DELIVERY SYSTEMS FOR CRYOABLATION DEVICE

In an embodiment, a cryoablation shaft is included having a working fluid circuit; a vacuum circuit; an insulated portion, wherein the vacuum circuit runs through the insulated portion; and an expansion chamber; a supply tube having a distal outlet in the expansion chamber, wherein fluid from the working fluid circuit travels distally down the cryoablation shaft through supply tube and expands in the expansion chamber; and a guidewire lumen including a metallic tube and a polymer sleeve configured to surround at least a portion of the metallic tube.

TECHNICAL FIELD

Embodiments herein relate to cryoablation systems and more particularly to delivery systems for cryoablation systems.

BACKGROUND

During cryosurgery, a surgeon may deploy one or more cryoprobes to ablate a target area of a patient anatomy by freezing and thawing the tissue. In one example, a cryoprobe uses the Joule-Thomson effect to produce cooling or heating of the probe tip. In such cases, the expansion of a cryofluid in the cryoablation probe from a higher pressure to a lower pressure leads to cooling of the device tip to temperatures at or below those corresponding to cryoablation a tissue in the vicinity of the tip. Heat transfer between the expanded cryofluid and the outer walls of the cryoprobe leads to formation of an ice ball, in the tissue around the tip and consequent cryoablation of the tissue.

SUMMARY OF THE INVENTION

In a first aspect, a cryoablation shaft includes a working fluid circuit, a vacuum circuit, an insulated portion, wherein the vacuum circuit runs through the insulated portion, and an expansion chamber extending distally to the insulated portion. The shaft further includes a guidewire lumen extending through a length of the cryoablation shaft, the guidewire lumen configured for insertion of a guidewire, the guidewire lumen can include a metallic tube and a polymer sleeve configured to surround at least a portion of the metallic tube. The shaft can further comprise a supply tube, the supply tube having a distal outlet in the expansion chamber, wherein fluid from the working fluid circuit travels distally down the cryoablation shaft through supply tube and expands in the expansion chamber, a return tube surrounding the supply tube, and an insulating shaft surrounding the return tube.

In a second aspect, in addition to one or more of the preceding or following aspects, or in the alternative to some aspects, the guidewire lumen can be concentrically located within the supply tube, the supply tube can be concentrically located within the return tube, and at least a portion of the return tube can be concentrically located within the insulating shaft.

In a third aspect, in addition to one or more of the preceding or following aspects, or in the alternative to some aspects, fluid from the working fluid circuit travels distally down the cryoablation shaft through an annular space defined between the return tube and the guidewire lumen.

In a fourth aspect, in addition to one or more of the preceding or following aspects, or in the alternative to some aspects, the metallic tube can include any of nitinol and stainless steel.

In a fifth aspect, in addition to one or more of the preceding or following aspects, or in the alternative to some aspects, the polymer sleeve can include any of polyether block amide and polyethylene terephthalate.

In a sixth aspect, in addition to one or more of the preceding or following aspects, or in the alternative to some aspects, at least a portion of the metallic tube includes slots, and the polymer sleeve can be configured to form a seal around the portion of the metallic tube can include the slots.

In a seventh aspect, in addition to one or more of the preceding or following aspects, or in the alternative to some aspects, the shaft further includes a distal tip configured to seal a distal end of the expansion chamber at a distal tip of the cryoablation shaft, wherein the distal tip includes metal.

In an eighth aspect, in addition to one or more of the preceding or following aspects, or in the alternative to some aspects, a distal end of the metallic tube can be joined to a proximal end of the distal tip using a metal-to-metal joining process.

In a ninth aspect, in addition to one or more of the preceding or following aspects, or in the alternative to some aspects, the distal tip defines a central channel, wherein the central channel can be configured to receive the guidewire, wherein a proximal end of the central channel of the distal tip can be joined to a distal end of the metallic tube.

In a tenth aspect, in addition to one or more of the preceding or following aspects, or in the alternative to some aspects, the shaft can include a first compressive wrap configured to seal the polymer sleeve to the metallic tube at a distal end of the polymer sleeve.

In an eleventh aspect, in addition to one or more of the preceding or following aspects, or in the alternative to some aspects, the shaft can include a second compressive wrap configured to seal the polymer sleeve to the metallic tube at a proximal end of the polymer sleeve.

In a twelfth aspect, in addition to one or more of the preceding or following aspects, or in the alternative to some aspects, the guidewire lumen may form a curve having a smallest radius of curvature of less than or equal to 30 mm.

In a thirteenth aspect, a guidewire lumen for a cryoablation shaft can include a metallic tube, wherein at least a portion of the metallic tube includes slots, a polymer sleeve, wherein the polymer sleeve can be configured to form a seal around the portion of the metallic tube can include the slots, and a distal tip. The guidewire lumen can be configured to extend through a length of the cryoablation shaft, the guidewire lumen can be configured for insertion of a guidewire, and the metallic tube can be configured to be joined to the distal tip at a distal end of the cryoablation shaft using a metal to metal joining processes.

In a fourteenth aspect, in addition to one or more of the preceding or following aspects, or in the alternative to some aspects, the guidewire lumen can be concentrically located within a supply tube of the cryoablation shaft, the supply tube can be concentrically located within a return tube of the cryoablation shaft, and at least a portion of the return tube can be concentrically located within an insulating shaft of the cryoablation shaft.

In a fifteenth aspect, in addition to one or more of the preceding or following aspects, or in the alternative to some aspects, the metallic tube can include any of nitinol and stainless steel.

In a sixteenth aspect, in addition to one or more of the preceding or following aspects, or in the alternative to some aspects, the polymer sleeve can include any of polyether block amide and polyethylene terephthalate.

In a seventeenth aspect, in addition to one or more of the preceding or following aspects, or in the alternative to some aspects, the guidewire lumen further can include a compressive wrap configured to seal the polymer sleeve to the metallic tube.

In an eighteenth aspect, in addition to one or more of the preceding or following aspects, or in the alternative to some aspects, the guidewire lumen may form a curve having a smallest radius of curvature of less than or equal to 30 mm.

In a nineteenth aspect, a cryoablation shaft can include a working fluid circuit, a vacuum circuit, an insulated portion, wherein the vacuum circuit runs through the insulated portion, and an expansion chamber, a guidewire lumen extending through a length of the cryoablation shaft, the guidewire lumen configured for insertion of a guidewire. The guidewire lumen can include a metallic tube wherein at least a portion of the metallic tube includes slots, and a polymer sleeve configured to surround at least a portion of the metallic tube, wherein the polymer sleeve can be configured to form a seal around the portion of the metallic tube that includes the slots. The shaft can further include a supply tube, the supply tube having a distal outlet in the expansion chamber, wherein fluid from the working fluid circuit travels distally down the cryoablation shaft through supply tube and expands in the expansion chamber, a return tube surrounding the supply tube, and an insulating shaft surrounding the return tube, wherein the guidewire lumen can be concentrically located within the supply tube, wherein the supply tube can be concentrically located within the return tube, wherein the return tube can be concentrically located within the insulating shaft.

In a twentieth aspect, in addition to one or more of the preceding or following aspects, or in the alternative to some aspects, the shaft further can include a distal tip configured to seal a distal end of the expansion chamber at a distal tip of the cryoablation shaft, wherein the distal tip includes metal.

DETAILED DESCRIPTION

Some cryoablation systems may be useful for ablating lesions in the biliary system or other difficult to access portions of the human anatomy. In such cases, the cryoprobes may have to navigate tortuous passageways. Cryoprobes with rigid shafts may not be suitable for such applications.

The present disclosure is directed towards a cryoablation system having a flexible shaft. The shaft may be sufficiently flexible to access particular portions of the human anatomy, such as the biliary system, while simultaneously maintaining adequate burst strength and thermal insulation to ensure patient safety.

In various embodiments, it is desirable for the cryoablation system to include a guidewire. A guidewire as defined herein is a flexible, medical wire inserted into the body to guide a larger instrument, such as a catheter, to a target location. Including a guidewire in the cryoablation system can enable the flexible shaft to access portions of the patient's anatomy (e.g., the biliary system) with increased accuracy and decreased damage. A guidewire may run through a guidewire lumen that extends either part way or all the way though the length of the shaft. A guidewire can be added to the cryoablation system in either a monorail or an over-the-wire configuration. In alternate embodiments, the cryoablation system may be introduced to a patient using a sheath rather than a guidewire. Advantageous guidewire lumen constructions are described herein.

The concepts described herein can be applied in the context of the cryoablation systems described in US Published Patent Application US2021/00045793, titled “Dual Stage Cryocooler,” and US Published Patent Application US2021/00045794, titled “Flexible Cryoprobe,” both filed Aug. 14, 2020, and both incorporated herein by reference in their entireties.

Referring now toFIG.1, a schematic view of a cryoablation system is shown in accordance with various embodiments herein. In various embodiments, the cryoablation system can include a handle102and a shaft104. In various embodiments, the shaft104is insertable into the handle102and can be securely attached to the handle with shaft-handle connector103. In various embodiments, the shaft104and the shaft-handle connector103of a cryoablation system100can form a catheter assembly. In some embodiments, the catheter assembly includes the components of the cryoablation system that are to be replaced each time a cryoablation procedure is performed. In some aspects, the cryoablation system100may include a working fluid source110, a pre-cooler fluid source112, and vacuum source114which are each connectible to the cryoablation system100.

The three sources correspond to three independent circuits in the cryoablation system100: pre-cooler, working fluid, and active vacuum. In some embodiments, the working fluid source110and pre-cooler fluid source112connect to the base of the handle102of the cryoablation system100and vacuum source114connects near the distal end of the handle, adjacent to the shaft-handle connector103. The cryoablation system may further include a pre-cooler gas exhaust116and a working gas exhaust118connecting to the handle102. In various embodiments, the shaft-handle connector103functions as a manifold to ensure each of the flow circuits remain isolated from one another.

In some embodiments, the cryoablation system100includes a console117. The console may be used to control the system and may be in electrical and fluid communication with the handle and cryoablation assembly. In some embodiments, the working fluid source110, pre-cooler fluid source112, vacuum source114may all be connectable to a console117of the cryoablation system100using conduits. In some embodiments, the pre-cooler gas exhaust116, working gas exhaust118, or both can connect to a conduit which carries the exhaust back to the console117or other location in the procedure room where the exhaust is vented to the ambient environment at an appropriate location. It should be noted that various sources and exhausts may be placed in position and in any suitable configuration along the handle102, and that the arrangement ofFIG.1is just one example of a suitable configuration.

An example of specifications and functions of each of these circuits is provided in the following paragraph. However, it should be noted that the particular fluids and pressure values are meant for exemplary purposes and other configurations are possible.

