Radial artery access catheter

Abstract

The catheter includes a catheter shaft deliverable via a radial artery access approach. The catheter shaft has a fluid lumen. A balloon is attached to the catheter shaft and has an interior in fluid communication with the fluid lumen. An ultrasound transducer is in the interior. A flow control device has an inlet port for receiving fluid from the fluid lumen through the interior. The flow control device is configured to expel fluid to the surrounding environment when the fluid has a predetermined pressure. Other embodiments are also described and claimed.

Description

Technical Field

[0001] [Priority Claim] The present application claims the benefit of priority from U.S. Provisional Patent Application No. 63 / 375,357, filed on September 12, 2022 and entitled "Radial Access Catheter". The entire content of said document is incorporated herein by reference to provide continuity of disclosure.

[0002] [Technical Field] The present application generally relates to minimally invasive devices, systems, and methods for delivering energy to a targeted anatomical site in a subject (patient), and more specifically to a catheter-based endoluminal device for treating tissue such as nerve tissue.

Background Art

[0003] According to the Centers for Disease Control and Prevention (CDC), approximately one in three adults suffers from hypertension, also known as hypertension. If left untreated, hypertension can lead to kidney disease, arrhythmias, and heart failure. In recent years, the treatment of hypertension has focused on minimally invasive interventional approaches to inactivate renal nerves around the renal arteries. Autonomic nerves tend to run along blood vessels towards the organs they supply. Catheters can reach certain structures that may be accessible within the body cavity they travel through. For example, one system uses a radio frequency (RF) generator connected to a catheter with multiple electrodes positioned against the intima of the renal artery to generate an electric field in the vessel wall and surrounding tissue, causing ohmic heating of the tissue to a temperature sufficient to excise the tissue and the renal nerves passing through it. To treat all the renal nerves surrounding the renal artery, the RF electrodes are repositioned several times around the inside of the renal artery. However, the relatively limited electric field generated by the RF electrodes may miss some renal nerves, resulting in incomplete treatment. Additionally, heating the renal nerves requires the RF electrodes to come into contact with the intima, which carries a risk of intima damage or necrosis, potentially leading to thrombus formation, fibrosis of the vessel walls, mechanical weakening of the vessels, and vascular damage.

[0004] Another approach to renal nerve inactivation is the use of high-intensity focused ultrasound (HIFU). This utilizes vibrational energy to cause frictional heating and destruction of tissue, further raising the tissue temperature enough to induce ablation and remodeling.

[0005] Warnking's U.S. Patents 9,943,666, 9,981,108, and 10,039,901, Schaer's U.S. Patents 9,700,372, 9,707,034, and 10,368,944, and Taylor's U.S. Patents 10,350,440, and 10,456,605, each of which is incorporated herein by reference in its entirety, disclose systems that use non-focus ultrasound to ablate nerves. Embodiments of such systems include an ultrasonic transducer positioned along the distal end of a catheter designed to be inserted into a blood vessel (e.g., a renal artery). An electrical cable received within the cable lumen of the catheter may be used to supply power to the ultrasonic transducer. An ultrasonic transducer emits one or more therapeutic doses of unfocused ultrasonic energy, which heats the tissue adjacent to the body cavity in which the transducer is located. The system may also include a balloon attached to the distal end of a catheter, which may be used to cool the transducer by circulating a coolant before, during, and after the transducer is activated, helping to prevent thermal damage to the inner surface of the blood vessel wall while nerves are being heated and damaged in depth. The coolant is circulated through two fluid lumens: an input fluid lumen that carries the fluid distally toward the balloon, and an output fluid lumen that returns the fluid proximal to the balloon.

[0006] This design allows for the creation of one or more ablation zones sufficient to achieve long-term nerve inactivation at different locations around the blood vessel. This enables the treatment of the patient's hypertension while minimizing damage to the blood vessel and surrounding organs.

[0007] An ultrasonic transducer may include first and second electrodes positioned on either side of a cylindrical piezoelectric material, such as lead zirconate titanate (PZT). To energize the transducer, a voltage is applied between the first and second electrodes at a frequency selected to resonate the piezoelectric material. This generates vibrational energy that is emitted radially outward from the transducer. The transducer is designed to provide a substantially uniform and predictable radiation profile.

[0008] Systems using non-focused ultrasound to ablate nerves can be delivered to target anatomical structures via various access routes. For example, a catheter holding a transducer can be inserted via a femoral access route through the femoral artery. [Overview of the Initiative]

[0009] The present invention is defined in the independent claims. Further embodiments of the present invention are defined in the dependent claims.

[0010] A catheter is provided herein. The catheter comprises a catheter shaft having a fluid lumen. The catheter comprises a balloon attached to the catheter shaft and having an interior that is in fluid communication with the fluid lumen. The catheter comprises an ultrasonic transducer located inside. The catheter comprises a flow control device having an inlet port for receiving fluid passing from the fluid lumen through the interior. The flow control device is configured to discharge the fluid into the ambient environment when the fluid has a predetermined pressure.

[0011] A catheter is provided herein, comprising a balloon having an interior. The catheter comprises an ultrasonic transducer located inside. The catheter comprises a catheter shaft having an outer member having a central lumen, an inner member having a fluid lumen extending through the central lumen for delivering fluid into the interior, and one or more steering wires extending through the central lumen between the inner wall of the outer member and the outer wall of the inner member. The one or more steering wires are connected to the outer member or the inner member at an anchor point proximal to the balloon.

[0012] The above summary does not constitute an exhaustive list of all aspects of the present invention. The present invention encompasses all systems and methods that can be practiced from all suitable combinations of the various aspects described above, as well as the aspects disclosed in the following detailed description and particularly indicated in the claims. Such combinations have special advantages not specifically described in the above summary.

[0013] Various features of this disclosure and the manner in which they are achieved will be described in more detail below with reference to the detailed description, claims and drawings. Reference numerals are reused where appropriate to indicate correspondences between the items they refer to. [Brief explanation of the drawing]

[0014] [Figure 1] Figure 1 shows an ultrasound-based tissue treatment system according to one embodiment.

[0015] [Figure 2] Figure 2 shows a side view of selected components of the ultrasound-based tissue treatment system shown in Figure 1, according to one embodiment.

[0016] [Figure 3] Figure 3 shows a side view of selected components of the ultrasound-based tissue treatment system shown in Figure 1, according to one embodiment.

[0017] [Figure 4] Figure 4 is a perspective view showing selected components of the ultrasound-based tissue treatment system shown in Figure 1, inserted into a body cavity, according to one embodiment.

[0018] [Figure 5] Figure 5 is a longitudinal cross-sectional view of a distal portion of a catheter of an ultrasound-based tissue treatment system according to one embodiment.

[0019] [Figure 6] Figure 6 is a cross-sectional view of the distal portion of the catheter of the ultrasound-based tissue treatment system taken along line A-A in Figure 5, according to one embodiment.

[0020] [Figure 7] Figure 7 is a cross-sectional view of the distal portion of the catheter of the ultrasound-based tissue treatment system taken along line A-A in Figure 5, according to one embodiment.

[0021] [Figure 8] Figure 8 is a side view of a distal portion of a catheter of an ultrasound-based tissue treatment system including a flow control device, according to one embodiment.

[0022] [Figure 9] Figure 9 is a cross-sectional view of a flow control device of a catheter of an ultrasound-based tissue treatment system according to one embodiment.

[0023] [Figure 10] Figure 10 is a cross-sectional view of a flow control device of a catheter of an ultrasound-based tissue treatment system according to one embodiment.

[0024] [Figure 11] Figure 11 is a cross-sectional view of a flow control device of a catheter of an ultrasound-based tissue treatment system according to one embodiment.

[0025] [Figure 12]Figure 12 is a side view of a catheter flow control device for an ultrasound-based tissue treatment system according to one embodiment.

[0026] [Figure 13] Figure 13 is a cross-sectional view of a catheter flow control device for an ultrasound-based tissue treatment system according to one embodiment.

[0027] [Figure 14] Figure 14 is a cross-sectional view of a catheter flow control device for an ultrasound-based tissue treatment system according to one embodiment.

[0028] [Figure 15] Figure 15 is a cross-sectional view of a catheter flow control device for an ultrasound-based tissue treatment system according to one embodiment.

[0029] [Figure 16] Figure 16 is a cross-sectional view of a catheter flow control device for an ultrasound-based tissue treatment system according to one embodiment.

[0030] [Figure 17] Figure 17 is a cross-sectional view of a catheter flow control device for an ultrasound-based tissue treatment system according to one embodiment.

[0031] [Figure 18] Figure 18 is a cross-sectional view of the catheter shaft of a catheter for an ultrasound-based tissue treatment system according to one embodiment.

[0032] [Figure 19] Figure 19 is a side view of a catheter for an ultrasound-based tissue treatment system according to one embodiment.

[0033] [Figure 20] Figure 20 is a side view of a catheter for an ultrasound-based tissue treatment system according to one embodiment.

[0034] [Figure 21] Figure 21 is a side view of a catheter for an ultrasound-based tissue treatment system according to one embodiment.

[0035] [Figure 22] Figure 22 is a side view of a catheter for an ultrasound-based tissue treatment system according to one embodiment.

[0036] [Figure 23] Figure 23 is a schematic diagram of an ultrasound-based tissue treatment system according to one embodiment. [Modes for carrying out the invention]

[0037] A system for treating tissue using non-focused ultrasonic energy and a method for using the same are provided herein. In certain embodiments, acoustically based tissue treatment transducers, devices, systems, and parts thereof are provided. The system may be catheter-based. The system may be delivered intraluminally (e.g., intravascularly) to position the transducer within a target anatomical region of a subject, such as within a suitable body cavity, such as a blood vessel. Once properly positioned within the target anatomical region, the transducer may be activated to deliver non-focused ultrasonic energy radially outward, thereby appropriately heating and treating the tissue within the target anatomical region. The transducer or piezoelectric material may be activated at a frequency, duration, and energy level suitable for treating the target tissue. In one non-limiting example, unfocused ultrasonic energy generated by a transducer or piezoelectric material, or radio frequency (RF) energy transmitted by an electrode, may target (select) nerve tissue of a subject and heat such tissue in a manner that neuromodulates it (e.g., completely or partially excises, necrotizes, or stimulates it).

