Cryoprobe

Abstract

A cryosurgical device, such as a cryosurgical probe (cryoprobe), is disclosed. Some exemplary embodiments may include an elongate shaft at least partially housing or defining a fluid inlet conduit and a fluid outlet conduit, the elongate shaft including a distal ablation portion terminating at a closed distal end, a housing at least partially surrounding at least a portion of the proximal end of the elongate shaft and receiving or defining at least a portion of the fluid inlet conduit and a portion of the fluid outlet conduit, and / or a flow restricting element in fluid communication with the fluid outlet conduit, the flow restricting element regulating fluid flow through at least a portion of the fluid outlet conduit.

Description

[Technical Field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims the benefit of U.S. Provisional Application No. 62 / 731,310, filed September 14, 2018, which is incorporated by reference.

[0002] The present disclosure is directed to cryoprobes, and more particularly to cryoprobes having a malleable shaft interconnecting an ablation tip and a handle control. Summary of the Invention [Problem to be solved by the invention]

[0003] The present disclosure contemplates that the temperature of a cryoprobe's ablation tip may be related to the boiling point (e.g., evaporation temperature) of the cryogen, which in turn may be related to the cryogen pressure at the ablation tip. The present disclosure contemplates that, for example, the cryogen pressure at the ablation tip may vary substantially, thereby affecting the ablation tip temperature within the cryoprobe and causing variations in the backpressure in the cryogen exhaust stream within the cryoprobe. The present disclosure provides methods and apparatus for improving regulation of the cryogen exhaust stream backpressure. Furthermore, the present disclosure contemplates that the cryogen pressure at the ablation tip may be affected by the characteristics of the flow path leading to the ablation tip. The present disclosure provides methods and apparatus for improving the delivery of cryogen to the ablation tip to achieve a desired temperature. In this manner, the present disclosure provides an improvement over the prior art for regulating the temperature at the ablation tip of a cryoprobe.

[0004] The present disclosure recognizes that while a cryoprobe may utilize cryogenic temperatures to achieve a desired effect at a desired location, exposure of other locations to cryogenic temperatures may result in undesirable effects. For example, the present disclosure recognizes that it may be desirable to cryogenically cool the ablation tip of a cryoprobe while maintaining a temperature above the tissue ablation temperature of the shaft on which the tip is disposed. The present disclosure provides methods and apparatus that improve the ability of a cryoprobe to cool the ablation tip to a desired temperature while simultaneously maintaining other exterior portions of the cryoprobe at a higher temperature. In this manner, the present disclosure provides an improvement over the prior art for cryoprobes.

[0005] The present disclosure contemplates that the rate of heat transfer and / or extent of ablation may depend on the manner in which the cryoprobe engages the target tissue. For example, the present disclosure contemplates that the configuration of the cryoprobe may affect the desired degree of access, engagement, and difficulty of ablation of a particular tissue. The present disclosure provides methods and devices that include cryoprobe configurations adapted to achieve desired tissue ablation, such as cryoanalgesia of intercostal nerves. In this manner, the present disclosure provides an improvement over the prior art for cryoprobes, which may be used, for example, for cryoanalgesia. [Means for solving the problem]

[0006] A first aspect of the present disclosure provides a cryogenic probe comprising: an elongate shaft at least partially housing or defining a fluid inlet tube and a fluid outlet tube, the elongate shaft including a distal ablation portion terminating at a closed distal end; a housing at least partially surrounding at least a portion of the proximal end of the elongate shaft and receiving or defining at least a portion of the fluid inlet tube and a portion of the fluid outlet tube; and / or a flow restricting element in fluid communication with the fluid outlet tube, the flow restricting element regulating fluid flow through at least a portion of the fluid outlet tube.

[0007] In one embodiment, the flow restricting element may include a constriction fluidly interposed between the fluid drain and the drain line. The cross-sectional fluid flow area of the constriction may be less than about 70% of the cross-sectional fluid flow area of the drain line. The cross-sectional fluid flow area of the constriction may be less than about 50% of the cross-sectional fluid flow area of the drain line. The cross-sectional fluid flow area of the constriction may be less than about 30% of the cross-sectional fluid flow area of the drain line. The cross-sectional fluid flow area of the constriction may be less than about 15% of the cross-sectional fluid flow area of the drain line. The cross-sectional fluid flow area of the constriction may be less than about 10% of the cross-sectional fluid flow area of the drain line.