In an embodiment, the pre-cooler circuit can contain 24.1 mega Pascals (MPa) pressurized Argon. The precooler circuit can cool the incoming stream of working fluid and can operate in the handle. In an embodiment, the working fluid circuit can contain 12.4 MPa pressurized Argon and/or 12.4 MPa pressurized Helium. The working fluid circuit generates and/or thaws ice balls. The working fluid circuit can operate in the handle, the insulated portion or insulated zone of the shaft, and the expansion chamber of the shaft. In an embodiment, the active vacuum can hold a vacuum of less than or equal to 6.67 Pascals (Pa). The active vacuum can insulate the shaft. The active vacuum can operate in the handle and the insulated zone of the shaft.

In various embodiments, the working fluid circuit runs through both the handle102and the shaft104of the cryoablation system100and carries the fluid which both generates and thaws the ice ball. The term “fluid circuit” is used throughout the application, and could be replaced with gas circuit, liquid circuit, fluid chamber, gas chamber, or liquid chamber in various embodiments. The term “fluid” is used throughout and could be replaced with gas or liquid in various embodiments. During the ablation (freeze cycle), 12.4 MPa argon is circulated through the probe to generate the ice ball in the patient's body surrounding the expansion chamber106. The working fluid can be any suitable cooling fluid (e.g., nitrogen, air, argon, krypton, xenon, N2O, CO2, CF4). In some embodiments, the pressure of the high-pressure stream of the working fluid can be greater than or equal to 6.9 MPa, 8.3 MPa, 9.7 MPa, 11.0 MPa, 12.4 MPa, 17.2 MPa, 27.6 MPa, or 41.4 MPa. In some embodiments, the pressure of the high-pressure stream of the working fluid can be less than or equal to 55.2 MPa, 34.5 MPa, 20.7 MPa, 18.6 MPa, 16.5 MPa, 14.5 MPa, or 12.4 MPa. In some embodiments, the pressure of the high-pressure stream of the working fluid can fall within a range of 6.9 MPa to 41.4 MPa, or 8.3 MPa to 27.6 MPa, or 9.7 MPa to 16.5 MPa, or 11.0 MPa to 14.5 MPa, or can be about 12.4 MPa. Accordingly, in the embodiments where the working fluid is a cooling fluid, the temperature of the working fluid at the expansion chamber106can be about 190 Kelvin. In some embodiments, the temperature of the working fluid can be less than or equal to 250 Kelvin, 200 Kelvin, 150 Kelvin, or 100 Kelvin, or can be an amount falling within a range between any of the foregoing.

In various embodiments, the pre-cooler circuit is fully contained within the handle102. In various embodiments, the pre-cooler circuit is located in a console117of the system. In various embodiments, the pre-cooler circuit is located in a part of the catheter just proximal to the handle. In various embodiments, the pre-cooler circuit is located in a part of the catheter just distal to the handle. The pre-cooler circuit operates using argon or any other suitable cooling fluid in various embodiments. In some embodiments, the high-pressure stream of the pre-cooler fluid may be at a pressure greater than the pressure of the high-pressure stream of the working fluid. The pre-cooler fluid may, for instance, be supplied at pressures greater than about 13.8 MPa. In some embodiments, the pressure of the pre-cooler fluid can be greater than or equal to 10.3 MPa, 13.8 MPa, 17.2 MPa, 20.7 MPa, or 24.1 MPa. In some embodiments, the pressure of the pre-cooler fluid can be less than or equal to 31.0 MPa, 29.3 MPa, 25.9 MPa, or 24.1 MPa. In some embodiments, the pressure of the pre-cooler fluid can fall within a range of 10.3 MPa to 31.0 MPa, or 13.8 MPa to 29.3 MPa, or 17.2 MPa to 27.6 MPa, or 20.7 MPa to 25.9 MPa, or can be about 24.1 MPa.

In some embodiments, the outer surface of the shaft104may be thermally insulated from the inner surface of the shaft. In various embodiments, the vacuum circuit or vacuum chamber runs through both the handle102and the insulated zone105of the shaft104. Vacuum is actively pulled along the insulated zone105of the shaft104throughout the cryoablation procedure, providing a protective barrier between the outer surface of the shaft104and the patient. In alternative embodiments, shaft insulation can be obtained by circulating fluid, gas, or a heated fluid throughout the shaft or by electrically heating portions of the shaft. In alternative embodiments, shaft insulation can be obtained by containing a non-circulating fluid or gas within an insulating shaft.

The shaft104can be of any suitable length capable of reaching the target anatomy in the subject. In some embodiments, the shaft length can be greater than or equal to 20 cm, 38 cm, 55 cm, 72 cm, or 90 cm. In some embodiments, the shaft length can be less than or equal to 150 cm, 135 cm, 120 cm, 105 cm, or 90 cm. In some embodiments, the shaft length can fall within a range of 20 cm to 150 cm, or 38 cm to 135 cm, or 55 cm to 120 cm, or 72 cm to 105 cm, or can be about 90 cm.

In various embodiments, certain portions of the shaft104may be flexible. In an embodiment, the entire length of the shaft may be flexible. For instance, the shaft may be bendable about its lengthwise axis. In some such embodiments, the shaft may have a shaft diameter configured such that the shaft may be sufficiently flexible to form a curve having a desired radius of curvature. For instance, the shaft may be sufficiently flexible, such that the shaft may form a curve having the smallest radius of curvature of less than or equal to 30 mm, 20 mm, 10 mm, or 5 mm.

In various embodiments, shaft104may include an insulated zone105and an expansion chamber106. The insulated zone105defines the portion of shaft104that is insulated by the vacuum chamber. The expansion chamber106defines the portion of the shaft104that is not insulated by the vacuum and where the ice ball is generated. In various embodiments, flexible shaft carries high pressure working fluid from the handle102to the expansion chamber106, where it undergoes a Joule-Thompson expansion and corresponding temperature change. The working fluid exits down the flexible shaft, through the handle, before venting to the atmosphere from the console, or into the handle and venting from the handle.

The distal end of the shaft may terminate in a distal operating tip108. During use, the distal operating tip108is deployed in the body of a patient, is surrounded by tissue, and cryogenically ablates the tissue in some instances. The distal operating tip108may be advantageously configured to pierce tissue in some instances. For example, the distal operating tip108may include a sharp tip, such as a trocar tip. Alternatively, the distal operating tip108may not be a sharp tip. In some embodiments, the distal operating tip108can be an atraumatic tip designed to cause minimal tissue injury. In some embodiments, the distal operating tip108may also contain a working port configured for any of aspiration, delivery of therapeutics, and delivery of other devices including, but not limited to guide wires, imaging catheters, sensing devices, biopsy devices, balloons, and stents.

Handle with Pre-Cooler Circuit (FIG.2)

Referring now toFIG.2, a schematic view of portions of a cryoablation system is shown in accordance with various embodiments herein. In some aspects, the cryoablation system100may include a working fluid source110connecting to a working fluid circuit and a pre-cooler fluid source112connecting to a pre-cooler fluid circuit. The working fluid circuit may include a working fluid supply conduit210for carrying a high-pressure stream of the working fluid from the working fluid source110to the distal end of the shaft104(not shown in this view). The working fluid circuit may also include a working fluid return conduit (not shown in this view) for carrying a low-pressure stream of the working fluid from the distal end of the shaft back to the base of the handle102.

The pre-cooler fluid circuit may include a pre-cooler supply circuit212, which terminates at pre-cooler Joule-Thomson orifice223and carries a high-pressure stream of a pre-cooler fluid from the pre-cooler fluid source112to the pre-cooler fluid expansion region222in the handle102. The pre-cooler fluid circuit may also include a pre-cooler return conduit (marked by arrows213). The pre-cooler return conduit may be configured to carry the pre-cooler fluid away from the pre-cooler fluid expansion region222back to the base of the handle102. The pre-cooler return conduit may be housed along with the pre-cooler supply circuit212and extend back to a control console and gas manifold.

In various embodiments, the pre-cooler fluid circuit may facilitate heat exchange between the working fluid and the pre-cooler fluid. For instance, the pre-cooler fluid circuit can be used to precool the high-pressure stream of the working fluid in embodiments where the working fluid cools upon expansion to cryogenically ablate tissue surrounding the distal operating tip108. In various embodiments, the working fluid supply conduit210may include a first heat exchanger216. The first heat exchanger216may facilitate heat exchange between the high-pressure stream of the working fluid in the working fluid supply conduit210and the low-pressure stream of the pre-cooler fluid in the pre-cooler return conduit.

In various embodiments, the pre-cooler supply conduit212may include a second heat exchanger218that permits heat exchange between the high-pressure stream of the pre-cooler fluid and the low-pressure stream of the pre-cooler fluid (e.g., recuperative heat exchange). In various embodiments aspects, the pre-cooler fluid may also be a cooling fluid. In such embodiments, recuperative heat exchange between the high-pressure stream of the pre-cooler fluid and the low-pressure stream of the pre-cooler fluid may remove heat from the high-pressure stream of the pre-cooler fluid. Accordingly, the second heat exchanger218may facilitate precooling the high-pressure stream of the pre-cooler fluid.

In various embodiments, the high-pressure stream of the pre-cooler fluid leaving the second heat exchanger218continues to flow through the pre-cooler supply conduit212to the pre-cooler fluid expansion region222. In the pre-cooler fluid expansion region, which is fully contained in handle102, the pre-cooler supply conduit212terminates in a Joule-Thomson orifice. The high-pressure stream of the pre-cooler fluid may undergo expansion at or downstream of the Joule-Thomson orifice in the pre-cooler fluid expansion region222. The rapid drop in pressure causes a corresponding drop in temperature. The pre-cooler fluid expansion region222may be in fluid communication with the pre-cooler return conduit to carry the expanded low-pressure stream of the pre-cooler fluid (e.g., to vent to atmosphere, if the pre-cooler fluid circuit is an open circuit, or back to a pre-cooler fluid source if the pre-cooler fluid circuit is a closed circuit). After expansion at the Joule-Thomson orifice, the chilled pre-cooler fluid passes back through handle102, in the annular space between the core tube215and the outer surface of the handle102. As the pre-cooler fluid passes through the pre-cooler return conduit, it cools the working fluid at the first heat exchanger216.

The working fluid circuit210may also include a third heat exchanger220in the shaft104of the cryoablation system that is configured for heat exchange (e.g., recuperative heat exchange) between the high-pressure stream of the working fluid in the working fluid supply circuit210and the low-pressure stream of the working fluid returning through the shaft104(not shown in this view).

Distal Tip and Expansion Chamber Details (FIG.3)

Referring now toFIG.3, a schematic view of a portion of a cryoablation shaft is shown in accordance with various embodiments herein. In various embodiments, the shaft includes an insulated zone105and an expansion chamber106. In various embodiments, the insulated zone105of shaft104includes a supply tube324which is located within a return tube326, which is located within an insulating shaft328. The concentric-shaft construction is designed to isolate the working fluid circuit210and vacuum chamber336from each other.

