Thermal management of high-intensity transducers

Abstract

A therapy intravascular ultrasound transducer assembly includes: a therapy transducer with a central void and an outer shell; a post positioned inside the central void of the therapy transducer, wherein the post comprises a first thermally conductive material; and one or more structures connecting the post to the outer shell from inside the central void, wherein the one or more structures comprise a second thermally conductive material, wherein the post and the one or more structures jointly form a thermally conductive heat sink that conducts heat generated by the therapy transducer out of the outer shell when the therapy transducer is activated.

Description

POMD04489SEC_WO01 THERMAL MANAGEMENT OF HIGH-INTENSITY TRANSDUCERS PRIORITY

[0001] This application claims the benefit of priority of U.S. Provisional Patent Application No. 63 / 677,365 titled THERMAL MANAGEMENT OF HIGH-POWER TRANSDUCERS, filed July 30, 2024, which is incorporated herein by reference in its entirety to provide continuity of disclosure. TECHNICAL FIELD

[0002] This description generally relates generally to minimally invasive apparatuses, systems, and methods that provide energy delivery to a targeted anatomical location of a subject, and more specifically, to catheter-based, intraluminal devices and systems configured to deliver ultrasonic energy to treat tissue, such as nerve tissue. BACKGROUND

[0003] High blood pressure, also known as hypertension, commonly affects adults. Left untreated, hypertension can result in renal disease, arrhythmias, and heart failure. Treatment of hypertension has focused on interventional approaches to inactivate the renal nerves surrounding a renal artery. Autonomic nerves tend to follow blood vessels to the organs that they innervate. Intraluminal devices, such as catheters, may reach specific structures, such as the renal nerves, that are proximate to the lumens in which the catheters travel. Accordingly, catheter-based systems can deliver energy from within the lumens to inactivate the renal nerves in and / or surrounding the vessel walls.

[0004] One approach to renal nerve deactivation uses radio frequency (RF) energy. The RF energy is delivered to a catheter having multiple electrodes placed against the intima of the renal artery to create an electrical field in the vessel wall and surrounding tissue. The electrical field results in resistive (ohmic) heating of the tissue to ablate the tissue and the renal nerve passing through that tissue. To treat the renal nerves surrounding the renal arteries, the RF electrodes are repositioned several times around the inside of the renal artery.

[0005] A system having an ultrasound transducer that emits one or more therapeutic doses of unfocused ultrasound energy has advantages over RF systems. The ultrasound transducer can be mounted at a distal end of catheter, and the unfocused ultrasound energy can heat tissue adjacent to a body lumen within which the catheter (and the transducer) is disposed. Theunfocused ultrasound energy system may also include a balloon mounted at the distal end of the catheter around the ultrasound transducer. A cooling fluid can be circulated through the balloon to cool the transducer and body lumen during ultrasound energy delivery. Such an unfocused ultrasound energy system may, for example, ablate target nerves surrounding the body lumen, without damaging non-target tissue such as the inner lining of the body lumen or unintended organs outside of the body lumen. Such a design enables creation of one or more ablation zones sufficient to achieve long-term nerve inactivation at different locations around the circumference of the blood vessel.

[0006] Catheters that output ultrasound energy advantageously allow ablative energy to be distributed around a vessel wall at greater depths than permissible with a radiofrequency ablative catheter. Ultrasound energy can be applied to nerves arranged around the vessel. For instance, ultrasound energy can be applied to the renal nerves surrounding the renal artery in order to deactivate these nerves. However, the arrangement of nerves can change from patient to patient and can be at different locations around the vessel. Additionally, the vessel can be located near tissues and / or organs. As a result, it would be desirable to be able to limit the application of ultrasound energy to the targeted nerves while eliminating or reducing the application of ultrasound energy to the tissues and / or organs in order to optimize procedural efficacy and safety. Further, the vessels can include features such as calcification or plaque. Depending on the conditions, it may be desirable to apply ultrasound energy to the feature or to avoid the feature. As a result, it is desirable to be able to control the application of ultrasound energy within the vessel.2 Atty Docket: POMD04489SEC_WO01SUMMARY

[0007] In some aspects, implementations provide a therapy intravascular ultrasound transducer assembly. The assembly comprises a therapy transducer with a central void, an outer shell, and a post positioned inside the central void of the therapy transducer. The post comprises a first thermally conductive material. The assembly further comprises one or more structures connecting the post to the outer shell from inside the central void. The one or more structures comprise a second thermally conductive material. The post and the one or more structures jointly form a thermally conductive heat sink.

[0008] In some variants, the therapy intravascular ultrasound transducer assembly may include: a therapy transducer shaped as a cylindrical shell with a central void and an outer shell; a post positioned inside the central void of the cylindrical shell, wherein the post extends axially outside the cylindrical shell to form a stud, wherein the post comprises a first thermally conductive material; and one or more structures connecting the post to the cylindrical shell from inside the central void, wherein the one or more structures comprise a second thermally conductive material, wherein the post and the one or more structures jointly form a thermally conductive heat sink between the post and the cylindrical shell.

[0009] In other aspects, implementations provide a method of manufacturing a therapy ultrasound transducer assembly, the method comprising: providing a therapy transducer with a central void and an outer shell; positioning a post inside the central void of the therapy transducer, wherein the post comprises a first thermally conductive material; mounting one or more structures connecting the post to the outer shell from inside the central void, wherein the one or more structures comprise a second thermally conductive material, wherein the post and the one or more structures jointly form a thermally conductive heat sink.

[0010] In some variants, the method comprises providing a therapy transducer shaped as a cylindrical shell with a central void and an outer shell; positioning a post inside the central void of the cylindrical shell with the post extending axially outside the cylindrical shell to form a stud, wherein the post comprises a first thermally conductive material; mounting one or more structures connecting the post to the cylindrical shell from inside the central void, wherein the one or more structures comprise a second thermally conductive material.

[0011] In some variants of any one of the aspects described herein, the outer shell may be shaped as a cylindrical shell.

[0012] In some variants of any one of the aspects described herein outer shell may comprise multiple shell elements arranged circumferentially about the central void. Each shell3 Atty Docket: POMD04489SEC_WO01element may have one of a rectangular form and an arced form. The shell elements may be spaced apart from each other in a circumferential direction about the central void.

[0013] In some variants of any one of the aspects described herein the post may extend axially outside the cylindrical shell to form a stud.

[0014] The details of one or more implementations of the subject matter of this specification are set forth in the description, the claims, and the accompanying drawings. Other features, aspects, and advantages of the subject matter will become apparent from the description, the claims, and the accompanying drawings.4 Atty Docket: POMD04489SEC_WO01DESCRIPTION OF DRAWINGS

[0015] The novel features of the present disclosure are set forth with particularity in the claims that follow. A better understanding of the features and advantages of the present disclosure will be obtained by reference to the following detailed description that sets forth illustrative examples of implementations, in which the principles of the innovative subject matter are utilized, and the accompanying drawings.

[0016] FIG. 1A illustrates a side view of a catheter system, in accordance with some implementations.

[0017] FIG. 1B illustrates a side view of a hub of a catheter system, in accordance with some implementations.

[0018] FIG.1C illustrates a section view along line 1C of the catheter shaft in FIG.1B, in accordance with many implementations.

[0019] FIG. 2A illustrates a transducer with an example heat sink according to many implementations.

[0020] FIG. 2B illustrates an for a transducer, in accordance with many implementations.

[0021] FIG. 2C illustrates a section view of a heat sink configuration on a transducer assembly design having one step at the proximal end of the transducer, in accordance with some implementations.

[0022] FIG. 2D illustrates a section view of a heat sink configuration on a transducer assembly design having one step at the proximal end of the transducer, in accordance with some implementations.

[0023] FIG.2E illustrates a side view of a heat sink configuration on a backing support member with a cap at the distal end, in accordance with many implementations.

[0024] FIG. 2F illustrates a heat sink configuration on a transducer assembly with a soldering design at the proximal and distal ends of a backing support member with stand-off posts, in accordance with many implementations.

[0025] FIG. 2G illustrates a cross-sectional view of a heat sink configuration on a transducer assembly, in accordance with many implementations.

[0026] FIG. 2H illustrates another example of a heat sink implementation using a transducer post with pass-through slots.

[0027] FIG. 3A illustrates a saline compatible transducer, in accordance with many implementations.5 Atty Docket: POMD04489SEC_WO01

[0028] FIG. 3B is a perspective view of a transducer in accordance with certain implementations of the present technology.