[0008] In one embodiment, the flow restricting element may include a pressure valve in fluid communication with the fluid inlet conduit and the fluid outlet conduit, the pressure valve regulating fluid flow through at least a portion of the fluid outlet conduit. The pressure valve may include a valve disc configured to engage a valve seat and form a seal between the pressure valve and the valve seat. The valve disc may be biased into engagement with the valve seat. The valve disc may be biased into engagement with the valve seat by a spring, at least a portion of which may be located within the distal ablation portion.

[0009] In one embodiment, the distal ablation portion may include a spherical outer surface. The spherical outer surface may include a hemispherical portion. The distal ablation portion may include a narrowed portion to vary the cross-section of the distal ablation portion. At least a portion of the fluid inlet tube may extend into the distal ablation portion. At least a portion of the fluid inlet tube that extends into the distal ablation portion may include a fluid flow constriction before reaching a nozzle in the distal ablation portion. A proximal aspect of the distal ablation portion may be fluid-sealed to a distal aspect of the elongate shaft using at least one of an adhesive and a weld.

[0010] In one embodiment, the cryogenic probe may include a flexible insulating tube surrounding the elongated shaft along at least a portion of the longitudinal length of the elongated shaft. The flexible insulating tube may surround the elongated shaft along a majority of the longitudinal length of the elongated shaft. The flexible insulating tube may include a spacer interposed between an outer cover of the flexible insulating tube and the exterior of the elongated shaft. The spacer may include a foam, a helix, and / or more polymer helixes. The polymer helixes may be offset longitudinally along the flexible insulating tube and / or each may have a common axial dimension. The spacer may terminate before reaching at least one of the proximal and distal ends of the flexible insulating tube. The flexible insulating tube may be narrowed to have an outer major dimension smaller than the outer diameter of the helix at at least one of the proximal and distal ends of the flexible insulating tube.

[0011] In one embodiment, the elongate shaft may bend more than 180 degrees without breaking. The interior of the elongate shaft and the exterior of the fluid inlet line may define a fluid outlet line. The interior of the elongate shaft and the exterior of the fluid outlet line may define a fluid inlet line.

[0012] In one embodiment, the spherical outer surface may extend longitudinally more than half the longitudinal length of the exposed outer surface of the distal ablation portion. The spherical outer surface may extend longitudinally less than half the longitudinal length of the exposed outer surface of the distal ablation portion.

[0013] In one embodiment, the distal ablation portion may be configured to withstand pressure during a heating operation that includes blocking fluid flow through the fluid outlet tube. The housing may include an internal cavity that accommodates an adapter operable to change the coaxial orientation of the fluid inlet tube and the fluid outlet tube to a parallel orientation.

[0014] A second aspect of the present disclosure provides a cryogenic probe comprising: an elongated tube that at least partially houses or defines a fluid inlet tube and a fluid outlet tube, the elongated tube including a distal ablation portion that terminates at a closed distal end, the elongated tube including at least one stagnant fluid pocket interposed between an exterior of the conduit and at least one of the fluid inlet tube and the fluid outlet tube; and / or a housing that at least partially surrounds at least a portion of the proximal end of the elongated tube and receives or defines at least a portion of the fluid inlet tube and a portion of the fluid outlet tube.

[0015] In one embodiment, the stagnant fluid pocket may be at least partially defined by a spacer helix. The spacer helix may include a plurality of spacer helixes. The plurality of spacer helixes may be longitudinally offset from one another along the length of the conduit. The spacer helix may include an insulating material.

[0016] In one embodiment, the at least one stagnant fluid pocket may be at least partially defined by an insert that also forms a passage for at least one of a fluid inlet tube and a fluid outlet tube. The insert may have a triangular cross-section and / or may include separate passages for the fluid inlet tube and the fluid outlet tube. The separate passages for the fluid inlet tube and the fluid outlet tube may include at least one of a plurality of fluid inlet tubes and a plurality of fluid outlet tubes. The insert may have a geometric cross-section and / or may include separate conduits for the fluid inlet tube and the fluid outlet tube, the geometric cross-section having four or more sides. The separate conduits for the fluid inlet tube and the fluid outlet tube may include at least one of a plurality of fluid inlet tubes and a plurality of fluid outlet tubes.

[0017] A third aspect of the present disclosure provides a cryogenic probe comprising an elongate tube including an insulating portion that at least partially houses or defines a fluid inlet tube and a fluid outlet tube, the elongate tube including a distal ablation portion that terminates at a closed distal end, the fluid inlet tube terminating proximate the closed distal end and within the distal ablation portion, the fluid inlet tube having a cross section at the terminal end that is substantially smaller than its cross section upstream from the terminal end, and / or a housing that at least partially surrounds at least a portion of the proximal end of the elongate tube and receives or defines at least a portion of the fluid inlet tube and a portion of the fluid outlet tube.

