herein provide good inflation consistency that allows a single device to be inflated several times during a single procedure to treat the same or different vessels.

[0073] Referring to FIG. 8, a side view of a tissue treatment system having a compliant balloon inflated to a predetermined inflation pressure by an arterial restriction procedure is shown, according to one embodiment. In an arterial procedure, a single large balloon 108 having an inflated diameter of, for example, 8 mm can be inflated to a low pressure, for example, 10 psi or less, in a target vessel 302. The target vessel 302 can have a vessel lumen diameter 320 less than the nominal inflated diameter. For example, the balloon 108 of FIG. 5 can have a nominal diameter of 8 mm rather than a nominal diameter of 3.5 mm. Thus, when the balloon 108 is placed in a target vessel 302 having a smaller vessel lumen diameter, for example an artery with an internal diameter of 4 mm, the balloon body 506 will come into contact with the vessel wall 303 before the balloon 108 reaches its nominal diameter. Thus, the hoop strength of the artery combined with the low inflation pressure can keep the balloon 108 below the nominal diameter and can keep the balloon body 506 in a generally cylindrical profile. More specifically, the hoop strength and inflation pressure of the renal arteries may prevent the compliant balloon 108 from inflating to its nominal inflated diameter.

[0074] Because the balloon 108 must accommodate a wide range of body lumen sizes, in smaller vessels the balloon 108 may have to be constructed with excess or thicker material compared to balloons 108 that are generally intended to accommodate only small body lumens. Thus, wrinkles 802 may result that would otherwise be ironed out by expansion in larger body lumens. More specifically, when the balloon 108 is inflated in the target vessel 302 using an arterial restriction technique, the target vessel 302 constrains the balloon 108, and therefore the balloon 108 may include some wrinkles 802 in the vessel wall 303 portion, where the excess material may fold over and accommodate less than the nominal diameter. The compliant balloon 108 may be a Pellethane® balloon having a Shore D durometer of 55, may have a double wall thickness of 0.01-0.04 mm (0.0004-0.0014 inches), e.g., 0.02 mm (0.0009 inches), and may include some wrinkles 802 that do not significantly impede energy delivery of the catheter. For example, the wrinkles 802 may have a predictable wrinkle pattern that does not substantially impede energy delivery. The predictable wrinkle pattern may have a low density of wrinkles or may have wrinkles that occur at specific sites that are not in the primary energy delivery path. Thus, the wrinkles may accommodate less than the nominal diameter without inhibiting treatment of the target tissue.

[0075] In an arterial restriction procedure, the balloon 108 is inflated to a predetermined inflation pressure regardless of vessel lumen diameter. More specifically, the low pressure used for the arterial restriction procedure may be a fixed pressure used regardless of vessel lumen diameter. For example, the predetermined inflation pressure may be 10 psi or less and may be used for any target vessel 302 having a vessel lumen diameter less than the nominal diameter of the balloon 108. It will be appreciated that this inflation paradigm differs from a pressure restriction procedure that utilizes an inflation pressure based on a target lumen diameter.

[0076] Referring to FIG. 9, a diagram of a balloon pressure curve for a compliant balloon 108 being inflated by a hybrid inflation technique, according to one embodiment, is shown. In a hybrid inflation technique, a single compliant balloon 108 having a nominal inflated diameter can be used to treat vessel lumen diameters smaller than the nominal inflated diameter and vessel lumen diameters larger than the nominal inflated diameter. The compliant balloon 108 can similarly treat lumen diameters of different vessels, or lumen diameters of different portions of the same vessel, such as the lumen diameters of distal and proximal portions of the vessel. The balloon 108 can be sized to be at or near the midpoint of appropriate sizes for a set of body lumen diameters. For example, for a typical renal artery lumen size, a balloon 108 can be provided having a nominal diameter of 6.75 mm.

[0077] A hybrid approach is a combination of an arterial restriction approach and a pressure restriction approach. In the above example of a balloon 108 having a nominal diameter of 6.75 mm for an artery less than 6.75 mm, the balloon 108 may be inflated to a low pressure, for example 10 psi. Above this inflation range, the balloon 108 may be in an arterial restricted operating range 902. In the arterial restricted operating range, the balloon 108 is arterial restricted as described above in connection with FIG. 8. Thus, when the compliant balloon 108 is inflated to a first inflation pressure in a renal artery (or renal artery portion) having a first arterial diameter less than the nominal inflated diameter of the compliant balloon 108, the hoop strength and inflation pressure of the renal artery prevents the compliant balloon 108 from inflating to the nominal inflated diameter of the compliant balloon 108.

[0078] On the other hand, for arteries (or arterial segments) larger than 6.75 mm, the balloon 108 can be increased in pressure to increase the size of the balloon 108. When operating at an inflated diameter greater than 6.75 mm, the balloon 108 can operate in a pressure-limited operating range 904. In the pressure-limited operating range 904, the balloon 108 is pressure limited as described above in connection with FIG. 7. Thus, when the compliant balloon 108 is inflated to a second inflation pressure, higher than the first inflation pressure, in a renal artery (or renal arterial segment) having a second arterial diameter larger than the nominal inflated diameter of the compliant balloon 108, the second inflation pressure causes the diameter of the compliant balloon 108 to expand to a diameter greater than the nominal inflated diameter of the compliant balloon 108. The balloon 108 can be inflated with progressively higher inflation pressures to adhere the balloon 108 to progressively larger arterial diameters. The 6.75 mm nominal diameter is provided as an example, and as in the above examples, the balloon 108 may have a nominal diameter of 3.5 mm, 3.7 mm, 4.5 mm, 5.5 mm, 6.5 mm, or any other diameter that delineates the arterial restriction range of the balloon 108 from the pressure restriction range of the balloon 108.

[0079] In one embodiment, the compliant balloon 108 has a nominal inflated diameter of about 4 mm. When the compliant balloon 108 is inflated to a first inflation pressure in a first arterial diameter of the renal artery having a diameter less than 4 mm, the hoop strength and inflation pressure of the renal artery prevents the compliant balloon 108 from inflating to a diameter greater than the first arterial diameter of the renal artery. However, when the compliant balloon 108 is inflated to a second inflation pressure, higher than the first inflation pressure, in a renal artery having a second diameter greater than 4 mm, the second inflation pressure causes the diameter of the compliant balloon 108 to expand and affix the compliant balloon 108 to the second arterial diameter.

[0080] As a further example of the hybrid approach, the compliant balloon 108 may be a Pellethane® balloon having a Shore D durometer of 55 and a nominal inflated diameter of 5.5 mm. The compliant balloon 108 can be inflated at a constant low balloon pressure to adhere in smaller artery diameters, but for progressively larger artery diameters, the pressure is increased to match the balloon size to the artery diameter. Table 1 lists the balloon pressures used to reach the balloon diameter size range. Note that the inflation pressure for diameters up to and slightly above the nominal inflated diameter of the compliant balloon is a single low pressure of 10 psi. The inflation pressure is then increased incrementally to achieve an inflated diameter 704 greater than 6 mm.

[0081] [Table 1]

[0082] As explained above, the inflation pressure is determined by the flow rate of the inflation fluid 306 in the balloon 108. Table 2 provides approximate flow rate values ​​for three selected pressures from the full range of 10-20 psi that can be used to inflate the balloon 108 using the hybrid approach. Note that flow rates near or above 30 mL / min have been found to effectively cool tissue during renal denervation.

[0083] [Table 2]

[0084] Referring to FIG. 10, a diagram of balloon pressure curves for two compliant balloons inflated with a pressure limiting approach is shown according to one embodiment. This diagram provides a basis for the option of offering a product portfolio with a limited number of device models. For example, two catheters with their respective compliant balloons may be used to cover a range of vessel lumen diameters, for example, arteries from 3-9 mm. A first compliant balloon curve for the first catheter may cover a first vessel size range, for example, 3-5 mm. A second compliant balloon curve for the second catheter may cover a second vessel size range, for example, 4-9 mm. The two balloon curves may overlap by a predetermined amount to ensure full coverage of the entire range of inflation from 3-9 mm. For example, the overlap between the first inflation diameter range of the first compliant balloon curve and the second inflation diameter range of the second compliant balloon curve may be in the range of 0.5-5 mm, for example, 1 mm. The individual balloons 108 can achieve their respective coverage using inflation pressures of 10 psi to 30 psi, corresponding to the effective cooling fluid flow rates described above. The total device portfolio can therefore cover a vessel size range of 3-9 mm, which is sufficient for most renal artery sizes. A tissue treatment system 100 portfolio having only two device models using compliant balloons 108 would provide a substantial improvement over a portfolio of five or more device models using non-compliant balloons 108. The two device models can be provided in a kit. More specifically, the kit can include two catheters having the balloon configurations described herein. The catheters of the kit can have respective compliance curves, such as the compliance curve shown in FIG. 10, to cover a vessel size range of 3-9 mm, which is typically sufficient for the general population of renal artery sizes.

[0085] 11, a flow chart of a method of delivering ultrasonic energy to a vessel wall using a tissue treatment system is shown, according to one embodiment. Now that the tissue treatment system 100 and various dilation paradigms have been described, a method of treating tissue in a target vessel 302 can be described.

[0086] The diameter of the target vessel, for example the arterial diameter of the renal artery, can be measured. Illustratively, a contrast agent can be injected into the renal artery and viewed under fluoroscopy to assess vessel size. The vessel diameter can be recorded and the balloon can be inflated to the measured vessel diameter using an appropriate inflation pressure. The process of measuring the diameter of the target vessel can be performed prior to the insertion of the treatment catheter or after the treatment catheter is inserted. For example, in the case of a one-size-fits-all catheter, the vessel measurement can be performed after the treatment catheter is inserted. Alternatively, when using a kit having two treatment catheters with balloons of different sizes, the vessel measurement can be performed prior to selecting one of the treatment catheters and inserting it into the vessel.

[0087] At operation 502, the tissue treatment system 100 can be inserted into a patient and positioned within a target anatomical structure. For example, after a guidewire 310 is positioned within a target vessel 302, the support tip 308 can be loaded onto the guidewire 310 and the distal region 202 can be passed over the guidewire 310 and into the target vessel 302.

[0088] In operation 504, the balloon 108 may be inflated against the vessel wall 303. The balloon 108 may be inflated according to any of the inflation paradigms described above. For example, the balloon 108 may be inflated using a pressure constraining technique by circulating a fluid within the balloon 108 based on the luminal diameter of the target vessel 302, thereby inflating the balloon 108 to attach to the vessel wall 303. Alternatively, the balloon 108 may be inflated using an arterial constraining technique by inflating the balloon 108 to a predetermined inflation pressure until the balloon 108 attaches to and is restrained by the target vessel 302, regardless of the luminal diameter of the target vessel 302. In a hybrid technique, the balloon 108 may be inflated by first circulating a fluid through the balloon 108 at a first flow rate to inflate the balloon 108 to a predetermined inflation pressure in a first portion of a renal artery having a first arterial diameter that is smaller than the nominal inflated diameter of the compliant balloon 108. In such a case, the hoop strength of the renal arteries and the first predetermined inflation pressure will prevent the compliant balloon 108 from inflating to a diameter greater than the first arterial diameter of the renal arteries.

[0089] In operation 506, ultrasonic energy is delivered from the transducer 214 to the vessel wall 303. More specifically, ultrasonic energy may be delivered to a first portion of a renal artery.

[0090] The compliant balloon 108 can be moved to a different artery or a different portion of the same artery. The hybrid approach can include an inflation fluid 306 circulating within the balloon 108 at a second flow rate greater than the first flow rate to inflate the balloon 108 to a second predetermined inflation pressure within a renal artery (or portion) having a second diameter greater than the nominal inflated diameter of the compliant balloon 108. The second inflated diameter can be greater than the first inflated diameter. More specifically, the second inflation pressure can inflate the compliant balloon 108 such that the diameter of the compliant balloon 108 is greater than the nominal inflated diameter of the compliant balloon 108. The balloon 108 can adhere to the vessel wall 303 at the first inflated diameter or the second inflated diameter depending on the size of the target vessel 302 site. When the balloon 108 is inflated within the target vessel 302 and adheres to the vessel wall 303, the balloon shape and materials described above maintain the catheter shaft 212 centered within the target vessel 302 and the transducer 214 centrally supported within the vessel lumen. Ultrasonic energy can be delivered from the transducer 214 to a second portion of the renal artery.