[0029] FIG. 4 is a flow chart illustrating a process for manufacturing a high-intensity transducer with a heat sink, according to many implementations.

[0030] FIGS.5A to 5C each illustrate a transducer assembly with a heat sink according to many implementations.

[0031] FIG. 5D illustrates a cross-sectional view of the transducer assembly shown in FIG. 5C.

[0032] FIG. 6A illustrates a transducer assembly with a heat sink according to many implementations.

[0033] FIG. 6B illustrates a cross-sectional view of the transducer assembly shown in FIG. 6A.

[0034] FIG. 7A illustrates a transducer assembly with a heat sink according to many implementations.

[0035] FIG. 7B illustrates a cross-sectional view of the transducer assembly shown in FIG. 7A.

[0036] Like reference numbers and designations in the various drawings indicate like elements. DETAILED DESCRIPTION

[0037] The disclosed technology is directed to systems and methods for a therapy intravascular ultrasound transducer assembly. The assembly comprises a therapy transducer with a central void, an outer shell, and a post positioned inside the central void of the therapy transducer. The post comprises a first thermally conductive material. The assembly further comprises one or more structures connecting the post to the outer shell from inside the central void. The one or more structures comprise a second thermally conductive material. The post and the one or more structures jointly form a thermally conductive heat sink.

[0038] In certain embodiments, a high-intensity ultrasound transducer shaped as a cylindrical shell with air-backing or water-backing at the back of the ultrasound transducer and inside the cylindrical shell is provided. The air-backed or water-backed cylindrical ultrasound transducer generates substantial acoustic output, for example, more than 100 W / cm2. Due to electrical losses and electrical-to-acoustic coupling losses, this high-intensity ultrasound transducer can generate large amounts of heat during operation. When electrical energy is converted into mechanical vibrations through the piezoelectric effect, the conversion process6 Atty Docket: POMD04489SEC_WO01tends to generate excessive heat. As the mechanical vibrations generated by the piezoelectric material propagate through the transducer, such vibrations are further converted into acoustic waves, which also involves the transfer of energy and can produce additional heat. The piezoelectric materials used in the construction of transducers may exhibit internal friction when subjected to mechanical stress. As the material undergoes deformation, heat can also be generated. The electrical components within the transducer, such as wires and connectors, are also characterized by corresponding resistances, which, when driven by electrical currents, can generate heat according to Joule's law (e.g., P = I²R).

[0039] In the context of operating the high-intensity ultrasound transducer in a continuous wave (CW) mode for a substantial period of duration (e.g., more than a few seconds) and from inside a catheter enclosing placed inside a subject’s vasculature for renal denervation or other intra vascular ablation applications, heat trapping can be particularly exacerbated. In the CW mode of operation, the high-intensity ultrasound transducer launches a series of ultrasound waves, typically hundreds or more cycles of sinusoidal oscillations, into the medium. In contrast, when the high-intensity ultrasound transducer operates in a pulsed mode of operation, the high-intensity ultrasound transducer emits no more than a few cycles of sinusoidal oscillation. The high-intensity ultrasound transducer’s hallmark features of a small form factor, compact enclosure, and light mass tend to render the high-intensity ultrasound transducer sensitive to heat management. Without cooling measures, the high-intensity ultrasound transducer can heat up dramatically within seconds, which can exceed the limit of piezoelectric materials to potentially lose the piezoelectric properties, and create microcracks, fractures, or other structural damage, thereby compromising the overall integrity of the transducer. Moreover, excessive heating is also a safety concern when operating inside the subject’s vasculature.

[0040] In some implementations of the present disclosure, a heat sink structure is provided inside the central void of the cylindrical-shell-shaped transducer. In certain embodiments, the heat sink structure is made of thermally conductive materials such as copper, brass, diamond, or graphite. The heat sink structure may or may not also be electrically conductive. The heat sink structure can include a post shaped and sized as a cylinder with circular fins or flanges laterally on the cylindrical surface. The fins or flanges can directly contact the inner diameter of the transducer to allow heat transfer. For example, the heat sink structure may be directly bonded to the inner diameter of the transducer, e.g. solder welded.7 Atty Docket: POMD04489SEC_WO01Thermally conductive epoxy, which may or may not also be electrically conductive, may be used to make a more stable contact between the heat sink structure and the transducer.

[0041] In another embodiment, the heat sink structure may not directly contact the inner diameter of the transducer. In such an embodiment, a layer of thermally conductive epoxy may be applied to attach the heat sink structure to the inner surface of the transducer so that heat can still be transferred from the back surface of the transducer to the outside of the cylindrical shell. In such an embodiment, the thermally conductive epoxy used to stabilize and / or attach the heat sink structure to the inner surface of the transducer may or may not be electrically conductive.

[0042] In certain embodiments, the heat sink structure comprises thermally and electrically conductive material, such as copper. In such an embodiment, the thermally conductive epoxy used to stabilize and / or attach the heat sink to the inner surface of the transducer may also be electrically conductive, e.g. epoxy comprising silver and / or graphite. In such an embodiment, a layer of thermally and electrically conductive epoxy may be applied to attach the heat sink structure to the inner surface of the transducer so that heat can still be transferred from the back surface of the transducer to the outside of the cylindrical shell and electrical current is transferred to the transducer.

[0043] In certain embodiments, the heat sink structure, e.g., post shaped and sized as a cylinder with circular fins or flanges laterally on the cylindrical surface, comprises thermally conductive but not electrically conductive material, e.g. diamond. In such an embodiment, the thermally conductive epoxy used to stabilize and / or attach the heat sink to the inner surface of the transducer may or may not be also electrically conductive.

[0044] In various implementations, the heat sink geometry is designed to improve acoustic efficiency by maintaining the acoustic boundary condition of the back surface so that the desired beam shape can be provided as the acoustic output. For example, the number of fins and the size of the area where the fins make contact with the back surface of the cylindrical shell can be kept as small as possible without disturbing the acoustic boundary conditions at the back surface. In these implementations, the thickness and mass of the heat sink post can be kept as large as possible to improve heat absorption from the back of the transducer so that such heat can be conducted to the outside of the cylindrical shell. For example, an outer surface of the cylindrical post can be positioned within 200μm of an inner surface of the central void of the cylindrical shell. Additionally, the cylindrical-shell-shaped transducer package may be8 Atty Docket: POMD04489SEC_WO01sealed with an additional layer of insulation so that the assembly is saline compatible, that is, capable of operating when immersed in a conductive fluid such as saline.

[0045] In certain embodiments, the heat sink geometry, especially the number of fins and their locations, can be designed to shape the beam profile or acoustic energy spatial distribution.

[0046] The implementations of the present disclosure enable high intensity acoustic ablation when sufficient active cooling (e.g., circulating coolant) is not feasible when driving using high intensity and for a sustained duration of time. Examples of some diseases that may be treated using an embodiment of the technology described in this specification include pulmonary hypertension, diabetes, metabolic disorder, insulin resistance, obesity, nonalcoholic fatty liver disease, chronic kidney disease (CKD), heart failure, myocardial infarction, contrast nephropathy, atrial fibrillation, end-stage renal disease, digestive disease, pancreatic cancer, other cancers, tumors, pain, asthma, sepsis, rheumatoid arthritis, Crohn’s disease, ulcerative colitis, gastrointestinal motility disorders, chronic obstructive pulmonary disease (COPD), sleep apnea, anxiety, and depression.

[0047] FIGS. 1A-1C show an exemplary catheter system 101 according to many implementations. The catheter system 101 may include a catheter 10 having a proximal end and a distal end. The catheter 10 may include a catheter shaft 12, a balloon 14, and a tip member 15. The balloon 14 can be positioned between the catheter shaft 12 and the tip member 15. The balloon 14 can be or include a compliant, semi-compliant, or non-compliant medical balloon 14. Suitable materials for the balloon 14 may include, but are not limited to nylon, polyimide films, thermoplastic elastomers such as those marketed under the trademark PEBAX™, medical-grade thermoplastic polyurethane elastomers such as those marketed under the trademarks PELLETHANE® or ISOTHANE®, and other suitable polymers, or any combination thereof.