[0018] In one embodiment, the cross-section of the fluid inlet tube at the distal end may be defined by at least one of a fluid flow element and a nozzle, the at least one of the fluid flow element and the nozzle having a cross-section that is substantially smaller than the cross-section of the fluid inlet tube upstream from the distal end.

[0019] A fourth aspect of the present disclosure provides a method of performing cryoanalgesia, comprising the steps of: positioning a spherical distal outer surface of an ablation tip of a cryogenic probe in proximity to a target nerve, the target nerve comprising an axon and a surrounding tubular structure; severing the axons of the target nerve while leaving at least a portion of the surrounding tubular structure intact by supplying a cryogenic fluid to the cryogenic probe to cool the ablation tip; heating the cryogenic probe; and / or removing the spherical distal outer surface from a position in proximity to the target nerve.

[0020] In one embodiment, positioning the spherical distal outer surface of the ablation tip of the cryoprobe adjacent to the target nerve may include positioning the spherical distal outer surface of the ablation tip in direct contact with the target nerve. Positioning the spherical distal outer surface of the ablation tip of the cryoprobe adjacent to the target nerve may include positioning the spherical distal outer surface of the ablation tip in direct contact with the target nerve. Heating the cryoprobe may include shutting off the flow of ejected cryofluid from the cryoprobe while continuing to supply cryofluid to the cryoprobe. The ablation tip may include an ablation tip proximal outer surface having a substantially constant axial profile, the diameter of the ablation tip proximal outer surface being smaller than the diameter of the spherical distal outer surface. The spherical outer surface may include a hemispherical surface having a diameter between about 3.0 mm and about 18.0 mm. The method may include repeating the positioning, severing, heating, and detaching operations for a second target nerve. The target nerve may include an intercostal nerve. The method may include bending the cryogenic probe before positioning the bulbous distal outer surface of the ablation tip of the cryogenic probe proximate to the target nerve. Severing the axons of the target nerve while leaving at least a portion of the surrounding tubular structure intact may include leaving at least one of the endoneurium, perineurium, fascicles, and epineurium intact. Severing the axons of the target nerve while leaving at least a portion of the surrounding tubular structure intact may include leaving the endoneurium and perineurium intact. [Brief explanation of the drawings]

[0021] [Figure 1] FIG. 1 is a schematic diagram of a first exemplary cryoprobe according to the present disclosure. [Figure 2] FIG. 2 is an outline view of one half of the handle housing of the first exemplary cryoprobe of FIG. 1, with the handle housing removed to show the internal components within the handle housing. [Figure 3]FIG. 2 is a top view of the adapter and hypotube of the first exemplary cryoprobe of FIG. 1. [Figure 4] 4 is a cross-sectional view of FIG. 3 taken along the longitudinal length of the major dimension. [Figure 5] 3 is a cross-sectional view of an exemplary adapter and related components shown in FIG. 2. [Figure 6] 2 is a longitudinal cross-sectional view of the first exemplary cryoprobe of FIG. 1 at a distal opening of the handle housing. [Figure 7] 2 is a longitudinal cross-sectional view of the first exemplary cryoprobe of FIG. 1 along the transition length between the insulating tubes. FIG. [Figure 8] 1 is a profile view of a first exemplary insulating tube according to the present disclosure. [Figure 9] FIG. 2 is a longitudinal cross-sectional view of a first exemplary insulating tube along most of the length of the insulating tube. [Figure 10] FIG. 2 is a longitudinal cross-sectional view of a first exemplary insulating tube at its proximal end. [Figure 11] 1 is a full view of a first exemplary spacer according to the present disclosure. [Figure 12] 1A-1C are elevated perspective views of a first exemplary cryoprobe showing the ablation tip and insulating tube in various bent positions. [Figure 13] FIG. 2 is an elevated perspective view of a second exemplary insulating tube according to the present disclosure. [Figure 14] FIG. 10 is an axial cross-sectional view of a second exemplary insulating tube and lead-in tube surrounding a malleable shaft. [Figure 15] 2 is a longitudinal cross-sectional view at the distal end of the first exemplary cryoprobe of FIG. 1. [Figure 16] FIG. 1B is a longitudinal cross-sectional view of a malleable shaft bonded to an ablation tip using a first exemplary attachment technique. [Figure 17] FIG. 10 is a longitudinal cross-sectional view of a malleable shaft joined to an ablation tip using a second exemplary attachment technique. [Figure 18]FIG. 10 is a profile view of an alternative exemplary ablation tip having a domed cylindrical shape. [Figure 19] FIG. 10 is a profile view of a further alternative exemplary ablation tip having a rounded cone shape with a spherical contact surface. [Figure 20] 10A-10C are longitudinal cross-sectional views of alternative adapters implementing fluid flow constrictions that may be used in accordance with the present disclosure to generate backpressure at the ablation tip. [Figure 21] FIG. 10 is a longitudinal cross-sectional view at the distal end of a second exemplary cryoprobe. [Figure 22] FIG. 10 is an elevated perspective view of an exemplary boiler that may be part of the second exemplary cryoprobe. [Figure 23] FIG. 23 is an elevated perspective view of the boiler of FIG. 22 with at least one hypotube shown in phantom and extending from the boiler itself to define a fluid flow path. [Figure 24] 1 is an axial cross-sectional view of a malleable shaft including a first exemplary longitudinal insert having a triangular shape with separate fluid flow paths and dedicated air pockets along its longitudinal length. FIG. [Figure 25] 1 is an axial cross-sectional view of a malleable shaft including a first exemplary longitudinal insert having a hexagonal shape with separate fluid flow paths and dedicated air pockets along its longitudinal length. FIG. [Figure 26] 1 is a process flow diagram illustrating an exemplary process for utilizing one or more of the exemplary cryoprobes of the present disclosure. [Figure 27] FIG. 1 is a diagram of the rib cage and associated tissues showing placement of a cryoprobe as part of a cryoanalgesia procedure for the intercostal area. [Figure 28] FIG. 1 is a cutaway perspective view of a nerve undergoing cryoanalgesia with a cryoprobe in accordance with at least some aspects of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0022] Exemplary embodiments of the present disclosure are described below, illustrating exemplary cryogenic probes, methods for manufacturing the cryogenic probes, and methods for using the cryogenic probes as part of a pain management procedure. Of course, it will be apparent to those skilled in the art that the embodiments described below are exemplary in nature and may be reconfigured without departing from the scope and spirit of the invention. However, for clarity and rigor, the exemplary embodiments described below may include optional steps, methods, and features that those skilled in the art would recognize as not required within the scope of the invention.