[0091] For a 3.5-8 mm compliant balloon, it is contemplated that the patient entry power will be in the range of 27-38 W. In certain embodiments, such patient entry power can be achieved using power settings. More specifically, a particular energy density (energy per balloon volume) can be achieved by controlling the generator power settings. In one embodiment, a 5.5 mm Pellethane® balloon 108 having a Shore D durometer of 55 can be used with an energy density in the range of 100-250 J / mL to achieve the patient entry power required to treat the target vessel. Using such energy densities, an acoustic power output can be reached that will ablate a renal nerve 304 having a vessel diameter of 3-9 mm. The programmed power settings of the controller 104 can be scaled with the lumen / balloon diameter to achieve a consistent ablation depth. In one embodiment, a programmable logic block is configured to select an acoustic output power that is adjusted based on the lumen diameter.

[0092] In certain embodiments, the tissue treatment system 100 and / or the compliant balloon 108 may incorporate features that contribute to centering the transducer 214 within the vessel lumen. As described below, the compliant balloon 108 may incorporate features in addition to, or in lieu of, rounded corners 508 and / or a cylindrical balloon body 506 that center the transducer 214 across a range of vessel sizes. Additionally, various centering mechanisms may be incorporated into the tissue treatment system 100 to complement the inherent centering capabilities of the balloon 108. Some such features are described below.

[0093] Referring to FIG. 12, a perspective view of a compliant balloon with longitudinal ribs is shown, according to one embodiment. In one embodiment, the shoulder 510 of the compliant balloon 108 can include one or more longitudinal ribs 1202. For example, several longitudinal ribs 1202 can extend longitudinally from the balloon body 506 to the attachment section (either the distal attachment section 514 or the proximal attachment section 514) of the balloon 108. The longitudinal ribs 1202 arranged circumferentially around the longitudinal axis of the balloon 108 can provide a reinforced and pleated section. More specifically, the ribs can act as a reinforcing element against lateral deformation. The pleats can thus stabilize the balloon 108 as it is inflated within the target vessel 302, allowing the balloon to be inflated and deflated in a predictable manner without mis-centering the transducer 214.

[0094] In certain embodiments, the pleated sections can also contribute to predictable folding of the balloon 108, for example, during deflation. For example, the pleated sections can incorporate multi-layer regions, elastomeric regions, heat-set regions, and / or magnetic regions. The reinforced regions can be configured such that the balloon 108 folds predominantly in a low-profile deflated state. The low-profile state can have a predominantly circular cross-section as opposed to a smooth cross-section having a larger maximum cross-sectional dimension. The low-profile circular cross-section allows the balloon 108 to be retrieved from the patient anatomy during removal with reduced risk of vasculopathy. Advantageously, the balloon fold memory can also facilitate reduced pinhole rates when the balloon 108 is exposed to puncture risks, such as exposed wires from the braiding of a guide catheter during a procedure. The pleated sections can thus assist in centering the transducer 214 to reduce the chance of patient injury and reduce the chance of device failure.

[0095] Referring to Figure 13, a cross-sectional view of the compliant balloon of Figure 12 is shown, according to one embodiment. In the cross-section, it can be seen that the longitudinal folds can be defined by peaks 1302 between several circumferential valleys 1304. The balloon surface can be curved or angled at the peaks and valleys. For example, the cross-section can have an arcuate transition as shown in Figure 13, or a circular corrugation if the peaks and valleys are angled.

[0096] A balloon mold that can be used during the manufacture of the balloon 108 can have an internal shape that creates longitudinal ribs 1202 when the balloon 108 is blown. In addition to the rounded corners 508 described above, the longitudinal ribs 1202 can be formed in the balloon 108. The rounded corners 508 and longitudinal ribs 1202 can reduce tension applied to the balloon body 506 from the shoulders 510 of the balloon 108, and the geometrically "folded" profile allows the shoulders 510 to expand as the balloon 108 is inflated, advantageously allowing the balloon 108 to expand more without bursting and to accommodate a range of vessels using less balloon material. The greater expansion provided by the longitudinal ribs 1202 can reduce wrinkling associated with other compliant (thicker walled) balloon embodiments.

[0097] The balloon shoulder 510 can have other features in addition to or instead of ribs that contribute to centering the transducer 214. In one embodiment, the balloon wall 502 is thicker at the shoulder 510 than at the balloon body 506. The thickness of the shoulder 510 can be uniform, e.g., the same balloon wall thickness between the attachment section 514 and the corner 508, or can be variable, e.g., the balloon wall thickness can be thicker or thinner from the attachment section 514 to the corner 508. The thicker shoulder 510 can be stiffer than the balloon body 506 and therefore less susceptible to deformation than the balloon body 506 when the balloon 108 is expanded in the target vessel 302. The thicker tapered section can therefore withstand lateral loads to keep the catheter shaft 212 and transducer 214 centered within the target vessel lumen. Additionally, the relatively thinner balloon body 506 can contribute to a more uniform energy delivery to the tissue surrounding the balloon. More specifically, the relatively thinner balloon body 506 can provide a relatively higher transmission of the ultrasonic energy emitted by the transducer, thus providing more uniform and effective energy delivery to the surrounding tissue.

[0098] The balloon 108 can be shaped in other ways to achieve the transducer centering function. For example, the balloon 108 can have an inverted cone shape that resists lateral deformation. The inverted cone shape includes a generally cylindrical balloon body 506 between a proximal corner 508B and a distal corner 508A. The shoulder 510 can converge axially inward from the corner 508 such that the attachment section 514 is at least partially radially located within the balloon body 506. For example, the distal attachment section 512A can have a proximal end that is proximal to the distal corner 508A. Similarly, the proximal attachment section 514B can have a distal end that is distal to the proximal corner 508B. As with the other reinforcing features described above, the inverted cone configuration allows the balloon 108 to inflate and deflate in a predictable manner without miscentering the transducer 214. The transducer 214 can thus provide a uniform injury circumferentially along the vessel wall 303.

[0099] It is contemplated that any of the above-described shoulder configurations can contribute to the balloon body 506 having a cylindrical shape when the balloon 108 is inflated within the target vessel 302. Maintaining a cylindrical balloon body shape can reduce the possibility of introducing inefficiencies into the system. More specifically, the cylindrical balloon body 506 can better propagate the waveform from the transducer 214 to the vessel wall 303 compared to a non-cylindrical balloon body. Thus, the balloon shape can center the transducer 214 and effectively transfer energy directed radially outward from the transducer 214.

[0100] 14A, a pictorial diagram of a tissue treatment system with a centering mechanism in a non-deployed state is shown, according to one embodiment. To treat a wider range of arterial sizes with only one device, the compliant balloon 108 can be used in combination with one or more centering mechanisms. At some expanded sizes, the compliant balloon 108 may not be able to provide sufficient centering force to properly and / or reliably center the transducer 214 within the body lumen. Thus, additional mechanical centering mechanisms can be used to supplement the inherent centering capabilities of the balloon 108.

[0101] The tissue treatment system 100 can include a distal centering mechanism 1402 mounted on the catheter shaft 212 distal to the balloon 108 and / or transducer 214, and a proximal centering mechanism 1404 mounted on the catheter shaft 212 proximal to the balloon 108 and / or transducer 214. The balloon 108 and / or transducer 214 can be axially between the centering mechanisms. The centering mechanism can be formed from a nickel-titanium alloy or another shape memory alloy and thus can be self-expanding. More specifically, the centering mechanism can be formed from a nickel-titanium alloy and can self-expand from a collapsed state (FIG. 14A) to an expanded state (FIG. 14B). In certain embodiments, the centering mechanism can include a flexible basket mounted on the catheter shaft 212. However, the centering mechanism can include other structures, such as a spiral spring, described below.

[0102] 14B, a pictorial diagram of a tissue treatment system with a centering mechanism in a deployed state is shown, according to one embodiment. The centering mechanism can be contained within a sleeve (not shown), for example a tubular sleeve that is deployed over the distal region 202 of the tissue treatment system 100 during delivery to the target anatomical structure. The sleeve can be retracted once the catheter 102 is properly positioned for ablation, exposing the centering mechanism and allowing the lateral dimensions of the centering mechanism's self-expanding structure to expand from a constrained state. As the sleeve is retracted, the structure expands to compress the arterial wall and center the transducer 214.

[0103] The centering mechanism works in cooperation with the balloon 108 to center the transducer 214 within the body lumen once the device is properly positioned for ablation, and can compress the arterial wall to center the transducer 214 before the compliant balloon 108 is inflated. Advantageously, the mechanical centering mechanism can be flexible, allowing the structure to be deployed into the target vessel 302 without predetermining the size of the vessel. More particularly, the structure can be flexible enough to be constrained by the vessel wall 303 once deployed into the target vessel 302.

[0104] In one embodiment, the centering mechanism can include a support such as a spiral spring. For example, the centering mechanism can include a spiral spring formed, for example, from a nickel titanium alloy, having a first end attached to the catheter shaft 212 and extending radially outwardly from the catheter shaft 212 in a helical manner around the catheter shaft 212 to a second end. As an illustrative example, the centering mechanism can be a conical or tapered spring that increases from a first diameter at an end connected to the catheter shaft 212 to a second, larger diameter at an end separated longitudinally from the first end.

[0105] In alternative embodiments, instead of or in addition to a flexible basket or spiral spring, the centering mechanism can include a balloon 108. The balloon centering mechanism can be stiffer than the compliant balloon 108 surrounding the transducer 214, e.g., not as compliant as the compliant balloon 108. More specifically, the durometer of the centering balloon can be higher than the durometer of the compliant balloon 108. The centering balloon can be compliant or semi-compliant. The centering balloon (and any of the supplemental centering mechanisms) can be mounted on the catheter shaft 212 distal and proximal to the transducer 214, and can be mounted outside of the ultrasonic treatment field generated by the transducer 214, such that the centering balloon does not interfere with the ultrasonic treatment.

[0106] In certain embodiments, the balloon 108 can be integrated with the transducer 214 such that the balloon 108 comprises a hollow piezoelectric material including an inner surface and an outer surface. The inner electrode 404 can be disposed on the inner surface and the outer electrode 406 can be disposed on the outer surface. Such embodiments can advantageously access smaller lumens, such as the adrenal arteries, ranging in diameter from about 2 mm to about 9 mm. In certain embodiments, a piezoelectric (PZT) membrane is attached to the inside of the balloon 108 or other inflatable member. The balloon 108 can comprise polyimide membrane, nylon, PEBAX®, Pellethane®, such as Pellethane® with a durometer of 80A, Isothane®, such as Isothane® with a durometer of 5095A, 7195A, or 5055D, and combination balloon materials, where the piezoelectric membrane can advantageously remain flexible. In certain embodiments, the PZT film is disposed only along a cylindrical portion of the balloon 108, such as along a portion of the balloon body 506. The PZT film coated length may be 3-7 mm in length, such as 5 mm, and may be surrounded by a memory fold ribbed shoulder 510 as described above. The burst pressure of the coated balloon 108 may be greater than 45 psi, and may range in size from 2.5 mm to 7 mm.

[0107] In certain embodiments, the guidewire lumen 213 may be located proximally relative to the catheter shaft 212 or may share a wall with the catheter shaft 212. More specifically, the tissue treatment system 100 may include a guidewire lumen 213 having a rapid exchange design to allow for rapid exchange of the catheter 102 during a procedure. Such an embodiment may increase the speed of the procedure, but displacement of the guidewire lumen 213 from the center of the catheter shaft 212 may cause the transducer 214 to be misaligned within the body lumen, resulting in non-uniform ablation. The centering mechanisms disclosed herein may assist with centering the transducer 214 in certain monorail embodiments. The monorail embodiment may or may not include a compliant balloon 108.

[0108] 15, a side view of a compliant balloon of a treatment system is shown, according to one embodiment. The balloon 108 can have an operating pressure range of 10-30 psi. At a nominal pressure of 10 psi, the balloon 108 can have a diameter of 4.0 mm. At an inflation pressure of 30 psi, the balloon 108 can have a diameter of 8.0 mm.