[0048] In some implementations, the catheter system for ablating target tissue may comprise an ultrasound energy generator 22 and a catheter 10 coupled to the ultrasound energy generator. The catheter 10 may be configured to be advanceable through at least one bodily vessel to a position at or near the target tissue. The catheter 10 may comprise a catheter shaft 12 and an ablation element on a distal portion of the catheter 10. The ablation element may comprise a piezoelectric component, e.g., ultrasound transducer 200, a heat sink post 210, and, optionally, an air chamber therebetween. The ultrasound energy generator 22 may be operatively coupled to the ablation element to energize the ultrasound transducer 200 to deliver9 Atty Docket: POMD04489SEC_WO01energy to the target tissue, ablating the target tissue. The target tissue may include one or more nerves or nerve branches. In an example, the target tissue may include nerves or nerve branches starting at about 1 mmm from the lumen of the blood vessel, e.g., within the adventitia (i.e., beyond the intima-media thickness) and ending at or less than about 10 mm from the lumen of the blood vessel, e.g., less than 6 mm from the lumen. In certain implementations, an imaging transducer is used to find the media-adventitia border and ablation is initiated at a set distance, e.g., 0.1 mm, from the media-adventitia border. In certain implementations, the target tissue may include nerves or nerve branches starting within about 0.3 mm to 10 mm from the lumen of the blood vessel, e.g., 0.5 mm to 6 mm, or 1 mm to 6 mm of the lumen of one or more blood vessels, e.g., a renal artery, superior mesenteric artery, inferior mesenteric artery, femoral artery, pelvic artery, portal vein, hepatic artery, gastroduodenal artery, splenic artery, gastric artery, celiac trunk, pulmonary artery, pulmonary vein, aorta, vena cava, etc. In some examples, the target tissue may include cardiac tissue, e.g., electrically conductive cardiac tissue. Because the ultrasound transducer 200 is advanceable through at least one bodily vessel of the patient, such as one or more blood vessels of the patient’s vasculature, the ultrasound transducer 200 is necessarily sized to fit within a blood vessel in proximity to the target tissue, from which that target tissue is treated. Thus, according to some embodiments, the ultrasound transducer 200 may have a diameter between 1 mm and 3 mm, in order to be advanceable to a location in a blood vessel from which target tissue is treated.

[0049] In some implementations, the generator 22 may be configured to energize the piezoelectric component, e.g., ultrasound transducer 200, for a time period of between 5 to 20 seconds, and at a frequency of 1 to 30 MHz , which is optionally within the range of 7 MHz to 15 MHz, is optionally within the range of 8 MHz to 13 MHz, and optionally within the range of 8.5 MHz to 9.5 MHz, or 8.7 MHz to 9.3 MHz. In one implementation, the generator may be configured to energize the piezoelectric component for a time period of between 6 to 10 seconds, at a frequency of 12 to 14 MHz. In one implementation, the generator 22 may be configured to energize the piezoelectric component for a time period of about 7 seconds at a frequency of about 9 to 13 MHz. Energizing the piezoelectric component by the generator 22 may increase a temperature of the piezoelectric component by no more than 50° C. In certain embodiments, the piezoelectric component is an ultrasound transducer 200 that is water or liquid-backed, having a water or liquid layer at the back or region next to the inner surface of the piezoelectric member component. In many cases, water or liquid transducers have an additional solid backing or supporting member going through the water or liquid layer. The10 Atty Docket: POMD04489SEC_WO01water or liquid-backed transducer is configured to generate ultrasonic waves having an average surface intensity within a range of 1 and 300 Watts per centimeter square (W / cm2), optionally 1 to 50 W / cm2.

[0050] In certain embodiments, the transducer is configured to generate ultrasonic waves having an average acoustic intensity at a surface of the outer shell of the therapy transducer exceeding 30 watts / cm2, e.g. exceeding 50 W / cm2, e.g., 250 W / cm2.

[0051] In certain embodiments, the ultrasound transducer 200 is an air-backed ultrasound transducer configured to generate ultrasonic waves having an average surface intensity within a range of 1 W / cm2to 300 W / cm2. The air-backed transducer may comprise an inner (back) and outer (front) surfaces, each of the inner and outer surfaces comprising an electrode; and a backing support member, wherein the ultrasound transducer 200 is mounted to the backing support member to define an air chamber adjacent the inner surface, the air chamber being insulated to prevent entry of fluid into the air chamber during use, the backing support member having a distal end and a proximal end, wherein the ultrasound transducer 200 is configured to deliver sufficient acoustic energy during sonication such as to thermally induce modulation of neural fibers surrounding a blood vessel sufficient to improve a measurable physiological parameter corresponding to a diagnosed condition of the patient.

[0052] The catheter 10 can have a handle 16 at the proximal end of the catheter shaft 12. The handle 16 can include one or more electrical couplings 18 for connecting the catheter system to one or more external electrical conductors 20 that are each in electrical communication with the generator 22. Suitable external electrical conductors 20 include, but are not limited to, wires, cables, and Flexible Printed Circuits (FPCs).

[0053] The generator 22 may be configured to control the catheter 10 to sweep the operating frequency, and / or may be configured to control the durations of the individual pulses and total time of series of pulses to control the temperature in the ablation zones and shape the lesion.

[0054] The catheter shaft 12 can include one or more electrical lumens 121. Each of the electrical lumens 121 may extend from one or more of the electrical couplings 18 along a longitudinal length of the catheter shaft 12 toward a distal end of the catheter shaft 12. Each of the electrical lumens 121 can each hold one or more electrical conductor carriers that each carry one or more internal electrical conductors. The internal electrical conductors can be in electrical communication with the generator 22 through the electrical coupling 18 and one or more of the external electrical conductors 20. Suitable internal electrical conductors include, but are not11 Atty Docket: POMD04489SEC_WO01limited to, wires, insulated wires, cables, and FPCs. When an electrical conductor carrier carries multiple electrical conductors 20, a suitable electrical conductor carrier can be an electrically insulating jacket. When an electrical conductor carrier carries a single internal electrical conductor, an electrical insulator on the electrical conductor can serve as the electrical conductor carrier.

[0055] The handle 16 can include one or more fluid ports 24 for connecting the catheter 10 to a corresponding conduit 26. Suitable conduits 26 include, but are not limited to, tubes and hoses. A conduit 26 can provide fluid communication between the fluid port 24 and a fluid source 28A, and a fluid sink 28B. Suitable fluid source 28A and fluid sink 28B include, but are not limited to, pumps, tanks, reservoirs, and vessels. The catheter shaft 12 can include one or more fluid lumens 241. Although one fluid source 28A and one fluid sink 28B are depicted in FIG.1A, the implementations can have more than one fluid source or more than one fluid sink. Each of the fluid lumens 241 can be in fluid communication with one of the fluid ports 24 along a longitudinal length of the catheter shaft 12 toward a distal end of the catheter shaft 12. Each fluid lumen 241 may be in fluid communication with a different fluid port 16, or at least one fluid lumen 241 may be in fluid communication with the same fluid port 16 as at least one other fluid lumen 241.

[0056] The handle 16 can include one or more guidewire ports 30 for receiving a guidewire 31. The catheter shaft 12 can include a guidewire lumen 301. The guidewire lumen 301 can extend along a longitudinal length of the catheter shaft 12 toward a distal end of the catheter shaft 12. The guidewire lumen 301 can be in fluid communication with the guidewire port 30 such that a guidewire 31 inserted into the guidewire port 30 can be received within the guidewire lumen 301.

[0057] In some implementations, the catheter 10 can include an ultrasonic imaging transducer 17, e.g., a transducer of a single element or an array, at the distal end of catheter 10. The imaging transducer 17 may have a center frequency of 15-50 MHz, e.g., 20-30 MHz, which can be used to identify target and nontarget structures. The imaging transducer 17 can be positioned proximal to or distal to the balloon 14. The imaging transducer 17 can comprise a ring array having a single ring or multiple rings. The imaging depth can be up to approximately 12 mm and can be used to size the vessel, and / or image anatomy, pathology, lesion formation, temperature changes, and / or heat sinks such as lymph nodes, vessel walls, plaques, calcification, tissue layers and nerves. The imaging frequency can be approximately 20 MHz – 35 MHz, the bandwidth can be equal or greater to 10 MHz, and / or the array size can comprise12 Atty Docket: POMD04489SEC_WO0116 to 256 elements, however, these characteristics are descriptive and not restrictive. The array element dimension can be 0.5 mm – 1.5 mm in length and 0.5 – 2 wavelengths in width. A multiple-row cylindrical array can help reduce the image slice thickness to achieve better contrast resolution. The elements may be individually controlled to transmit and receive, for example, by an ASIC circuit, to reduce the number of cables needed. In other embodiments, the ultrasound transducer 200 is utilized for imaging as well as for treatment, and a separate ultrasonic imaging transducer 17 thus may be omitted. In still other embodiments, imaging is not performed utilizing the catheter 10.