[0038] In the manner described in the aforementioned Warnking, Schaer, and Taylor patents, renal nerve neuromodulation may be used to treat a variety of conditions, such as hypertension, chronic kidney disease, atrial fibrillation, autonomic nervous system disorders, arrhythmias, heart failure, end-stage renal failure, myocardial infarction, anxiety, contrast-induced nephropathy, diabetes, metabolic disorders, and insulin resistance. However, it should be understood that balloon catheters may be appropriately used to treat other nerves and conditions, such as the sympathetic nerves of the hepatic plexus in the hepatic artery involved in blood glucose levels important for treating diabetes, or any appropriate tissue, such as cardiac tissue causing abnormal heart rhythms, and are not limited to their use in the treatment of renal nerve tissue (e.g., neuromodulation). In another example, tissue therapy catheters are used to ablate the sympathetic nerves of the renal and hepatic arteries to treat diabetes and other metabolic disorders. In certain embodiments, tissue therapy catheters are used to treat autoimmune and / or inflammatory diseases such as rheumatoid arthritis, sepsis, Crohn's disease, ulcerative colitis, and / or gastrointestinal motility disorders by neuromodulating the sympathetic nerves in one or more of the splenic artery, celiac artery, superior mesenteric artery, or inferior mesenteric artery. In certain embodiments, tissue therapy catheters are used to ablate nerve fibers of the celiac ganglion and / or renal artery to treat hypertension. In certain embodiments, transducers are used to treat (reduce) pain, such as pain associated with pancreatic cancer, by neuromodulating nerves that innervate the pancreas, for example. Ultrasound or RF energy may also be used to ablate nerves in both the pulmonary veins and renal arteries to treat atrial fibrillation. In yet another example, ultrasound or RF energy may be used additionally or alternatively to ablate nerves that innervate the carotid body to treat hypertension and / or chronic kidney disease.

[0039] In intraluminal systems, an ultrasonic transducer may be placed inside a balloon filled with a cooling fluid before and during treatment. More specifically, the balloon may surround the transducer. The balloon may be in contact with the inner surface of a body cavity (e.g., the intima). In certain embodiments, the transducer may be used to output an acoustic signal when the balloon completely occludes the body cavity, and the cooling fluid inside the balloon may be used to cool both the body cavity and the transducer. In certain embodiments, the balloon may surround the transducer to cool it during sonication, but the balloon may not be in contact with or occlude the body cavity, and the cooling of the body cavity may rely on the blood in the body cavity instead of the cooling fluid.

[0040] In certain embodiments, the transducer may be connected to a controller using one or more conductive wires. The controller may be configured to supply power to the transducer or transmit electrical signals. In one embodiment, the controller generates radio frequency (RF) signals to the transducer. The balloon ablation therapy device may comprise one or more lumens, e.g., a guidewire lumen, one or more fluid lumens, and / or a cable lumen.

[0041] Existing tissue treatment systems are sized to be delivered to the target anatomical structure via a femoral access route. However, femoral access routes can be painful for patients, may require long procedure times, and may cause health complications. Delivery via a radial access route (radial access route) can reduce pain, procedure time, and complications. More specifically, radial access is a more comfortable delivery route than inguinal access and has fewer complications such as bleeding.

[0042] To provide a catheter suitable for tissue treatment via radial artery access, it is advantageous to provide a catheter longer than the length required for access via femoral artery. More specifically, radial access may require a longer catheter than that required for femoral access. On the other hand, increased length may require an increased cross-sectional area of ​​the fluid lumen used to circulate cooling fluid to the transducer within the balloon. An increased fluid lumen cross-sectional area can maintain pressure and fluid flow rates suitable for safe and effective energy delivery. Furthermore, a larger diameter fluid lumen can be primed more reliably, so an increased fluid lumen cross-sectional area can facilitate effective priming of the system. On the other hand, since the radial artery is typically smaller (thinner) than the femoral artery, the overall diameter of the catheter needs to be reduced to 5 French or less to ensure patient comfort and safety. In other words, the conflicting requirements of increasing the fluid lumen diameter and decreasing the overall catheter diameter limit the ability (possibility) of existing catheter configurations to be adapted to radial artery access (radial access) platforms.

[0043] In one embodiment, a catheter is provided having a cross-sectional area and length suitable for radial artery access. The catheter may include a single fluid lumen having a cross-sectional area suitable for providing safe and effective nerve ablation and system priming. In one embodiment, the catheter does not require a second fluid lumen, unlike existing tissue treatment systems, and therefore the catheter can be delivered to a target anatomical structure via a radial artery access route. By eliminating the second fluid lumen, the size of the single fluid lumen can be allowed to be large enough to allow sufficient cooling fluid flow to the transducer, and small enough to provide a catheter shaft that can be delivered via a radial artery access route. The catheter may include a flow control device for passing the fluid delivered from a fluid reservoir to the catheter to the surrounding environment. The fluid can then flow distally through the catheter to cool the transducer of the catheter and be discharged to the surrounding environment. By draining the fluid instead of returning it to a fluid reservoir, the need for a second fluid lumen can be eliminated, allowing the catheter to be delivered to the target anatomical structure via the radial artery access route.

[0044] Figures 1, 2, and 3 illustrate the features of various forms of ultrasound-based tissue therapy systems provided herein. Referring to Figure 1, an ultrasound-based tissue therapy system according to one embodiment is shown. The tissue therapy system 100 is shown as including a catheter 102, a controller 120, and a connecting cable 140. In a particular embodiment, the system 100 further includes an ultrasound transducer in a balloon 112, a reservoir 110, a fluid transfer cartridge 130, and a control mechanism such as a handheld remote control.

[0045] In the embodiment shown in Figure 1, the controller 120 is shown as being connected to the catheter 102 via a cartridge 130 and a connecting cable 140. In certain embodiments, the controller 120 interfaces with the cartridge 130 to provide a cooling fluid to the catheter 102 in order to selectively inflate and deflate the balloon 112. The balloon 112 may be made from, but is not limited to, nylon, polyimide film, thermoplastic elastomer (such as those sold under the trademark PEBAX®), medical-grade thermoplastic polyurethane elastomer (such as Pellethane®, Isothane®, other suitable polymers, or any combination thereof).

[0046] Referring to Figure 2, a side view of an ultrasound-based tissue treatment system according to one embodiment is shown. The tissue treatment catheter 102 may include a distal region 210 and a proximal region 220. The catheter 102 may have a length depending on the treatment application. For example, in a particular embodiment suitable for renal nerve debridement via radial access delivery, the catheter 102 may have a working length of 150-160 cm (e.g., 155 cm). Furthermore, the total length of the catheter 102 for such applications may be longer, including the length of the electrical cable 230 extending to the electrical coupling 232. More specifically, the cable 230 may have a length of approximately 305 cm from the proximal hub 240 to the electrical coupling 232.

[0047] The catheter 102 may have a profile (outer shape) suitable for accessing the renal artery through a radial artery access site. For example, the catheter 102 may include a catheter shaft 214 having a shaft diameter of 4 to 6 French, e.g., 5 French or less. This profile is partially facilitated by the catheter shaft 214 having an outer diameter in the range of 0.050 to 0.060 inches (e.g., 0.057 inches).

[0048] The distal region 210 of the tissue treatment catheter 102 may be part of a device that is advanced into the anatomical structure of a target, for example, into a target blood vessel having a blood vessel wall, to treat the target blood vessel. The distal region 210 may include a balloon 112 attached to the catheter shaft 214. The catheter shaft 214 may be an elongated tubular structure extending longitudinally from a proximal end to a distal end. The balloon 112 may be attached to and supported by the catheter shaft 214 at its distal end. Furthermore, an ultrasonic transducer 111 may be attached to the catheter shaft 214 and housed inside the balloon 112. Thus, the catheter shaft 214 can facilitate the supply (delivery) of cooling fluid to the balloon 112 and the supply (delivery) of electrical energy to the transducer 111.

[0049] The catheter shaft 214 may include one or more lumens that can be used as a fluid conduit, an electrical cable passage, a guidewire lumen, etc. In one embodiment, for example, the catheter shaft 214 may include a guidewire lumen 213 that is shaped, sized, and otherwise configured to receive a guidewire. In one embodiment, the guidewire lumen 213 is a wire-over-guidewire lumen and extends from the distal tip of the catheter 102 through the entire length of the catheter shaft 214 to the exit port 225 of the proximal hub 240 of the catheter 102. As described below, the lumen of the catheter shaft 214 can transmit the inflation / cooling fluid from the proximal region 220 to the balloon 112 during balloon inflation.

[0050] In one embodiment, the transducer 111 is attached to the catheter shaft 214 in the distal region 210 inside the balloon 112. The transducer 111 may be an ultrasonic transducer used to radiate energy toward the vessel wall. For example, the transducer 111 may radiate ultrasonic energy circumferentially around the vessel wall, for example, in 360 degrees. In one embodiment, an electrical cable 230 extends from the proximal region 220 to the distal region 210 and is connected to the transducer 111 to generate energy for emission toward the target tissue.

[0051] The ultrasonic transducer 111 may include first and second electrodes positioned on either side of a cylindrical piezoelectric material such as lead zirconate titanate (PZT). To supply energy to the transducer 111, a voltage is applied between the first and second electrodes at a frequency selected to resonate the piezoelectric material. This generates vibrational energy that radiates outward from the transducer 111. The transducer 111 is designed to provide a substantially uniform and predictable radiation profile to minimize damage to surrounding non-target tissue. Furthermore, before, during, and after the activation of the transducer 111, a cooling fluid is circulated through the balloon 112 to reduce heating of the inner lining of the body cavity and cool the transducer 111. In this way, the peak temperature achieved by the tissue within the cooling zone remains lower than that of the tissue located outside the cooling zone.

[0052] The proximal region 220 may include one or more connectors or couplings. These connectors or couplings may be electrically connected to the transducer 111 via the electrical cable 230. For example, the proximal region 220 may include one or more electrical couplings 232 connected to the proximal end of the electrical cable 230. The distal end of the electrical cable 230 may be connected to the transducer 111.

[0053] The catheter 102 can be coupled to the controller 120 by connecting its electrical coupling 232 to a connecting cable 140. The connecting cable 140 can be detachably connected to the controller 120 and / or the catheter 102 via a port on the controller 120 and / or the catheter 102. Thus, the controller 120 can be used with multiple catheters 102 by disconnecting the coupling of the first catheter during a procedure (surgery), replacing the first catheter with the second catheter, and connecting the coupling of the second catheter to the controller 120. In certain embodiments, for example, if only one catheter needs to be used during a procedure, the connecting cable 140 can be permanently connected to the controller 120.