[0109] Notably, the balloon 108 can have material and construction (e.g., wall thickness, contour, etc.) characteristics such that the balloon body 506 of the balloon 108 can be substantially cylindrical at both 10 psi and 30 psi. More specifically, when measuring the outer diameter of the balloon 108, the diameter of the proximal end 1502, the midpoint 1504, and the distal end 1506 of the balloon body 506 can have the same diameter within a small tolerance. For example, the diameter of the balloon 108 at the proximal end, the midpoint, and the distal end along the balloon body 506 can be the same within a tolerance of 0.020 inches when inflated to 2 atm, 10 atm, or 30 atm. Thus, the balloon body 506 of the balloon 108 may be cylindrical at inflation pressures of both 10 psi and 30 psi. The property of having the balloon body 506 remain cylindrical at inflation pressure ranges above 20 atm contributes to effective centering of the transducer 214 and also provides good contact with the vessel wall 303 to ensure that ultrasonic energy is effectively transferred from the transducer 214 to the vessel wall 303.

[0110] In addition to the cylindrical balloon body 506 of the balloon 108, the balloon 108 can have well-defined contours that contribute to the effective centering and sonication properties described above. In one embodiment, the compliant balloon 108 includes a distal attachment section 1508 and a proximal attachment section 1510. These attachment sections can have a cylindrical contour over their length and can be attached onto the catheter shaft 212 of the catheter 102. For example, the attachment sections can be adhesively or thermally bonded to the catheter shaft 212. In one embodiment, the attachment sections are sized differently. For example, the inner diameter of the distal attachment section 512 can be less than the inner diameter of the proximal attachment section 514. The inner diameters can match the respective shafts of the catheter 102 on which the attachment sections are disposed.

[0111] The region of the balloon 108 in the axial direction between the balloon body 506 and the attachment section can be referred to as a shoulder. The balloon 108 can include several shoulders, such as a distal shoulder 1512 between the balloon body 506 and the distal attachment section 1508, and a proximal shoulder 1514 between the balloon body 506 and the proximal attachment section 1510. When the compliant balloon 108 is inflated to certain inflation pressures, such as 10 psi and / or 30 psi, the shoulders can have a rounded contour.

[0112] As discussed above, the rounded contour of the shoulder during balloon expansion can contribute to effective centering of the balloon 108 within the body lumen. The rounded contour can be defined by the length and height of the shoulder. For example, the distal shoulder 1512 can have a shoulder length 1520 and a shoulder width 1522. The shoulder length can be the longitudinal distance from the distal end of the balloon body to the proximal end of the distal attachment section. The shoulder width can be the radial distance between the exterior surface of the distal attachment section 1508 and a radial portion of the balloon body 506. In one embodiment, the shoulder length can be greater than the shoulder width. For example, the shoulder length can be in the range of 0.150-0.200 inches and the shoulder width can be in the range of 0.025-0.075 inches. A greater ratio of the shoulder length to the shoulder width can contribute to effective centering of the transducer 214 within the body lumen. In one embodiment, the ratio may be 3 or greater, ie, the shoulder length divided by the shoulder width is at least 3.

[0113] In addition to the overall balloon 108 profile, the balloon wall thickness is also a contributing factor to transducer centering. A compliant balloon 108 can have a balloon wall thickness that meets several criteria. The thickness can be thick enough to make the balloon wall stiff enough to support the transducer 214 within the body lumen. The wall thickness can be thick enough to ensure that a target inflation pressure of 30 psi can be safely and reliably achieved in vivo. Also, the wall thickness can be thin enough to ensure that the wall material through which the ultrasonic energy passes to travel from the transducer 214 to the target ablation region does not unduly impede the passage of that ultrasonic energy. In one embodiment, these criteria are met by a balloon wall 502 having a dual wall thickness in the range of 0.005-0.05 mm (0.0002-0.002 inches). More specifically, it is contemplated that the dual wall thickness can range from 0.01 to 0.036 mm (0.0004 to 0.0014 inches) to effectively center the transducer 214 and still be thin enough to transmit greater than 98% of the acoustic energy emitted by the transducer 214 to the vessel wall 303.

[0114] The double wall thickness can be measured by squeezing opposing balloon wall portions of the balloon 108 together and measuring the thickness of the combined balloon wall portions. It is contemplated that a balloon 108 having the characteristics described above can have a nominal double wall thickness of 0.02 mm (0.0009 inches). Such a thickness can transmit approximately 99% of the emitted acoustic energy to the vessel wall 303.

[0115] It should be noted that the power loss caused by acoustic attenuation by the balloon wall 502 is linearly related to the wall thickness. The balloon material may have an acoustic attenuation of 2 dB / MHz / CM to 3 dB / MHz / CM. For example, the balloon material may have an acoustic attenuation of 2.5 dB / MHz / CM, and assuming a 9.0 MHz acoustic energy source, a balloon wall thickness of 0.01 mm (0.0004 inches) would provide an attenuation of 0.0229 dB (translating as 99.47% acoustic energy transmission), while a balloon wall thickness of 0.036 mm (0.0014 inches) would provide an attenuation of 0.08 dB (translating as 98.17% acoustic energy transmission). Thus, if the wall thickness is increased, the power loss can be compensated for by increasing the power output by the acoustic energy source. However, a bi-wall thickness of 0.01 mm to 0.036 mm (0.0004 inches to 0.0014 inches) provides excellent transmission which reduces the energy output requirements of the generator, provides good balloon flexibility, and allows for proper centering of the transducer 214 within the body lumen as described above. Thus, the balloon wall thickness range is not limiting, but these ranges have been found to be effective in achieving desired performance results.

[0116] Additionally, a balloon 108 having the characteristics described above can benefit from fewer foreign particles or bubbles within the balloon wall 502. Furthermore, the size of any such foreign particles or bubbles can be limited to ensure that voids or other weaknesses in the balloon wall 502 do not result in the balloon failing during use. In one embodiment, a compliant balloon 108 has a diameter of 0.2 mm or less. 2 It may be free of larger foreign particles or air bubbles, and thus the balloon 108 may be adapted to mechanically support the transducer 214 within the body lumen, and by being so robust, the likelihood of failure is reduced.

[0117] In addition to the mechanical properties of the balloon 108, material processing of the raw material into the balloon 108 may also be an important consideration to achieve the balloon properties described above. The balloon formation process may include extruding the balloon raw material, e.g., Isothane® particles, into a single lumen tubing. The single lumen tubing may then be blown into a balloon mold to form the balloon 108 having the dimensional and mechanical properties described above. It has been found that the draw ratio used while extruding the single lumen tubing contributes to the formation of the balloon 108 and, in combination with the dimensional properties described above, can produce a compliant balloon having sufficient stiffness, flexibility, and robustness to reliably center the transducer 214 within the body lumen during ultrasonic processing. The draw ratio is the ratio between the inner diameter of the single lumen tubing and the inner diameter of the tool used during extrusion. Typically, the draw ratio used in balloon manufacturing is 2:1. In one embodiment, the draw ratio used while processing the balloon 108 described above ranges from 1.1:1 to 1.25:1. This lower draw ratio, while not typical when compared to conventional balloon forming processes, has been found to provide the advantageous balloon properties discussed above.

[0118] Examples of compliant balloons suitable for use with catheters configured to treat a wide range of body lumen diameters are described above. For example, the embodiments of FIGS. 5-6 and 15 described above have characteristics suitable for such catheters 102. It will be appreciated that these characteristics may be combined in alternative embodiments. For example, the embodiment described below in connection with FIGS. 16-20 may include the characteristics of the compliant balloon 108 described above. The following description is therefore intended to add to, and not necessarily replace, any of the above descriptions. Furthermore, the embodiments of FIGS. 5-6 and 15 are not limiting and other balloon designs having similar characteristics may be provided. For example, the particular compliant balloon embodiment described below in connection with FIGS. 21-23 may include different features, e.g., square shoulders instead of rounded shoulders, and still exhibit the advantages described in connection with the embodiment of FIGS. 5-6 and 15. This description is therefore intended to be read as enabling, and not as limiting.

[0119] 16, a profile view of a compliant balloon of a treatment system is shown, according to one embodiment. As described above, the treatment system includes a compliant balloon 108 mounted over a catheter shaft 212. The compliant balloon 108 includes an interior 504 that is in fluid communication with the fluid passageway 420 of the catheter shaft 212. Additionally, the compliant balloon 108 contains an ultrasound transducer 214 within the interior 504.

[0120] It will be appreciated that the contour diagram illustrates the balloon 108 at two inflated diameters. More specifically, a first contour 1602 represents the balloon 108 as it expands such that the balloon body 506 has a first diameter 1604. Similarly, a second contour 1606 represents the balloon 108 as it expands such that the balloon body 506 has a second diameter 1608. Thus, FIG. 16 illustrates the change in balloon contour as the balloon 108 expands from a smaller diameter to a larger diameter. As explained above, the balloon 108 may be compliant and therefore may grow substantially during expansion.

[0121] By way of non-limiting example, the first diameter 1604 of the balloon body 506 may be in the range of 3.5-6 mm. For example, the first diameter 1604 may be 5 mm. Also by way of example, the second diameter 1608 of the balloon body 506 may be in the range of 8-9 mm. For example, the second diameter 1608 may be 8.5 mm. Thus, the second diameter 1608 of the balloon 108 may be at least 2 mm larger than the first diameter 1604 of the balloon 108. Due to balloon compliance, such substantial growth may occur even in response to a relatively small change in pressure. For example, the first contour 1602 can represent the balloon 108 inflated to a first inflation pressure between 2 and 10 psi, e.g., 2 psi, and the second contour 1606 can represent the balloon 108 inflated to a second inflation pressure between 10 and 30 psi, e.g., 12 psi. The 2 psi inflation pressure can be a specific balloon pressure, meaning an inflation pressure at which the balloon 108 will expand to its original contour without stretching. The specific balloon pressure can be a pressure at which the balloon 108 will expand to its original contour without plastic deformation. Inflating the balloon 108 beyond the specific inflation pressure, e.g., beyond 2 psi, can cause the balloon 108 to stretch and expand to a contour that is larger than the original contour. It will be appreciated that a 2 mm growth in diameter for a 10 psi pressure change is characteristic of a compliant balloon, and not a semi-compliant or non-compliant balloon.

[0122] For conventional compliant balloons, when the balloon is inflated, the balloon profile typically assumes a spherical shape. A spherical shape would still result in a substantially round, i.e., curved, balloon body. In contrast, the compliant balloon 108 described herein has a balloon body 506 and / or a working section 1600 of the balloon body 506 that maintains a predetermined straightness, as described below. Maintaining a predetermined straightness for diameter growth of 2 mm or more has the technical effect of allowing compliant expansion of the balloon for a range of vessel diameters while also maintaining a uniform shape. More specifically, the compliant balloon can have an essentially cylindrical shape at both smaller diameters and at relatively larger diameters that differ from the smaller diameter by 2 mm or more. The essentially cylindrical shape can support and center the transducer in vessels of varying sizes to provide uniform energy delivery in anatomical structures of different sizes.

[0123] The balloon body 506 can have a working section 1600 disposed between the balloon shoulders. The working section 1600 of the balloon wall 502 can be defined relative to the ultrasonic transducer 214. More specifically, the working section 1600 can include a portion of the balloon wall 502 that radially surrounds the ultrasonic transducer 214. In one embodiment, the working section 1600 extends between a distal plane 1610 that extends transversely to a central axis of the transducer 214 and a proximal plane 1612 that also extends transversely to the central axis. The distal plane 1610 and the proximal plane 1612 can be parallel to one another. These planes can intersect the balloon contour to define the working section 1600 as the portion of the balloon contour or balloon body 506 that is longitudinal between the distal plane 1610 and the proximal plane 1612.

[0124] It will be appreciated that the operating section 1600 may be a variable portion of the balloon wall 502 once it is defined relative to the transducer 214. More specifically, the portion of the balloon wall 502 that radially surrounds the ultrasonic transducer 214 at the first diameter 1604 may be different than the portion of the balloon wall 502 that radially surrounds the ultrasonic transducer 214 at the second diameter 1608. Nonetheless, the operating section 1600 may have a predetermined linearity once the operating section 1600 has both the first diameter 1604 and the second diameter 1608.