[0058] In some implementations, the catheter 10 may additionally or alternatively include electrodes on the balloon 14, configured to sense nerve activity and / or confirm the effectiveness of the treatment, as disclosed in U.S. Patent Publication No. 20230021354, to Zhai et al., which is incorporated herein by reference in its entirety.

[0059] In some implementations, the catheter system may additionally or alternatively include the nerve sensing and / or treatment confirmation components disclosed in components disclosed in U.S. Patent Application Publication No. US20230293229A1 of Barman et al., having a priority date of March 15, 2022, which is incorporated herein by reference in its entirety. As disclosed in further detail in U.S. Patent Publication No. US20230293229A1, treatment confirmation components may be used to determine a latency of sensed electrical impulses to determine the type, size, function and / or health of the fibers whose neural response is being sensed. The delay (aka latency) may be indicative of a depth of nerves surrounding a biological lumen (e.g., a renal artery) within which a catheter 10 used to measure the delay is located. In accordance with some implementations of the present technology, the above- described delay (aka latency) can be used to select the frequency used for the ablations. The electronics 22 controls the catheter 10 to sweep the operating frequency and control the durations of the individual and total treatment times to control the temperature in the ablation zones, and shape the tissue lesion caused by the application of ultrasound to tissue. Application of lower frequency ultrasound by the transducer 200 may be used to aim at deeper regions, when it is determined that nerves are located in the deeper regions. Application of higher frequency ultrasound by the transducer 200 may be used to target shallower regions, when it is determined that nerves are located in the shallower regions. Additional details are disclosed in US Patent Application Publication No. US 20240058028 A1, filed on August 16, 2023, which is incorporated herein by reference in its entirety.13 Atty Docket: POMD04489SEC_WO01

[0060] The implementations described here provide a tissue treatment catheter 10 that includes a therapy intravascular ultrasound transducer assembly 211. The therapy intravascular ultrasound transducer assembly 211, in turn, includes an ultrasound transducer 200 positioned at the distal end of the catheter 10, and a heat sink post structure 210. The therapy intravascular ultrasound transducer assembly 211 may also include impedance matching circuitry (not shown), and one or more electrical cables connecting transducer to driving circuitry (not shown). As illustrated in FIGS.2A-2H, ultrasound transducer 200 may include a piezoelectric transducer body 208 that includes a hollow cylindrical tube of piezoelectric material having an inner surface 207 and an outer surface 206. Each of the inner 207 and outer surfaces 206 has an electrode for receiving an oscillating electrical signal that causes the ultrasound transducer 200 to vibrate.

[0061] In certain embodiments, ultrasound transducer 200 is an air-backed transducer constructed to provide an air chamber 230 at the inner surface 207 of the piezoelectric transducer body 208. The interface between the air and the piezoelectric transducer body 208 is highly reflective, because air has an acoustic impedance far lower than that of the ceramic of which the piezoelectric transducer body 208 is composed. This interface can serve as a backing interface and can help direct acoustic vibrations through the outer surface 206 of the piezoelectric transducer body 208, which serves as the front or emitting surface of the ultrasound transducer 200. Air-backed transducers can provide good efficiency and can be compact. However, the emitting power of such a transducer may be limited by thermal considerations. Air and other gases can provide only a limited cooling effect at the inner surface 207 of the piezoelectric transducer body 208. The power of the applied drive signal may be limited to avoid overheating the ultrasound transducer 200. This problem may be particularly severe in the case of using the ultrasound transducer 200 that is small (e.g., under 2 mm in diameter) for applications such as ablation. In some implementations, the fluid within the balloon 14 surrounding the ultrasound transducer 200 contributes to cooling and temperature regulation of the ultrasound transducer 200. In some implementations, the ultrasound transducer 200 may be cooled and / or thermally regulated by direct contact with the blood (in balloon-less implementations). In certain implementations, the ultrasound transducer 200 is water-backed.

[0062] The therapy intravascular ultrasound transducer assembly 211 also includes a heat sink post structure 210, which extends through the inner surface 207 of the ultrasound transducer 200 to outside the cylindrical tube of the piezoelectric transducer body 208 so that14 Atty Docket: POMD04489SEC_WO01heat can be transferred from inside the cylindrical tube of the piezoelectric transducer body 208, along a longitudinal axis of the cylindrical tube, to outside the cylindrical tube of the piezoelectric transducer body 208. In some cases, the central void 210C of heat sink post structure 210 can be in fluid communication with lumen 241. The heat sink post structure 210 is not limited to a cylindrical shape with a generally constant diameter, and may be shaped in any other suitable manner. As one example, a tapered configuration with a larger diameter at one end (e.g., towards cap 214 in FIG. 2E), and a smaller diameter at the other end (e.g., towards portion 209 in FIG. 2E), can be used in some cases. The heat sink post structure 210 can be coaxial with the cylindrical tube of ultrasound transducer 200. The heat sink post structure 210 alternately can be eccentric with respect to the cylindrical tube of ultrasound transducer 200 when viewed on a cross-section.

[0063] The hollow appearance of heat sink post structure 210 (e.g., FIGS. 2C to 2E) is not drawn to scale. In fact, heat sink post structure 210 can be a solid mass with a central void 210C for mounting a guide wire, as illustrated in FIGS. 2G-2H. In some cases, the heat sink post structure 210 can also include a frame of thermally and electrically conductive metal as a backbone.

[0064] The heat sink post structure 210 may include a short post or connecting structure 210-1 for thermal connection with the inner surface 207 of the transducer. Connecting structure 210-1 can be fin / flange structures mounted on the radially outward surface of, e.g., the solid cylinder mass of metal with the central void 210C (as illustrated in FIG. 2G), or the block of thermally conductive and electrically non-conductive material (as described below) for reaching the inner surface 207 of the piezoelectric transducer body 208.

[0065] The heat sink post structure 210 may be made of copper or other metal materials with comparably high thermal conductivity such as silver, gold, aluminum. The heat sink post structure 210 can also be made of alloy materials such as brass and bronze. In situations where the heat sink material is also electrically conductive, a layer of thermally conductive and electrically conductive epoxy 210-3 is applied to attach a portion of the heat sink post structure 210, such as one or more flanges 210-1, to the inner surface 207, which is also referred to as the back surface, of the piezoelectric transducer body 208, as shown in FIGS.2A, and 2E. The implementations are not limited to flanges that can wrap completely around the heat sink post structure 210.

[0066] Some implementations may include fin structures 210-1 scattered around the circumference of the cylindrical post. On a cross section view that cuts across fin structures15 Atty Docket: POMD04489SEC_WO01210-1, the number of fins is not limited by the illustrated example in FIG. 2G. Rather, the number of fins can be more than two per cross section. Each fin structure 201-1 may be coated with a layer of thermally conductive epoxy210-3, which may or may not also be electrically conductive to connect to the inner surface 207 of the piezoelectric transducer body 208, as shown in the cross-sectional view of FIG. 2G.

[0067] The contact areas between the fin structure 201-1 and the inner surface 207 where the layer of thermally conductive epoxy 210-3, which may or may not also be electrically conductive is applied can be more limited than a cross-sectional area of the underlying fin / flange structure 210-1. In this manner, the mechanical contact between the fin structure 201-1 and the inner surface is reduced so that disturbance of the air-backing or water-backing condition of transducer is also reduced. In other words, implementations may reduce the contact area where the fin / flange structure 210-1 reaches the inner surface of the transducer for thermal conductivity. The contact area can be kept small so that the inner surface remains as much air-backed or water-backed as possible to avoid alteration of the acoustic operation of the piezoelectric transducer body 208. When thermally conductive and electrically non- conductive epoxy is being used, the contact area between the epoxy and the inner surface of the transducer can be kept to a minimum for similar considerations.