[0054] In certain embodiments, the proximal region 220 of the catheter 102 may further include one or more fluid ports. For example, the proximal hub 240 may include a fluid port 234 through which an expandable member (e.g., a balloon 112) can be fluidly connected to a reservoir 110 (see Figure 1). The reservoir 110 can therefore supply cooling fluid to the balloon 112 via the fluid port 234. The reservoir 110 may optionally be provided together with a controller 120 and may be mounted on the outer housing of the controller 120, for example, as shown in Figure 1. Alternatively, the reservoir 110 may be provided separately.

[0055] Referring to Figure 3, a side view of an ultrasound-based tissue treatment system according to one embodiment is shown. In one embodiment, the catheter 102 may have a rapidly replaceable guidewire lumen 213. More specifically, the guidewire lumen 213 may extend from the distal tip of the catheter 102 through a portion of the length of the catheter shaft 214 to an exit port 225 in the distal portion 210 of the catheter 102. For example, the distance from the distal tip to the rapidly replaceable port may be in the range of 20-30 cm, e.g., 23 cm. The proximal hub 240 shown in Figure 3 may differ from the proximal hub 240 shown in Figure 2, considering that the exit port may move from the proximal portion 220 to the distal portion 210. Since other components of the rapidly replaceable version of the catheter 102 may be similar to those of the wire-over version of the catheter 102, the description of the components shown in Figure 2 may also apply to components of similar reference numerals shown in Figure 3.

[0056] Referring to Figure 4, a perspective view of an ultrasound-based tissue therapy system inserted into a body cavity according to one embodiment is shown. Components of the distal portion 210 of the catheter 102 can be inserted into the body cavity of a subject. In Figure 4, the body cavity is a blood vessel (e.g., a renal artery) having a plurality of nerves 401 in the outer layer (e.g., the adventitia) of the blood vessel. As previously stated, the distal portion 210 may include an ultrasound transducer 111, a balloon 112 filled with cooling fluid 403, a catheter shaft 214, and / or a guidewire support tip 404 configured to receive a guidewire 406.

[0057] The transducer 111 may be partially or completely positioned within the balloon 112. The balloon 112 may be inflated with a cooling fluid 403 to contact the inner surface of a body cavity (e.g., the intima). In certain embodiments, the transducer 111 may be used to output an acoustic signal when the balloon 112 completely occludes the body cavity which is the target blood vessel 200. The balloon 112 may center the transducer 111 within the body cavity. In a particular embodiment suitable for, for example, renal denervation, the balloon 112 is inflated with the cooling fluid 403 while being inserted into the patient's body cavity under treatment at an operating pressure of about 10 to about 30 psi. The balloon 112 may be or include compliant, semi-compliant, or non-compliant medical balloons. The balloon 112 is sized to be insertable into a body cavity. For example, when inserted into a renal artery, the balloon 112 may be selected from available sizes including, but not limited to, outer diameters of 3.5 mm, 4.2 mm, 5 mm, 6 mm, 7 mm, and 8 mm.

[0058] In some embodiments, as shown in Figure 4, when filled with cooling fluid 403 and inflated under the control of controller 120, the outer wall of the balloon 112 may be substantially parallel to the outer surface of the transducer 111. Optionally, the balloon 112 may be inflated sufficiently to be in junction with a body cavity. For example, when inflated, the balloon 112 may be in at least partial contact with the inner surface of the blood vessel wall 450, which is a body cavity, and may be in junction with that inner surface. When the balloon 112 is in junction with a body cavity, more specifically the inner circumferential wall of the body cavity, the balloon 112 may substantially prevent blood in the body cavity from passing through the balloon.

[0059] In other embodiments, the balloon 112 is configured not to contact a body cavity when expanded. The balloon 112 may surround the transducer to cool it during sonication, but it does not have to contact or occlude a body cavity, and cooling of the body cavity can rely on the blood in the body cavity instead of a cooling fluid. When the balloon 112 surrounds the transducer 111 but does not contact or occlude a body cavity, the balloon 112 may be non-compliant. In certain embodiments, the balloon 112 is made of nylon.

[0060] For blood vessels matching the diameter of the balloon, a non-compliant balloon (e.g., 112) can act as a centering mechanism. Cooling of the vessel wall can be managed by the generator's cooling system by flowing water or other cooling fluids (e.g., dextrose or saline) through the balloon as needed. Advantageously, non-compliant balloons offer more precise control over balloon design. Advantageously, non-compliant balloons (e.g., 112) can be configured so that a wrinkle-free balloon surface maintains the desired shape without interfering with sonication during inflation. Additionally or alternatively, balloon 112 can be maintained at a specified size by pushing and / or withdrawing cooling fluid through balloon 112 at a specified flow rate.

[0061] Referring to Figure 5, a longitudinal cross-sectional view of the distal portion of a catheter of an ultrasound-based tissue treatment system according to one embodiment is shown. The ultrasound transducer 111 may include a cylindrical hollow tube made of a piezoelectric material (e.g., lead zirconate titanate (PZT)), with an inner electrode 504 and an outer electrode 502 positioned on the inner and outer surfaces of the cylindrical tube, respectively. Such a cylindrical hollow tube of piezoelectric material is an example of a piezoelectric transducer body 201 and may therefore be referred to as a piezoelectric transducer body. The piezoelectric transducer body may have various other shapes and does not need to be hollow. For example, in a particular embodiment suitable for renal denervation, the piezoelectric material constituting the piezoelectric transducer body is lead zirconate titanate 8 (PZT8), also known as Navy III piezoelectric material. The raw PZT transducer may be plated with layers of copper, nickel and / or gold to create electrodes on the surface (e.g., inner and outer surfaces) of the piezoelectric transducer body. The application of voltage and alternating current between the inner electrode 504 and the outer electrode 502 causes the piezoelectric material to vibrate in a direction lateral to the longitudinal direction of the cylindrical tube, and to emit ultrasonic waves radially (radially).

[0062] In one embodiment, an ultrasonic transducer 111 may be positioned inside 506 of a balloon 112. The balloon 112 may have an interior 506 that is in fluid communication with a fluid lumen 508 of a catheter shaft 214. The fluid lumen 508 may supply a cooling fluid 403 to the interior 506 to cool the transducer 111. More specifically, the balloon 112 may house the transducer 111 inside 506, and the transducer 111 is cooled by contact with the cooling fluid 403 flowing into the interior 506 from the fluid lumen 508.

[0063] As shown in Figure 5, the ultrasonic transducer 111 may generally be supported via a backing member or post 507. In certain embodiments, the backing member 507 includes stainless steel coated with nickel and gold, where nickel is used as a bonding material between the stainless steel and the gold plating. In a particular embodiment suitable for renal denervation, for example, the outer diameter of the transducer 111 is approximately 1.5 mm, the inner diameter of the transducer 111 is approximately 1 mm, and the length of the transducer 111 is approximately 6 mm. Transducers having other inner diameters, outer diameters and lengths, more generally dimensions and shapes, are also within the scope of embodiments described herein. Furthermore, it should be noted that the drawings in each figure are not necessarily drawn to a constant scale, and are often not drawn to a constant scale.

[0064] The backing member 507 may extend from the distal portion of the catheter shaft 214 to the distal tip 510 of the catheter 102. For example, the distal end of the backing member 507 may be positioned within an adjacent opening at the distal tip 510, and the proximal end of the backing member 507 may be movably coupled to the distal portion of the catheter shaft 214 via an electrical cable 230. In other embodiments, a gap exists between the distal end of the catheter shaft 214 and the proximal end of the ultrasonic transducer 111.

[0065] To allow liquid cooling along both the inner electrode 504 and the outer electrode 502, the backing member 507 may include one or more standoff assemblies 512. The standoff assemblies 512 may define one or more annular openings through which the cooling fluid 403 can enter the space of the transducer 111 (which may be selectively insulated) between the backing member 507 and the inner electrode 504. Thus, the backing member 507 may function as a fluid barrier between the cooling fluid 403 circulating within the balloon 112 and the lumen of the backing member 507 that receives the guidewire 406.

[0066] In certain embodiments, the standoff assembly 512 is conductive in order to electrically couple the inner electrode 504 of the ultrasonic transducer 111 to the backing member 507. One or more conductors of the electrical cable 230 may be electrically coupled to the backing member 507. Thus, when the controller 120 is activated, current can be delivered from the electrical cable 230 to the inner electrode 504 of the ultrasonic transducer 111 via the backing member 507 and the standoff assembly 512, which advantageously eliminates the need to directly couple the cable 230 to the inner electrode 504 of the transducer 111. In other embodiments, the backing member 507 and the standoff assembly 512 are made of one or more electrical insulating materials, or coated with one or more electrical insulating materials, even if they are made of conductive materials. In certain embodiments, one or more electrical conductors of the cable 230 are directly coupled (e.g., soldered) to the inner electrode 504 of the transducer 111.

[0067] The backing member 507 may have an insulating tube positioned along its inner surface to prevent or reduce the possibility of electrical conduction between the guidewire 406 and the backing member 507. This is used in embodiments where such electrical conduction is not desired. The insulating tube may be formed of a non-conductive material (e.g., a polymer such as polyimide), which may also be referred to as an electrical insulator. As shown in Figure 5, the insulating tube may extend through the lumen of the backing member 507 within the transducer 111 toward the distal tip 510. In this embodiment, the transducer 111 is offset distally from the distal end of the catheter shaft 214.

[0068] Referring to Figure 6, a cross-sectional view of the distal portion of a catheter in an ultrasound-based tissue treatment system according to one embodiment is shown, line AA of Figure 5. The catheter shaft 214 includes one or more lumens. For example, the catheter shaft 214 may include a fluid lumen 508 for transporting an inflation / cooling fluid (e.g., water, sterile water, saline, 5% dextrose (D5W), other liquids or gases, etc.) to and from a fluid source located in the proximal region 220 of the catheter 102 outside the patient, such as a reservoir 110. In one embodiment, the catheter shaft 214 includes a single fluid channel for moving the fluid toward a balloon 112. For example, the fluid channel may, under the control of a controller 120, deliver the inflation fluid from a fluid port 234 to the balloon 112. Thus, the channel inlet is in fluid communication with the balloon 112 and allows the fluid to pass through the balloon 112 at a selected flow rate to inflate the balloon 112. The flow rate controls heat transfer between the balloon 112 and the blood vessel wall, reducing the possibility of tissue overheating during treatment. For example, the flow rate may provide active cooling of the first approximately 1 millimeter of tissue to maintain the integrity of, for instance, the renal artery wall.