[0125] The predetermined straightness can be defined in a number of ways. The compliant balloon 108 can have a substantially cylindrical working section 1600 at both the first diameter 1604 and the second diameter 1608, similar to the balloon body 506 shown in and described in connection with FIG. 15. However, the idealized cylindrical balloon body 506 of FIG. 15 may be an approximation of an actual balloon working section. More specifically, the working section 1600 can have some curvature and still be substantially cylindrical. The substantial cylindrical nature of the working section 1600 can be compared favorably to the spherical shape of a typical inflated compliant balloon.

[0126] In one embodiment, the predetermined straightness of the working section 1600 includes cylindricity of the working section 1600 below a predetermined threshold. Cylindricity may be defined as the difference between the maximum and minimum diameters of the working section 1600 over the length of the working section 1600. For example, with reference to the first contour 1602, the first diameter 1604 may be measured at a location approximately halfway between the distal plane 1610 and the proximal plane 1612. The inflated balloon 108 may have a slight outward curvature along the working section 1600, and thus the first diameter 1604 may be larger than the diameter of the working section 1600 at either the distal plane 1610 or the proximal plane 1612. More specifically, the first minimum diameter 1614 of the working section 1600 when the balloon 108 has the first contour 1602 may be less than the first diameter 1604. The cylindricity of the working section 1600 when the balloon 108 has the first contour 1602 can be determined by subtracting the first minimum diameter 1614 from the first diameter 1604. In one embodiment, the cylindricity is less than a predetermined threshold. For example, the cylindricity may be less than 1 mm, meaning that the difference between the first diameter 1604 and the first minimum diameter 1614 is 1 mm or less. As a practical example, experimental data generated shows that when the compliant balloon 108 is inflated to a pressure of 10 psi, the maximum diameter deviation across the working section 1600 is approximately 0.5 mm. That is, the cylindricity is approximately 0.5 mm, which is less than 1 mm.

[0127] The cylindricity of the working section 1600 when the balloon wall 502 has the second contour 1606 may also be less than a predetermined threshold. For example, the difference between the second diameter 1608 measured halfway between the distal plane 1610 and the proximal plane 1612 and the second minimum diameter measured at the distal plane 1610 may be less than 1 mm. As a practical example, experimental data generated indicates that when the compliant balloon 108 is inflated to a pressure of 30 psi, the maximum diameter deviation across the working section 1600 is approximately 0.75 mm. That is, the cylindricity is approximately 0.75 mm, which is less than 1 mm.

[0128] It will be appreciated that the 1 mm cylindricity threshold is provided by way of example. As explained above, compliant balloons 108 having a substantially cylindrical working section 506 can have a cylindricity of less than 0.75 mm, less than 0.5 mm, etc., over their normal inflation range. Thus, the 1 mm cylindricity threshold is not limiting. The predetermined threshold of cylindricity may be between 0.25 mm and 1 mm. Nevertheless, it is understood that such cylindricity is relatively linear when compared to a typical compliant balloon that expands to a spherical shape. The cylindricity contributes to effective support of the transducer 214 such that the ultrasonic transducer 214 is radially centered within the compliant balloon 108 as the compliant balloon 108 expands to the second inflation pressure. Additional methods of defining the predetermined linearity are described below.

[0129] Referring to FIG. 17, a contour diagram of a compliant balloon of a treatment system is shown, according to one embodiment. The contours shown may be characteristic of a compliant balloon 108 inflated in free space (unconstrained, outside of a body vessel) at several inflation pressures. Additionally, the contours may be characteristic of a compliant balloon 108 formed from Pellethane® and sized and shaped for use in the hybrid approach described above. A first contour 1602 is the contour that may be imposed by the balloon wall 502 when the balloon 108 is inflated to an inflation pressure of 2 psi. A second contour 1606 is the contour that may be imposed by the balloon wall 502 when the balloon 108 is inflated to an inflation pressure of 20 psi.

[0130] In one embodiment, the predetermined straightness of the working section 1600 may include a ratio of a measurement of the working section 1600 to a measurement of the entire balloon 108. For example, a ratio of a radius of curvature 1702 of the working section 1600 to a length 1704 of the compliant balloon 108 may be greater than a predetermined threshold. The curvature of the working section 1600 may be defined by a radius of curvature 1702. The radius of curvature 1702 may be a distance from an imaginary point to the balloon wall 502, where the imaginary point is placed such that each point along the working section 1600 is an equal distance from the imaginary point. The length 1704 of the compliant balloon 108 may be measured from a proximal location where the balloon wall 502 meets the catheter shaft 212 to a distal location where the balloon wall 502 meets the catheter shaft 212. In an illustrative example, the predetermined threshold may be 1.0. Thus, the radius of curvature 1702 of the working section 1600 may be greater than the length 1704 of the compliant balloon 108. However, such predetermined thresholds are provided by way of example only, and other predetermined thresholds that also represent substantial straightness of the compliant balloon 108 may be used.

[0131] It will be appreciated that as the balloon 108 expands, the radius of curvature 1702 may become smaller. More specifically, as the balloon 108 expands, the curvature of the working section 1600 may become slightly more pronounced, thus resulting in a smaller radius of curvature 1702. Nevertheless, as the balloon 108 expands to the second contour 1606, the ratio of the radius of curvature 1702 to the length 1704 of the compliant balloon 108 may be less than a predetermined threshold. For example, the ratio of the radius of curvature 1702 of the balloon working section 1600 to the length 1704 of the balloon may be greater than 1.0 when the balloon has the second contour 1606. It will be appreciated that the radius of curvature shown in FIG. 17 is not greater than the length 1704 of the balloon 108. This is precisely because the actual radius of curvature 1702 may not even fit on the drawing sheet if the working section 1600 were extremely straight. Thus, the radii shown are provided merely for visualization purposes and are not intended to be limiting.

[0132] Referring now to FIG. 18, a diagram of balloon pressure curves for a compliant balloon being continuously inflated in free space is shown, according to one embodiment. The compliance curves represent the inflated diameter 704 of the balloon 108 described in connection with FIG. 17 at various inflation pressures over several runs. More specifically, each run has its own compliance curve that changes as the balloon 108 is inflated and deflated several times. For example, the compliance curve for the first run 1802 has an initial inflated diameter of 7.0 mm at an inflation pressure of 10 psi, then gradually increases in diameter to 8.3 mm at an inflation pressure of 20 psi.

[0133] The compliance curve for the second run 1804 is shifted upward relative to the first run 1802. For example, the compliance curve for the second run 1804 has an initial inflated diameter of 7.4 mm at an inflation pressure of 10 psi, then increases in diameter to 8.5 mm at an inflation pressure of 20 psi. Similarly, the compliance curve for the fifth run 1806 is shifted upward relative to the second run 1804. For example, the compliance curve for the fifth run 1806 has an initial inflated diameter of 7.5 mm at an inflation pressure of 10 psi, then increases in diameter to 8.6 mm at an inflation pressure of 20 psi.

[0134] The compliance curves for the third and fourth runs of compliant balloon 108 have been omitted to avoid clutter, but it will be appreciated that these compliance curves fit between second run 1804 and fifth run 1806. More specifically, the difference in diameter at the respective inflation pressures for the third and fourth runs is between the diameters at those inflation pressures for second run 1804 and fifth run 1806.

[0135] In one embodiment, when the compliant balloon 108 is inflated five times to an inflation pressure, the diameter of the working section 1600 after the fourth inflation is within 10% of the diameter of the working section 1600 after the fifth inflation. With continued reference to FIG. 18, such a characteristic is supported by a comparison between the second run 1804 compliance curve and the fifth run 1806 compliance curve. More specifically, at an inflation pressure of 10 psi, the difference in diameter of the working section 1600 between the second run 1804 and the fifth run 1806 is 0.1 mm, which is approximately 1% of the working section diameter during the fifth run 1806. Similarly, at an inflation pressure of 20 psi, the difference in diameter of the working section 1600 between the second run 1804 and the fifth run 1806 is 0.1 mm, which is approximately 1% of the working section diameter during the fifth run 1806. Thus, the diameter of the working section 1600 over successive runs is tightly controlled so that the balloon 108 exerts similar pressure on the vessel wall 303 during each successive inflation.

[0136] Referring to FIG. 19, a contour diagram of a compliant balloon of a treatment system is shown, according to one embodiment. The contours shown may be characteristic of a compliant balloon 108 inflated in free space (unconstrained, outside of a body vessel) at several inflation pressures. Additionally, the contours may be characteristic of a compliant balloon 108 formed from Isothane® and sized and shaped for use in the hybrid approach described above. A first contour 1602 is the contour that may be imposed by the balloon wall 502 when the balloon 108 is inflated to an inflation pressure of 2 psi. A second contour 1606 is the contour that may be imposed by the balloon wall 502 when the balloon 108 is inflated to an inflation pressure of 20 psi.

[0137] In one embodiment, the predetermined linearity of the working section 1600 can include a difference in measurements of the working section 1600 when measured at each of the inflation states. For example, the difference in the first radius of curvature 1902 of the working section 1600 when the working section has a first diameter of the first contour 1602 can be within a predetermined percentage difference of the second radius of curvature 1904 of the working section 1600 when the working section has a second diameter of the second contour 1606. As explained above, the radius of curvature can be the distance from a virtual point to the balloon wall 502, where the virtual point is placed such that the distance from the virtual point to each of the points along the working section 1600 is equal. It can also be the distance from a virtual point to the balloon wall 502, where the virtual point is placed such that the distance from the virtual point to each of the points along the working section 1600 is equal. Illustratively, the predetermined percentage difference can be 30% or less, such as 20%. Thus, in one embodiment, the first radius of curvature 1902 is within 20% of the second radius of curvature 1904. However, such predetermined threshold is provided by way of example only, and other predetermined thresholds that also represent substantial straightness of the compliant balloon 108 may be used.

[0138] It will be appreciated that as the balloon 108 expands, the radius of curvature 1702 may decrease. More specifically, as the balloon 108 expands, the curvature of the working section 1600 may become slightly more pronounced, thus resulting in a smaller radius of curvature 1702. Nevertheless, as the balloon 108 expands to the second contour 1606, the difference in the radius of curvature may be less than a predetermined threshold. For example, the percentage difference in the radius of curvature when the balloon 108 has the first contour 1602 may be less than 20% compared to when the balloon 108 has the second contour 1606. It will be appreciated that the radii of curvature shown in FIG. 19 are provided merely for visualization purposes and are not intended to be limiting.

[0139] Referring to FIG. 20, there is shown a diagram of balloon pressure curves for a compliant balloon being continuously inflated in free space. The compliance curves represent the inflated diameter 704 of the balloon 108 described in connection with FIG. 19 at various inflation pressures over several runs. More specifically, each run has its own compliance curve that changes as the balloon 108 is inflated and deflated several times. For example, the compliance curve for the first run 1802 has an initial inflated diameter of 3.5 mm at an inflation pressure of 10 psi, then gradually increases in diameter to 7.5 mm at an inflation pressure of 30 psi.

[0140] The compliance curve for the second run 1804 is shifted upward relative to the first run 1802. For example, the compliance curve for the second run 1804 has an initial inflated diameter of 4.5 mm at an inflation pressure of 10 psi, then gradually increases in diameter to 8.0 mm at an inflation pressure of 30 psi. Similarly, the compliance curve for the fifth run 1806 is shifted upward relative to the second run 1804. For example, the compliance curve for the fifth run 1806 has an initial inflated diameter of 5.3 mm at an inflation pressure of 10 psi, then gradually increases in diameter to 8.3 mm at an inflation pressure of 30 psi.

[0141] The compliance curves for the third and fourth runs of compliant balloon 108 have been omitted to avoid clutter, but it will be appreciated that these compliance curves fit between second run 1804 and fifth run 1806. More specifically, the difference in diameter at the respective inflation pressures for the third and fourth runs is between the diameters at those inflation pressures for second run 1804 and fifth run 1806.