[0023] Referring to FIG. 1 , a first exemplary cryogenic probe (cryoprobe) 100 may include a distal ablation section 101 including an ablation tip 102 connected to an elongated flexible or malleable shaft 104 extending through an insulating tube 106 and into a handle housing 108. By way of example, the distance between the ablation tip 102 and the handle housing 108 may vary depending on the intended application, but in an exemplary embodiment is between approximately 4 inches and 30 inches. In an exemplary embodiment, the insulating tube 106 may be substantially rigid and fixedly attached to the handle housing 108, shielding a portion of the malleable shaft 104 from contact with its immediate surroundings, including adjacent tissue when inserted into a mammalian body. In this exemplary embodiment, the handle housing 108 may include a pistol grip 110 and an internal cavity extending through the handle housing 108 to accommodate a connection between the malleable shaft 104 and a connecting bundle 112. In addition to the pistol grip 110, other methods known in the art may be used.

[0024] The connection bundle 112, in an exemplary form, may include a braided sleeve 113 surrounding an inlet line 114 that carries hydraulic fluid from a fluid source (not shown) to the interior of the handle housing 108, and an outlet line 116 that carries hydraulic fluid from within the handle housing to a collection location (not shown), such as a fluid circulation tank, without restriction. In addition to the exemplary braided sleeve 113, braided sleeves of other thicknesses and configurations may be used to cover the inlet line 114. An exemplary braided sleeve that may be used as part of the present disclosure includes, without limitation, a polyethylene terephthalate (PET) braided monofilament yarn, such as commercially available from TechFlex of Sparta, New Jersey. Additionally, an exemplary inlet line 114 and outlet line 116 that may be used as part of the present disclosure include, without limitation, a microbore high-pressure hose, such as commercially available from Hydrotechnik of the United Kingdom. In addition to the inlet line 114 and the outlet line 116, the braided sleeve 113 may also, in an exemplary embodiment, enclose one or more thermocouple leads 118 in electrical communication with one or more thermocouples disposed within or adjacent to at least one of the ablation tip 102 and the malleable shaft 104. Additionally, exemplary thermocouple leads 118 that may be used as part of the present disclosure include, without limitation, 24 AWG thermocouples commercially available from Physitemp of Clifton, New Jersey. In this exemplary embodiment, the inlet line 114 and the outlet line 116 and the thermocouple leads 118 may include quick-connect adapters 120 to make the cryoprobe 100 modular. In this manner, the cryoprobe 100 may be disposable and configured to interconnect with multiple-use or repeated-use components, such as, without limitation, a cryogenic fluid tank, a cryogenic fluid recycling device, and a medical device operable to display a temperature reading.