[0069] In one embodiment, the catheter shaft 214 includes a guidewire lumen 213. The guidewire lumen 213 may extend through the catheter shaft 214 and optionally through the transducer 111. Furthermore, the guidewire lumen 213 may extend through the distal tip 510. Thus, the distal tip 510 may travel along the guidewire 406 through the patient's anatomical structure. As previously stated, the catheter 102 may include an electrical cable 230. The electrical cable 230 may be a single electrical cable that runs longitudinally through the catheter shaft 214.

[0070] Referring to Figure 7, a cross-sectional view of the distal portion of a catheter in an ultrasound-based tissue treatment system, shown along line AA in Figure 5, is shown according to one embodiment. The catheter shaft 214 may include a fluid lumen 508 and a guidewire lumen 213, as previously described. In one embodiment, the electrical cable 230 includes multiple electrical cables. For example, a first electrical cable 702 and a second electrical cable 704 may extend parallel to each other within a common sheath.

[0071] In one embodiment, the catheter 102 includes a unidirectional fluid flow of cooling fluid 403 from the controller 120 through the balloon 112 to the surrounding environment. As the cooling fluid 403 passes through the balloon 112, the fluid cools the transducer 111 and transfers heat downstream in the blood vessel. The catheter 102 may include a flow control device for regulating the flow rate of the cooling fluid 403 to the surrounding environment. It will be understood that the difference in flow rates between the cooling fluid 403 entering the balloon 112 and the cooling fluid 403 leaving the balloon 112 can affect the balloon's expansion. For example, when the inflow rate is higher than the outflow rate, the balloon 112 expands. The reverse is also true. Therefore, a flow control device may be used to control the expansion of the balloon 112.

[0072] Referring to Figure 8, a side view of the distal portion of a catheter of an ultrasound-based tissue treatment system including a flow control device is shown according to one embodiment. In one embodiment, the catheter 102 includes a flow control device 802. The flow control device 802 may be located at the distal tip 510 of the catheter 102. For example, the flow control device 802 may be attached to an inner member 804 of the catheter shaft 214. The inner member 804 may include one or more holes 806 that are in fluid communication with a fluid lumen 508. More specifically, the fluid lumen 508 may be coupled to the lumen (inner cavity) of the inner member 804, allowing a cooling fluid 403 to pass (be delivered) through the holes 806 of the inner member 804 into the interior 506 of the balloon 112.

[0073] The flow control device 802 can also be coupled to the balloon 112. More specifically, the balloon 112 can be sealed to the outer surface of the flow control device 802. Thus, the cooling fluid 403 can flow from the inside 506 of the balloon 112 to the flow control device 802 and then to the distal ambient environment. By allowing the cooling fluid 403 to flow through the inside 506 of the balloon to the ambient environment, rather than directly through the fluid lumen 508, the exchange of cooling fluid inside the balloon can be facilitated, thereby enhancing the cooling of the transducer and / or tissue. For example, the cooling fluid 403 heated by sonication inside the balloon 112 can be discharged and replenished with fresh cooling fluid. Such replenishment can be performed without requiring a return lumen, allowing for a reduction in the overall size of the device.

[0074] As will be described later, the flow control device 802 may provide a unidirectional fluid flow to provide a variable pressure to the balloon 112, for example, a compliant balloon. The flow control device 802 may have an inlet port 808 for receiving fluid passing from the fluid lumen 508 through the interior 506. The flow control device 802 may also have an outlet port, for example on the distal or side surface of the device, for discharging the fluid to the surrounding environment. When the fluid reaches a predetermined pressure, a fluid flow may occur through the flow control device 802. More specifically, the flow through the flow control device 802 may be adjusted to turn on when the fluid pressure exceeds a threshold and to turn off when the fluid pressure falls below that threshold. In this way, the flow control device 802 is configured to allow the fluid to pass to the surrounding environment when the fluid has a predetermined pressure.

[0075] Referring to Figure 9, a cross-sectional view of a catheter flow control device for an ultrasound-based tissue healing system is shown according to one embodiment. The flow control device 802 allows for the omission of a second fluid lumen by discharging the cooling fluid 403 rather than circulating it, and can control the outlet flow using a one-way valve. In one embodiment, the flow control device 802 includes a check valve 902. The check valve 902 may be located at the distal end 510 of the catheter 102, and a pressure on the input side of the valve, such as a cracking pressure, that is higher than the pressure on the output side of the valve, such as the outlet port 904, can cause the check valve 902 to open. When the valve is open, the cooling fluid 403 can flow out into the surrounding environment through the valve and the distal end 510 of the catheter 102. In contrast, when the input pressure is lower than the cracking pressure, the valve may be closed, and the fluid does not flow out into the surrounding environment through the valve and the distal end 510.

[0076] The check valve 902 may include an inlet port 808 for receiving fluid from the inside 506 of the balloon 112. The inlet port 808 can carry the fluid toward the elastomer valve 906 of the check valve 902. The elastomer valve 906 may be, for example, a duckbill valve, a slit membrane, etc. The elastomer valve 906 may be backed by a sealing plunger 908. By backing the elastomer valve 906, the sealing plunger 908 can maintain the shape of the elastomer valve 906 and prevent deformation of the elastomer valve 906 that would cause, for example, the discharge of unwanted fluid.

[0077] In one embodiment, the elastomer valve 906 may be formed from a soft polyurethane, such as Shore A polyurethane, and may recover consistently even when opened and closed under pressure. The elastomer valve 906 may have a crack pressure equal to a predetermined pressure at which the check valve 902 is to open. For example, the predetermined pressure may be a desired expansion pressure for the balloon 112. The desired expansion pressure may be the pressure required to expand the balloon 112 to a predetermined corresponding diameter. Thus, when the fluid pressure inside the balloon 506 is at the predetermined pressure, the balloon 112 may have a predetermined diameter, and the elastomer valve 906 may open to allow the cooling fluid 403 to pass through to the surrounding environment, cooling the transducer 111 and maintaining the balloon at the predetermined diameter.

[0078] Referring to Figure 10, a cross-sectional view of a catheter flow control device for an ultrasound-based tissue treatment system is shown according to one embodiment. The flow control device 802 may include one or more vent holes 1002 for discharging (venting) or dumping (releasing) the cooling fluid 403 into the surrounding environment. The vent holes 1002 may extend through the outer wall 1004 of the flow control device 802. More specifically, the flow control device 802 may have an outer wall 1004 surrounding an internal channel (internal flow path) 1006, and the vent holes 1002 may extend from the internal channel 1006 through the outer wall 1004 into the surrounding environment. Thus, the vent holes 1002 provide an outlet path for the cooling fluid 403.

[0079] The internal channel 1006 can be in fluid communication with the interior 506 of the balloon 112 via the inlet port 808. Thus, the cooling fluid 403 can flow from the interior 506 through the inlet port 808 toward the vent hole 1002. However, in one embodiment, the fluid flow is regulated by a plunger 1008. The plunger 1008 is movable within the internal channel 1006 relative to the vent hole 1002. For example, the plunger 1008 may include an annular body that rests on a guide wire lumen 213. The movement of the plunger 1008 may be influenced by other components of the flow control device 802. For example, the flow control device 802 may include a spring 1010 for biasing the plunger 1008 toward the vent hole 1002.

[0080] The spring 1010 can bias the plunger 1008 within the internal channel 1006, for example, in the proximal direction. In the biased position, the plunger 1008 can approach the vent hole 1002 and seal against the outer wall 1004, preventing the fluid from flowing through the vent hole 1002. On the other hand, when the fluid pressure increases, this fluid pressure can press against the plunger 1008 against the biasing force of the spring 1010. When the fluid pressure reaches a predetermined pressure, it can overcome the biasing force of the spring 1010, compress the spring 1010, and allow the plunger 1008 to slide distally. In this operating position, the plunger 1008 can be located distal to the vent hole 1002. Therefore, the cooling fluid 403 can flow into the internal channel 1006 and flow into the surrounding environment through the vent hole 1002, which is close to the plunger 1008. The fluid flow rate and / or pressure can be automatically adjusted by the spring 1010.

[0081] Referring to Figure 11, a cross-sectional view of a catheter flow control device for an ultrasound-based tissue healing system is shown according to one embodiment. The position of the plunger 1008 relative to the vent hole 1002 can be adjusted using one or more pull wires 1102. The pull wires 1102 may be connected to the plunger 1008, for example, by thermal or adhesive bonding, and may extend proximal through the catheter 102 to a proximal end. The proximal end may be coupled to an activation member such as a lever or knob, allowing a user to pull and / or push the pull wire 1102. By pulling and pushing the pull wire 1102, the position of the plunger 1008 relative to the vent hole 1002 can be controlled. More specifically, the pull wire 1102 may move the plunger 1008 relative to the vent hole 1002. The fluid flow rate and / or pressure may be manually adjusted by the pull wire 1102.

[0082] The flow control device 802 may have several vent holes 1002, and the position of the plunger 1008 may determine the amount of fluid flow through the vent holes 1002. For example, several vent holes 1002 may be arranged staggered in the axial direction, such that a first vent hole 1002A may be offset distally from a second vent hole 1002B. The plunger 1008 may slide past the first vent hole 1002A, exposing the first vent hole 1002A to the cooling fluid 403. Meanwhile, the second vent hole 1002B remains closed. Therefore, when the plunger 1008 is in the first position, the cooling fluid 403 may flow through the first vent hole 1002A but not through the second vent hole 1002B. Subsequently, the plunger 1008 may slide past the second vent hole 1002B, exposing both vent holes 1002 to the cooling fluid 403. Thus, the cooling fluid 403 can flow through both vent holes 1002A and 1002B. In this way, the position of the plunger can control the open vent area for discharging the cooling fluid 403 to the surrounding environment, and consequently, the amount of fluid passing through the vent holes 1002. Changing the flow of the cooling fluid 403 at the outlet can affect the pressure of the cooling fluid 403 inside the balloon 112 506.

[0083] Referring to Figure 12, a side view of a catheter flow control device for an ultrasound-based tissue healing system is shown according to one embodiment. The flow control device 802 may include a plurality of orifices that crack (open) at a predetermined fluid pressure. For example, in one embodiment, the flow control device 802 includes several vent holes 1002 for leaking a cooling fluid 403 at a predetermined pressure. The vent holes 1002 may extend through the outer wall 1004 of the flow control device 802. Each hole may be in fluid communication with the interior 506 of the balloon 112 and may have a crack pressure to allow the flow of the cooling fluid 403 when the fluid pressure inside 506 reaches a predetermined pressure.