[0142] In one embodiment, when the compliant balloon 108 is inflated five times to a certain inflation pressure, the diameter of the working section 1600 during the fourth inflation is within 20% of the diameter of the working section 1600 during the fifth inflation. With continued reference to FIG. 20, such a characteristic is supported by a comparison between the compliance curves of the second run 1804 and the fifth run 1806. More specifically, at an inflation pressure of 10 psi, the difference in diameter of the working section 1600 between the second run 1804 and the fifth run 1806 is 0.8 mm, which is approximately 15% of the working section diameter during the fifth run 1806. Similarly, at an inflation pressure of 30 psi, the difference in diameter of the working section 1600 between the second run 1804 and the fifth run 1806 is 0.3 mm, which is approximately 4% of the working section diameter during the fifth run 1806. Thus, the diameter of the working section 1600 over successive runs is tightly controlled, and therefore the balloon 108 will apply similar pressure to the vessel wall 303 during each successive inflation.

[0143] Notably, the compliance curve of the first run 1802 has an upwardly concave shape. More specifically, during the first run 1802, the balloon diameter increases at a smaller rate between the inflation pressures of 10-20 psi than between the inflation pressures of 20-30 psi. Meanwhile, the compliance curve profiles of the second run 1804 and the fifth run 1806 have a downwardly concave shape. The difference in the profile shape of the first run 1802 may be due to the balloon design. The compliant balloon 108 described in connection with FIG. 19 may be formed with a more rounded shoulder as compared to the shoulder of the compliant balloon 108 described in connection with FIG. 17. Thus, it will be appreciated that the balloon design may be manipulated to adjust the rate at which the balloon diameter increases over successive runs.

[0144] With reference to both FIG. 17 and FIG. 20, it will be appreciated that the compliance curve of the first run 1802 may be substantially different than the compliance curves of the second and larger runs. In particular, the initial inflated diameter at an inflation pressure of 10 psi may be substantially different between the first run and subsequent runs. Such differences may be due to time-dependent polymer chain relaxation of the balloon material that occurs after the balloon 108 is inflated once. The relaxation may result in a larger initial inflated diameter after the first run 1802 is completed. However, the relaxation of the balloon material reaches a plateau after the first run 1802, and the initial inflated diameter 704 between the second and subsequent runs may be similar. It is contemplated that this balloon characteristic may be utilized to ensure that successive inflations of the balloon 108 within the target lumen are similar. For example, the balloon 108 may be inflated several times outside the patient to allow the balloon material to relax. The balloon 108 can then be deployed into the target vessel 302 as described above and inflated one or more times to a tightly controlled diameter corresponding to the compliance curve of the second and larger runs.

[0145] The tight control of the inflated diameter over successive runs can be expressed in ways other than the percentage difference in the working section diameter. In one embodiment, the run-to-run stability of the balloon 108 can be expressed in terms of the standard deviation of the maximum diameter of the working section 106. For example, if the same balloon is inflated over a range of inflation pressures from 10 to 30 psi during the third to fifth runs, the standard deviation of the maximum diameter of the working section 106 may be less than 0.2 mm. The maximum diameter may be measured at the longitudinal midpoint of the balloon. Thus, if the balloon is inflated five times to an inflation pressure of 20 psi, the standard deviation of the maximum diameter of the balloon measured during the third, fourth, and fifth runs may be less than 0.2 mm.

[0146] A generalized description of balloon 108 is provided above, and it will be appreciated that the concepts contained in that generalized description can be applied to develop a compliant balloon having the advantageous properties described. Some of the dimensions of the balloon shown in FIGS. 21-23 may be exactly the same as those described above. For example, the balloon double wall thickness may be 0.02 mm (0.0009 inches). However, other dimensions may vary. Accordingly, to further describe balloon 108, several specific examples of balloons and their respective dimensions are provided below.

[0147] Referring to FIG. 21, a side view of a compliant balloon according to one embodiment is shown. The balloon 108 can be used in the arterial restriction procedure described above. The balloon 108 can be formed from materials described above. The balloon 108 can include portions corresponding to those described above, for example, in connection with FIG. 5. More specifically, these portions of the balloon can include an attachment section, shoulders, corners, and a balloon body, each having a respective length and characterized by a respective diameter at a given inflation pressure. The balloon 108 is shown in FIG. 21 at a nominal (intrinsic) inflation pressure of 202.65 kPa (2 ATM). Each of these balloon portions and their respective dimensions are described in more detail below.

[0148] The distal mounting section 512A can have a distal mounting section length 2102 and a distal mounting section diameter 2104. The distal mounting section length 2102 can be between 0.155 and 0.160 inches, such as 0.157 inches. The distal mounting section diameter 2104 can be between 0.050 and 0.055 inches, such as 0.052 inches.

[0149] The proximal mounting section 512B can have a proximal mounting section length 2106 and a proximal mounting section diameter 2108. The proximal mounting section length 2106 can be between 0.155 and 0.160 inches, for example, 0.157 inches. The proximal mounting section diameter 2108 can be between 0.060 and 0.070 inches, for example, 0.064 inches.

[0150] The distal shoulder 510A and the proximal shoulder 510B can have respective shoulder lengths 2110 and 2112. For example, the shoulder length can be 0.150 to 0.200 inches, such as 0.170 inches. One or more of the distal shoulder 510A and the proximal shoulder 510B can transition to the working length 506 at respective corners 508A, 508B. It will be appreciated that the corners may be angled instead of rounded. The angled shoulders may be evident at the specific inflation pressure. Upon inflation above the specific inflation pressure, the angled corners may become slightly rounded. The angled corners at the specific diameter balloon can provide effective support and centering of the transducer 214 within the target vessel.

[0151] The balloon body 506 can have a balloon body length 2114 and a balloon body diameter 2116. The balloon body length 2114 can be between 0.245 and 0.255 inches, such as 0.250 inches. The balloon body diameter 2116 can be between 7.5 and 8.5 mm, such as 8.0 mm. The total length 2120 of the balloon 108 can be measured between the proximal attachment section and the distal attachment section. The total length 2120 can include the length of the balloon body 506 and the shoulders 510A, 510B. In one embodiment, the total length 2120 is between 0.550 and 0.650 inches, such as 0.590 inches.

[0152] Referring to FIG. 22, a side view of a compliant balloon according to one embodiment is shown. The balloon 108 can be used with the hybrid inflation technique described above. The balloon 108 can be formed from materials described above. The balloon 108 can include portions corresponding to those described above, for example, in connection with FIG. 5. More specifically, these portions of the balloon can include an attachment section, shoulders, corners, and a balloon body, each having a respective length and characterized by a respective diameter at a given inflation pressure. The balloon 108 is shown in FIG. 22 at a nominal (intrinsic) inflation pressure of 202.65 kPa (2 ATM). Each of these balloon portions and their respective dimensions are described in more detail below.

[0153] The distal mounting section 512A can have a distal mounting section length 2102 and a distal mounting section diameter 2104. The distal mounting section length 2102 can be between 0.155 and 0.160 inches, such as 0.157 inches. The distal mounting section diameter 2104 can be between 0.050 and 0.055 inches, such as 0.052 inches.

[0154] The proximal mounting section 512B can have a proximal mounting section length 2106 and a proximal mounting section diameter 2108. The proximal mounting section length 2106 can be between 0.155 and 0.160 inches, for example, 0.157 inches. The proximal mounting section diameter 2108 can be between 0.060 and 0.070 inches, for example, 0.064 inches.

[0155] The distal shoulder 510A and the proximal shoulder 510B can have respective shoulder lengths 2110 and 2112. For example, the shoulder length can be 0.150 to 0.200 inches, such as 0.170 inches. One or more of the distal shoulder 510A and the proximal shoulder 510B can transition to the working length 506 at respective corners 508A, 508B. It will be appreciated that the corners may be angled instead of rounded. The angled shoulders may be evident at the specific inflation pressure. Upon inflation above the specific inflation pressure, the angled corners may become slightly rounded. The angled corners at the specific diameter balloon can provide effective support and centering of the transducer 214 within the target vessel.

[0156] The balloon body 506 can have a balloon body length 2114 and a balloon body diameter 2116. The balloon body length 2114 can be between 0.245 and 0.255 inches, such as 0.250 inches. The balloon body diameter 2116 can be between 5.5 and 6.5 mm, such as 6.0 mm. The total length 2120 of the balloon 108 can be measured between the proximal attachment section and the distal attachment section. The total length 2120 can include the length of the balloon body 506 and the shoulders 510A, 510B. In an embodiment, the total length 2120 is between 0.550 and 0.650 inches, such as 0.590 inches.

[0157] Referring to FIG. 23, a side view of a compliant balloon according to one embodiment is shown. The balloon 108 can be used with the hybrid inflation technique described above. The balloon 108 can be formed from materials described above, such as Isothane® having a Shore D durometer of 55. The balloon 108 can include portions corresponding to those described above, for example, in connection with FIG. 5. More specifically, these portions of the balloon can include an attachment section, shoulders, corners, and a balloon body, which have respective lengths and are characterized by respective diameters at a given inflation pressure. The balloon 108 is shown in FIG. 22 at a nominal (intrinsic) inflation pressure of 202.65 kPa (2 ATM). Each of these balloon portions and their respective dimensions are described in more detail below.

[0158] The distal mounting section 512A can have a distal mounting section length 2102 and a distal mounting section diameter 2104. The distal mounting section length 2102 can be at least 0.0157 inches. The distal mounting section diameter 2104 can be between 0.050 and 0.055 inches, for example 0.052 inches.

[0159] The proximal mounting section 512B can have a proximal mounting section length 2106 and a proximal mounting section diameter 2108. The proximal mounting section length 2106 can be at least 0.157 inches. The proximal mounting section diameter 2108 can be between 0.060 and 0.070 inches, for example, 0.062 inches.

[0160] The distal shoulder 510A and the proximal shoulder 510B can have respective shoulder lengths 2110 and 2112. For example, the shoulder length can be 0.075 to 0.110 inches, such as 0.098 inches. One or more of the distal shoulder 510A and the proximal shoulder 510B can transition to the working length 506 at respective corners 508A, 508B. It will be appreciated that the corners may be angled instead of rounded. The angled shoulders may be evident at the specific inflation pressure. Upon inflation above the specific inflation pressure, the angled corners may become slightly rounded. The angled corners at the specific diameter balloon can provide effective support and centering of the transducer 214 within the target vessel.

[0161] The balloon body 506 can have a balloon body length 2114 and a balloon body diameter 2116. The balloon body length 2114 can be 0.250 to 0.300 inches, such as 0.276 inches. The balloon body diameter 2116 can be 4.25 to 4.75 mm, such as 4.5 mm, at a specific inflation pressure. At an inflation pressure of 30 psi, the balloon body diameter 2116 can be 8 mm. The total length 2120 of the balloon 108 can be measured between the proximal attachment section and the distal attachment section. The total length 2120 can include the length of the balloon body 506 and the shoulders 510A, 510B. In one embodiment, the total length 2120 is between 0.425 and 0.525 inches, for example 0.472 inches.

[0162] The balloon 108 can include a cone angle 2302 that corresponds to an angle that one or more of the shoulders have with respect to a central axis of the balloon. The cone angle 2302 can be a total angle, for example, an angle measured between opposite sides of the shoulders. In one embodiment, the cone angle 2302 can be between 55° and 70°. For example, the cone angle 2302 can be 60° or 65°. The cone angle 2302 of the distal shoulder 510A can be different than the cone angle 2302 of the proximal shoulder 510B. For example, the distal shoulder 510A can have a cone angle 2302 of 65° and the proximal shoulder 510B can have a cone angle 2302 of 60°.

[0163] Embodiments of tissue treatment systems have been described above. More particularly, embodiments of tissue treatment systems have been described either explicitly or implicitly. The following paragraphs summarize some of the embodiments described.

[0164] In one embodiment, the catheter includes a catheter shaft having a fluid passageway. The catheter includes an ultrasound transducer. The catheter includes a compliant balloon mounted on the catheter shaft, in fluid communication with the fluid passageway, and having an interior containing the ultrasound transducer. The compliant balloon includes a balloon wall having a working section radially surrounding the ultrasound transducer. The working section has a predetermined straightness when the working section has a first diameter and when the working section has a second diameter at least 2 mm greater than the first diameter.

[0165] In one embodiment, the first diameter is in the range of 3.5 to 6 mm, and the second diameter is in the range of 8 to 9 mm.