In various embodiments, after exiting the handle102, the high-pressure flow of the working fluid travels down the supply tube324. When the working fluid reaches the working fluid expansion chamber106, the supply tube324terminates in a Joule-Thomson orifice332or distal outlet332. The high-pressure stream of the working fluid may undergo expansion at or downstream of the Joule-Thomson orifice332in expansion chamber106. The rapid drop in pressure causes a corresponding drop in temperature. Heat transfer between the expanded working and the outer walls of expansion chamber106leads to formation of an ice ball in the tissue around the tip108resulting in cryoablation of the tissue.

The expansion chamber106may be in fluid communication with the working fluid return conduit (defined by the annular space between the supply tube324and the inner surface of the return tube326of the expansion chamber) to carry the expanded low pressure stream of the working fluid (e.g., to vent to atmosphere, if the working fluid circuit is an open circuit, or back to a working fluid source if the working fluid circuit is a closed circuit). As the working fluid passes through the working fluid return conduit, it cools the working fluid input stream at the third heat exchanger220(FIG.2).

In various embodiments, the working fluid is a cooling fluid and a cooling gas (e.g., nitrogen, air, argon, krypton, xenon, N2O, CO2, CF4). In such cases, the high-pressure stream of the working fluid may be at a pressure such that expansion via the

Joule-Thomson orifice332may result in the working fluid cooling to temperatures for cryogenically ablating tissue surrounding the expansion chamber106. In certain aspects, the pressure of the high-pressure stream of the working fluid upstream of the Joule-Thomson orifice332can be between about 6.9 MPa and about 13.8 MPa (e.g., about 12.4 MPa). Accordingly, in the embodiments where the working fluid is a cooling fluid, the temperature of the working fluid after expansion from the Joule-Thomson orifice332can be greater than or equal to 150, 160, 170, 180, 190, or 200 Kelvin, or can be an amount falling within a range between any of the foregoing.

Cryoablation system100can be designed such that the outermost surface of the shaft does not cause thermal damage to non-target structures. In various embodiments, Ice ball formation is limited to the expansion chamber106of the shaft104, which can also be referred to as the active region of the device. Selective ice ball formation is achieved by pulling a vacuum through the insulated zone105of shaft104. In various embodiments, the cryoablation system100may be configured for establishing vacuum communication between the shaft104and vacuum source114.

Referring back toFIG.1, cryoablation system100may be configured to connect to a vacuum source114at handle102. In various embodiments, the vacuum source114is configured to pull vacuum along the length of the insulated zone105of shaft104. In an embodiment, vacuum is pulled between the outer diameter of the return tube326and the inner diameter of the insulating shaft328throughout the insulated zone105of shaft104.

In various embodiments, the vacuum source114is configured to pull a vacuum within at least a portion of the handle102. Such a configuration can insulate the handle102and protect the cryoablation system operator from cryogenic exhaust gases. In some embodiments the vacuum source114is connected to the handle102and the shaft104is in fluid communication with the handle102such that pulling a vacuum in the handle can also evacuate the space between the supply tube324and return tube326. In other embodiments, the vacuum source114is connected directly to the shaft104, for example, with the use of a t-fitting along the length of the shaft104.

To provide for thermal insulation along the insulated zone105of shaft104, the wall of the flexible shaft is a double wall (a return tube surrounded by an insulating shaft) with a small gap between the return tube326and the insulating shaft328. By pulling a vacuum between the return tube and the insulating shaft, convective heat transfer is prevented, so that the temperature of the working fluid does not ablate or cause uncontrolled apoptosis/necrosis to healthy non-target patient tissue along the insulated zone of the shaft. Adequate thermal insulation is obtained by actively pumping out the air in the gap and maintaining a vacuum of about 0.05 torr. However, other vacuum pressures may be appropriate depending on the configuration of the cryoablation system. In some embodiments, a supporting filament330is wrapped around the outer diameter of the return tube326. One option for the filament material is a polymer such as polyether ether ketone (PEEK). The filament may prevent direct contact between the return tube outer surface and insulating shaft inner surface. Filament330minimizes thermal conduction between the inner and insulating shafts. Other alternatives may be used in place of the filament330such as an extruded tubing/co-extrusion shape or other features placed onto the shaft.

In some embodiments, the shaft may not include a filament. In such embodiments the return tube326and the insulating shaft328are selected to have material properties that are sufficient to minimize thermal conduction between the inner shaft and the insulating shaft.

A joint334is present at the junction of the insulated zone105and the expansion chamber106. This joint is capable of sealing the vacuum layer.

Flexible Shaft Cross-Section, Dimensions and Materials (FIG.4)

Referring now toFIG.4, a cross sectional view of the shaft ofFIG.3taken along section4-4is shown in accordance with various embodiments herein. In various embodiments, the insulated zone105of shaft104includes a supply tube324concentrically located within a return tube326, which is concentrically located within an insulating shaft328. The insulated zone105can include a shaft portion of the vacuum chamber336and an insulated portion of the working gas circuit210. In various embodiments, the vacuum chamber336surrounds and is isolated from the insulated portion of the working gas circuit210.

In various embodiments, after exiting the handle102, the high-pressure flow of the working fluid travels distally down the insulated zone of the shaft through supply tube324. After cooling and expansion in the expansion chamber106, the working fluid travels proximally back through the insulated zone105of the shaft104in the annular space between the supply tube324and return tube326.

In various embodiments, the materials and dimensions of each of the layers of the shaft104may be selected to provide sufficient degree of flexibility for the shaft to be bendable about its longitudinal axis at the working temperatures of the device.

In various embodiments, the supply tube324, which also may be referred to as a capillary tube herein, is constructed from any suitable material or materials such as flexible metals, polymers, composites, or the like. In an embodiment, the supply tube324is constructed from Nitinol (NiTi), stainless steel, or the like.

In some embodiments, the inner diameter of the supply tube324can be greater than or equal to 0.30 mm, 0.35 mm, 0.40 mm, or 0.45 mm. In some embodiments, the inner diameter of the supply tube324can be less than or equal to 0.60 mm, 0.55 mm, 0.50 mm, or 0.45 mm. In some embodiments, the diameter of the supply tube324can fall within a range of 0.30 mm to 0.60 mm, or 0.35 mm to 0.55 mm, or 0.40 mm to 0.50 mm, or can be about 0.45 mm.

In some embodiments, the outer diameter of the supply tube324can be greater than or equal to 0.38 mm, 0.43 mm, 0.48 mm, 0.53 mm, or 0.58 mm. In some embodiments, the outer diameter can be less than or equal to 0.78 mm, 0.73 mm, 0.68 mm, 0.63 mm, or 0.58 mm. In some embodiments, the outer diameter can fall within a range of 0.38 mm to 0.78 mm, or 0.43 mm to 0.73 mm, or 0.48 mm to 0.68 mm, or 0.53 mm to 0.63 mm, or can be about 0.58 mm.

In some embodiments, the thickness of the supply tube324can be greater than or equal to 0.10 mm, 0.11 mm, 0.12 mm, 0.14 mm, or 0.15 mm. In some embodiments, the thickness of the supply tube324can be less than or equal to 0.20 mm, 0.19 mm, 0.18 mm, 0.16 mm, or 0.15 mm. In some embodiments, the thickness of the supply tube324can fall within a range of 0.10 mm to 0.20 mm, or 0.11 mm to 0.19 mm, or 0.12 mm to 0.18 mm, or 0.14 mm to 0.16 mm, or can be about 0.15 mm.

In various embodiments, the return tube326is constructed from any suitable material or materials such as flexible metals, polymers, or the like. In various embodiments, the return tube326can be made of polyimide, fluorinated ethylene propylene (FEP), Teflon, or the like. In an embodiment, the return tube326is formed from a polyimide material as it is highly impermeable to gases at a wide range of temperatures and can thus contain the working fluid inside and hold vacuum on the outside. In a particular example, the return tube326is made of a braid-reinforced polyimide tube to enhance gas impermeability, burst strength, and flexibility. In some embodiments, the return tube326is formed from a single layer of material. In some embodiments, the return tube326can be formed from two or more layers of material selected to optimize the performance of the shaft104. The layers of material can be bonded together using any suitable technique or techniques such as adhesives, reflow processes, or the like.

In some embodiments, the outer diameter of the return tube326can be greater than or equal to 1 mm, 1.1 mm, 1.2 mm, 1.3 mm, or 1.4 mm. In some embodiments, the outer diameter of the return tube326can be less than or equal to 1.8 mm, 1.7 mm, 1.6 mm, 1.5 mm, or 1.4 mm. In some embodiments, the outer diameter of the return tube326can fall within a range of 1.0 mm to 1.8 mm, or 1.1 mm to 1.7 mm, or 1.2 mm to 1.6 mm, or 1.3 mm to 1.5 mm, or can be about 1.4 mm.

In some embodiments, the inner diameter of the return tube326can be greater than or equal to 0.9 mm, 1.0 mm, 1.1 mm, 1.2 mm, or 1.3 mm. In some embodiments, the inner diameter of the return tube326can be less than or equal to 1.7 mm, 1.6 mm, 1.5 mm, 1.4 mm, or 1.3 mm. In some embodiments, the inner diameter of the return tube326can fall within a range of 0.9 mm to 1.7 mm, or 1.0 mm to 1.6 mm, or 1.1 mm to 1.5 mm, or 1.2 mm to 1.4 mm, or can be about 1.3 mm.

In some embodiments, the thickness of the return tube326can be greater than or equal to 0.10 mm, 0.11 mm, 0.12 mm, 0.14 mm, or 0.15 mm. In some embodiments, the thickness of the return tube326can be less than or equal to 0.20 mm, 0.19 mm, 0.18 mm, 0.16 mm, or 0.15 mm. In some embodiments, the thickness of the return tube326can fall within a range of 0.10 mm to 0.20 mm, or 0.11 mm to 0.19 mm, or 0.12 mm to 0.18 mm, or 0.14 mm to 0.16 mm, or can be about 0.15 mm.

In various embodiments, the insulating shaft328is constructed from any suitable material or materials such as flexible metals, polymers, or the like. In various embodiments, the insulating shaft328is made of polyimide, fluorinated ethylene propylene (FEP), Teflon, or the like. In a particular embodiment, the insulating shaft328may include polytetrafluoroethylene (PTFE), and/or one or more polyether block amides (known under the tradename Pebax®, hereinafter “Pebax”).

In some embodiments, the insulating shaft328is formed from a single layer of material. In some embodiments, the insulating shaft328can be formed from two or more layers of material selected to optimize the performance of the shaft104. The layers of material can be bonded together using any suitable technique or techniques such as adhesives, reflow processes, or the like.

In an embodiment, the insulating shaft may be formed using a braid-reinforced polyimide tube skim-coated with a Pebax outer layer. Such a tri-layer construction enables the deep vacuum to be maintained between the return tube and the insulating shaft without causing the insulating shaft328to collapse onto the return tube326.