[0084] The crack pressure in each hole may be the same. Each hole may have the same shape and size so that the resistance to flow in each hole is similar. Therefore, the vent holes 1002 can discharge fluid under a constant flow condition. More specifically, each vent hole 1002 can discharge the cooling fluid 403 to the surrounding environment at the same rate.

[0085] The crack pressure of each hole, or the crack pressure of each group of holes in a group of holes, may differ. For example, some of the vent holes 1002 may have a smaller diameter than the others. The smaller vent holes 1002 may have a higher flow impedance and therefore a higher crack pressure than the larger vent holes 1002. The flow may selectively pass through the larger holes 1002 at the first expansion pressure, and then pass through both the larger and smaller holes 1002 when the fluid pressure exceeds the crack pressure of the smaller holes 1002. Thus, the vent holes 1002 can discharge more fluid as the expansion pressure increases, and the balloon expansion pressure can be maintained within a desired range greater than the predetermined pressure.

[0086] In one embodiment, the flow control device 802 includes a plug 1202. The plug 1202 may have several holes 1204 that penetrate the plug body axially and / or radially. For example, the plug 1202 may be formed from a semipermeable material such as electrospun fiber material. The holes and / or channels formed in the plug 1202 can receive the cooling fluid 403 from the inside 506 of the balloon 112 and allow the cooling fluid 403 to pass distally and outward toward the vent hole 1002 of the flow control device 802. Thus, the plug 1202 can provide some resistance to the distal flow of the cooling fluid 403 while transmitting the cooling fluid 403 toward the vent hole 1002 for discharge into the surrounding environment.

[0087] Referring to Figure 13, a cross-sectional view of the flow control device is shown according to one embodiment. In this cross-section, a network of flow channels formed by a plurality of holes is evident. This network of flow channels can carry the cooling fluid 403 from the interior 506 of the balloon 112 to the vent holes 1002 of the outer wall 1004 of the flow control device. Therefore, when the balloon 112 is inflated to a pressure exceeding the crack pressure between the flow channel network and the vent holes 1002, for example, the combined impedance, fluid can be discharged from the interior 506.

[0088] Referring to Figure 14, a cross-sectional view of a catheter flow control device for an ultrasound-based tissue treatment system is shown according to one embodiment. The flow control device 802 can allow relative movement between the distal end of the balloon 112 and the catheter shaft 214. Such movement can groom (shape) the balloon 112. More specifically, by allowing the distal end of the balloon 112 to move relative to the catheter shaft 214, the balloon 112 can be stretched, and as a result, its profile can be reduced. When the balloon 112 is stretched and its profile is reduced, the balloon can more easily traverse the anatomical structure of the target. The reduced profile can allow the balloon 112 to traverse narrow vessels, such as the radial artery, during delivery and / or retrieval.

[0089] In one embodiment, a self-grooming (self-adjusting) balloon 112 includes a flow control device 802 having a proximal tip 1402 and a distal tip 1404. The balloon 112 can self-groom because, when the fluid pressure within the balloon 112 is removed, it can be biased to wrap around or adjust to a lower profile (e.g., stretch). For example, the balloon 112 may be manufactured in a wrapped and / or stretched configuration and, based on the biasing force provided by the flow control device 802, may preferentially return to that configuration upon deflation. When the balloon 112 is in a lower profile, it can be traversed through narrow channels or blood vessels. For example, the balloon 112 can be delivered through a radial artery or drawn into a guide sheath without snagging on or damaging adjacent structures.

[0090] The proximal tip 1402 may be independently movable relative to the distal tip 1404. For example, the proximal tip 1402 may be attached to the catheter shaft 214, and the distal tip 1404 may be movably attached to the proximal tip 1402. The proximal tip 1402 may be fixed relative to the catheter shaft 214, and the distal tip 1404 may be coupled to the balloon 112. Therefore, when the distal tip 1404 moves relative to the proximal tip 1402, the distal end of the balloon 112 may move relative to the catheter shaft 214.

[0091] In one embodiment, the distal tip portion 1404 is slidable on the proximal tip portion 1402. The distal tip portion 1404 may have a recess 1403 that extends to the proximal end of the portion. The recess 1403 may be sized to receive the distal projection of the proximal tip portion 1402. More specifically, the projection of the proximal tip portion 1402 may extend into the recess 1403 of the distal tip portion 1404. Thus, the distal tip portion 1404 can move axially and be radially constrained by the proximal tip portion 1402. The distal tip portion 1404 is essentially movable relative to the proximal tip portion 1402 as a collar and is constrained by the shaft.

[0092] The flow control device 802 may include a spring 1406 that applies a reaction force to the distal tip 1404, thereby biasing the distal tip 1404 toward the proximal tip 1402. This reaction force may counteract the proximal load applied to the distal tip 1404 by the balloon 112. When the balloon 112 inflates, the balloon wall expands radially outward, and the length of the balloon decreases. As the balloon 112 grows (gets larger), the distal end of the balloon 112 pulls the distal tip 1404 toward the proximal direction. This proximal load may act in a direction different from the biasing force of the spring 1406. More specifically, the spring 1406 may be a compression spring that biases the distal tip 1404 toward the proximal tip 1402. When the fluid pressure inside balloon 112 506 is at a lower level, the spring force of the spring can overcome the contraction force applied to the distal tip 1404 by the distal end of balloon 112. Thus, the spring 1406 can expand the balloon and maintain the balloon in a small profile.

[0093] Referring to Figure 15, a cross-sectional view of a catheter flow control device for an ultrasound-based tissue treatment system is shown according to one embodiment. When the fluid pressure inside the balloon 112 506 is at a higher level, the spring force of the spring 1406 may be insufficient to overcome the contractile force applied to the distal tip 1404 by the distal end of the balloon 112. As the balloon 112 grows, the distal tip 1404 may be pulled proximal and move relative to the proximal tip 1402. This expansion and contraction motion may compress the spring 1406 between the distal tip 1404 and the proximal tip 1402. For example, the distal tip 1404 may slide on the proximal tip 1402 to reduce the gap between the proximal end of the distal tip and the adjacent wall of the base of the proximal tip 1402.

[0094] For example, when the fluid pressure inside the balloon 112 drops from a higher level due to the discharge (venting) of the cooling fluid 403 through the vent hole 1002 at the distal tip 510, the spring 1406 can again overcome the proximal force applied by the balloon 112 and return the distal tip 1404 away from the proximal tip 1402. Thus, the flow control device 802 can be a self-grooming device that discharges the cooling fluid 403 into the surrounding environment and extends the balloon 112 after balloon deflation to create a profile suitable for the balloon to follow through narrow blood vessels.

[0095] Referring to Figure 16, a cross-sectional view of a catheter flow control device for an ultrasound-based tissue treatment system is shown according to one embodiment. In one embodiment, the distal tip 1404 of the flow control device 802 may be rotatable on the proximal tip 1402. For example, these parts may have paired threaded portions, such as a helical male thread on the proximal tip 1402 that engages with a female thread on the distal tip 1404, in order to allow the parts to be screwed to each other. More specifically, the distal tip 1404 may be screw-coupled (screwed) to the proximal tip 1402. When a proximal load of the balloon 112 on the distal tip 1404 pulls the part in the proximal direction, these threads may cause the distal tip 1404 to slide and rotate on the proximal tip 1402. The balloon 112 may be twisted in a low-profile state before inflation, so that when the balloon inflates, the rotation of the distal tip 1404 can untwist the balloon 112. Similarly, when the cooling fluid 403 inside the balloon 112 is released into the surrounding environment and the balloon deflates, the distal tip 1404 may be biased forward by the spring 1406 and rotated in the opposite direction to twist the balloon 112. The twisted balloon may be wound into a low profile suitable for traversing narrow blood vessels.

[0096] Referring to Figure 17, a cross-sectional view of a catheter flow control device for an ultrasound-based tissue treatment system is shown according to one embodiment. The flow control device 802 may include a self-grooming device incorporating one or more activatable vent holes 1002. The distal portion may have vent holes 1002 extending along the central axis of the flow control device 802 to discharge fluid from the balloon 112, similar to the embodiments described with respect to Figures 14 to 16. The axial vent holes 1002 may always be open, or they may discharge fluid each time the cooling fluid 403 is circulated through the balloon 112. Furthermore, the distal portion may include lateral vent holes 1701 extending radially outward with respect to the central axis. The distal tip 1404, and therefore the lateral vent holes 1701, may be movable relative to the proximal tip 1402.

[0097] In one embodiment, the proximal tip 1402 includes a fluid port 1702. The fluid port 1702 may extend through the proximal tip 1402 from an inlet that fluidly communicates with the interior 506 of the balloon 112 to an outlet on the side of the proximal tip 1402. For example, the fluid port 1702 may face laterally outward from a projection of the proximal tip 1402 that slides within the distal tip 1404. Thus, when the fluid port 1702 and the vent hole 1002 are aligned axially, the outlet of the fluid port 1702 may face the lateral vent hole 1701. More specifically, the distal tip 1404 may be movable relative to the proximal tip 1402 so that the lateral vent hole 1701 can be aligned with the fluid port 1702. In the operating state shown in Figure 17, the fluid port 1702 and the lateral vent hole 1701 are aligned, and the cooling fluid 403 can flow into the surrounding environment through the fluid port 1702 and the lateral vent hole 1701. In particular, in this operating state, when the balloon 112 is inflated and the distal tip 1404 is pulled in the proximal direction, the spring 1406 is compressed, a fluid flow can be established.

[0098] As the fluid exits the vent hole 1002 through the side wall of the distal tip 1404, pressure may be released within the balloon 112, and the spring 1406 may bias the distal tip 1404 away from the proximal tip 1402. The flow control device 802 can be biased to an operating state in which the fluid port 1702 and the lateral vent hole 1701 are misaligned. The distal tip 1404 and the proximal tip 1402 may be engaged in a sliding fit with insufficient clearance between the components, taking into account the fluid flow when the fluid port 1702 and the lateral vent hole 1701 are misaligned. Thus, in this operating state, the cooling fluid 403 can be discharged only from the vent hole 1002. Thus, when the balloon pressure rises above a threshold limit, the lateral vent hole 1701 may be activated to rapidly discharge the cooling fluid 403 and rapidly reduce the balloon pressure to a predetermined pressure. At the predetermined pressure, the balloon 112 may have a predetermined expansion diameter.