[0166] In one embodiment, the first diameter is 5 mm and the second diameter is 8.5 mm.

[0167] In one embodiment, the predetermined straightness comprises a cylindricity of the working section that is less than 1 mm.

[0168] In one embodiment, the predetermined straightness comprises a ratio of the radius of curvature of the working section to the length of the compliant balloon that is greater than one.

[0169] In one embodiment, the predetermined straightness includes a first radius of curvature of the working section when the working section has a first diameter that is within 20% of a second radius of curvature of the working section when the working section has the second diameter.

[0170] In one embodiment, the compliant balloon has a first inflation pressure of between 2 psi and 10 psi when the working section has a first diameter and a second inflation pressure of 30 psi when the working section has a second diameter.

[0171] In one embodiment, when the compliant balloon is inflated five times to the second inflation pressure, the fourth diameter of the working section during the fourth inflation is within 10% of the fifth diameter of the working section during the fifth inflation.

[0172] In one embodiment, the ultrasound transducer is radially centered within the compliant balloon when the compliant balloon has a second inflation pressure.

[0173] In one embodiment, fluid is circulated through the interior at a rate of 15-35 mL / min to inflate the compliant balloon to a first inflation pressure, and fluid is circulated through the interior at a rate of 35-50 mL / min to inflate the compliant balloon to a second inflation pressure.

[0174] In one embodiment, the balloon wall includes a proximal shoulder proximal to the working section and a distal shoulder distal to the working section, The proximal and distal shoulders are rounded in shape.

[0175] In one embodiment, the proximal and distal shoulders include a number of longitudinal ribs.

[0176] In one embodiment, the balloon wall is thicker at the proximal and distal shoulders than at the working section.

[0177] In one embodiment, the compliant balloon is formed from an elastomeric material.

[0178] In one embodiment, the elastomeric material includes a polyether-based thermoplastic polyurethane.

[0179] In one embodiment, the polyether-based thermoplastic polyurethane has a Shore D durometer in the range of 50-60.

[0180] In one embodiment, the polyether-based thermoplastic polyurethane has a Shore D durometer of 55.

[0181] In one embodiment, the balloon wall is 0.2 mm 2 It is free of larger foreign particles or air bubbles.

[0182] In one embodiment, the working section of the balloon wall has a double wall thickness of 0.01 to 0.04 mm (0.0004 to 0.0014 inches).

[0183] In one embodiment, the catheter further comprises a distal centering mechanism mounted on the catheter shaft distal to the compliant balloon, and a proximal centering mechanism mounted on the catheter shaft proximal to the compliant balloon.

[0184] In one embodiment, the compliant balloon is configured to treat a blood vessel having a vessel lumen diameter between 3 mm and 9 mm in diameter.

[0185] In one embodiment, the blood vessel is a renal artery.

[0186] In one embodiment, a method includes advancing a catheter of a tissue treatment system into a target vessel having a vessel wall. The catheter includes a catheter shaft having a fluid passageway, an ultrasound transducer, and a compliant balloon mounted on the catheter shaft, in fluid communication with the fluid passageway, and having an interior containing the ultrasound transducer. The compliant balloon includes a balloon wall having a working section radially surrounding the ultrasound transducer. The working section has a predetermined linearity when the working section has a first diameter and when the working section has a second diameter at least 2 mm greater than the first diameter. The method includes inflating the compliant balloon to an inflation pressure against the vessel wall. The method includes delivering ultrasonic energy from the ultrasound transducer to the vessel wall.

[0187] In one embodiment, the target vessel includes a vessel lumen diameter that is smaller than the nominal inflated diameter of the compliant balloon such that the hoop strength of the target vessel prevents the compliant balloon from inflating to the nominal inflated diameter of the compliant balloon.

[0188] In one embodiment, the constrained compliant balloon includes several wrinkles in the vessel wall.

[0189] In one embodiment, the target vessel includes a vessel lumen diameter that is greater than the nominal inflated diameter of the compliant balloon such that the inflation pressure causes the compliant balloon to expand to a diameter that is greater than the nominal inflated diameter of the compliant balloon.

[0190] In one embodiment, inflating the compliant balloon includes circulating a fluid through the compliant balloon at a first flow rate that inflates the compliant balloon to an inflation pressure.

[0191] In one embodiment, circulating a fluid within the compliant balloon is based on a luminal diameter of the target vessel.

[0192] In one embodiment, inflating the compliant balloon includes inflating the compliant balloon to a predetermined inflation pressure regardless of a lumen diameter of the target vessel, the target vessel constraining the compliant balloon.

[0193] In one embodiment, the kit includes a first catheter, the first catheter including a first catheter shaft having a first compliant balloon mounted on the first catheter shaft, in fluid communication with a first fluid passageway of the first catheter, the first compliant balloon having a first interior containing a first ultrasound transducer. The first compliant balloon has a first inflated diameter range when fluid is circulated through the first fluid passageway at a first flow rate that results in a first inflation pressure in the range of 10 to 30 psi. The kit includes a second catheter, the second catheter including a second catheter shaft, the second catheter shaft having a second compliant balloon mounted on the second catheter shaft, in fluid communication with a second fluid passageway of the second catheter, the second compliant balloon having a second interior containing a second ultrasound transducer. The second compliant balloon has a second inflated diameter range when fluid is circulated through the second fluid passage at a second flow rate resulting in a second inflation pressure in the range of 10 to 30 psi. Each compliant balloon includes a respective balloon wall having a respective working section radially surrounding a respective ultrasonic transducer. Each working section has a predetermined linearity when each working section has a respective inflated diameter range. The first inflated diameter range overlaps with the second inflated diameter range.

[0194] In one embodiment, the first expanded diameter range is between 3 and 5 mm, and the second expanded diameter range is between 4 and 9 mm.

[0195] In one embodiment, the tissue treatment system includes a catheter configured to treat renal arteries of various sizes, the catheter including a catheter shaft having an inlet fluid passage and an outlet fluid passage. The catheter includes an ultrasound transducer mounted on the catheter shaft. The catheter includes a compliant balloon mounted on the catheter shaft. The compliant balloon has an interior in fluid communication with the inlet fluid passage and the outlet fluid passage. The catheter includes a balloon wall having a shape and stiffness such that when the compliant balloon is inflated to a first inflation pressure of 10 psi, a working section of the balloon wall has a cylindrical profile and a first inflated diameter of 3.5 mm to 6 mm, and when the compliant balloon is inflated to a second inflation pressure of 30 psi, the working section has a cylindrical profile and a second inflated diameter of 8 to 9 mm.

[0196] In one embodiment, the tissue treatment system is configured to treat renal arteries of various sizes. The tissue treatment system includes a catheter including a catheter shaft having an inlet fluid passageway and an outlet fluid passageway. The catheter includes an ultrasound transducer mounted on the catheter shaft. The catheter includes a compliant balloon mounted on the catheter shaft. The compliant balloon has an interior in fluid communication with the inlet fluid passage and the outlet fluid passage, and includes a balloon wall having a shape and stiffness such that when fluid is circulated through the interior between the inlet fluid passage and the outlet fluid passage at a flow rate of 15-35 mL / min, the compliant balloon is inflated to a first inflation pressure of 68.95 kPa (10 psi) and a working section of the balloon wall has a cylindrical contour and a first inflated diameter of 3.5 mm to 6 mm, and when fluid is circulated through the interior between the inlet fluid passage and the outlet fluid passage at a flow rate of 35-50 mL / min, the compliant balloon is inflated to a second inflation pressure of 206.84 kPa (30 psi) and the working section has a cylindrical contour and a second inflated diameter of 8-9 mm.

[0197] In one embodiment, the balloon wall has a shape and stiffness such that when fluid circulates through the interior between the inlet fluid passage and the outlet fluid passage at a flow rate of 30 mL / min, the compliant balloon inflates to a first inflation pressure of 68.95 kPa (10 psi) and the working section has a cylindrical contour and a first inflated diameter of 3.5 mm, and when fluid circulates through the interior between the inlet fluid passage and the outlet fluid passage at a flow rate of 40-45 mL / min, the compliant balloon inflates to a second inflation pressure of 206.84 kPa (30 psi) and the working section has a cylindrical contour and a second inflated diameter of 8 mm.

[0198] In one embodiment, when fluid circulates through the interior between the inlet fluid passage and the outlet fluid passage at a flow rate of 40-45 mL / min, the cylindrical profile of the working section has a proximal profile end proximal to the ultrasonic transducer and a distal profile end distal to the ultrasonic transducer.

[0199] In one embodiment, the compliant balloon is formed from a polyether-based thermoplastic polyurethane having a Shore D durometer of 55.

[0200] In one embodiment, the balloon wall is 0.2 mm 2 It is free of larger foreign particles or air bubbles.

[0201] In one embodiment, the renal artery vessel wall has a vessel diameter of 3 mm to 9 mm.

[0202] In one embodiment, the catheter is placed within the renal artery and as fluid circulates therethrough between the inlet and outlet fluid passages, the ultrasound transducer is centered within the renal artery such that the ultrasonic energy generated by the ultrasound transducer is uniformly distributed around the vessel wall to a depth of 1 mm to 6 mm.

[0203] In one embodiment, the tissue treatment system is configured to treat renal arteries of various sizes. The tissue treatment system includes a catheter including a catheter shaft having an inlet fluid passage and an outlet fluid passage. The catheter includes an ultrasound transducer mounted on the catheter shaft. The tissue treatment system includes a compliant balloon mounted on the catheter shaft. The compliant balloon has an interior in fluid communication with the inlet fluid passage and the outlet fluid passage. The compliant balloon includes a distal mounting section and a proximal mounting section mounted on the catheter shaft, and a number of shoulders connecting each mounting section to a working section. The mounting sections have a cylindrical profile. When the compliant balloon is inflated to a first inflation pressure, the shoulders have a rounded profile.

[0204] In one embodiment, the rounded profile of the shoulder has an axial length between the respective mounting and working sections that is at least three times longer than the radial dimension between the mounting and working sections.

[0205] In one embodiment, the compliant balloon is formed from a polyether-based thermoplastic polyurethane having a Shore D durometer of 55.

[0206] In one embodiment, the balloon wall is 0.2 mm 2 It is free of larger foreign particles or air bubbles.

[0207] In one embodiment, when a compliant balloon is inflated five times to a first inflation pressure, a first inflated diameter of the compliant balloon during the first inflation is within 10% of a second inflated diameter of the compliant balloon during the fifth inflation.

[0208] In one embodiment, the renal artery vessel wall has a vessel diameter of 3 mm to 9 mm.

[0209] In one embodiment, the catheter is placed within the renal artery and as fluid circulates therethrough between the inlet and outlet fluid passages, the ultrasound transducer is centered within the renal artery such that the ultrasonic energy generated by the ultrasound transducer is uniformly distributed around the vessel wall to a depth of 1 mm to 6 mm.

[0210] In one embodiment, the tissue treatment system is configured to treat renal arteries of various sizes. The tissue treatment system includes a catheter including a catheter shaft having an inlet fluid passageway and an outlet fluid passageway. The catheter includes an ultrasound transducer mounted on the catheter shaft. The catheter includes a compliant balloon mounted on the catheter shaft. The compliant balloon has an interior in fluid communication with the inlet fluid passageway and the outlet fluid passageway. The working section of the compliant balloon has a dual wall thickness of 0.01 mm to 0.04 mm (0.0004 in to 0.0014 in) at a proximal contour end, a middle, and a distal contour end of the working section.

[0211] In one embodiment, the compliant balloon is formed from a polyether-based thermoplastic polyurethane having a Shore D durometer of 55.

[0212] In one embodiment, the balloon wall is 0.2 mm 2 It is free of larger foreign particles or air bubbles.

[0213] In one embodiment, when a compliant balloon is inflated five times to a first inflation pressure, a first inflated diameter of the compliant balloon during the first inflation is within 10% of a second inflated diameter of the compliant balloon during the fifth inflation.

[0214] In one embodiment, the renal artery vessel wall has a vessel diameter of 3 mm to 9 mm.

[0215] In one embodiment, the catheter is placed within the renal artery and as fluid circulates therethrough between the inlet and outlet fluid passages, the ultrasound transducer is centered within the renal artery such that the ultrasonic energy generated by the ultrasound transducer is uniformly distributed around the vessel wall to a depth of 1 mm to 6 mm.