[0068] FIG. 2H provides a front view as well as a side view of another example of a heat sink implementation using a post with pass-through slots. In this example, the ultrasound transducer 200 has an inner diameter of 0.040” (or 1.016 mm). The heat sink post structure 210 with pass-through slots 210H is inserted in the space defined by the inner diameter of the piezoelectric transducer body 208. The pass-through slots 210H can include longitudinal conduits that carry circulating fluid for active cooling. The circulating fluid can include saline, sterilized water, dextrose, or other suitable fluids. In some cases, the pass-through slots are longitudinal channels drilled through the heat sink post structure 210 and parallel to the core of the post 210C. The diameter of the pass-through slots 210H can be around 0.003” (0.0762mm). The active cooling incorporates circulating fluid to keep the post 210 cool as it absorbs heat generated by the ultrasound transducer 200 during sonication when the ultrasound transducer 200 is turned on to emit ultrasound waves for therapy. In some cases, the core of the heat sink post structure 210C is a void for mounting the catheter assembly 10 on a guidewire. The post 210 may be a solid mass with varied wall thickness where a wall of the heat sink post structure 210 becomes thicker in wall sections between the pass-through slots 210H, which are longitudinal conduits that function as cooling slots for active cooling. In some cases, the post16 Atty Docket: POMD04489SEC_WO01core can be about 0.003” (0.0762mm) from the pass-through slots 210H. In some cases using an air-backed transducer, the pass-through slots 210H can be about 0.003” (0.0762mm) from an air coupling layer at the back of the ultrasound transducer 200. An air-back coupling is present at the back of transducer 200. In some cases, the air-backing can be as thin as 0.001” (0.0254mm). At the edge of the inner surface 207 bordering the two ends (proximal and distal) of the piezoelectric transducer body 208, conductive material (such as solder or conductive epoxy) can be placed as reservoir traps 210R on respective post lugs 210P so that the post 210 is mechanically attached to transducer 200 by the conductive material. Here, each reservoir trap 210R holds any solder / epoxy overflow so that none of that solder / epoxy overflow enters the air chamber 230. For context, solder or conductive epoxy can be absorbed (or drawn off) via capillary action and enter the air chamber 230 in the absence of the reservoir trap 210R. Post lugs 201P are raised features on the heat sink post structure 210 that may be used for sealing the inner surface 207 of the piezoelectric transducer body 208, such as by using solder / conductive epoxy.

[0069] The epoxy as described in this application is thermally conductive and may or may not be electrically conductive. An epoxy that is thermally conductive and electrically conductive may comprise silver and / or graphite. Examples of epoxies that are thermally and electrically conductive suitable for use according to the present disclosure include Bondline 2080 and Bondline 2158 from BONDLINE® Electronic Adhesives. Examples of epoxies that are thermally conductive and electrically insulative suitable for use according to the present disclosure include epoxies comprising aluminum nitride and / or aluminum oxide, e.g. EP5TC- 80 from MASTER BOND® and 5390 Epoxy from APPLI-TEC®, Inc.

[0070] Referring to FIGS. 2C-2F, a portion of the heat sink post structure 210, for example, portion 209, protrudes longitudinally out from inside the inner surface of the piezoelectric transducer body 208 to facilitate heat dissipation to the outside of the transducer. Examples of good thermal conductors can include copper, brass, or silver, which can be used for constructing heat sink 210.

[0071] Additionally or alternatively, the heat sink post structure 210 can be made of thermally conductive materials that are electrically non-conductive, such as diamond, aluminum nitride (AlN), sapphire, and / or mica mineral. When using such electrically non- conductive but thermally conductive materials, a cylindrical heat sink post structure 210 with multiple flanges 210-1 can be used. The flanges 210-1 may radially contact the inner surface 207 of the piezoelectric transducer body 208 of the transducer 200.17 Atty Docket: POMD04489SEC_WO01

[0072] The heat sink post structure 210 may be non-monolithic. For example, the heat sink post structure 210 may be solid, rather than hollow. Instead, the heat sink post structure 210 may include a metal core for providing mechanical rigidity as well as thermal conductivity. That metal core can be coated with a different thermally conductive material, such as an alloy that is not electrically conductive, so that flanges 210-1 made of the same alloy can contact the inner surface 207 of the piezoelectric transducer body 208 directly and without additive epoxy or adhesives.

[0073] When a small cylindrical transducer, such as an air-backed ultrasound transducer 200, is activated to insonify or ablate tissue at high intensity, temperature within the inner surface 207 of the piezoelectric transducer body 208 (e.g., inside air chamber 230) can increase rapidly, reaching over 100oC within a few seconds in the absence of cooling mechanisms. Such rapid temperature rise can melt the electrical connectors (e.g., solder spot 303 that connects transducer 200 to electrical conductor 20, as illustrated in FIG. 3A) and / or damage the ultrasound transducer 200. The heat sink post structure 210 can conduct heat dissipated by the ultrasound transducer 200 longitudinally away from inside the inner surface 207 to the outside of the transducer. As illustrated in FIG.2H, some implementations can also use active cooling by circulating working fluid through pass-through slots 210H. In other words, the heat sink post structure 210 can draw heat from the back of the ultrasound transducer 200 longitudinally to the outside of the piezoelectric transducer body 208 so that the ultrasound transducer 200 can operate within a reasonable temperature range. The implementations can achieve an airtight design of the piezoelectric transducer body 208 with sufficient electrical insulation, thereby rendering the intravascular therapy ultrasound transducer assembly 211 as a saline compatible device, which can be immersed in conductive fluid (such as saline and / or blood) while electrically activated to deliver therapy. The implementations may provide adequate thermal management even when the ultrasound transducer 200 has no active cooling.

[0074] The heat sink post structure 210 may include a first stand-off post 212D at the distal end of the heat sink post structure 210 and a second stand-off post 212P at the proximal end of the heat sink post structure 210, as shown in FIG.2B. Each stand-off post (e.g., the first stand-off post 212D) includes an inner face 212A and an outer face 212B. A step portion 250 may be located at the proximal end of the ultrasound transducer 200, as shown in FIGS. 2C and 2D. Alternatively, a chamfered portion instead of a step portion 250 is located at the proximal end of the ultrasound transducer 200. Alternatively, there is neither a stepped portion 250 nor a chamfered portion at the proximal end of the ultrasound transducer 200. The18 Atty Docket: POMD04489SEC_WO01ultrasound transducer 200 may optionally be mounted to at least the first and second stand-off posts 212D and 212P of the heat sink post structure 210 to define an air chamber 230 adjacent the inner surface 207. In this case, the air chamber 230 can be insulated to prevent entry of fluid into the air chamber 230 during use so that the transducer 200 is saline compatible. Specifically, the transducer 200 inside the therapy intravascular ultrasound transducer assembly 211 can operate when immersed in electrically conductive fluid to deliver sufficient acoustic energy during sonication to thermally induce modulation of neural fibers surrounding the blood vessel, e.g., to create an ablation zone about 3 mm to 6 mm wide, e.g., 5 mm wide, and about 0.5 mm to 10 mm, e.g., 1 mm to 6 mm, in depth from the lumen of the blood vessel. The modulation is sufficient to improve a measurable physiological parameter corresponding to a diagnosed condition of the patient (e.g., hypertension).

[0075] FIG.2E illustrates another implementation addressing solder migration into the air chamber 230. The heat sink post structure 210 can include a cap 214 at the distal end and a stand-off post 212P at the proximal end. Step portion 250 on the cap 214 can be used for centering the heat sink post structure 210 relative to the ultrasound transducer 200. A plating surface 260, which refers to a portion of surface area for depositing material such as solder and epoxy to connect the transducer to an electrical wire, can be removed at the chamfered edge 216 of the ultrasound transducer 200. Removing the plating surface 260 can be done, for example, by grinding. Additionally or alternatively, removing the plating surface is done before attaching the heat sink posture structure 210 to the ultrasound transducer 200. Solder material 201 can be placed at the interface between the cap 214 and the plating surface 260 of the inner surface 207. Solder material 201 can be placed at the proximal end of the heat sink post structure 210 where the first stand-off post 212 meets the plating surface 260 of the inner surface 207. This arrangement facilitates placement of the heat sink post structure 210 by allowing for smooth insertion of the heat sink post structure 210 through the distal end of the ultrasound transducer 200.