In some embodiments, the outer diameter of the insulating shaft328can be greater than or equal to 1.2 mm, 1.4 mm, 1.5 mm, 1.6 mm, or 1.8 mm. In some embodiments, the outer diameter of the insulating shaft can be less than or equal to 2.2 mm, 2.1 mm, 2.0 mm, 1.9 mm, or 1.8 mm. In some embodiments, the outer diameter of the insulating shaft can fall within a range of 1.3 mm to 2.3 mm, or 1.4 mm to 2.1 mm, or 1.5 mm to 2.0 mm, or 1.6 mm to 1.9 mm, or can be about 1.8 mm.

In some embodiments, the inner diameter of the insulating shaft328can be greater than or equal to 1.0 mm, 1.2 mm, 1.3 mm, 1.4 mm, or 1.6 mm. In some embodiments, the inner diameter of the insulating shaft328can be less than or equal to 2.2 mm, 2.0 mm, 1.9 mm, 1.8 mm, or 1.6 mm. In some embodiments, the inner diameter of the insulating shaft328can fall within a range of 1.0 mm to 2.2 mm, or 1.2 mm to 2.0 mm, or 1.3 mm to 1.9 mm, or 1.4 mm to 1.8 mm, or can be about 1.6 mm.

In some embodiments, the thickness of the insulating shaft328can be greater than or equal to 0.10 mm, 0.11 mm, 0.12 mm, 0.14 mm, or 0.15 mm. In some embodiments, the thickness of the insulating shaft328can be less than or equal to 0.20 mm, 0.19 mm, 0.18 mm, 0.16 mm, or 0.15 mm. In some embodiments, the thickness of the insulating shaft328can fall within a range of 0.10 mm to 0.20 mm, or 0.11 mm to 0.19 mm, or 0.12 mm to 0.18 mm, or 0.14 mm to 0.16 mm, or can be about 0.15 mm.

In some embodiments, a PEEK filament330is wound around the return tube326. PEEK filament330may have pitch that is greater than or equal to 0.5 mm, 1.0 mm, 1.5 mm, or 2.0 mm, or can be an amount falling within a range between any of the foregoing. Alternatively, the filament may be a plurality of discrete pieces attached along the return tube326. The PEEK filament330prevents direct contact between the return tube326and the insulating shaft328, maintaining their coaxial alignment. In some embodiments, an adhesive (e.g., Loctite) is applied on the filament at the end of the return tube326and the insulating shaft328to attach the PEEK filament330. In various embodiments, the PEEK filament wrap is configured to minimize or prevent conductive heat transfer from the return tube to the insulating shaft. In alternative embodiments, other insulating polymers may be used as a substitute for the PEEK filament such as expanded PTFE (ePTFE), nylon, or the like.

In some embodiments, the diameter of the PEEK filament330can be greater than or equal to 0.002 mm, 0.004 mm, or 0.005 mm. In some embodiments, the diameter of the PEEK filament330can be less than or equal to 0.007 mm, 0.006 mm, or 0.005 mm. In some embodiments, the diameter of the PEEK filament330can fall within a range of 0.002 mm to 0.007 mm, or 0.004 mm to 0.006 mm, or can be about 0.005 mm.

Shaft in the Expansion Chamber (FIG.5)

Referring now toFIG.5, a cross-sectional view of the shaft ofFIG.3taken along section5-5is shown in accordance with various embodiments herein. The cross-sectional view ofFIG.5depicts expansion chamber106of the shaft104. In various embodiments, the expansion chamber106is distal to the insulated zone105along the shaft104. The expansion chamber106can include an expansion portion of the working fluid circuit210.

In various embodiments, after exiting the handle102, the high-pressure flow of the working fluid travels down the supply tube324. After cooling and expansion in expansion chamber106, the working fluid travels back down through the expansion chamber106in the annular space between the supply tube324and the outer wall of the expansion chamber. In various embodiments, the expansion chamber106is configured to maximize the heat transfer between the working gas and the patient's tissue through the optimization of parameters such as wall thickness, materials, and the like.

In various embodiments, the expansion chamber106is constructed from any suitable material or materials such as flexible metals, polymers, or the like. In various embodiments, the expansion chamber106is made of polyimide, fluorinated ethylene propylene (FEP), Teflon, or the like. In some embodiments, the expansion chamber106includes a continuation of the return tube326of the insulated zone105of the shaft104. Alternatively, the expansion chamber is a separate component from the return tube326that can be joined to the shaft104using any suitable joint and/or fitting, such as reflow processes, glue joints, solder joints, or any other suitable mechanical joining process capable of withstanding cryogenic pressures and temperatures.

In some embodiments, the expansion chamber106is formed from a single layer of material. In some embodiments, the expansion chamber106is formed from two or more layers of material. The layers of material can be bonded together using any suitable technique or techniques such as adhesives, reflow processes, or the like.

In some embodiments, the outer diameter of the expansion chamber106can be greater than or equal to 1.3 mm, 1.4 mm, 1.5 mm, 1.6 mm, or 1.7 mm. In some embodiments, the outer diameter of the expansion chamber106can be less than or equal to 2.1 mm, 2.0 mm, 1.9 mm, 1.8 mm, or 1.7 mm. In some embodiments, the outer diameter of the expansion chamber106can fall within a range of 1.3 mm to 2.1 mm, or 1.4 mm to 2.0 mm, or 1.5 mm to 1.9 mm, or 1.6 mm to 1.8 mm, or can be about 1.7 mm.

In some embodiments, the inner diameter of the expansion chamber106can be greater than or equal to 1.0 mm, 1.1 mm, 1.2 mm, 1.3 mm, or 1.4 mm. In some embodiments, the inner diameter of the expansion chamber106can be less than or equal to 1.8 mm, 1.7 mm, 1.6 mm, 1.5 mm, or 1.4 mm. In some embodiments, the inner diameter of the expansion chamber106can fall within a range of 1.0 mm to 1.8 mm, or 1.1 mm to 1.7 mm, or 1.2 mm to 1.6 mm, or 1.3 mm to 1.5 mm, or can be about 1.4 mm.

In some embodiments, the thickness of the wall of expansion chamber106can be greater than or equal to 0.20 mm, 0.22 mm, 0.25 mm, 0.28 mm, or 0.30 mm. In some embodiments, the thickness of the wall of the expansion chamber106can be less than or equal to 0.40 mm, 0.38 mm, 0.35 mm, 0.32 mm, or 0.30 mm. In some embodiments, the thickness of the wall of the expansion chamber106can fall within a range of 0.20 mm to 0.40 mm, or 0.22 mm to 0.38 mm, or 0.25 mm to 0.35 mm, or 0.28 mm to 0.32 mm, or can be about 0.30 mm.

Treatment Area Examples (FIG.6)

The cryoablation systems and structures described herein are flexible and well-suited to cryoablate an area along a lumen, vessel, or passageway of the body. The present cryoablation system100is configured to be adequately flexible to access and ablate many different such structures. The expansion chamber may be shaped and sized to generate an ice ball or ice cylinder of appropriate geometry for ablating structures along the length of a body lumen. Moreover, the materials and configuration of the probes described herein are selected to protect patient tissue and withstand high operating pressures and low temperatures.

Referring now toFIG.6, a schematic view of the biliary system is shown in accordance with various embodiments herein. The biliary system includes organs and ducts that make and store bile (a fluid made by the liver that helps digest fat) and release it into the small intestine. The biliary system includes the gallbladder and bile ducts inside and outside the liver.

Bile duct cancer or cholangiocarcinoma is a rare disease in which cancer cells form in the bile ducts. Treatment outcomes for cholangiocarcinoma are generally poor. Current treatment options such as a Whipple procedure or biliary drains are high risk and often ineffective.

Cryoablation is a promising treatment for cholangiocarcinoma. The present cryoablation system100is configured to be adequately flexible to access and ablate the bile ducts of a patient. The expansion chamber may be shaped and sized to generate an ice ball of appropriate geometry for ablating tumors in the bile ducts.

In addition to the treatment of cholangiocarcinoma, the cryoablation system100can be used to treat a number of conditions including other cancerous tumors (e.g., skin, liver, kidney, bone, lung, prostate and breast), pain, skin conditions (e.g., atypical moles, warts, skin tags or actinic keratosis), arrythmia, or the like. The cryoablation system100can additionally ablate benign masses, soft tissue, and healthy tissue.

Ice Ball Formation (FIG.7)

Referring now toFIG.7, a schematic view of the growth of an ice ball generated by a cryoablation system is shown in accordance with various embodiments herein. Cryoablation is defined as cell destruction using cold temperatures. An ice ball is formed at the expansion chamber of a cryoablation system, which freezes intra cellular and extracellular material to temperatures colder than 173 Kelvin. The application of these extremely cold temperatures causes cell death. In order to cause complete cell death, sufficiently low ablation temperatures are achieved. Lethal temperatures for various tissues have been reported between 253 Kelvin and 233 Kelvin.

FIG.7illustrates the growth of an ice ball over the course of a cryoablation procedure. The time points in this example are at 60 seconds, 120 seconds, 180 seconds, and 240 seconds. Isotherms for 273 Kelvin, 253 Kelvin and 233 Kelvin are depicted for each period of time. As the cryoablation procedure progresses in time, the overall ice ball size increases. More critically, the cell killing isotherms (the 253 Kelvin and 233 Kelvin isotherms) grow along both the major and minor axes of the ice ball.

It should be noted that the times and temperatures given byFIG.7are for exemplary purposes only. Ice ball formation can vary based on the configuration of the cryoablation system and the patient's tissue. Moreover, ice ball growth can stabilize after a certain ablation time has been reached. For example, in some embodiments, an ice ball can reach its maximum diameter after ablating the tissue for approximately 10 minutes. In some embodiments, the cryoablation system operator can terminate a cryoablation procedure upon the ice ball reaching its maximum size. In some embodiments, the cryoablation system operator can continue the cryoablation procedure upon the ice ball reaching its maximum size for a predetermined amount of time, as holding the tissue at cryogenic temperatures for longer times may have therapeutic benefits.

In some embodiments, the ice ball is produced and then thawed, and then produced again. In some embodiments, active thawing techniques are used while in other embodiments passive thawing is used.

In the example ofFIG.7, the ice balls are oblong in shape (e.g., they are longer along a primary axis than a secondary axis). The primary axis of the ice ball corresponds to a lengthwise axis of the expansion chamber. The ratio of expansion chamber height to diameter can be correlated to ice ball shape. In particular, an expansion chamber that is much longer than it is wide will result in a more oblong ice ball. Such an ice ball is generally more suitable for the treatment of cholangiocarcinoma, as it is more compatible with the anatomy of the bile ducts. However, other cryoablation applications may require a more spherical ice ball. In such scenarios, the expansion camber can be modified to have a smaller length to diameter ratio.

In some embodiments, the major axis length of an ice ball can be greater than or equal to 0.5 mm, 2 mm, 4 mm, 6 mm, 8 mm, or 10 mm, or can be an amount falling within a range between any of the foregoing. In some embodiments, the minor axis length of an ice ball can be greater than or equal to 0.5 mm, 2 mm, 4 mm, 6 mm, 8 mm, or 10 mm, or can be an amount falling within a range between any of the foregoing.