[0099] In the embodiments described above, the operation of the flow control device for moving the distal tip 1404 relative to the proximal tip 1402 is automatically controlled. More specifically, the pressure inside the balloon 112 applies a counter-force to the distal tip 1404 that acts against the biasing force of the spring. Thus, the spring 1406 and the balloon 112 work together to determine whether or not the flow control device 802 is activated. However, in one embodiment, the operation of the flow control device 802 is performed manually. For example, the catheter 102 may include a pull wire extending from a handle at the proximal end of the device to the distal tip 1404. The pull wire can either pull the distal tip 1404 relative to the proximal tip 1402 or push the distal tip 1404 forward over the proximal tip 1402. The relative movement of the distal tip 1404 and the proximal tip 1402 can control the flow of the cooling fluid 403 and / or groom (adjust) the balloon 112, as described above.

[0100] Referring to Figure 18, a cross-sectional view of the catheter shaft of an ultrasound-based tissue treatment system catheter is shown according to one embodiment. As previously stated, the catheter shaft 214 may have a shaft diameter of 5 French or less to facilitate radial artery access. To achieve such a diameter, the catheter shaft 214 may not include a guidewire lumen 213. More specifically, by omitting the guidewire lumen 213, the components of the catheter shaft 214 can be reduced, and thus the overall dimensions of the catheter shaft 214 can be reduced. However, if there is no guidewire lumen 213 for guiding the catheter 102 along the guidewire 406, another method may be required to maneuver the device through the vascular system. Thus, the catheter 102 may be configured as a maneuverable catheter.

[0101] In one embodiment, the catheter shaft 214 includes an outer member 1802 having a central lumen 1804. The outer member 1802 may include a tubular structure having an inner wall 1806 that accommodates the central lumen 1804. In one embodiment, the inner member 804 of the catheter 102 may extend through the central lumen 1804. For example, the inner member 804 may include a tubular structure extending from the proximal end of the catheter 102 to the distal end of the catheter 102, for example, through a balloon 112. The inner member 804 may have a fluid lumen 508 for delivering fluid to the interior 506 of the balloon 112. For example, the inner member 804 may include a hole 806 for diffusing a cooling fluid 403 into the interior 506 of the balloon 112 (Figure 8). The wall 1808 of the inner member 804 provides a tubular structure having an outer wall 1808 that faces radially outward toward the inner wall 1806 of the outer member 1802. Therefore, the outer member 1802 and the inner member 804 can be coaxial tubular structures that form a gap between the outer wall 1808 and the inner wall 1806.

[0102] The gap between the inner member 804 and the outer member 1802 may be part of the central lumen 1804 through which one or more steering wires 1810 pass. More specifically, the steering wire(s) 1810 may extend through the central lumen 1804 between the inner wall 1806 of the outer member 1802 and the outer wall 1808 of the inner member 1804. The steering wire(s) 1810 may be pulled or pushed, for example, via the activation of a handle element, to steer the catheter 102.

[0103] In one embodiment, the catheter 102 includes a first steering wire 1820 extending through a central lumen 1804. The catheter 102 may also include a second steering wire 1822 extending through the central lumen 1804. The first steering wire 1820 may be located in the central lumen 1804 on the diametrically opposite side to the second steering wire 1822. More specifically, the first steering wire 1820 may be located on a first side surface of the inner member 804, and the second steering wire 1822 may be located on a second side surface of the inner member 804, opposite to the first steering wire 1820.

[0104] The steering wire 1810 may be formed from an elongated element of metal or polymer, such as a polyimide wire. In one embodiment, at least one of the one or more steering wires 1810 may be an electrical cable 1824. The electrical cable 1824 may extend to the distal end of the catheter 102 to deliver energy to the ultrasonic transducer 111.

[0105] Referring to Figure 19, a side view of a catheter for an ultrasound-based tissue treatment system is shown according to one embodiment. One or more steering wires 1810 may be connected to an outer member 1802 or an inner member 804 of the catheter shaft 214. More specifically, each steering wire 1810 may be attached to the catheter shaft 214 at its respective anchor point 1902. The anchor point 1902 may be located, for example, proximal to the balloon 112.

[0106] Referring to Figure 20, a side view of a catheter for an ultrasound-based tissue treatment system is shown according to one embodiment. When the steering wire 1810 is pulled, a force may be transmitted to the anchor point 1902, and then to the catheter shaft 214. For example, when the first steering wire 1820 is pulled, the outer member 1802 is compressed along the side adjacent to the first steering wire 1820, thereby causing the catheter to bend, for example, in the direction of that side. Similarly, when the second steering wire 1822 is pulled, the catheter 102 may be steered in the opposite direction, i.e., toward the side adjacent to the second steering wire 1822. The steering wire 1810 may be bidirectional and may also be pushed to steer the catheter 102. More specifically, the catheter 102 can be steered by applying a load to the catheter 102 via the steering wire 1810 by pushing or pulling the wire. Therefore, the catheter 102 can be guided through the vascular system and manipulated to the target anatomical structure without the help of a guidewire.

[0107] Referring to Figure 21, a side view of a catheter for an ultrasound-based tissue therapy system is shown according to one embodiment. By omitting the guide sheath, it may be possible to reduce the overall dimensions of the catheter system introduced into the patient's anatomical structure. A guide sheath may typically be used to introduce the catheter 102 into a specific anatomical structure and may have complex curvatures to facilitate delivery to that structure. However, the guide sheath has wall thickness, which can increase the overall dimensions of the catheter system. Therefore, by removing the guide sheath, the overall dimensions can be reduced, allowing the catheter system to access specific anatomical structures more easily.

[0108] In one embodiment, the catheter 102 is configured to bend from a straight shape to a curved shape. In the curved shape, the catheter 102 may have a complex curvature. More specifically, different sections (parts) of the catheter 102 may be curved differently such that the overall profile of the curved catheter shaft 214 exhibits a variety of curvatures from the proximal end to the distal end of the catheter 102. The catheter shaft 214 may include several shaft sections 2102. Each shaft section 2102 may have its own rigidity. For example, the shaft section 2102 may include a distal section 2104, an intermediate section 2106, and a proximal section 2108. For example, the distal section 2104 may include the most distal 1-3 cm, e.g., 2 cm, of the catheter shaft 214 extending proximal from the balloon 112; the intermediate section 2106 may include 3-5 cm, e.g., 4 cm, of the catheter shaft 214 extending proximal from the distal section 2104; and the proximal section 2108 may include the remaining length of the catheter shaft extending proximal from the intermediate section 2106. The stiffness of each of these sections may differ and may increase distally. Thus, the stiffness of each section in the distal section 2104 may be lower than the stiffness of each section in the intermediate section 2106, and the stiffness of each section in the intermediate section 2106 may be lower than the stiffness of each section in the proximal section 2108.

[0109] In one embodiment, the catheter 102 includes a steering wire 1810 attached to the catheter shaft 214 at an anchor point 1902. The anchor point 1902 may be located at the distal end of the catheter shaft 214, for example, within the distal section 2104 of the catheter 102. The steering wire 1810 may have a structure similar to that described above with respect to Figures 18 to 20.

[0110] The rigidity of the catheter 102 may also be influenced by the central support 2103. The central support 2103 may be a reinforcing member extending through the central lumen 1804 of the catheter shaft 214. The central support 2103 may be, for example, a hypotube. The hypotube may have a semi-rigid structure and may have sufficient rigidity to contribute to the ability to push it into the catheter shaft 214.

[0111] Referring to Figure 22, a side view of a catheter for an ultrasound-based tissue treatment system is shown according to one embodiment. The variable stiffness of the catheter shaft 214 can cause the catheter 102 to take on complex curvature when the steering wire 1810 is pulled. When the steering wire 1810 is pulled, a deflection load may act on the anchor point 1902, bending the catheter 102 along the entire shaft section 2102. The shaft may have individual angular changes at the transitional portions between sections. More specifically, when the catheter 102 is deflected, the radius of curvature of the proximal section 2108 may be greater than that of the intermediate section 2106, and the radius of curvature of the intermediate section 2106 may be greater than that of the distal section 2104. The change in deflection curvature from section to section may be based on the stiffness of the outer member 1802 or the inner member 804 along the entire section.

[0112] The change in catheter stiffness that contributes to the complex curvature can also be influenced by the central support 2103. In one embodiment, the central support 2103 includes an inner member 804. For example, the inner member 804 may be a hypotube for carrying the cooling fluid 403 to the balloon 112. The inner member 804 may have a wall 1808 (Figure 18), which in one embodiment is thinner in the distal section 2104 than in the intermediate section 2106. For example, the hypotube may be centerless polished to vary the wall thickness over its length. The thin wall 1808 over the distal section 2104 may make the distal section 2104 more flexible than the intermediate section 2106 or the proximal section 2108. Thus, similar to the change in stiffness of the outer member 1802 described above, the change in stiffness of the inner member 804 may cause the section to bend in different directions when the catheter is manipulated, resulting in complex curvature. Complex curvature may have a shape provided by a guide sheath in other embodiments, and therefore, catheter 102 can be used in radial artery access approaches without requiring such a guide sheath.

[0113] Referring to Figure 23, a schematic diagram of an ultrasound-based tissue treatment system is shown according to one embodiment. In one embodiment, the system incorporates a hybrid flow configuration in which a cooling fluid 403 is discharged into the ambient environment through the distal end of the catheter 102, and the cooling fluid 403 is also returned to the controller 120. Thus, the catheter 102 may include an inlet line 2301 that delivers the cooling fluid 403 from an inlet pump 2302 of the controller 120 to a balloon 112, and an outlet line 2303 that delivers the cooling fluid 403 from the balloon 112 to the controller 120 (e.g., a reservoir 110). The catheter 102 may also include a flow control device 802 for discharging the fluid into the ambient environment. Thus, the hybrid flow system may deliver more fluid to the balloon 112 than the amount that needs to be returned to the reservoir 110 via the outlet line 2303.

[0114] The flow of fluid circulating to and from the controller 120 can be regulated by the valve control unit 2310. For example, the valve control unit 2310 may be integrated within the controller 120 and electrically coupled to the flow valve 2312. The flow valve 2312 may be integrated within the catheter hub 2314 of the catheter 102. Alternatively, the flow valve 2312 may be integrated within the controller 120. The flow valve 2312 may be activated by the valve control unit 2310 to allow or restrict the flow from the balloon 112 to the reservoir 10.