[0076] In FIG. 2F, a small amount of electrically conductive solder 201 may infiltrate the air chamber 230 in order to provide an electrical connection between the inner surface 207 of the transducer 200 and an electrically conductive heat sink post structure 210. A solder preform 203 can be placed at its proper location on heat sink post structure 210, e.g., adjacent to both stand-off posts 212P and 212D. Thereafter, the solder preform 203 can be heated so that solder may flow into air chamber 230 sufficiently to electrically connect the inner diameter 207 of the piezoelectric transducer body 208 and the electrically conductive heat sink post19 Atty Docket: POMD04489SEC_WO01structure 210. The solidified solder may form a seal between the stand-off post 212 (or other type of stand-off member) and an inner surface 207 at an edge of the cylindrical shell of the piezoelectric transducer body 208 to provide an airtight seal for the air chamber 230 at the edge of the cylindrical shell.

[0077] In some implementations, the ultrasound transducer 200 may withstand the levels of intensity required to ablate target tissue, e.g., renal nerves, for example, up to about 150 W / cm2or more across the outer surface area of the transducer 200, such that the transducer 200 is configured to deliver sufficient acoustic energy during sonication such as to thermally induce modulation of neural fibers surrounding the blood vessel, the thermally induced modulation being sufficient to improve a measurable physiological parameter corresponding to a diagnosed condition of the patient, while being sufficiently small to fit in a renal artery and / or permit radial access using a 5F or smaller catheter, e.g., a 4F catheter.

[0078] In some implementations, the ultrasound transducer 200 includes a step portion 250 on at least the proximal end where electrical conductor 20 may connect to the outer electrode of the transducer. Connection of the electrical conductor 20 and solder material 201 at the step portion 250 of the ultrasound transducer 200 may additionally improve a transducer design that does not interfere with the acoustic output of the ultrasound transducer 200 by allowing the ultrasound transducer 200 to be attached to the cable that supplies the oscillating electrical signal to the ultrasound transducer 200 while maintaining a smaller profile than other configurations.

[0079] FIG. 3A illustrates a side view while FIG. 3B provides a perspective view of an ultrasound transducer 200. As illustrated, the inner shell of the ultrasound transducer 200 is isolated from fluid (i.e., fluid within the balloon 14 or body fluid, e.g., blood, in a balloonless implementation) to render the therapy ultrasound transducer assembly 211 saline compatible. The packaging materials 303 and 304 used to keep the seal intact may include a bond that adheres to the backing support member material which may be made of a metal. The packaging materials 303 and 304 are sufficiently durable to withstand vibration of the ultrasound transducer 200 without delaminating. Examples of packaging materials 303 and 304 may include epoxy.

[0080] In some implementations, a proximal end of the ultrasound transducer 200 can include a stepped portion 250, while a distal end of the ultrasound transducer 200 may or may not include a similar stepped portion, depending upon the specific implementation. In certain implementations, the axial length of stepped portion 250 of the transducer 200 is about 0.4 mm20 Atty Docket: POMD04489SEC_WO01and the axial length of a non-stepped portion of the transducer 200 is about 6 mm. Other variations are also possible and within the scope of the examples described herein. In certain implementations, the non-stepped portion of the transducer 200 is the portion of the transducer that produces the bulk of the ultrasonic energy delivered from the catheter 10. In some implementations, the stepped portion 250 has a different outer diameter than the non-stepped portion and behaves in a different manner than the non-stepped portion.

[0081] Between the proximal and distal portions of the piezoelectric transducer body 208 is a center portion of the piezoelectric transducer body 208 that vibrates in response to application of the voltage between the inner and outer electrodes 204, 205. In accordance with certain implementations, a pair of stand-off posts 212P and 212D are respectively attached (e.g., using solder, adhesive, laser welding, and / or other methodologies) to proximal and distal portions of the piezoelectric transducer body 208 spaced apart longitudinally from the center portion thereof. The pair of stand-off posts 212P and 212D can define the longitudinal boundaries of the air chamber 230.

[0082] FIG. 4 is a flow chart illustrating a process 400 for manufacturing the catheter 10 including the therapy ultrasound transducer assembly 211. In step 401, process 400 may include providing a therapy transducer, for example, the air-backed or water-backed ultrasound transducer 200 that includes the piezoelectric transducer body 208 shaped as a cylindrical shell, with a central void 210C and an outer shell. As described above in association with FIGS. 1A to 3C, the air-backed or water-backed ultrasound transducer 200 is capable of generating an average acoustic intensity that exceeds 30 Watts / cm2, preferably exceeding 50W / cm2, or 250W / cm2. The piezoelectric transducer body 208 can have a length less than about 10 mm, preferably less than about 6mm, and has a diameter between about 1 and about 3 mm, preferably about 1.5 mm.

[0083] In step 402, the process 400 may include positioning a heat sink post structure 210 inside the central void 210C of the cylindrical shell with the heat sink post structure 210 extending axially outside the cylindrical shell. As described above in association with FIGS. 1A to 3C, the heat sink post structure 210 can be shaped as a cylinder positioned inside the central void 210C of the cylindrical shell, preferably coaxial with respective to the cylindrical shell of the transducer. The heat sink post structure 210C may be positioned such that an outer surface of the heat sink post structure 210C is within 200μm of an inner surface 207 of the piezoelectric transducer body 208 in the radial direction. In certain embodiments, the outer surface of the heat sink post structure 210 and the inner surface 207 of the piezoelectric21 Atty Docket: POMD04489SEC_WO01transducer body 208 may be separated by air or any other gas so that the therapy transducer remains air-backed both radially and longitudinally.

[0084] In step 403, the process 400 may include mounting one or more structures connecting the heat sink post structure 210 to the cylindrical shell of the piezoelectric transducer body 208. As described above in association with FIGS.1A to 3C, the one or more structures may be shaped as fin structures or flange structures (e.g., flanges 210-1). A layer of material that is thermally conductive, which may or may not also be electrically conductive, may be applied to attach the fin / flange structures (e.g., flanges 210-1) to the inner surface 207 of the piezoelectric transducer body 208. The layer of material can be a layer of epoxy, which may be thermally conductive, and which may or may not also be electrically conductive.

[0085] By virtue of the innovative configuration of the heat sink feature, the process 400 can thus provide a saline compatible transducer assembly (e.g., therapy ultrasound transducer assembly 211) capable of operating when immersed in electrically conductive fluid. When the ultrasound transducer 200 is activated, for example, in continuous wave (CW) mode to emit ultrasound waves inside a vessel, the heat sink feature provides passive cooling (e.g., through a block of thermally conductive material of heat sink post structure 210) as well as active cooling (e.g., circulating fluid through pass-through slots 210H) and / or can conduct heat generated by the therapy ultrasound transducer 200 longitudinally out of the cylindrical shell of the piezoelectric transducer body 208, as explained in additional details above in association with FIGS. 1A to 3C.

[0086] FIGS. 5A to 5C each illustrate a transducer assembly 211 with a heat sink post structure 210 according to many implementations. FIG. 5A shows an outer shell 208 comprising three shell elements 208-A, 208-B, 208-C. The shell elements 208-A, 208-B, 208- C are formed as arced structures extending circumferentially about the central void of the transducer assembly 211, wherein the shell elements 208-A, 208-B, 208-C are spaced apart from each other circumferentially about the central void of the transducer assembly 211. The one or more structures connecting the shell elements to the post 210 comprise a flange 210-1 extending circumferentially about the post 210 to transport heat from all shell elements 208-A, 208-B, 208-C to the post 210. Multiple flanges 210-1 may be provided spaced apart from each other along a length of post 210, the length extending perpendicular to the circumferential direction of the central void. Providing multiple shell elements 208-A, 208-B, 208-C instead of a single cylindrical shell structure 208 may facilitate manufacturing the transducer assembly 211. Further it may reduce maintenance costs because not the whole shell structure 208 has to22 Atty Docket: POMD04489SEC_WO01be replaced in case of a malfunction. Still further, different elements 208-A, 208-B, 208-C may be used to adapt the form of the emitted ultrasound waves, i.e., to provide a desired beam shape.

[0087] Fig. 5B shows a transducer assembly 211 that differs from the assembly of FIG.5A in that separate structures 210-1-A, 210-1-B, 210-1-C for connecting each of the shell elements 208-A, 208-B, 208-C to the post 210 are provided instead of the flange(s) 210-1 connecting all of the shell elements 208-A, 208-B, 208-C to the post 210. Using smaller, separate structures 210-1-A, 210-1-B, 210-1-C may reduce production and maintenance cost while still providing sufficient heat transport between the shell elements 208-A, 208-B, 208-C.