[0025] 2-5 , in an exemplary configuration, the connection bundle 112 may extend into and terminate at a proximal opening 130 of the handle housing 108. In this exemplary embodiment, the handle housing 108 may include left and right housing sections that, when connected, define an interior cavity and corresponding proximal and distal openings 130, 138. At the distal end of the connection bundle 112, a band 132 may surround the connection bundle end, the inlet and outlet lines 114, 116, and the thermocouple lead 118. In an exemplary configuration, the distal end of the inlet line 114 may be fluidly coupled via a fluid-tight seal to a fluid inlet tube, such as an inlet hypotube 136, using an adapter 134. As an example, the adapter 134 may include a ribbed male proximal end that is received within the distal end of the inlet line 114, while the female distal end of the adapter receives the inlet hypotube 136. In an exemplary configuration, the connection between the inlet adapter 134 and the inlet line 114 may be facilitated using a crimp ring 138 that surrounds both the adapter and the inlet hypotube, maintaining a compression fit between the adapter and the inlet line. Additionally, the connection between the inlet adapter 134 and the inlet hypotube 136 may be fluid-tight and may be achieved by placing the hypotube within the adapter using a welding or brazing process. In this exemplary embodiment, the inlet line 114 may be flexible or malleable and may be fabricated from single or multi-layer constructions of various metals and polymers, including, without limitation, aluminum, copper, stainless steel, and thermoplastics (including extruded thermoplastics). As a further example, the inlet line may include an inner layer for chemical compatibility (e.g., extruded polymer tubing) and one or more outer layers for strength (e.g., braided yarn and braided stainless steel), flexural strength, and / or appearance. The hypotube 136 and the service adapter 134 may generally have a higher stiffness than the service line 114, may be fabricated from stainless steel, and may have a single or multi-layer construction.As a further example, the hypotube 136 and retraction adapter 134 may be fabricated from single or multi-layered compositions of various metals and polymers, including, without limitation, aluminum, copper, stainless steel, and thermoplastics (including extruded thermoplastics). Additionally, the hypotube 136 and retraction adapter 134 may include an inner layer for chemical compatibility (e.g., extruded polymer tubing) and one or more outer layers for strength (e.g., aluminum, stainless steel, braided yarn), flexural strength, and / or appearance.

[0026] In exemplary configurations, the annular space between the exterior of the hypotube 136 and the interior of the malleable shaft 104 may form a fluid exhaust conduit 105, which may route exhaust flow from the ablation tip 102 to the exhaust line 116. The distal end of the exhaust line 116 may be fluidly coupled to the exhaust adapter 140 via a fluid-tight seal. Generally, in some exemplary embodiments, the exhaust adapter 140 may be operable to change the arrangement of the fluid exhaust conduit 105 and the fluid inlet conduit 136 from a coaxial position to a parallel (non-coaxial) position. As an example, the exhaust adapter 140 may include a ribbed male proximal end 141 that is received within the distal end of the exhaust line 116, while the female distal end 143 of the adapter receives the proximal end of the malleable shaft 104. FIG. 4 illustrates an exemplary adapter 140 having a substantially constant cross-sectional area for routing exhaust flow between its inlet and outlet ends. However, it should be noted that the cross-sectional area available for exhaust flow need not be constant between the inlet and outlet ends as a means for managing backpressure (see FIG. 20 ). In an exemplary configuration, the connection between the exhaust adapter 140 and the exhaust line 116 may be aided by using a crimp ring 142 that surrounds both the adapter and the exhaust line 116 to maintain a compression fit between the adapter and the exhaust line. Additionally, the connection between the adapter 140 and the malleable shaft 104 may be a fluid-tight connection, which may be achieved using a brazing process by placing the malleable shaft within the adapter such that the proximal end of the shaft abuts a distal shoulder 145 of the adapter, forming a seal between the adapter 140 and the malleable shaft 104. To help facilitate maintaining a fluid-tight seal between the malleable shaft 104 and the adapter 140, the distal end of the adapter includes a frusto-conical taper 144 that receives a frusto-conical compression fitting 146 (e.g., a ferrule). Compression fitting 146 is repositioned proximally using a nut 148 that threadably engages helical threads 150 located on the outer periphery of the distal end of adapter 140 .In this manner, as the nut 148 is tightened, it presses against the compression fitting 146, thereby reducing the circumference of the compression fit and tightly gripping the exterior of the malleable shaft 104. Continued tightening of the nut 148 creates a tighter grip between the compression fitting 146 and the exterior of the malleable shaft 104, restricting relative movement between them. A thread locking agent (not shown) may be applied between the threads of the nut 148 and the threads of the adapter 140 to restrict relative movement between the nut and the adapter, thus collectively maintaining the relative position of the malleable shaft 104 in a fluid-tight seal against the distal shoulder 145 of the adapter 140. In an exemplary embodiment, the adapter 140 includes a passageway that accommodates the flow of the hypotube 136, such that the distal end of the adapter concentrically aligns the hypotube and the malleable shaft 104. In this exemplary embodiment, the exhaust line 116 may be flexible or malleable and may be fabricated from a variety of metals and polymers, including, without limitation, aluminum, copper, stainless steel, and thermoplastics (including extruded thermoplastics), in single or multi-layer constructions. By way of further example, the exhaust line may include an inner layer (e.g., an extruded polymer tubing) for chemical compatibility and one or more outer layers for strength (e.g., braided yarn and braided stainless steel), flexural strength, and / or appearance. The malleable shaft 104 and adapter 140 may generally be more rigid than the exhaust line 116, may be fabricated from stainless steel, and may have a single or multi-layer construction. By way of further example, the malleable shaft 104 and adapter 140 may be fabricated from a variety of metals and polymers, including, without limitation, aluminum, copper, stainless steel, and thermoplastics (including extruded thermoplastics), in single or multi-layer constructions.Additionally, the malleable shaft 104 and adapter 140 may include an inner layer for chemical compatibility (e.g., extruded polymer tubing) and one or more outer layers for strength (e.g., copper, aluminum, stainless steel, braided yarn), flexural strength, and / or appearance.