Cryoablation Shaft Including a Slotted Tube Portion, a Polymer Layer, and a Reinforcing Layer (FIG.8)

Referring now toFIG.8, a schematic view of a tip portion of a cryoablation shaft is shown in accordance with various embodiments herein. In various embodiments, the shaft includes an insulated zone105and an expansion chamber106. In various embodiments, the insulated zone105of shaft104includes a supply tube324concentrically located within a return tube326, which is concentrically located within an insulating shaft328. The concentric-shaft construction is designed to isolate the working gas and active vacuum circuits from each other.

In various embodiments, after exiting the handle102, the high-pressure flow of the working fluid travels down the supply tube324. The high-pressure stream of the working fluid may undergo expansion at or downstream of the Joule-Thomson orifice332and returns down the shaft in the annular space between the supply tube324and the return tube326.

In various embodiments, the expansion chamber106of shaft104includes a supply tube324concentrically located within the return tube326. The return tube326includes multiple layers in various embodiments.

In various embodiments, the innermost layer of the return tube is a slotted tube830which includes slots840along at least a portion of the length of shaft104. Slots840are formed in the tube material by any suitable means, such as laser cutting. The slots840can be laser cut into the shaft using any suitable pattern to optimize the strength and flexibility of the return tube326. The material of the slotted tube830can be metal such as stainless steel, nitinol, or other durable materials. Many different configurations and patterns of slotted tube830are available and one can be selected with the flexibility desirable in this application. The slotted tube forms the core of the return tube326in various embodiments.

In some embodiments, the slotted tube830includes the slots only in the expansion chamber106. In this embodiment, the portion of the slotted tube830that extends through the insulated zone105has solid walls.FIG.8illustrates this embodiment by showing a schematic side view of the slotted tube830, including slots840in the expansion chamber106, and showing the supply tube324in dashed lines within the slotted tube830. In an alternative embodiment, the slotted tube830has slots along its entire length.

The slotted tube may be configured to be sufficiently flexible to form a curve having a desired radius of curvature. For instance, the slotted tube may be sufficiently flexible, such that the shaft may form a curve having the smallest radius of curvature of less than or equal to 30 mm, 20 mm, 10 mm, 5 mm, or 3 mm. The slotted tube830may have different levels of flexibility in the expansion chamber and the insulated zone105.

In various embodiments, a first polymer layer842surrounds the portion of the slotted tube830which includes the slots, in order to contain the working fluid within the shaft104. In various embodiments, a reinforcing layer844surrounds the first polymer layer842and is configured to provide additional strength and reinforcement to the first polymer layer842, thus reducing the likelihood of any leak or rupture in the first polymer layer.

In various embodiments, the first polymer layer842can be formed from any suitable polymer such as polyethylene terephthalate (PET), PTFE, ePTFE, PEEK, polyetherimide (PEI), polyimide (PI), or the like. In various embodiments, the reinforcing layer844can be a second polymer layer formed from any suitable polymer such as PET, PTFE, PEEK, polyetherimide (PEI), polyimide (PI), or the like. In various embodiments, the reinforcing layer is gas impermeable. In various embodiments, the reinforcing layer844is not impermeable and can include a braided polymer material and/or a coiled polymer or metallic material and/or coatings & encapsulants.

In various embodiments, the return tube may include two, three, four, or more polymer layers. In various embodiments, the return tube may include two, three, four, or more total layers.

In the embodiment ofFIG.8, where the slotted portion of the slotted tube830is within the expansion chamber, the first polymer layer842and the reinforcing layer844extend from just within the insulated zone105to the distal end. In various embodiments, the first polymer layer842is bonded to the slotted tube830at first bond846near the proximal end of the expansion chamber106and at a second bond848near the tip108of the shaft104.

In various embodiments, the reinforcing layer844is bonded to the slotted tube830at first bond847near the proximal end of the expansion chamber106and/or at a second bond849near the tip108of the shaft104.

Additional bonds can be placed along any other suitable location of the shaft. The bonds can be formed from any suitable material or materials such as Vectran, UHMWPE,

PEEK, Polyimide, Metallic Wire. Vectran is a manufactured fiber, spun from a liquid-crystal polymer that displays increased tensile strength at cold temperatures, making it advantageous for use in cryoablation systems. In alternative embodiments, the bonds846,847,848and849may be formed from alternate techniques such as crimp or swage rings, polymer reflow joints, adhesive joints, solder joints or the like.

In various embodiments, the wrap materials of the bonds846,847,848and849, can also be wrapped along the entire length of the expansion chamber around the polymer layer, the reinforcing layer, or both. The wrap layer may have a higher pitch of wraps at the bond location and extend along the remainder of the expansion chamber at a lower pitch level. The wrap may extend from the proximal end to the distal end and then reverse direction and extend back in a proximal direction. The number of wrap layers may be one, two, three, four or more.

In various embodiments, the bonds846,847,848and849are configured to increase the burst strength of the layers of the return tube326.

In some embodiments, the burst strength of each of the first polymer layer842and the reinforcing layer844can be greater than or equal to 12.4 MPa, 13.1 MPa, 13.8 MPa, 14.5 MPa, 15.2 MPa, or 41.4 MPa. In some embodiments, the burst strength of each of the first polymer layer842and the reinforcing layer can be less than or equal to 41.4 MPa, 20.7 MPa, 19.3 MPa, 17.9 MPa, 16.5 MPa, or 15.2 MPa. In some embodiments, the burst strength can fall within a range of 12.4 MPa to 41.4 MPa, or 13.1 MPa to 27.6 MPa, or 13.8 MPa to 17.9 MPa, or 14.5 MPa to 16.5 MPa, or can be about 15.2 MPa.

In some embodiments, the burst strength of the bonded first polymer layer842and the reinforcing layer844together can be greater than or equal to 12.4 MPa, 13.1 MPa, 13.8 MPa, 14.5 MPa, 15.2 MPa 27.6 MPa, or 41.4 MPa. In some embodiments, the burst strength of the bonded first polymer layer842and the reinforcing layer844together can be less than or equal to 41.4 MPa, 20.7 MPa, 19.3 MPa, 17.9 MPa, 16.5 MPa, or 15.2 MPa. In some embodiments, the burst strength of the bonded first polymer layer842and the reinforcing layer844together can fall within a range of 12.4 MPa to 41.4 MPa, or 13.1 MPa to 27.6 MPa, or 13.8 MPa to 17.9 MPa, or 14.5 MPa to 16.5 MPa, or can be about 15.2 MPa.

In some embodiments, the burst strength of each of the bonds846,847,848and849can be greater than or equal to 1.4 MPa, 4.8 MPa, 8.3 MPa, 11.7 MPa, 15.2 MPa, 27.6 MPa, or 41.4 MPa. In some embodiments, the burst strength of each of the bonds can be less than or equal to 41.4 MPa, 34.8 MPa, 28.3 MPa, 21.7 MPa, or 15.2 MPa. In some embodiments, the burst strength of each of the bonds can fall within a range of 1.4 MPa to 41.4 MPa, or 4.8 MPa to 34.8 MPa, or 8.3 MPa to 28.3 MPa, or 11.7 MPa to 21.7 MPa, or can be about 15.2 MPa.

In some embodiments, the bonds846,847,848and849can have the same burst strength. Alternatively, some of the bonds can have a higher burst strength than others. For instance, proximal bonds846,847may have a lower burst strength than distal bonds848,849.

In various embodiments, the return tube326may be configured to be sufficiently flexible to form a curve having a desired radius of curvature. For instance, the return tube may be sufficiently flexible, such that the shaft may form a curve having the smallest radius of curvature of less than or equal to 30 mm, 20 mm, 10 mm, 5 mm, or 3 mm.

Slotted Tube Portion Can Extend the Entire Length of the Return Tube

FIG.8illustrates that the slotted tube830includes the slots only in the expansion chamber106, but in an alternative embodiment, the slotted tube830has slots along its entire length. In this alternative embodiment, the first polymer layer842and the reinforcing layer844will also extend along the entire length of the return tube326. The reinforcing wrap layer, such as a wrap of a Vectran material, may also extend along the entire return tube length. The presence of slots along the entire return tube length may be desirable to achieve the desired level of flexibility along the return tube.

Cryoablation Shaft Including a Slotted Tube Portion and a Gradient Braid (FIG.9)

Referring now toFIG.9, a schematic view of a portion of a cryoablation shaft is shown in accordance with various embodiments herein. In various embodiments, the shaft includes an insulated zone105and an expansion chamber106. In various embodiments, the insulated zone105of shaft104includes a supply tube324located within a return tube326. The return tube326ofFIG.9includes multiple layers.

The innermost layer of the return tube of326is a slotted tube830, which can be constructed using the options and details described herein. The slotted tube830is surrounded by a polymer layer956, which is concentrically surrounded by a reinforcing gradient braid layer940.

In various embodiments, gradient braid layer940includes zones of different density of braid, increasing in density toward the distal end of the device. A first braid zone958is present in the insulated zone and is the least dense. A second braid zone960overlaps the insulated zone105and the expansion chamber106and is more dense than the first braid zone958. The third braid zone962is the densest and is present in the expansion zone. The return tube may include one, two, three, or more braid layers.

In various embodiments, the polymer layer956is configured to contain the working fluid in the return tube and not allow the working fluid to escape radially through the slots in the slotted tube. The polymer layer may be constructed from the options and materials discussed herein with respect to the first polymer layer herein. In some embodiments, the expansion chamber106may include an additional braided layer between the slotted tube830and the polymer layer956(not shown in this view). The additional braided layer is configured to prevent friction between the polymer layer956and the slotted tube830.

Braid Materials, Braid Element Diameters, Braid Density Zones, Coils, and Burst Strength Examples

Braided tubes are used in a variety of medical applications. Braid reinforced tubing can improve functional properties such as strength, stiffness, burst pressure resistance, torque transmission, and kink resistance of a medical device. Such features enable can enable a cryoablation shaft to navigate tortuous portions of a patient's anatomy, such as the biliary ducts. Design considerations such as braid pattern, pick count (ppi), material, wire dimension, wire size/shape and durometer of plastics can have significant impact on device performance.

The braided portions of the shaft can be formed from any suitable material or materials such as metals (e.g., nitinol, stainless steel, tungsten, MP35N, or other such materials), polymers, (e.g., PET, Kevlar, Carbon fiber, Vectran, or other such materials), or the like. Braided materials are formed by weaving a metal or fiber filament in a braid pattern. In various embodiments, the cross section of the filament is circular, however other cross-sectional shapes are possible (e.g., flat, star, triangle). In some embodiments, the diameter of the filament can be greater than or equal to 0.01 mm, 0.1 mm, 0.2 mm, 0.3 mm, or 0.5 mm. In some embodiments, the diameter of the filament can be less than or equal to 2 mm, 1.6 mm, 1.2 mm, 0.8 mm, or 0.5 mm. In some embodiments, the diameter of the filament can fall within a range of 0.01 mm to 2.00 mm, or 0.1 mm to 1.6 mm, or 0.2 mm to 1.2 mm, or 0.3 mm to 0.8 mm, or can be about 0.5 mm.