[0088] FIG. 5C shows another transducer assembly 211 similar to the assembly 211 shown in Fig. 5B. Here, each of the separate structures 210-1-A, 210-1-B, 210-1-C for connecting one of the shell elements 208-A, 208-B, 208-C to the post 210 extends over the same circular section of the central void of the transducer assembly 211 as the shell element 208-A, 208-B, 208-C connected by respective structures 210-1-A, 210-1-B, 210-1-C. In this variant, the contact surface between the shell elements 208-A, 208-B, 208-C and the connecting structures is maximized in the circumferential direction of the central void of the transducer assembly 211 for increased heat dissipation capacity compared to the structures 210-1-A, 210- 1-B, 210-1-C shown in Fig. 5B. FIG. 5D shows a cross-sectional view of the transducer assembly shown in FIG. 5C.

[0089] FIG. 6A shows another transducer assembly 211 similar to the assembly 211 shown in Fig. 5A, wherein six shell elements 208-A to 208-F are provided and wherein each of the shell elements 208-A to 208-F has a rectangular form instead of an arced form as shown in FIG.5A. FIG. 6B shows a cross-sectional view of the transducer assembly shown in FIG. 6A. As can be seen in FIG. 6B, the shell elements 208-A to 208-F abut each other to form an inner void having a hexangular shape. Correspondingly, the shown flange 210-1 connecting the post 210 with all of the shell elements 208-A to 208-F has a hexangular outer surface. As already described with reference to the previous figures, multiple flanges spaced apart along the length of the post 210 may be provided.

[0090] FIG. 7A shows another transducer assembly 211. The shown transducer assembly 211 is similar to the assembly shown in FIG. 6A, with the difference that separate structures 210-1-A to 210-1-F for connecting each of the shell elements 208-A to 208-F to the post 210 are provided instead of the flange(s) 210-1 connecting all of the shell elements 208- A to 208-F to the post 210.

[0091] Different embodiments are readily contemplated. For example,23 Atty Docket: POMD04489SEC_WO01implementations with different numbers of shell elements as well as shell elements with different shapes than the shown examples are readily contemplated. Further, a combination of differently shaped shell elements is readily contemplated. The numbers and shapes of the shell elements may be adapted to the desired form of the emitted ultrasound waves, i.e., to provide a desired beam shape. Moreover, alternative structures suitable for thermally connecting the outer shell, e.g., the shell elements, with the post 210, e.g., fin structures, are contemplated.

[0092] While various embodiments and implementations of the present disclosure have been shown and described herein, it will be obvious to those skilled in the art that such embodiments and implementations are provided by way of example only. Numerous variations, changes, and substitutions may occur to those skilled in the art without departing from the present disclosure. It should be understood that various alternatives to the embodiments and implementations of the present disclosure described herein may be employed. In particular, some elements described with reference to a specific implementation may be combined with some elements described with reference to another specific implementation.

[0093] Whenever the term “at least,” “greater than,” or “greater than or equal to” precedes the first numerical value in a series of two or more numerical values, the term "at least," “greater than” or “greater than or equal to” applies to each of the numerical values in that series of numerical values. For example, greater than or equal to 1, 2, or 3 is equivalent to greater than or equal to 1, greater than or equal to 2, or greater than or equal to 3.

[0094] Whenever the term “no more than,” “less than,” or “less than or equal to” precedes the first numerical value in a series of two or more numerical values, the term “no more than, “less than,” or “less than or equal to” applies to each of the numerical values in that series of numerical values. For example, less than or equal to 3, 2, or 1 is equivalent to less than or equal to 3, less than or equal to 2, or less than or equal to 1.

[0095] Certain implementations herein contemplate numerical ranges. When ranges are present, the ranges include the range endpoints. Additionally, every sub range and value within the range is present as if explicitly written out. The term “about”, “substantially”, or “approximately” refer to values within an acceptable error range or range of manufacturing tolerances for the particular value, which will depend in part on how the value is measured or determined, e.g., the limitations of the measurement system.

[0096] The following numbered clauses define further embodiments of the present disclosure.

[0097] 1. A therapy intravascular ultrasound transducer assembly comprising:24 Atty Docket: POMD04489SEC_WO01

[0098] a therapy transducer shaped as a cylindrical shell with a central void and an outer shell;

[0099] a post positioned inside the central void of the cylindrical shell, wherein the post extends axially outside the cylindrical shell to form a stud, wherein the post comprises a first thermally conductive material; and

[0100] one or more structures connecting the post to the cylindrical shell from inside the central void, wherein the one or more structures comprise a second thermally conductive material,

[0101] wherein the post and the one or more structures jointly form a thermally conductive heat sink between the therapy transducer and the post.

[0102] 2. The therapy intravascular ultrasound transducer assembly of clause 1, wherein an average acoustic intensity at a surface of the cylindrical shell of the therapy transducer exceeds 30 watts / cm2, preferably exceeding 50W / cm2, or 250W / cm2.

[0103] 3. The therapy intravascular ultrasound transducer assembly of clauses 1 or 2, wherein the therapy transducer operates in a continuous wave (CW) mode when activated.

[0104] 4. The therapy intravascular ultrasound transducer assembly of any one of clauses 1-3, wherein the cylindrical shell has a length less than about 10 mm, preferably less than about 6mm, and has a diameter between about 1 and about 3 mm, preferably about 1.5mm.

[0105] 5. The therapy intravascular ultrasound transducer assembly of any one of clauses 1-4, wherein the post is shaped as a cylinder positioned inside the central void of the cylindrical shell, preferably coaxial with respective to the cylindrical shell of the transducer.

[0106] 6. The therapy intravascular ultrasound transducer assembly of any one of clauses 1-5, wherein the post is positioned such that an outer surface of the post is within 200μm of an inner surface of the central void of the cylindrical shell.

[0107] 7. The therapy intravascular ultrasound transducer assembly of clauses 5 or 6, wherein the outer surface of the post and the inner surface of the central void of the cylindrical shell are separated by air or any other gas so that the therapy transducer remains air backed.

[0108] 8. The therapy intravascular ultrasound transducer assembly of any one of clauses 1-7, wherein the first thermally conductive material and the second thermally conductive material are identical.

[0109] 9. The therapy intravascular ultrasound transducer assembly of any one of clauses 1-8, wherein the one or more structures are separated from an inside wall of the central25 Atty Docket: POMD04489SEC_WO01void by a layer of material that is thermally conductive and electrically non-conductive.

[0110] 10. The therapy intravascular ultrasound transducer assembly of clause 9, wherein the layer of material is made of epoxy.

[0111] 11. The therapy intravascular ultrasound transducer assembly of any one of clauses 1-10, wherein the post comprises at least one of: copper, silver, or brass.

[0112] 12. The therapy intravascular ultrasound transducer assembly of any one of clauses 1-11, wherein the therapy intravascular ultrasound transducer assembly is saline compatible, and capable of operating when immersed in a conductive fluid.

[0113] 13. The therapy intravascular ultrasound transducer assembly of any one of clauses 1-12, wherein the therapy transducer is activated for intervention such as renal denervation.

[0114] 13a. The therapy intravascular ultrasound transducer assembly of any one of clauses 1-12, wherein the therapy transducer is activated to denervate a renal artery, superior mesenteric artery, inferior mesenteric artery, femoral artery, pelvic artery, portal vein, hepatic artery, gastroduodenal artery, splenic artery, gastric artery, celiac trunk, pulmonary artery, pulmonary vein, aorta, and / or vena cava.

[0115] 13b. The therapy intravascular ultrasound transducer assembly of any one of clauses 1-12, wherein the therapy transducer is activated to denervate a renal artery, hepatic artery, and / or pulmonary vein.

[0116] 13c. The therapy intravascular ultrasound transducer assembly of any one of clauses 1-12, wherein the therapy transducer is activated to denervate a renal artery and hepatic artery.

[0117] 13d. The therapy intravascular ultrasound transducer assembly of any one of clauses 1-12, wherein the therapy transducer is activated to denervate a renal artery and / or pulmonary vein.

[0118] 14. The therapy intravascular ultrasound transducer assembly of any one of clauses 1-13, wherein the one or more structures are shaped as fins or flanges.

[0119] 15. The therapy intravascular ultrasound transducer assembly of any one of clauses 1-14, wherein the thermally conductive heat sink conducts heat generated by the therapy transducer out of the cylindrical shell through the stud when the therapy transducer is activated.