[0027] 6 , the distal end of the handle housing 108 defines a distal opening 138 through which the hypotube 136, malleable shaft 104, thermocouple lead 118, and insulating tube 106 may extend. As a further example, the hypotube 136 may be concentrically located within the malleable shaft 104, while the thermocouple lead 118 extends along the exterior of the malleable shaft 104. Additionally, the insulating tube 106 may be compression fit over the malleable shaft 104 and thermocouple lead 118.

[0028] As shown in FIG. 7 , the longitudinal cross section reflects the configuration within and distal to the insulating tube 106, beyond where the insulating tube terminates. One or more thermocouples 160 may be positioned along the length of the malleable shaft 104 and in electrical communication with the thermocouple leads 118 to provide temperature measurements. In an exemplary configuration, the thermocouple 160 may be soldered to the outside of the malleable shaft 104 and further covered by the insulating tube 106. As a further example, the thermocouple 160 may be partially embedded in the malleable shaft 104 and operable to provide temperature measurements specific to the fluid flow (exhaust or intake) through the malleable shaft. As yet another example, the thermocouple 160 may be offset between approximately one-half inch and three inches (including 1.34 inches) from the distal end of the insulating tube, although other thermocouples may be positioned along the length of the insulating tube.

[0029] With continued reference to FIGS. 7 and 8-12, by way of example, the malleable shaft 104 may surround the hypotube 136, or both the malleable shaft 104 and the hypotube 136 may be surrounded by the insulating tube 106. Near the distal end of the insulating tube 106, the insulating tube 106 may be hollow to form a circumferential gap between the insulating tube and the malleable shaft 104. In this exemplary embodiment, the gap may be sized to receive the more flexible insulating tube 170, and the longitudinal length of the gap may vary from about 0.1 inches to over 1.0 inches, including 0.32 inches. By way of example, the insulating tube 170 may include a spacer 174 interposed between the flexible cover 176 and the malleable shaft 104, which may maintain an insulating gap (e.g., an air gap) between the flexible cover and the malleable shaft. In exemplary configurations, the spacer 174 may comprise, at any given axial cross-section, one or more (e.g., four) helices 174a, 174b, 174c, 174d (having a generally uniform circular axial cross-section and / or a common axial dimension) longitudinally offset along its longitudinal length, with each helix oriented at 12, 3, 6, and 9 o'clock, respectively. At each longitudinal end, the helices 174a, 174b, 174c, 174d may be bonded or interconnected with static structures to maintain the position of the segment ends. For example, each helix may comprise a variety of non-conductive materials, such as, without limitation, polymers, including thermoplastics. In some exemplary embodiments, the individual helices 174a, 174b, 174c, 174d may be formed as hollow tubes, which may optionally comprise insulating materials. At the proximal end 175 of insulating tube 170, the outer diameter may be reduced or narrowed (173) to allow the proximal end to be inserted into the gap between malleable shaft 104 and the distal end of insulating tube 106. For example, insulating tube 170 may be narrowed such that its outer major dimension is smaller than the outer diameter of helices 174a, 174b, 174c, 174d.The insulating tube 170 may increase in outer diameter with distal movement and may include a proximal shoulder 180 against which the proximal end of the spacer 174 rests. For example, the insulating tube may comprise any insulating material having any number of configurations to form a vacuum gap or a fluid gap (e.g., a stagnant fluid pocket), such as, without limitation, polystyrene foam. The insulating tube 170 may be operable to insulate the malleable shaft 104 from the external environment. In this exemplary embodiment, the malleable shaft 104, hypotube 136, and insulating tube 170 may be flexible enough to allow bending of more than 180 degrees to reposition the ablation tip 102 between the start and end positions (see FIG. 12 ).