[0216] In one embodiment, the tissue treatment system is configured to treat renal arteries of various sizes. The tissue treatment system includes a catheter including a catheter shaft having an inlet fluid passageway and an outlet fluid passageway. The catheter includes an ultrasound transducer mounted on the catheter shaft. The catheter includes a compliant balloon mounted on the catheter shaft. The compliant balloon has an interior in fluid communication with the inlet fluid passageway and the outlet fluid passageway and includes a balloon wall having a shape and stiffness such that when the compliant balloon is inflated five times to an inflation pressure, a first inflated diameter of the compliant balloon at a first inflation is within 10% of a second inflated diameter of the compliant balloon at a fifth inflation.

[0217] In one embodiment, a tissue treatment system is configured to treat renal arteries of various diameters. The tissue treatment system includes a catheter including a catheter shaft having an inlet fluid passageway and an outlet fluid passageway. The catheter includes an ultrasound transducer mounted on the catheter shaft. The catheter includes a compliant balloon mounted on the catheter shaft. The compliant balloon has an interior in fluid communication with the inlet fluid passageway and the outlet fluid passageway, the compliant balloon having a nominal inflated diameter and including a balloon wall having a shape and stiffness such that when the compliant balloon is inflated to a first inflation pressure in a renal artery having a first arterial diameter smaller than the nominal inflated diameter of the compliant balloon, the hoop strength and inflation pressure of the renal artery prevent the compliant balloon from inflating to the nominal inflated diameter of the compliant balloon. When the compliant balloon is inflated to a second inflation pressure, higher than the first inflation pressure, in a renal artery having a second diameter greater than the nominal inflated diameter of the compliant balloon, the second inflation pressure causes the compliant balloon to expand to a diameter greater than the nominal inflated diameter of the compliant balloon.

[0218] In one embodiment, the compliant balloon has a nominal inflated diameter of about 4 mm. When the compliant balloon is inflated to a first inflation pressure in a first arterial diameter of the renal artery having a diameter less than 4 mm, the hoop strength and inflation pressure of the renal artery prevent the compliant balloon from inflating to a diameter greater than the first arterial diameter of the renal artery. When the compliant balloon is inflated to a second inflation pressure, higher than the first inflation pressure, in a renal artery having a second diameter greater than 4 mm, the second inflation pressure expands the diameter of the compliant balloon to affix the compliant balloon to the second arterial diameter.

[0219] In one embodiment, the compliant balloon wall is formed from a urethane material having a Shore D durometer in the range of 50-60.

[0220] In one embodiment, the urethane material has a Shore D durometer of 55.

[0221] In one embodiment, the urethane material is Isothane® having a Shore D durometer of 55.

[0222] In one embodiment, the method includes advancing a distal region of a catheter of a tissue treatment system into a target vessel having a vessel wall. The distal region includes a balloon mounted on a catheter shaft. The balloon includes a balloon wall having a distal mounting section, a proximal mounting section, and a number of shoulders connecting the distal mounting section and the proximal mounting section to a working section. The working section and the number of shoulders meet at a rounded corner such that when the balloon is inflated within the target vessel, the catheter shaft remains centered within the target vessel. The method includes circulating fluid within the balloon at a first flow rate that inflates the balloon to a first predetermined inflation pressure within a first portion of a renal artery having a first arterial diameter smaller than a nominal inflated diameter of the compliant balloon, wherein a hoop strength of the renal artery and the first predetermined inflation pressure prevent the compliant balloon from expanding to a diameter larger than the first arterial diameter of the renal artery. The method includes delivering ultrasonic energy from the transducer to the first portion of the renal artery. The method includes circulating fluid through the balloon at a second flow rate to inflate the balloon to a second predetermined inflation pressure within a second portion of the renal artery having a second diameter greater than the nominal inflated diameter of the compliant balloon, inflating the compliant balloon with the second inflation pressure to a diameter greater than the nominal inflated diameter of the compliant balloon, and delivering ultrasonic energy from the transducer to the second portion of the renal artery.

[0223] In one embodiment, the kit includes a first catheter and a second catheter configured to treat renal arteries of various sizes, each of the catheters including a respective catheter shaft having a respective inlet fluid passageway and a respective outlet fluid passageway, a respective ultrasound transducer mounted on the respective catheter shaft, and a respective compliant balloon mounted on the respective catheter shaft, such that when fluid is circulated through the inlet and outlet fluid passageways of the first catheter at a flow rate that results in an inflation pressure of 10 to 30 psi, the compliant balloon expands to a diameter of 3 mm to 5 mm, and when fluid is circulated through the inlet and outlet fluid passageways of the second catheter at a flow rate that results in an inflation pressure of 10 to 30 psi, the compliant balloon expands to a diameter of 4 mm to 8 mm.

[0224] In one embodiment, a tissue treatment system is configured to treat renal arteries of various diameters. The tissue treatment system includes a catheter including a catheter shaft having an inlet fluid passageway and an outlet fluid passageway. The catheter includes an ultrasound transducer mounted on the catheter shaft. The catheter includes a compliant balloon mounted on the catheter shaft. The compliant balloon has an interior in fluid communication with the inlet fluid passageway and the outlet fluid passageway, the compliant balloon has a nominal inflated diameter and includes a balloon wall having a shape and stiffness such that the compliant balloon is inflated to an inflation pressure in a renal artery of a first arterial diameter that is smaller than the nominal inflated diameter of the compliant balloon, and the hoop strength and inflation pressure of the renal artery prevent the compliant balloon from inflating to the nominal inflated diameter of the compliant balloon.

[0225] In one embodiment, the compliant balloon has a nominal inflated diameter of 8 mm and an inflation pressure of 68.95 kPa (10 psi).

[0226] In one embodiment, the compliant balloon wall is formed from a urethane material having a Shore D durometer in the range of 50-60.

[0227] In one embodiment, the urethane material has a Shore D durometer of 55.

[0228] In one embodiment, the urethane material is Isothane® having a Shore D durometer of 55.

[0229] In one embodiment, the medical balloon includes a balloon wall having a distal attachment section, a proximal attachment section, and a number of shoulders connecting the distal attachment section and the proximal attachment section to a working section. The working section and the number of shoulders meet at a rounded corner. The balloon wall is formed from a urethane material having a Shore D durometer in the range of 50 to 60.

[0230] In one embodiment, the urethane material has a Shore D durometer of 55.

[0231] In one embodiment, the medical balloon has a first inflated diameter of about 3.5 mm at a first inflation pressure of 10 psi and a second inflated diameter of about 8 mm at a second inflation pressure of 30 psi.

[0232] In one embodiment, the first inflated diameter the first time the medical balloon is inflated is within 10% of the first inflated diameter the fifth time the medical balloon is inflated.

[0233] In one embodiment, some of the shoulders include some longitudinal ribs.

[0234] In one embodiment, the balloon wall is thinner at some shoulders than in the working section.

[0235] In one embodiment, the tissue treatment system includes a catheter including a catheter shaft. The tissue treatment system includes a balloon including a balloon wall having a distal attachment section and a proximal attachment section attached to the catheter shaft. The catheter includes a number of shoulders connecting the distal attachment section and the proximal attachment section to a working section. The working section and the number of shoulders meet at a rounded corner such that when the balloon is inflated within the target vessel, the catheter shaft remains centered within the target vessel.

[0236] In one embodiment, the balloon wall is formed from a urethane material.

[0237] In one embodiment, the urethane material has a Shore D durometer in the range of 50-60.

[0238] In one embodiment, the urethane material has a Shore D durometer of 55.

[0239] In one embodiment, the catheter shaft includes an inlet fluid passageway and an outlet fluid passageway in fluid communication with the balloon for circulating fluid through the balloon at a flow rate of 25 mL / min to 45 mL / min, and an inflation pressure for inflating the balloon is proportional to the flow rate.

[0240] In one embodiment, the catheter includes an ultrasound transducer mounted on the catheter shaft within the interior of the balloon, the ultrasound transducer being surrounded by the working section of the balloon.

[0241] In one embodiment, the catheter includes a distal centering mechanism mounted on the catheter shaft distal to the balloon and a proximal centering mechanism mounted on the catheter shaft proximal to the balloon.

[0242] In one embodiment, the method includes advancing a distal region of a catheter into a target vessel having a vessel wall. The distal region includes a balloon mounted on a catheter shaft. The balloon includes a balloon wall having a distal mounting section, a proximal mounting section, and a number of shoulders connecting the distal mounting section and the proximal mounting section to a working section. The working section and the number of shoulders meet at a rounded corner such that when the balloon is inflated within the target vessel, the catheter shaft remains centered within the target vessel. The method includes inflating the balloon against the vessel wall. The method includes delivering ultrasonic energy from a transducer to the vessel wall.

[0243] In one embodiment, the balloon wall is formed from a urethane material.

[0244] In one embodiment, the urethane material has a Shore D durometer in the range of 50-60.

[0245] In one embodiment, inflating the balloon includes circulating a fluid within the balloon based on a lumen diameter of the target vessel.

[0246] In one embodiment, inflating the balloon includes inflating the balloon to a predetermined inflation pressure regardless of the lumen diameter of the target vessel, the target vessel constraining the balloon.

[0247] In one embodiment, the constrained balloon includes several wrinkles in the vessel wall.

[0248] In one embodiment, a method of treating a target tissue from a target vessel includes measuring a size of the target vessel and advancing a catheter of a tissue treatment system into the target vessel having a vessel wall. The catheter includes a catheter shaft having a fluid passageway, an ultrasound transducer, and a compliant balloon mounted on the catheter shaft, in fluid communication with the fluid passageway, and having an interior containing the ultrasound transducer. The compliant balloon includes a balloon wall having a working section radially surrounding the ultrasound transducer. The method includes inflating the compliant balloon based on a size of the target vessel such that a substantial portion of the working section of the balloon contacts the vessel wall and the ultrasound transducer is centered within the target vessel. The method includes delivering ultrasonic energy from the ultrasound transducer to the target tissue based on a size of the target vessel. The balloon is configured to have a predetermined linearity within the working section when the balloon is inflated in free space from a first diameter to a second diameter that is 2 mm greater than the first diameter.

[0249] In one embodiment, a method for treating a target tissue includes measuring a size of a target vessel after advancing a catheter.

[0250] In the foregoing specification, the invention has been described with reference to certain exemplary embodiments thereof. It will be apparent that various modifications can be made to those exemplary embodiments without departing from the scope of the invention as set forth in the following claims. The specification and drawings are therefore to be regarded in an illustrative rather than a restrictive sense.

Claims

1. a catheter shaft (212) having a fluid passageway (420); An ultrasonic transducer (214); a compliant balloon (108) mounted on the catheter shaft (212), in fluid communication with the fluid passageway (420), and having an interior (504) containing the ultrasound transducer (214); the compliant balloon (108) having a balloon wall (502) having an operating section (1600) radially surrounding the ultrasonic transducer (214), a proximal shoulder (510B) proximal to the operating section (1600), and a distal shoulder (510A) distal to the operating section (1600), the balloon wall (502) being thicker at the proximal shoulder (510B) and the distal shoulder (510A) than at the operating section (1600).

2. 2. The catheter of claim 1, wherein the operating section (1600) has a predetermined straightness when the operating section (1600) has a first diameter and when the operating section (1600) has a second diameter that is at least 2 mm larger than the first diameter.

3. 3. The catheter of claim 2, wherein the first diameter is in the range of 3.5 to 6 mm, preferably 5 mm, and the second diameter is in the range of 8 to 9 mm, preferably 8.5 mm, with the proviso that the second diameter is at least 2 mm larger than the first diameter.

4. The catheter of claim 2 or 3, wherein the predetermined straightness comprises a cylindricity of the working section (1600) that is less than 1 mm.

5. 5. The catheter of claim 2, wherein the predetermined straightness comprises a ratio of a radius of curvature of the working section (1600) to a length of the compliant balloon (108) that is greater than 1.

6. A catheter as described in any one of claims 2 to 5, wherein the predetermined straightness includes a first radius of curvature of the operating section (1600) when the operating section (1600) has the first diameter that is within 20% of a second radius of curvature of the operating section (1600) when the operating section (1600) has the second diameter.