[0115] When the flow valve 2312 is integrated into the catheter hub 2314, the flow valve 2312 can be activated manually. For example, the catheter hub 2314 may have a switch, button, or knob to allow the user to manually adjust the valve state (open or close the valve). When the flow valve 2312 is closed, the balloon 112 can be inflated. When the flow valve 2312 is open, the balloon 112 can be deflated. Thus, the user can manually control the balloon's inflation diameter by activating the flow valve 2312.

[0116] When some fluid is discharged into the ambient environment and some cooling fluid 403 is recirculated to the controller 120, the injection rate from the inlet pump 2302 and the return to the reservoir 110 can be adjusted to control the balloon's expansion. For example, when the flow rate to the balloon 112 is equal to the sum of the discharge flow rate and the return flow rate, the balloon's expansion diameter may remain constant. The balloon's diameter can be increased by increasing the inlet flow rate beyond the sum of the discharge flow rate and the return flow rate. Conversely, the balloon's diameter can be reduced by decreasing the inlet flow rate (or increasing the discharge and return flow rates) so that more fluid leaves the balloon than enters it. Thus, the inlet pump 2302, the flow control device 802, and / or the flow valve 2312 can be controlled to adjust the balloon's expansion and contraction.

[0117] In one embodiment, the outlet line 2303 may include a lumen for sending the cooling fluid 403 to the controller 120. The flow rate of the fluid being returned may be smaller than the flow rate of the fluid to the balloon 112, as described above, and therefore the outlet line 2303 may have a smaller lumen than the lumen for sending fluid to the balloon 112. More specifically, because the amount of fluid being returned is small, the return lumen may be smaller. Reducing the lumen size can lead to a reduction in the overall dimensions of the catheter 102. Therefore, miniaturizing the return line can contribute to making the catheter shaft 214 suitable for radial artery access.

[0118] On the other hand, the fluid lumen 508 of the catheter 102 may be sized to avoid clogging of the catheter shaft 214 during priming. Smaller lumens may become clogged by bubbles generated during priming, so it may be advantageous to increase the size of specific lumens that are prone to such clogging. In one embodiment, the return line has a larger lumen than the inlet line. This makes the return line less prone to clogging, for example, by bubbles during priming.

[0119] In one embodiment, the catheter comprises a catheter shaft, a balloon, an ultrasonic transducer, and a flow control device. The catheter shaft has a fluid lumen. The balloon is attached to the catheter shaft and has an interior that is in fluid communication with the fluid lumen. The ultrasonic transducer is located inside the balloon. The flow control device has an inlet port for receiving fluid passing from the fluid lumen through the interior. The flow control device is configured to discharge the fluid into the ambient environment when the fluid reaches a predetermined pressure.

[0120] In one embodiment, the flow control device includes a check valve.

[0121] In one embodiment, the check valve includes a sealing plunger that backs an elastomer valve. The elastomer valve has a crack pressure equal to the predetermined pressure.

[0122] In one embodiment, the flow control device includes a vent hole and a plunger. The vent hole extends from an internal channel through the outer wall. The plunger is movable within the internal channel relative to the vent hole.

[0123] In one embodiment, the catheter is equipped with a spring for biasing the plunger against the vent hole.

[0124] In one embodiment, the catheter includes a pull wire for moving the plunger relative to the vent hole.

[0125] In one embodiment, the flow control device includes a plug having several holes for leaking the fluid having the predetermined pressure.

[0126] In one embodiment, the flow control device comprises a proximal tip, a distal tip movable relative to the proximal tip, and a spring between the proximal tip and the distal tip.

[0127] In one embodiment, the proximal tip is attached to the catheter shaft, and the balloon is coupled to the distal tip.

[0128] In one embodiment, the distal tip portion is slidable on the proximal tip portion.

[0129] In one embodiment, the distal tip is rotatable on the proximal tip.

[0130] In one embodiment, the distal tip is screwed onto the proximal tip.

[0131] In one embodiment, the distal tip includes a vent hole. The proximal tip includes a fluid port. The distal tip is movable relative to the proximal tip so as to align the vent hole with the fluid port.

[0132] In one embodiment, the catheter shaft has a shaft diameter of 5 French or less.

[0133] In one embodiment, the catheter comprises a catheter shaft, a balloon, an ultrasonic transducer, and a check valve. The catheter shaft has a fluid lumen. The balloon is attached to the catheter shaft and has an interior that is in fluid communication with the fluid lumen. The ultrasonic transducer is located inside the balloon. The check valve has an inlet port for receiving fluid passing from the fluid lumen through the interior. The check valve is configured to discharge the fluid to the ambient environment when the fluid reaches a predetermined pressure.

[0134] In one embodiment, the check valve includes a sealing plunger that backs an elastomer valve. The elastomer valve has a crack pressure equal to the predetermined pressure.

[0135] In one embodiment, the catheter comprises a catheter shaft, a balloon, an ultrasonic transducer, and a flow control device. The catheter shaft has a fluid lumen. The balloon is attached to the catheter shaft and has an interior that is in fluid communication with the fluid lumen. The ultrasonic transducer is located inside. The flow control device has an inlet port for receiving fluid passing from the fluid lumen through the interior. In one embodiment, the flow control device comprises a vent hole and a plunger. The vent hole extends from an internal channel through the outer wall. The plunger is movable within the internal channel relative to the vent hole. The flow control device is configured to discharge the fluid into the ambient environment.

[0136] In one embodiment, the catheter is equipped with a spring for biasing the plunger against the vent hole.

[0137] In one embodiment, the catheter includes a pull wire for moving the plunger relative to the vent hole.

[0138] In one embodiment, the catheter comprises a catheter shaft, a balloon, an ultrasonic transducer, and a flow control device. The catheter shaft has a fluid lumen. The balloon is attached to the catheter shaft and has an interior that is in fluid communication with the fluid lumen. The ultrasonic transducer is located inside the balloon. The flow control device has an inlet port for receiving fluid passing from the fluid lumen through the interior. The flow control device includes a plug with several holes for leaking the fluid into the ambient environment when the fluid has a predetermined pressure.

[0139] In one embodiment, the catheter comprises a catheter shaft, a balloon, an ultrasonic transducer, and a flow control device. The catheter shaft has a fluid lumen. The balloon is attached to the catheter shaft and has an interior that is in fluid communication with the fluid lumen. The ultrasonic transducer is located inside the balloon. The flow control device has an inlet port for receiving fluid passing from the fluid lumen through the interior. The flow control device has a proximal tip attached to the catheter shaft, a distal tip coupled to the balloon and movable relative to the proximal tip, and a spring between the proximal tip and the distal tip. The flow control device is configured to discharge the fluid into the ambient environment when the fluid has a predetermined pressure.

[0140] In one embodiment, the catheter comprises a catheter shaft, a balloon, an ultrasonic transducer, and a flow control device. The catheter shaft has a fluid lumen. The balloon is attached to the catheter shaft and has an interior that is in fluid communication with the fluid lumen. The ultrasonic transducer is located inside the balloon. The flow control device has an inlet port for receiving fluid passing from the fluid lumen through the interior. The flow control device has a proximal tip, a distal tip movable relative to the proximal tip, and a spring between the proximal tip and the distal tip. The flow control device is configured to discharge the fluid into the surrounding environment when the fluid has a predetermined pressure.

[0141] In one embodiment, the distal tip portion is slidable on the proximal tip portion.

[0142] In one embodiment, the distal tip is rotatable on the proximal tip.

[0143] In one embodiment, the distal tip is screwed onto the proximal tip.

[0144] In one embodiment, the distal tip includes a vent hole. The proximal tip includes a fluid port. The distal tip is movable relative to the proximal tip so as to align the vent hole with the fluid port.

[0145] In one embodiment, the catheter comprises a catheter shaft, a balloon, an ultrasonic transducer, and a flow control device. The catheter shaft has a fluid lumen. The catheter shaft has a shaft diameter of 5 French or less. The balloon is attached to the catheter shaft and has an interior that communicates with the fluid lumen. The ultrasonic transducer is located inside the balloon. The flow control device has an inlet port for receiving fluid passing from the fluid lumen through the interior. The flow control device is configured to discharge the fluid into the ambient environment when the fluid has reached a predetermined pressure.

[0146] In one embodiment, the catheter comprises a catheter shaft, a balloon, an ultrasonic transducer, and a flow control device. The balloon has an interior. The ultrasonic transducer is located inside the balloon. The catheter shaft has an outer member having a central lumen, an inner member having a fluid lumen extending through the central lumen to deliver fluid into the interior, and one or more steering wires extending through the central lumen between the inner wall of the outer member and the outer wall of the inner member. The one or more steering wires are connected to the outer member or the inner member at an anchor point proximal to the balloon.

[0147] In one embodiment, the one or more steering wires include a first steering wire on the diametrically opposite side of the second steering wire.

[0148] In one embodiment, one or more of the first steering wire and the second steering wire include an electrical cable for delivering energy to the ultrasonic transducer.

[0149] In one embodiment, the catheter shaft has several shaft sections, each shaft section having its own rigidity.

[0150] In one embodiment, the several shaft sections include a distal section, an intermediate section, and a proximal section. The stiffness of each of the distal sections is lower than the stiffness of each of the intermediate sections. The stiffness of each of the intermediate sections is lower than the stiffness of each of the proximal sections.

[0151] In one embodiment, the inner member has a wall, which is thinner in the distal section than in the intermediate section.

[0152] In one embodiment, an ultrasound-based tissue treatment system comprises a catheter according to any of the embodiments described above, a controller, and a connecting cable that interconnects the catheter and the controller.