[0030] 13 and 14 , in an alternative exemplary embodiment, the previously described insulating tube 170 may be replaced with an alternative exemplary flexible covering 190 to surround the malleable shaft 104 and hypotube 136. In an exemplary configuration, the flexible covering 190 may include a plurality of internal protrusions 192 extending from the interior of a circumferentially continuous covering 194, and the protrusions may be arranged in an alternating circular and axial pattern along its longitudinal length. The protrusion arrangement defines an air gap (e.g., a stagnant fluid pocket) 193 between the malleable shaft 104 and the continuous covering 194, thereby providing thermal insulation regardless of whether the malleable shaft 104 has a straight orientation or has some arcuate shape indicative of being bent (see FIG. 12 ). The use of the protrusion 192 arrangement may result in a larger volumetric air space being created compared to the previously described insulating tube 170. Additionally, the protrusions 192 may be formed in a conical, frustoconical, or hemispherical shape to reduce the contact surface area between the protrusions and the malleable shaft 104 for conductive heat transfer. Those skilled in the art will appreciate that the shape and pattern of the protrusions may be modified to improve thermal insulation performance.

[0031] 15-17, the distal end 196 of the flexible insulating tube 170 may exhibit a reduced or narrowed (197) outer diameter (as may the flexible covering 190 if used instead). For example, the insulating tube 170 may be narrowed such that its outer major dimension is smaller than the outer diameter of the helices 174a, 174b, 174c, and 174d. The reduced outer diameter of a portion of the insulating tube 170 may form a distal shoulder 184 thereon, upon which the distal end of the spacer 174 may be disposed. The malleable shaft 104 may be fitted proximally to the distal end 196 of the insulating tube 170 and may be joined at its distal end to the ablation tip 102 by a fluid-tight seal. 16, a fluid-tight seal may be achieved via a weld 198 at the joint between the ablation tip 102 and the malleable shaft 104, such as, without limitation, a circumferential surface weld and a circumferential butt weld. Alternatively, as shown in FIG. 17, the malleable shaft 104 may extend into a cavity formed in the ablation tip 102, and a fluid-tight seal may be achieved via a weld 198 at the lap joint, such as, without limitation, a circumferential fillet weld. Those skilled in the art will appreciate that other forms of fluidly joining the malleable shaft 104 and the ablation tip 102 are contemplated herein and include chemical bonding (e.g., adhesives), brazing, welding (e.g., spin and friction welding), staking, and mechanical connections (e.g., threaded connections, friction fits, etc.).

[0032] Referring back to FIG. 15 , in the exemplary configuration, the ablation tip 102 comprises a solid metal casing terminating in a closed distal end 103 and having an internal cavity 200 configured to receive the distal end 202 of a hypotube 136 extending beyond the malleable shaft 104. In this exemplary embodiment, the metal forming the ablation tip 102 may include any metal or alloy usable in a surgical environment, including, without limitation, aluminum, titanium, stainless steel, copper, silver, gold, and any other thermally conductive metal or alloy, including coatings comprising one or more of the above metals. By way of example, the cavity 200 may comprise a cylindrical shape that tapers conically to a distal point 204. In this exemplary embodiment, the distal end of the hypotube 136 comprises a nozzle 206 through which a cryogenic fluid may be ejected and flow into the portion of the cavity 200 not occupied by the hypotube. In an exemplary configuration, the nozzle 206 has a nozzle opening between 0.05 inches and 0.001 inches in diameter and may be located anywhere between 0.005 inches and 2.0 inches (including 0.100 inches) from the distal end of the cavity 200. Although not required, the hypotube 136 may include a fluid flow element 208, such as upstream of the nozzle 206 (e.g., between the hypotube 136 and the nozzle 206), to vary the cross-sectional area available for the cryogenic fluid to flow through the nozzle 206. By way of example, the hypotube 136 may be coupled to a fluid flow element (e.g., a fluid flow constriction) 208 operable to reduce the cross-sectional area available for cryogenic fluid flow immediately adjacent the nozzle 206, the fluid flow element 208 operating to increase the pressure of the cryogenic fluid at the nozzle 206 compared to the pressure of the cryogenic fluid flowing upstream of the fluid flow element. In general, the nozzle 206 and / or fluid flow element 208 may have a cross-section that is substantially smaller than the cross-section of the fluid inlet conduit (e.g., hypotube 136) upstream from the end of the fluid inlet conduit. The nozzle may have a fluid flow cross-section that is substantially smaller than the fluid flow cross-section of the fluid flow element 208.