In various embodiments, the density of the braided portions can be altered with more dense braids offering more radial strength and rigidity and less dense braids offering more flexibility. The shaft can include multiple braids having varying material properties. In various embodiments, the shaft may include a light braid (e.g., have relatively low braid density) between the return tube326and the polymer layer956. As described above, the light braid may offer limited structural support but can prevent undue friction between the slotted return tube326and the polymer layer956.

In various embodiments, the density of the braided materials can increase from the base of the shaft104to the tip108of the shaft. In the event that there is a device failure, such a configuration improves the likelihood of the shaft failing closer to the base. Such a failure mode is generally preferable compared to a failure closer to the tip108of the shaft in terms of patient safety outcomes.

In various embodiments, the first gradient braid zone958spans the insulated zone105of the shaft104(starting from where the shaft connects to the handle102and terminating at or before the expansion chamber106). In various embodiments, the gradient braid958portion can have a first burst strength. The first burst strength can be constant along the insulated zone of the shaft. Alternatively, the first burst strength of the gradient braid portion958can increase from the base of the shaft to the expansion chamber. In various embodiments, the gradient braid portion958can have a first braid density. The first braid density can be constant along the insulated zone of the shaft. Alternatively, the first braid density of the gradient braid portion958can increase from the base of the shaft to the expansion chamber.

In some embodiments, the minimum burst strength of the gradient braid portion958can be less than or equal to 20.7 MPa, 13.8 MPa, 6.9 MPa, 5.5 MPa, 4.1 MPa, 2.8 MPa, 1.4 MPa, or 0.7 MPa, or can be an amount falling within a range between any of the foregoing. In some embodiments, the maximum burst strength of the gradient braid portion958can be greater than or equal to 0.7 MPa, 2.0 MPa, 3.4 MPa, 4.8 MPa, 6.2 MPa, 6.9 MPa, 13.8 MPa, or 20.7 MPa or can be an amount falling within a range between any of the foregoing.

In various embodiments, the second braid portion960spans the expansion chamber106of the shaft104. In some embodiments, the second braid portion960may start at the beginning of the expansion chamber and terminate at or near the tip108of the shaft. Alternatively, the second braid portion960may start towards the distal end of the insulated zone105of the shaft (as depicted byFIG.9) and terminate at or near the tip108of the shaft. In some embodiments, the second braid portion960is a continuation of the first braid portion958. Alternatively, the second braid portion960may be made of elements that are physically separate from the elements of first braid zone958.

In various embodiments, the second braid portion960can have a second burst strength. The second burst strength can be constant along the length of the first braid layer. Alternatively, the second burst strength of the second braid portion960can increase from the along the length of the first braid layer (from the end of the insulated zone105to the tip108). In various embodiments, the second braid portion960can have a second braid density. The second braid density can be constant along the length of the second braid portion. Alternatively, the second braid density of the second braid portion960can increase along the length of the second braid portion.

In some embodiments, the burst strength of the second braid portion960can be greater than or equal to 10.3 MPa, 12.9 MPa, 15.5 MPa, 18.1 MPa, or 20.7 MPa, or 41.4 MPa. In some embodiments, the burst strength of the second braid portion960can be less than or equal to 34.5 MPa, 31.0 MPa, 27.6 MPa, 24.1 MPa, or 20.7 MPa. In some embodiments, the burst strength of the second braid portion960can fall within a range of 10.3 MPa to 34.5 MPa, or 12.4 MPa to 31.0 MPa, or 15.5 MPa to 27.6 MPa, or 17.9 MPa to 34.5 MPa, or can be about 20.7 MPa.

In various embodiments, the third braid zone962spans the expansion chamber106of the shaft104. In some embodiments, the third braid zone962may start at the beginning of the expansion chamber and terminate at or near the tip108of the shaft.

In various embodiments, the third braid zone962can have a third burst strength. The third burst strength can be constant along the length of the third braid zone. Alternatively, the burst strength of the third braid zone962can increase from the along the length of the third braid zone. In various embodiments, the third braid zone962can have a third braid density. The braid density can be constant along the length of the third braid zone. Alternatively, the braid density of the third braid zone962can increase along the length of the first braid layer.

In some embodiments, the burst strength of the third braid zone962can be greater than or equal to 10.3 MPa, 12.9 MPa, 15.5 MPa, 18.1 MPa, or 20.7 MPa. In some embodiments, the burst strength of the third braid zone962can be less than or equal to 34.5 MPa, 31.0 MPa, 27.6 MPa, 24.1 MPa, or 20.7 MPa. In some embodiments, the burst strength of the third braid zone962can fall within a range of 10.3 MPa to 34.5 MPa, or 12.4 MPa to 31.0 MPa, or 15.5 MPa to 27.6 MPa, or 17.9 MPa to 24.1 MPa, or can be about 20.7 MPa.

In alternative embodiments, any, or all of the gradient braid zones958,960,962can be formed from coils. A coil, as defined herein is a filament of material wound around the shaft. Like in braided materials, as detailed above, the filament can be selected to have suitable material(s) and cross-sectional shapes including round, rectangular, or other shapes. The zones can include coils of different density, radial strength, rigidity, and flexibility. The coils can be single layered or multi layered. In some embodiments, the multi-layer coils can have alternate wind directions (e.g., first layer is wound clockwise, and the second layer is wound counterclockwise). In various embodiments, the pitch of the coil can be varied to optimize the properties of the shaft, such as flexibility, burst strength, or the like. For instance, tighter pitches of coil can increase the burst strength of the shaft while looser pitches of coil can increase the flexibility of the shaft. In various embodiments, the pitch of the coil materials can increase from the base of the shaft104to the tip108of the shaft.

Transitions Between Braid Zones

In some embodiments, the transitions between the first, second and third braid portions are transitions in density of the same physical braid elements, so that one braid zone is a continuation of a neighboring braid zone. Alternatively, one braid portion may be made of elements that are physically separate from the elements of a neighboring braid zone.

Referring now toFIG.10, a schematic view of a portion of a cryoablation shaft is shown in accordance with various embodiments herein. In various embodiments, the expansion chamber106of shaft104includes a supply tube324, located concentrically within a composite return tube1064In various embodiments, the return tube can be a composite shaft. In various embodiments, the composite return tube1064is formed from one or more discrete layers. One possible return tube layer is a braid layer1066shown inFIG.10.

In various embodiments, composite return tube1064can be formed from one or more polymer and/or braided layers as described in detail herein. After forming the discrete layers, the composite shaft may be heated to such a temperature that the discrete layers bond to each other forming a single composite layer. In some embodiments, some of the discrete layers may contribute to the radial strength of the expansion chamber and other discrete layers may contribute to the gas containment capability of the expansion chamber. In such embodiments, radial strength and gas containment may be achieved from a single composite layer. Such a configuration can enhance the tunability of the expansion chamber material properties while decreasing the diameter of the expansion chamber.

In some embodiments, an additional braid layer1066may be disposed over the remainder of the composite return tube1064. The additional braid layer is selected to have braid properties that enhance the radial strength of the expansion chamber106.

Distal Fitting Examples (FIG.10)

In various embodiments, the working fluid may be contained at the tip108of the shaft using a plug1068and one or more joints1070. In various embodiments, the joints1070and/or the plug1068may be of a material or materials that are compatible to bond with the composite return tube1064and/or the braid layer1066to enhance the seal of the shaft104. In various embodiments, the joints1070and/or the plug1068may be of a material or materials that are sufficiently strong as to enhance the burst strength of the expansion chamber.

In various embodiments, plug1068includes ridges1072. The ridges1072improve the mechanical strength of the bonded joints1070by providing additional structural support to the bonds to resist the pressure within the expansion chamber.

Markers for Imaging Systems

The joint334(FIG.3) and the distal tip108(FIGS.8and10) are configured to appear on imaging systems. The joint334can include a marker band of radiopaque materials, such as tungsten or platinum iridium or other appropriate materials. The material and dimensions of the distal tip108can be configured to appear on imaging systems. Examples of materials for the distal tip108include stainless steel and nitinol. The markers at either end of the active zone of the device assist the physician with visually identifying the location of the active zone of cryoablation with respect to the patient's anatomy and the target zone for cryoablation. Examples of imaging systems include ultrasound, fluoroscopy, cone beam CT, and MRI systems.

Introduction Options

In some embodiments, the catheter system is delivered using a sheath introduction system. An example of a sheath introduction system is a steerable sheath. Alternatively, the catheter system can be steerable. In another embodiment, the catheter system includes a monorail lumen along a portion of the catheter to facilitate introduction.

Guidewire Delivery Options

In various embodiments, it is desirable for the cryoablation system to include a guidewire. A guidewire as defined herein is a flexible, medical wire inserted into the body to guide a larger instrument, such as a catheter, to a target location. Implementing a guidewire with a cryoablation system can enable the flexible shaft to access portions of the patient's anatomy (e.g., the biliary system) with increased accuracy and decreased damage. A guidewire may run through a guidewire lumen that extends either part way or all the way though the length of the shaft. A guidewire lumen, as defined herein, is a channel or hollow space that facilitates the insertion of a guidewire. A guidewire lumen can be added to the cryoablation system in either a monorail or an over-the-wire configuration. In alternate embodiments, the cryoablation system may be introduced to a patient using a sheath rather than a guidewire.

In a monorail configuration, the guidewire and guidewire lumen only run through a portion of the length of the shaft. For the case of the cryoablation system100, the guidewire and guidewire lumen may run only though a distal portion of the shaft104(e.g., only through a portion adjacent to or slightly space away from the tip108) in a monorail configuration. In some embodiments, the distal tip108can include a lumen for the guidewire to pass through. Monorail configurations do not require running a guidewire lumen all the way through the shaft resulting in smaller possible shaft diameters and reduced shaft complexity compared to over-the-wire configurations, in which the guidewire lumen runs the entire length of the shaft. In various embodiments, when using a monorail guidewire, most of the cross section of shaft104is not altered from the shaft embodiment depicted byFIG.3.

In an over-the-wire configuration, an additional guidewire lumen is present and extends along the length of the shaft. In various embodiments, the lumen extends along the entire length of the shaft. Over-the-wire catheter configurations are particularly useful in positioning medical devices in difficult to navigate portions of the anatomy (e.g., the biliary system). Compared to monorail lumen configurations, over-the-wire catheter configurations decrease the possibility of uneven strain being placed on portions of the catheter construction during the bending that occurs during the shaft navigation and/or positioning processes, thereby decreasing the chances of structural damage or failure in the catheter device. However, the requirement of running an additional lumen and guidewire through the shaft can increase both the size of the outer diameter and complexity of the cryoablation shaft.