[0153] In the aforementioned specification, the present invention was described with reference to certain exemplary embodiments thereof. It is evident that various modifications can be made without departing from the broader spirit and scope of the invention as described in the following claims. Accordingly, the specification and drawings should be considered illustrative rather than restrictive. The claims at the time of filing are as follows: [Claim 1] A catheter shaft having a fluid lumen, A balloon attached to the catheter shaft and having an interior that communicates fluidly with the fluid lumen, The ultrasonic transducer located inside, A flow control device having an inlet port for receiving fluid passing through the interior from the fluid lumen, Equipped with, The flow control device is configured to discharge the fluid into the surrounding environment when the fluid has a predetermined pressure. A catheter characterized by the following features. [Claim 2] The flow control device includes a check valve. The catheter according to feature 1. [Claim 3] The aforementioned check valve includes a sealing plunger that backs the elastomer valve. The elastomer valve has a crack pressure equal to the predetermined pressure. The catheter according to claim 2. [Claim 4] The flow control device has a vent hole extending from an internal channel through the outer wall, and a plunger that is movable within the internal channel relative to the vent hole. The catheter according to feature 1. [Claim 5] A spring for biasing the plunger relative to the vent hole. The catheter according to claim 4, further comprising the above. [Claim 6] A pull wire for moving the plunger relative to the vent hole. The catheter according to claim 4 or 5, further comprising the above. [Claim 7] The flow control device includes a plug having a plurality of holes for leaking the fluid having the predetermined pressure. The catheter according to feature 1. [Claim 8] The flow control device comprises a proximal tip, a distal tip movable relative to the proximal tip, and a spring between the proximal tip and the distal tip. The catheter according to feature 1. [Claim 9] The proximal tip portion is attached to the catheter shaft. The balloon is connected to the distal tip. The catheter according to feature 8. [Claim 10] The distal tip portion is slidable on the proximal tip portion. The catheter according to feature 8 or 9. [Claim 11] The distal tip portion is rotatable on the proximal tip portion. A catheter according to any one of claims 8 to 10. [Claim 12] The distal tip portion is screwed into the proximal tip portion. The catheter according to feature 11. [Claim 13] The distal tip portion includes a vent hole, The aforementioned proximal tip portion includes a fluid port, The distal tip is movable relative to the proximal tip so as to align the vent hole with the fluid port. A catheter according to any one of 8 to 12, characterized by the above. [Claim 14] The catheter shaft has a shaft diameter of 5 French or less. A catheter according to any one of claims 1 to 13. [Claim 15] A catheter shaft having a fluid lumen, A balloon attached to the catheter shaft and having an interior that communicates fluidly with the fluid lumen, The ultrasonic transducer located inside, A check valve having an inlet port for receiving fluid passing through the interior from the fluid lumen, Equipped with, The check valve is configured to discharge the fluid into the surrounding environment when the fluid has a predetermined pressure. A catheter characterized by the following features. [Claim 16] The aforementioned check valve includes a sealing plunger that backs the elastomer valve. The elastomer valve has a crack pressure equal to the predetermined pressure. The catheter according to claim 15. [Claim 17] A catheter shaft having a fluid lumen, A balloon attached to the catheter shaft and having an interior that communicates fluidly with the fluid lumen, The ultrasonic transducer located inside, A flow control device having an inlet port for receiving fluid passing through the interior from the fluid lumen, Equipped with, The flow control device has a vent hole extending from an internal channel through the outer wall, and a plunger that is movable within the internal channel relative to the vent hole. The flow control device is configured to discharge the fluid into the surrounding environment. A catheter characterized by the following features. [Claim 18] A spring for biasing the plunger relative to the vent hole. The catheter according to claim 17, further comprising the above. [Claim 19] A pull wire for moving the plunger relative to the vent hole. The catheter according to claim 17 or 18, further comprising the above. [Claim 20] A catheter shaft having a fluid lumen, A balloon attached to the catheter shaft and having an interior that communicates fluidly with the fluid lumen, The ultrasonic transducer located inside, A flow control device having an inlet port for receiving fluid passing through the interior from the fluid lumen, Equipped with, The flow control device includes a plug having multiple holes for leaking the fluid into the surrounding environment when the fluid has a predetermined pressure. A catheter characterized by the following features. [Claim 21] A catheter shaft having a fluid lumen, A balloon attached to the catheter shaft and having an interior that communicates fluidly with the fluid lumen, The ultrasonic transducer located inside, A flow control device having an inlet port for receiving fluid passing through the interior from the fluid lumen, Equipped with, The flow control device comprises a proximal tip attached to the catheter shaft, a distal tip connected to the balloon and movable relative to the proximal tip, and a spring between the proximal tip and the distal tip. The flow control device is configured to discharge the fluid into the surrounding environment when the fluid has a predetermined pressure. A catheter characterized by the following features. [Claim 22] A catheter shaft having a fluid lumen, A balloon attached to the catheter shaft and having an interior that communicates fluidly with the fluid lumen, The ultrasonic transducer located inside, A flow control device having an inlet port for receiving fluid passing through the interior from the fluid lumen, Equipped with, The flow control device comprises a proximal tip, a distal tip movable relative to the proximal tip, and a spring between the proximal tip and the distal tip. The flow control device is configured to discharge the fluid into the surrounding environment when the fluid has a predetermined pressure. A catheter characterized by the following features. [Claim 23] The distal tip portion is slidable on the proximal tip portion. The catheter according to claim 22. [Claim 24] The distal tip portion is rotatable on the proximal tip portion. The catheter according to claim 22 or 23. [Claim 25] The distal tip portion is screwed into the proximal tip portion. The catheter according to feature 24. [Claim 26] The distal tip portion includes a vent hole, The aforementioned proximal tip portion includes a fluid port, The distal tip is movable relative to the proximal tip so as to align the vent hole with the fluid port. The catheter according to any one of claims 22 to 25. [Claim 27] A catheter shaft having a fluid lumen, A balloon attached to the catheter shaft and having an interior that communicates fluidly with the fluid lumen, The ultrasonic transducer located inside, A flow control device having an inlet port for receiving fluid passing through the interior from the fluid lumen, Equipped with, The catheter shaft has a shaft diameter of 5 French or less. The flow control device is configured to discharge the fluid into the surrounding environment when the fluid has a predetermined pressure. A catheter characterized by the following features. [Claim 28] A balloon having an interior, The ultrasonic transducer located inside, A catheter shaft comprising an outer member having a central lumen, an inner member having a fluid lumen extending through the central lumen for delivering fluid into the interior, and one or more steering wires extending through the central lumen between the inner wall of the outer member and the outer wall of the inner member, Equipped with, The one or more steering wires are connected to the outer member or the inner member at the anchor point proximal to the balloon. A catheter characterized by the following features. [Claim 29] The one or more steering wires include the first steering wire on the diametrically opposite side of the second steering wire. The catheter described in Feature 28. [Claim 30] One or more of the first steering wire and the second steering wire include an electrical cable for delivering energy to the ultrasonic transducer. The catheter according to feature 29. [Claim 31] The catheter shaft has multiple shaft sections, Each shaft section has its own rigidity. A catheter according to any one of claims 28 to 30. [Claim 32] The plurality of shaft sections include a distal section, an intermediate section, and a proximal section. The stiffness of each of the distal sections is lower than the stiffness of each of the intermediate sections. The stiffness of each of the aforementioned intermediate sections is lower than the stiffness of each of the aforementioned proximal sections. The catheter according to feature 31. [Claim 33] The inner member has a wall, The wall is thinner in the distal section than in the intermediate section. The catheter according to feature 32. [Claim 34] A catheter according to any one of claims 1 to 33, Controller and A connecting cable that interconnects the catheter and the controller, An ultrasound-based tissue treatment system characterized by having the following features. [Claim 35] A catheter shaft having a fluid lumen, A balloon attached to the catheter shaft and having an interior that communicates fluidly with the fluid lumen, The ultrasonic transducer located inside, A flow control device having an inlet port positioned to receive the fluid that has passed through the interior, Equipped with, The flow control device is configured to discharge the fluid into the surrounding environment when the fluid has a predetermined pressure. A catheter characterized by the following features. [Claim 36] The aforementioned flow control device is non-return valve, A vent hole extending from an internal channel through the outer wall, and a plunger that is movable within the internal channel relative to the vent hole. A plug having a plurality of holes for leaking the fluid having the predetermined pressure, and A proximal tip, a distal tip that is movable relative to the proximal tip, and a spring between the proximal tip and the distal tip. Includes at least one of the following The catheter according to feature 35.

Claims

1. A catheter shaft having a fluid lumen, A balloon attached to the catheter shaft and having an interior that communicates fluidly with the fluid lumen, The ultrasonic transducer located inside, A flow control device having an inlet port arranged to receive the fluid that has passed through the interior, Equipped with, The flow control device is configured to discharge the fluid into the surrounding environment when the fluid has a predetermined pressure. The flow control device includes a check valve, The aforementioned check valve includes a sealing plunger that backs the elastomer valve. The elastomer valve has a crack pressure equal to the predetermined pressure. A catheter characterized by the following features.

2. The check valve is located at the distal end of the catheter. The catheter according to feature 1.

3. The check valve is configured to open when the pressure on the input side of the check valve is higher than the pressure on the output side of the check valve. The catheter according to feature 2.

4. The output side of the check valve includes an outlet port configured to allow the fluid to pass through the distal tip of the catheter to the surrounding environment. The catheter according to feature 3.

5. The check valve is configured to close when the pressure on the input side of the check valve is lower than the crack pressure, thereby preventing the fluid from flowing out of the check valve into the surrounding environment. The catheter according to feature 4.

6. The inlet port is configured to receive the fluid from the inside of the balloon and transport the fluid toward the elastomer valve. The catheter according to feature 1.

7. The elastomer valve includes a duckbill valve The catheter according to feature 6.

8. The elastomer valve includes a slit membrane The catheter according to feature 6.

9. The sealing plunger is configured to maintain the shape of the elastomer valve. The catheter according to feature 6.

10. The sealing plunger is configured to prevent deformation of the elastomer valve, which would cause unwanted discharge of the fluid. The catheter according to feature 9.

11. The elastomer valve comprises soft polyurethane The catheter according to feature 1.

12. The soft polyurethane includes Shore A polyurethane The catheter according to feature 11.

13. The predetermined pressure is the desired inflation pressure of the balloon. The catheter according to feature 1.

14. The desired inflation pressure is the pressure required to inflate the balloon to a predetermined diameter. The catheter according to feature 13.

15. When the fluid inside the balloon has the predetermined pressure, the balloon has the predetermined diameter, and the elastomer valve opens to allow the fluid to pass through to the surrounding environment. The catheter according to feature 14.

16. The fluid is a cooling fluid, Allowing the cooling fluid to pass through the surrounding environment cools the ultrasonic transducer and maintains the balloon at the predetermined diameter. The catheter according to feature 15.

17. The catheter shaft has a shaft diameter of 5 French or less. A catheter according to any one of claims 1 to 16.

18. A catheter according to any one of claims 1 to 16, Controller and A connecting cable that interconnects the catheter and the controller, An ultrasound-based tissue treatment system characterized by having the following features.

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