7. 7. The catheter of claim 1, wherein when the working section (1600) has the first diameter, the compliant balloon (108) has a first inflation pressure of 13.79 kPa (2 psi) to 68.95 kPa (10 psi), and when the working section (1600) has the second diameter, the compliant balloon (108) has a second inflation pressure of 206.84 kPa (30 psi).

8. 8. The catheter of claim 7, wherein when the compliant balloon (108) is inflated five times to the second inflation pressure, a fourth diameter of the working section (1600) when inflated a fourth time is within 10% of a fifth diameter of the working section (1600) when inflated a fifth time.

9. 9. The catheter of claim 7 or 8, wherein the ultrasonic transducer (214) is radially centered within the compliant balloon (108) when the compliant balloon (108) has the second inflation pressure.

10. 10. The catheter of claim 7, wherein a fluid (306) circulates through the interior (504) at a flow rate of 15-35 mL / min to inflate the compliant balloon (108) to the first inflation pressure, and a fluid (306) circulates through the interior (504) at a flow rate of 35-50 mL / min to inflate the compliant balloon (108) to the second inflation pressure.

11. The catheter of claim 1 , wherein the proximal shoulder (510B) and the distal shoulder (510A) are rounded.

12. The catheter of claim 1 , wherein the proximal shoulder (510B) and the distal shoulder (510A) include a plurality of longitudinal ribs (1202).

13. 13. The catheter of any one of claims 1 to 12, wherein the compliant balloon (108) is formed from an elastomeric material, preferably the elastomeric material comprises a polyether-based thermoplastic polyurethane, preferably the polyether-based thermoplastic polyurethane having a Shore D durometer in the range of 50 to 60, preferably a Shore D durometer of 55.

14. The balloon wall (502) is 0.2 mm ２ 14. The catheter of claim 1, which is free of larger foreign particles or air bubbles.

15. The catheter of any one of claims 1 to 14, wherein the working section (1600) of the balloon wall (502) has a dual wall thickness of 10.16 μm (0.0004 inch) to 35.56 μm (0.0014 inch).

16. the catheter shaft (212) extends longitudinally from a proximal end to a distal end and includes an inlet fluid passageway (403), an outlet fluid passageway (405), electrical cabling, and a guidewire lumen (213) extending therethrough, the catheter (102): a proximal hub (240) coupled to the proximal end, the hub (240) including an inlet port (208) coupled to the inlet fluid passage (403) and an outlet port (210) coupled to the outlet fluid passage (405), the electrical cabling extending through the proximal hub (240) to a proximal cabling end; an electrical coupling (206) mounted on the proximal cabling end and configured to receive electrical power from a generator; Further comprising: the ultrasonic transducer (214) is mounted on the catheter shaft (212) and electrically connected to the electrical coupling (206) via the electrical cabling; the compliant balloon (108) having an interior (504) in fluid communication with the inlet fluid passage (403) and the outlet fluid passage (405); A catheter according to any one of claims 1 to 15.

17. a catheter shaft (212) having a fluid passageway (420); An ultrasonic transducer (214); a compliant balloon (108) mounted on the catheter shaft (212), in fluid communication with the fluid passage (420), and having an interior (504) containing the ultrasonic transducer (214), the compliant balloon (108) including a balloon wall (502) having an operating section (1600) radially surrounding the ultrasonic transducer (214), wherein when the operating section (1600) has a first diameter, and when the operating section (1600) has a second diameter at least 2 mm greater than the first diameter, the operating section (1600) has a predetermined straightness.

18. 18. The catheter of claim 17, wherein the first diameter is in the range of 3.5 to 6 mm, preferably 5 mm, and the second diameter is in the range of 8 to 9 mm, preferably 8.5 mm, with the proviso that the second diameter is at least 2 mm larger than the first diameter.

19. 19. The catheter of claim 17 or 18, wherein the predetermined straightness comprises a cylindricity of the working section (1600) that is less than 1 mm.

20. 20. The catheter of claim 17, wherein the predetermined straightness comprises a ratio of a radius of curvature of the working section (1600) to a length of the compliant balloon (108) that is greater than 1.

21. A catheter as described in any one of claims 17 to 20, wherein the predetermined straightness includes a first radius of curvature of the operating section (1600) when the operating section (1600) has the first diameter that is within 20% of a second radius of curvature of the operating section (1600) when the operating section (1600) has the second diameter.

22. 22. The catheter of claim 17, wherein when the working section (1600) has the first diameter, the compliant balloon (108) has a first inflation pressure of 13.79 kPa (2 psi) to 68.95 kPa (10 psi), and when the working section (1600) has the second diameter, the compliant balloon (108) has a second inflation pressure of 206.84 kPa (30 psi).

23. 23. The catheter of claim 22, wherein when the compliant balloon (108) is inflated five times to the second inflation pressure, a fourth diameter of the working section (1600) when inflated a fourth time is within 10% of a fifth diameter of the working section (1600) when inflated a fifth time.

24. 24. The catheter of claim 22 or 23, wherein the ultrasonic transducer (214) is radially centered within the compliant balloon (108) when the compliant balloon (108) has the second inflation pressure.

25. 25. The catheter of claim 22, wherein a fluid (306) circulates through the interior (504) at a flow rate of 15-35 mL / min to inflate the compliant balloon (108) to the first inflation pressure, and a fluid (306) circulates through the interior (504) at a flow rate of 35-50 mL / min to inflate the compliant balloon (108) to the second inflation pressure.

26. 26. The catheter of claim 22, wherein the balloon wall (502) includes a proximal shoulder (510B) proximal to the working section (1600) and a distal shoulder (510A) distal to the working section (1600), the proximal shoulder (510B) and the distal shoulder (510A) being rounded in shape.

27. 27. The catheter of claim 26, wherein the proximal shoulder (510B) and the distal shoulder (510A) include a plurality of longitudinal ribs (1202).

28. 28. The catheter of claim 26 or 27, wherein the balloon wall (502) is thicker at the proximal shoulder (510B) and at the distal shoulder (510A) than in the working section (1600).

29. 29. The catheter of any one of claims 17 to 28, wherein the compliant balloon (108) is formed from an elastomeric material, preferably the elastomeric material comprises a polyether-based thermoplastic polyurethane, preferably the polyether-based thermoplastic polyurethane having a Shore D durometer in the range of 50 to 60, preferably a Shore D durometer of 55.

30. The balloon wall (502) is 0.2 mm ２ 30. The catheter of any one of claims 17 to 29, which is free of larger foreign particles or air bubbles.

31. The catheter of any one of claims 17 to 30, wherein the working section (1600) of the balloon wall (502) has a dual wall thickness of 10.16 μm (0.0004 inch) to 35.56 μm (0.0014 inch).

32. 32. The catheter of claim 17, further comprising a distal centering mechanism (1402) mounted on the catheter shaft (212) distal to the compliant balloon (108), and a proximal centering mechanism (1404) mounted on the catheter shaft (212) proximal to the compliant balloon (108).

33. The catheter of any one of claims 17 to 32, wherein the compliant balloon (108) is configured for insertion into a blood vessel, preferably a renal artery, having a vessel lumen diameter of between 3 mm and 8 mm in diameter.

34. the catheter shaft (212) extends longitudinally from a proximal end to a distal end and includes an inlet fluid passageway (403), an outlet fluid passageway (405), electrical cabling, and a guidewire lumen (213) extending therethrough, the catheter (102): a proximal hub (240) coupled to the proximal end, the proximal hub (240) including an inlet port (208) coupled to the inlet fluid passage (403) and an outlet port (210) coupled to the outlet fluid passage (405), the electrical cabling extending through the proximal hub (240) to a proximal cabling end; an electrical coupling (206) mounted on the proximal cabling end and configured to receive electrical power from a generator; Further comprising: the ultrasonic transducer (214) is mounted on the catheter shaft (212) and electrically connected to the electrical coupling (206) via the electrical cabling; the compliant balloon (108) having an interior (504) in fluid communication with the inlet fluid passage (403) and the outlet fluid passage (405); A catheter according to any one of claims 17 to 33.

35. A first catheter (102) according to any one of claims 1 to 34; A second catheter (102) according to any one of claims 1 to 34, when fluid is circulated through the fluid passageway of the first catheter at a first flow rate resulting in an inflation pressure in the range of 10-30 psi, the compliant balloon of the first catheter has a first inflated diameter range; when fluid is circulated through the fluid passageway of the second catheter (102) at a second flow rate resulting in an inflation pressure in the range of 10-30 psi, the compliant balloon (108) of the second catheter (102) has a second inflated diameter range; the first expanded diameter range overlaps with the second expanded diameter range; kit.

36. advancing a catheter (102) of a tissue treatment system (100) into a target blood vessel having a blood vessel wall (303), the catheter (102) comprising a catheter shaft (212) having a fluid passageway (403), an ultrasonic transducer (214), and a compliant balloon (108) mounted on the catheter shaft (212) and in fluid communication with the fluid passageway (403), the compliant balloon (108) having an interior containing the ultrasonic transducer (214), the compliant balloon (108) comprising a balloon wall (502) having an operating section (1600) radially surrounding the ultrasonic transducer (214), the operating section (1600) having a predetermined straightness when the operating section (1600) has a first diameter and when the operating section (1600) has a second diameter at least 2 mm greater than the first diameter; inflating the compliant balloon (108) against the vessel wall (303) at an inflation pressure; delivering ultrasonic energy from the ultrasonic transducer (214) to the vessel wall (303); A method comprising:

37. 37. The method of claim 36, wherein the target vessel comprises a vessel lumen diameter that is less than the nominal inflated diameter of the compliant balloon (108), such that a hoop strength of the target vessel prevents the compliant balloon (108) from inflating to the nominal inflated diameter of the compliant balloon (108).

38. 38. The method of claim 36 or 37, wherein the constrained compliant balloon (108) comprises a plurality of wrinkles in the vessel wall (303).

39. 39. The method of any one of claims 36 to 38, wherein the target vessel comprises a vessel lumen diameter greater than a nominal inflated diameter of the compliant balloon (108) such that the inflation pressure causes the compliant balloon (108) to inflate to a diameter greater than the nominal inflated diameter of the compliant balloon (108).

40. 40. The method of any one of claims 36 to 39, wherein inflating the compliant balloon (108) comprises circulating a fluid through the compliant balloon (108) at a first flow rate that inflates the compliant balloon (108) to the inflation pressure.

41. 41. The method of claim 40, wherein circulating fluid within the compliant balloon (108) is based on a luminal diameter of the target vessel.

42. 42. The method of any one of claims 36 to 41, wherein inflating the compliant balloon (108) comprises inflating the compliant balloon (108) to a predetermined inflation pressure regardless of the lumen diameter of the target vessel, the target vessel constraining the compliant balloon (108).

43. 1. A method of treating a target tissue from a target vessel, comprising: measuring the size of the target vessel; advancing a catheter (102) of a tissue treatment system (100) into the target blood vessel having a blood vessel wall (303), the catheter (102) including a catheter shaft (212) having a fluid passageway (403), an ultrasound transducer (214), and a compliant balloon (108) mounted on the catheter shaft (212) and in fluid communication with the fluid passageway (403), the compliant balloon (108) having an interior containing the ultrasound transducer (214), the compliant balloon (108) including a balloon wall (502) having a working section (1600) radially surrounding the ultrasound transducer (214); inflating the compliant balloon (108) based on the size of the target vessel such that a substantial portion of the working section (1600) of the compliant balloon (108) contacts the vessel wall (303) and the ultrasound transducer (214) is centered within the target vessel; delivering ultrasonic energy from the ultrasonic transducer (214) to the target tissue based on the size of the target vessel; Including, The method of claim 1, wherein the compliant balloon (108) is configured to have a predetermined straightness within the working section (1600) when the compliant balloon (108) is inflated in free space from a first diameter to a second diameter that is 2 mm greater than the first diameter.

44. 44. The method of claim 43, wherein the step of measuring the size of the target vessel is after advancing the catheter (102).

45. The method of claim 43 or 44, wherein the ultrasonic transducer (214) is centered within the target vessel when the compliant balloon (108) is inflated to a pressure range of 20-30 psi.

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