[0120] 16. A method of manufacturing a therapy intravascular ultrasound transducer assembly, the method comprising:26 Atty Docket: POMD04489SEC_WO01

[0121] providing a therapy transducer shaped as a cylindrical shell with a central void and an outer shell;

[0122] positioning a post inside the central void of the cylindrical shell with the post extending axially outside the cylindrical shell, wherein the post comprises a first thermally conductive material;

[0123] mounting one or more structures connecting the post to the cylindrical shell from inside the central void, wherein the one or more structures comprise a second thermally conductive material.

[0124] 17. The method of clause 16, wherein the therapy transducer is capable of generating an average acoustic intensity that exceeds 30 watts / cm2, preferably exceeding 50W / cm2, or 250W / cm2.

[0125] 18. The method of clauses 16 or 17, wherein the cylindrical shell has a length less than about 10 mm, preferably less than about 6mm, and has a diameter between about 1 and about 3 mm, preferably about 1.5mm.

[0126] 19. The method of any one of clauses 16-18, wherein the post is shaped as a cylinder positioned inside the central void of the cylindrical shell, preferably coaxial with respective to the cylindrical shell of the transducer.

[0127] 20. The method of any one of clauses 16-19, wherein the post is positioned such that an outer surface of the post is within 200μm of an inner surface of the central void of the cylindrical shell.

[0128] 21. The method of any one of clauses 16-20, wherein an outer surface of the post and an inner surface of the central void of the cylindrical shell are separated by air or any other gas so that the therapy transducer remains air backed.

[0129] 22. The method of any one of clauses 16-21, wherein the first thermally conductive material and the second thermally conductive material are identical.

[0130] 23. The method of any one of clauses 16-22, wherein the one or more structures are separated from an inside wall of the central void by a layer of material that is thermally conductive and electrically non-conductive.

[0131] 24. The method of clause 23, wherein the layer of material is made of epoxy.

[0132] 25. The method of any one of clauses 16-24, wherein the post comprises at least one of: copper, silver, or brass.

[0133] 26. The method of any one of clauses 16-25, wherein the therapy intravascular ultrasound transducer assembly is saline compatible.27 Atty Docket: POMD04489SEC_WO01

[0134] 27. The method of any one of clauses 16-26, wherein the one or more structures are shaped as fins or flanges.28 Atty Docket: POMD04489SEC_WO01

Claims

CLAIMS What is claimed is:

1. A therapy intravascular ultrasound transducer assembly comprising: a therapy transducer with a central void and an outer shell; a post positioned inside the central void of the therapy transducer, wherein the post comprises a first thermally conductive material; and one or more structures connecting the post to the outer shell from inside the central void, wherein the one or more structures comprise a second thermally conductive material, wherein the post and the one or more structures jointly form a thermally conductive heat sink.

2. The therapy intravascular ultrasound transducer assembly of claim 1, wherein an average acoustic intensity at a surface of the outer shell of the therapy transducer exceeds 30 watts / cm2, preferably exceeding 50 W / cm2, or 250 W / cm2.

3. The therapy intravascular ultrasound transducer assembly of claims 1 or 2, wherein the therapy transducer operates in a continuous wave (CW) mode when activated.

4. The therapy intravascular ultrasound transducer assembly of any one of claims 1-3, wherein the outer shell has a length less than about 10 mm, preferably less than about 6mm, and has a diameter between about 1 and about 3 mm, preferably about 1.5mm.

5. The therapy intravascular ultrasound transducer assembly of any one of claims 1-4, wherein the post is shaped as a cylinder positioned inside the central void of the outer shell, preferably coaxial with respective to the outer shell of the transducer.

6. The therapy intravascular ultrasound transducer assembly of any one of claims 1-5, wherein the post is positioned such that an outer surface of the post is within 200μm of an inner surface of the central void of the outer shell.29 Atty Docket: POMD04489SEC_WO017. The therapy intravascular ultrasound transducer assembly of claims 5 or 6, wherein the outer surface of the post and the inner surface of the central void of the outer shell are separated by air or any other gas so that the therapy transducer remains air backed.

8. The therapy intravascular ultrasound transducer assembly of any one of claims 1-7, wherein the first thermally conductive material and the second thermally conductive material are identical.

9. The therapy intravascular ultrasound transducer assembly of any one of claims 1-8, wherein the one or more structures are separated from an inside wall of the central void by a layer of material that is thermally conductive and electrically non-conductive.

10. The therapy intravascular ultrasound transducer assembly of claim 9, wherein the layer of material is made of epoxy.

11. The therapy intravascular ultrasound transducer assembly of any one of claims 1-10, wherein the post comprises at least one of: copper, silver, or brass.

12. The therapy intravascular ultrasound transducer assembly of any one of claims 1-11, wherein the therapy intravascular ultrasound transducer assembly is saline compatible, and capable of operating when immersed in a conductive fluid.

13. The therapy intravascular ultrasound transducer assembly of any one of claims 1-12, wherein the therapy transducer is activated for intervention such as renal denervation.

14. The therapy intravascular ultrasound transducer assembly of any one of claims 1-13, wherein the one or more structures are shaped as fins or flanges.

15. The therapy intravascular ultrasound transducer assembly of any one of claims 1-14, wherein the thermally conductive heat sink conducts heat generated by the therapy transducer out of the outer shell through the stud when the therapy transducer is activated.30 Atty Docket: POMD04489SEC_WO0116. The therapy ultrasound transducer of any one of claims 1 to 15, wherein the outer shell is shaped as a cylindrical shell.

17. The therapy ultrasound transducer of any one of claims 1 to 15, wherein the outer shell comprises multiple shell elements arranged circumferentially about the central void.

18. The therapy ultrasound transducer of claim 17, wherein each shell element has one of a rectangular form and an arced form.

19. The therapy ultrasound transducer of claim 17 or 18 wherein the shell elements are spaced apart from each other in a circumferential direction about the central void.

20. The therapy ultrasound transducer of any one of claims 1 to 19, wherein the post extends axially outside the outer shell to form a stud.

21. A method of manufacturing a therapy intravascular ultrasound transducer assembly, the method comprising: providing a therapy transducer with a central void and an outer shell; positioning a post inside the central void of the therapy transducer, wherein the post comprises a first thermally conductive material; mounting one or more structures connecting the post to the outer shell from inside the central void, wherein the one or more structures comprise a second thermally conductive material, wherein the post and the one or more structures jointly form a thermally conductive heat sink.

22. The method of claim 21, wherein the therapy transducer is capable of generating an average acoustic intensity that exceeds 30 watts / cm2, preferably exceeding 50W / cm2, or 250W / cm2.31 Atty Docket: POMD04489SEC_WO0123. The method of claims 21 or 22, wherein the outer shell has a length less than about 10 mm, preferably less than about 6mm, and has a diameter between about 1 and about 3 mm, preferably about 1.5mm.

24. The method of any one of claims 21-23, wherein the post is shaped as a cylinder positioned inside the central void of the outer shell, preferably coaxial with respective to the outer shell of the transducer.

25. The method of any one of claims 21-24, wherein the post is positioned such that an outer surface of the post is within 200μm of an inner surface of the central void of the outer shell.

26. The method of any one of claims 21-25, wherein an outer surface of the post and an inner surface of the central void of the outer shell are separated by air or any other gas so that the therapy transducer remains air backed.

27. The method of any one of claims 21-26, wherein the first thermally conductive material and the second thermally conductive material are identical.

28. The method of any one of claims 21-27, wherein the one or more structures are separated from an inside wall of the central void by a layer of material that is thermally conductive and electrically conductive.

29. The method of claim 28, wherein the layer of material is made of epoxy.

30. The method of any one of claims 21-29, wherein the post comprises at least one of: copper, silver, or brass.

31. The method of any one of claims 21-30, wherein the therapy intravascular ultrasound transducer assembly is saline compatible.

32. The method of any one of claims 21-31, wherein the one or more structures are shaped as fins or flanges.32 Atty Docket: POMD04489SEC_WO0133. The method of any one of claims 21 to 32, wherein the outer shell is shaped as a cylindrical shell.

34. The method of any one of claims 21 to 32, wherein the outer shell comprises multiple shell elements arranged circumferentially about the central void.

35. The method of claim 34, wherein each shell element has one of a rectangular form and an arced form.

36. The method of claim 34 or 35 wherein the shell elements are spaced apart from each other in a circumferential direction about the central void.

37. The method of any one of claims 21 to 36, wherein the post extends axially outside the outer shell to form a stud.33 Atty Docket: POMD04489SEC_WO01

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