In a particular example, to illustrate the size difference between a monorail shaft and an over-the-wire shaft, the outer diameter of a monorail shaft can be about 6-7 French (2.00 to 2.33 mm) and the outer diameter of an over-the-wire shaft can be about 8-9 French (2.67 to 3.00 mm). These ranges are for exemplary purposes only, but it should be noted that over-the-wire shafts generally require an equal or larger diameter than their monorail counterparts. To implement an over-the wire configuration, shaft104of the cryoablation system needs to be altered to accommodate an additional guidewire lumen and guidewire. This may be done in any suitable manner, but three possible examples are illustrated inFIGS.11-13.

In each of the examples described below with respect toFIGS.11-13, the outer profile of each of the following elements of the cryoablation system can be circular: supply tube, return tube, guidewire lumen, and insulation shaft. In other words, these elements have a circular outer profile in a radial cross-sectional view. In alternate embodiments, the outer profile of the supply tube, return tube, guidewire lumen, and/or insulation shaft can be any other suitable shape, such as oblong, rectangular, or any other shape that facilitates positioning within a body lumen.

In each of the examples described below with respect toFIGS.11-13, the inner space defined by the guidewire lumen is circular and does not house any other components other than the guidewire during the introduction process. The guidewire can be removed from the guidewire lumen after introduction of the catheter to a target body location. Alternatively, depending on the procedure to be performed, the guidewire may be left inside the guidewire lumen during the cryoablation procedure. In each of the examples described below with respect toFIGS.11-13, the supply tube is located within the return tube, either concentrically (FIGS.11and13) or off-center (FIG.12).

In each of the examples described below with respect toFIGS.11-13, the inner space of the insulation shaft is occupied by the other elements and, as a result, its inner space used by the vacuum insulation chamber is not circular and varies in its shape between the examples. The inner space defined by the return tube and supply tube also varies between the different examples because the inner spaces defined by these elements are sometimes occupied by one or more of the other elements.

Isolated Exhaust Configuration (FIG.11)

Referring now toFIG.11, a cross sectional view of a cryoablation shaft is shown in accordance with various embodiments herein. In various embodiments, the shaft104may include a supply tube324, return tube326, insulation shaft328, and filament330. The shaft also includes a guidewire lumen1132extending throughout the length of the shaft104for the insertion of a guidewire. In the example ofFIG.11, the supply tube324is concentrically located within the return tube326and the guidewire lumen1132is tangent to the return tube326. The guidewire lumen1132and return tube326are each tangentially connected to the insulation shaft328by a supporting filament330. The supply tube324, return tube326, guidewire lumen1132, and filament330are all enclosed by the insulation shaft328. In alternate embodiments, the shaft may not include filament330.

In various embodiments, after exiting the handle102, the high-pressure flow of the working fluid travels distally down the shaft104through supply tube324. After cooling and expansion in the expansion chamber106, the working fluid travels proximally back through the shaft104in the annular space between the supply tube324and return tube326.

In the example ofFIG.11, the supply tube has a substantially circular cross section and does not house any other elements. In the example ofFIG.11, the supply tube324is housed concentrically within the return tube326.

In the example ofFIG.11, the return tube326and guidewire lumen1132are positioned to be adjacent, side-by-side to each other. The outer profile of the return tube326combined with the guidewire lumen1132is similar to the outer profile of a Figure-8shape.

The vacuum chamber space is defined between the inner wall of the insulation shaft328and the outer walls of the return tube326and guidewire lumen1132. The vacuum chamber space is a circle without the inner Figure-8space occupied by the guidewire lumen1132and return tube326.

The supporting filament330is wound around the outer surfaces of the supply tube324and the guidewire lumen1132, holding those two components in a fixed relationship to each other. In alternate embodiments, the shaft may not include filament330.

Common Exhaust Configuration (FIG.12)

Referring now toFIG.12, a cross sectional view of a cryoablation shaft is shown in accordance with various embodiments herein. In various embodiments, the shaft may include a supply tube324, return tube326, insulation shaft328, and a supporting filament330. The shaft also includes a guidewire lumen1132extending throughout the length of the shaft104for the insertion of a guidewire. In the example ofFIG.12, the return tube326is concentrically located within the insulation shaft328and the filament330is disposed between return tube326and the insulation shaft328. The supply tube324and the guidewire lumen1132are both disposed within the return tube326. In alternate embodiments, the shaft may not include filament330.

In various embodiments, after exiting the handle, the high-pressure flow of the working fluid travels distally down the shaft104through supply tube. After cooling and expansion in the expansion chamber106, the working fluid travels proximally back through the shaft104in the space between the supply tube324and return tube326. As can be seen in the example ofFIG.12, the guidewire lumen1132is also positioned in the space between the supply tube324and return tube326. As such, the return passage for the working fluid is defined by the cross-sectional area of the return tube326minus the cross-sectional area of the guidewire lumen1132and the cross-sectional area of the supply tube324.

In the example ofFIG.12, the supply tube324and guidewire lumen1132both have a circular cross-section and do not house any other components. The supply tube324and guidewire lumen1132are located side-by-side. In some embodiments, the supply tube324and guidewire lumen1132are adjacent to each other.

In the example ofFIG.12, the supply tube324and guidewire lumen1132are both positioned within the return tube326. The return tube326defines the space for working gas to return, and that space has a circular outer profile, with an inner profile defined around the circular profiles of the supply tube324and guidewire lumen1132.

The supply tube324and guidewire lumen1132are positioned to be side-by-side with each other. There may or may not be a gap between the supply tube324and the guidewire lumen1132. In various embodiments, the supply tube324and guidewire lumen1132are adjacent to each other, and the outer profile of the supply tube324combined with the guidewire lumen1132is similar to the outer profile of a Figure-8shape.

The working gas return space within the return tube326is defined between the inner wall of the return tube326and the outer walls of the supply tube324and guidewire lumen1132. The working gas return space is defined around the inner space, which may be occupied by the guidewire lumen1132and supply tube324, with a circular outer profile.

The return tube326is located concentrically within the insulation shaft328. The vacuum chamber space is annular, between the insulation shaft inner wall and the return tube outer wall.

Central Guidewire Lumen Configuration (FIG.13)

Referring now toFIG.13, a cross sectional view of a cryoablation shaft is shown in accordance with various embodiments herein. In various embodiments, the shaft104may include a guidewire lumen1132concentrically located within a supply tube324, which is concentrically located within a return tube326, which is concentrically located within an insulation shaft328, with the filament330disposed between the return tube and the insulation shaft. In alternate embodiments, the shaft may not include filament330.

In various embodiments, after exiting the handle102, the high-pressure flow of the working fluid travels distally down the shaft104through supply tube324. As the guidewire lumen1132is located concentrically within the supply tube324, the working gas fluid supply travels down the annular space between the return tube326and the guidewire lumen1132. After cooling and expansion in the expansion chamber106, the working fluid travels proximally back through the shaft104in the annular space between the supply tube324and return tube326.

In the example ofFIG.13, the supply tube324is located concentrically within the return tube326. The return tube326is located concentrically within the insulation shaft328. The vacuum chamber space is annular, between the insulation shaft inner wall and the return tube outer wall.

Referring now toFIG.14, a cross sectional view of a guidewire lumen is shown in accordance with various embodiments herein. In various embodiments, when inserted into a cryoablation shaft, the guidewire lumen1132is configured to extend through the length of the cryoablation shaft104. In various embodiments, the guidewire lumen1132is configured for insertion of a guidewire. In various embodiments, the guidewire lumen1132can include a metallic tube1432and a polymer sleeve1442configured to surround at least a portion of the metallic tube.

In various embodiments, the guidewire lumen1132can include a metallic tube1432. The metallic tube can be formed from any suitable material or material such as nitinol, stainless steel, or the like. In various embodiments, at least a portion of the metallic tube1432can include one or more slots1434. Slots1434can be formed in the tube material by any suitable means, such as laser cutting or the like. The slots1434can be laser cut into the metallic tube1432using any suitable pattern to optimize the strength and flexibility of the metallic tube1432. Many different configurations and patterns of slots1434are available and one can be selected with the flexibility desirable in this application.

In some embodiments, the metallic tube1432can contain slots1434along its entire length. In some embodiments, the metallic tube1432can define slots1434along its length between portions of metallic tube1432that do not contain slots. For instance, the metallic tube1432may be devoid of slots1434at a distal end portion1443at its distal end. In various embodiments, the metallic tube1432may be devoid of slots1434at a proximal end portion1445located at its proximal end. In various embodiments, the metallic tube1432may be devoid of slots1434at both a distal end portion1443and at a proximal end portion1445.

The metallic tube1432may be configured to be sufficiently flexible to form a curve having a desired radius of curvature. For instance, the metallic tube1432may be sufficiently flexible, such that the guidewire lumen1132may form a curve having the smallest radius of curvature of less than or equal to 30 mm, 20 mm, 10 mm, 5 mm, or 3 mm. The flexibility of the metallic tube1432enables the overall cryoablation shaft to have a flexibility that allows steering to treatment sites.

In various embodiments, the guidewire lumen1132can include a polymer sleeve1442. The polymer sleeve1442can be formed form any suitable material or material such as polyether block amide, polyethylene terephthalate, or the like. In various embodiments, the polymer sleeve1442is configured to cover at least a portion of the metallic tube1432. In the example ofFIG.14, at least a portion of the metallic tube1432includes slots1434and the polymer sleeve1442is configured to form a seal around the slotted portion of the metallic tube1432. In such an embodiment, the polymer sleeve1442is configured to provide a gas-tight seal around the metallic tube1432, preventing gases from entering the metallic tube through the slots while maintaining the flexibility of the metallic tube.

In various embodiments, the polymer sleeve1442covers the entire length of the metallic tube1432. Alternatively, such as shown inFIG.14, the polymer sleeve1442does not cover the metallic tube1432at a distal end portion1443. In various embodiments, the polymer sleeve1442does not cover the metallic tube1432at a proximal end portion1445. In various embodiments, the polymer sleeve1442does not cover the metallic tube1432at both a distal end portion1443and at a proximal end portion1445. In various embodiments, the polymer sleeve1442extends along the length of the metallic tube1432between the distal end portion1443and the proximal end portion1445. Exposure of the metallic tube1432at either the distal end, the proximal end, or both ends, provides a metallic surface to bond other components to create a gas-tight seal.

In various embodiments, the guidewire lumen1132can include a first compressive wrap1440configured to seal the polymer sleeve1442to the metallic tube1432at a distal end of the polymer sleeve1442. In various embodiments, the guidewire lumen1132can include a second compressive wrap1441configured to seal the polymer sleeve1442to the metallic tube1432at a proximal end of the polymer sleeve1442. In the example ofFIG.14, the polymer sleeve1442is sealed to the metallic tube1432such that distal end portion1443and proximal end portion1445of the metallic tube1432are not covered by the polymer sleeve or the compressive wrap.

In various embodiments, the first compressive wrap1440and the second compressive wrap1441are configured to apply a consistent compressive force around the polymer sleeve1442, sealing the polymer sleeve to the metallic tube1432.

In various embodiments, the first compressive wrap1440and the second compressive wrap1441include a filament wrapped around the polymer sleeve1442and the metallic tube1432of the guidewire lumen1132. In various embodiments, the filament is configured to be wrapped around the polymer sleeve1442and the metallic tube1432of the guidewire lumen1132with a wrap threshold tension. For instance, the filament should be able to withstand hanging an object of predetermined mass without breaking. The predetermined mass can be 0.5 kg, 1 kg, 1.5 kg, or greater. In some embodiments, the filament is hung with the predetermined mass during the wrapping process to apply sufficient wrap tension.

In various embodiments, the compressive wrap can have a tensile strength. In some embodiments, the tensile strength can be greater than or equal to 1.0 gigapascal (GPa), 1.8 GPa, 2.7 GPa, or 3.5 GPa. In some embodiments, the tensile strength can be less than or equal to 6.0 GPa, 5.2 GPa, 4.3 GPa, or 3.5 GPa. In some embodiments, the tensile strength can fall within a range of 1.0 GPa to 6.0 GPa, or 1.8 GPa to 5.2 GPa, or 2.7 GPa to 4.3 GPa, or can be about 3.5 GPa.

In various embodiments, the compressive wrap can be a monofilament, a multi-filament material, a unifilar material, a multi-filar material, a metal, a plastic, or a composite material. In various embodiments, the compressive wrap is configured to allow termination of the wrap while maintaining tension. In various embodiments, the compressive wraps1440,1441can be formed from monofilament sutures and/or multi-strand sutures. In various embodiments, the compressive wrap can be formed from material or materials including, but not limited to fibrous materials, such as stainless steel, tungsten, platinum-iridium alloys (Pt-Ir), fiber base materials (e.g., Technora, Dektran), or the like.

In various embodiments, the compressive wrap can have a closed pitch (each wind of the filament is touching an adjacent wind). Alternatively, the compressive wrap may have pitch that is greater than or equal to 0.5 mm, 1.0 mm, 1.5 mm, or 2.0 mm, or can be an amount falling within a range between any of the foregoing.

In some embodiments where the compressive wrap is a filament, the diameter of the filament can vary depending on the material of the filament and its ability to hold tension during manufacturing. In some embodiments, the diameter of the filament can be greater than or equal to 0.002 mm, 0.004 mm, or 0.005 mm. In some embodiments, the diameter of the filament can be less than or equal to 0.007 mm, 0.006 mm, or 0.005 mm. In some embodiments, the diameter of the filament can fall within a range of 0.002 mm to 0.007 mm, or 0.004 mm to 0.006 mm, or can be about 0.005 mm.

In various embodiments, the first compressive wrap1440and the second compressive wrap1441can include an adhesive configured to encapsulate the compressive wrap. The adhesive is configured to maintain the wrap threshold tension and can enhance the material properties of the compressive wrap such as biocompatibility, radiopacity, or the like. Alternatively, the adhesive can be applied to discrete portions of compressive wraps1440,1441, such as at the ends. Examples of suitable adhesive or adhesives that can be used to encapsulate the compressive wrap include cyanoacrylate adhesive and LOCTITE® adhesive available from Henkel Adhesive Technologies, which has a location in Bridgewater, New Jersey, USA, or the like.

In various embodiments, the filament of the first compressive wrap1440can be formed from a material or materials configured to transmit electrical signals (e.g., conductive wire). In such an embodiment, one or more sensors can be placed at the distal end of the shaft104and the sensor data can be conveyed from the sensor(s) to the console via the electrically conductive filament. In one example, an electromagnetic position sensor can be included at the distal tip1436of the shaft104and is configured to aid the physician in positioning the shaft within the patient's anatomy. In such a configuration, the first compressive wrap1440can be configured to carry a low voltage that would be translated into a position from the distal tip1436to the console. In another example, the first compressive wrap1440could incorporate fiber optic cable(s) configured to provide information regarding the shape of the target anatomy. Any other suitable sensor or combination of sensors can be included at the distal end of the shaft including but not limited to temperature sensors, pressure sensors, strain sensors, or the like.

In various embodiments, the filament of the first compressive wrap1440can be formed from one or more high resistance wires. The high resistance wires can be configured to enable electrical heating of the expansion chamber106of the shaft104. The electrical heating can facilitate more rapid thawing of ice balls, which can decrease cryoablation procedure time and reduce the likelihood of tract seeding, where harmful tissue adheres to the shaft be distributed to other portions of a patient's anatomy.

In various embodiments, the guidewire lumen1132is configured to seal to a distal tip1436of a cryoablation shaft104. In various embodiments, the distal tip1436is configured to seal a distal end of the expansion chamber106of the cryoablation shaft104. The distal tip1436can be formed form any suitable material or material such as nitinol, stainless steel, or the like.

In various embodiments, distal end portion1443of the metallic tube1432is joined to a proximal end of the distal tip1436using a metal-to-metal joining process such as welding, soldering, brazing, or the like. In the example ofFIG.14, the distal end portion1443of the metallic tube is devoid of slots1434and is not covered by the polymer sleeve1442. Such an embodiment allows for the distal end portion1443of the metallic tube1432to form a robust metal-to-metal joint1438with the distal tip1436.

In various embodiments, the distal tip1436defines a central channel1437. The central channel1437is configured to receive a guidewire. In various embodiments, a proximal end of the central channel1437of the distal tip1436can be joined to the distal end portion1443of the metallic tube1432to form the metal-to-metal joint1438.

In various embodiments, the proximal end portion1445of the metallic tube1432can be joined to the cryoablation probe at any suitable location such as at a proximal end of the shaft104or at the handle102.

In various embodiments, the guidewire lumen1132is configured to be sufficiently robust as to not be compressed by the high-pressure gas flows in the cryoablation shaft104. In various embodiments, the guidewire lumen1132is configured to withstand compressive pressures during normal operation of the cryoablation system of about 1 MPa or 150 psi. In various embodiments, the burst strength of the guidewire lumen1132can be greater than or equal to 0.4 MPa, 0.6 MPa, 0.7 MPa, 0.8 MPa, or 1.0 MPa.

In various embodiments, the guidewire lumen1132is configured to be sufficiently robust to withstand larger compressive pressures of about 15 MPa or 2200 psi that might occur during a fault condition of the cryoablation system. In some embodiments, the burst strength of the guidewire lumen1132can be greater than or equal to 9.0 MPa, 10.5 MPa, 12.0 MPa, 13.5 MPa, or 15.0 MPa. In some embodiments, the burst strength can be less than or equal to 21.0 MPa, 19.5 MPa, 18.0 MPa, 16.5 MPa, or 15.0 MPa. In some embodiments, the burst strength can fall within a range of 9.0 MPa to 21.0 MPa, or 10.5 MPa to 19.5 MPa, or 12.0 MPa to 18.0 MPa, or 13.5 MPa to 16.5 MPa, or can be about 15.0 MPa.

Central Guidewire Lumen Embodiment with Distal Tip (FIG.15)

Referring now toFIG.15, a schematic view of a portion of the guidewire lumen and distal tip ofFIG.14is shown within a cryoablation shaft in accordance with various embodiments herein. In the example ofFIG.15, the shaft has a central guidewire lumen configuration such as shown and described byFIG.13. Alternatively, it is possible for the guidewire construction options described with respect toFIG.14to be used in an isolated exhaust embodiment ofFIG.11or in a common exhaust embodiment ofFIG.12.

Referring again toFIG.15, in various embodiments, the shaft104may include a guidewire lumen1132concentrically located within a supply tube324, which is concentrically located within a return tube326, and at least a portion of the return tube is concentrically located within an insulation shaft328.

In various embodiments, after exiting the handle102, the high-pressure flow of the working fluid travels down the supply tube324. The high-pressure stream of the working fluid may undergo expansion at or downstream of the Joule-Thomson orifice332and returns down the shaft in the annular space between the supply tube324and the return tube326.

In various embodiments, after being bonded to the distal tip1436, the guidewire lumen1132is configured to be inserted into the distal end of the shaft104. In various embodiments, an outer perimeter1554of the distal tip1436is configured to be joined to the inner surface of the distal end of the return tube326. In various embodiments, the inner surface of the return tube326is metal. Depending on the material of the innermost layer of the return tube, the distal tip1436can be joined to the return tube326by any suitable means such as metal-to-metal joining processes, adhesives, compressive elements, or the like.

In various embodiments, the outer diameter of the distal tip1436is configured to be substantially equal to the inner diameter of the return tube326. In such an embodiment, bonding the distal tip1436to the inner surface of the return tube326is configured to center the guidewire lumen1132within the shaft104.

In various embodiments, an exterior surface of the distal tip1436includes ridges, barbs, ramps, shoulders, or more than one of these structures which improve the mechanical strength of the bond between the distal tip and the return tube326and resist the pressure within the expansion chamber. Examples of such exterior surface structures for distal tip1436and structures and techniques for securing the distal tip1436to the return tube326are shown and described in U.S. Nonprovisional patent application Ser. No. ______, titled “Distal Tip Structure for Cryoablation Probe,” having attorney docket number 115.0438US01, filed on the even date herewith and incorporated herein by reference in its entirety.

The concepts described herein can be applied in the context of and used in connection with cryoablation systems and components described in the following four U.S. nonprovisional patent applications, which are filed on the even date herewith, which are incorporated by reference herein in their entireties: U.S. Nonprovisional patent application Ser. No.______, titled “Cryoablation Catheter Shaft Construction,” having attorney docket number 115.0421USU1; U.S. Nonprovisional patent application Ser. No., ______, titled “Safety Devices for Cryoablation Probe,” having attorney docket number 115.0422USU1; U.S. Nonprovisional patent application Ser. No.______, titled “Multiple Gas Circuit Connector and Method for Cryoablation System,” having attorney docket number 115.0423USU1; and U.S. Nonprovisional patent application Ser. No.______, titled “Distal Tip Structure for Cryoablation Probe,” having attorney docket number 115.0438US01.

As used herein, the recitation of numerical ranges by endpoints shall include all numbers subsumed within that range (e.g., 2 to 8 includes 2.1, 2.8, 5.3, 7, etc.).

The headings used herein are provided for consistency with suggestions under 37 CFR 1.77 or otherwise to provide organizational cues. These headings shall not be viewed to limit or characterize the invention(s) set out in any claims that may issue from this disclosure. As an example, although the headings refer to a “Field,” such claims should not be limited by the language chosen under this heading to describe the so-called technical field. Further, a description of a technology in the “Background” is not an admission that technology is prior art to any invention(s) in this disclosure. Neither is the “Summary” to be considered as a characterization of the invention(s) set forth in issued claims.