[0033] In this exemplary embodiment, it is envisioned that the cryogen exiting the nozzle 206 is subjected to a higher pressure upstream from the nozzle and is allowed to expand at a significantly lower pressure downstream of the nozzle within the cavity 200, resulting in Joule-Thomson expansion and significantly reducing the temperature of the cryogen and the ablation tip 102. By way of example, the cryogen may include any number of cryogens, such as, without limitation, nitrous oxide, argon, carbon dioxide, and phase change fluids. As a further example, in the case of nitrous oxide, the cryogen may be supplied as a liquid at a temperature of 26.7°C and a pressure of 800 psi upstream of the nozzle and may comprise a gas phase or a mixed gas-liquid phase at approximately 45 psi and -68°C within the ablation tip cavity 200. A counterflow may be established by the lower pressure cryogenic fluid flowing through the cavity 200, around the hypotube 136, and subsequently into and through the malleable shaft 104 surrounding the hypotube, thereby pre-cooling the cryogenic fluid flowing through the hypotube as Joule-Thomson expansion within the ablation tip 102 continues. Although not required, a vacuum or low-pressure purge may be applied on the exhaust line 116 (see FIG. 1 ), forcing the expanded cryogenic fluid flow rapidly through the malleable shaft 104, through the exhaust adapter 140, and into the exhaust line. As Joule-Thomson expansion continues at the ablation tip 102, contacting the tip with tissue to be ablated cools the exterior of the tip 102 sufficiently for use in an ablation procedure. By way of example, depending on the cryogenic fluid utilized, exemplary flow rates of the cryogenic fluid through the nozzle 206 range from between 15 cubic centimeters per minute to over 100 cubic centimeters per minute.

[0034] 15-19 , in this exemplary embodiment, the ablation tip 102 may comprise a spherical distal outer surface 107, such as a hemispherical surface having a diameter ranging between approximately 3.0 millimeters and 18.0 millimeters. In general, as used herein, “spherical” may refer to an enlarged (relative to adjacent structures) generally rounded outer surface. Other geometries and surfaces may be utilized for the ablation tip 102, such as, without limitation, a domed cylindrical surface as shown in FIG. 18 and a rounded conical surface as shown in FIG. 19 , or any of a variety of other spherical surfaces known to those skilled in the art. For non-spherical outer surfaces, the major axial dimension may be between 1.0 millimeters and 25 millimeters. As a further example, the ablation tip 102 may comprise any spherical outer surface 107. Those skilled in the art will appreciate that the outer surface of the ablation tip 102 may be adapted to any number of geometries specifically designed to perform specific ablation of an anatomical feature. In exemplary configurations, the ablation tip 102 may have a generally constant axial profile and may be narrowed to include a proximal outer surface having a diameter smaller than the diameter of the spherical exterior. This narrowing may terminate in a gradual change in axial diameter to facilitate a fluid-tight seal between the ablation tip 102 and the malleable shaft 104. Additionally, the ablation tip 102 may be attached to and detached from the malleable shaft 104 by methods known in the art. Generally, in some exemplary embodiments, the spherical distal outer surface 107 of the distal ablation portion 101 has a longitudinal length L B and may extend over a longitudinal length L B is the longitudinal length L of the exposed outer surface of the distal ablation section AS In another exemplary embodiment, the longitudinal length L of the spherical distal outer surface 107 of the distal ablation portion 101 may be at least half of the longitudinal length L of the spherical distal outer surface 107 of the distal ablation portion 101. B is the longitudinal length L of the exposed outer surface of the distal ablation section AS It may extend by less than half the length of the

[0035] Referring to FIG. 20 , an exemplary alternative adapter 240 including a flow-restricting element may be used in place of the previously described exemplary adapter 140 to throttle the cryogen exhaust flow from the malleable shaft 104, thereby generating backpressure. In an exemplary configuration, the temperature that the ablation tip 102 can achieve may be directly proportional to the backpressure of the cryogen exhaust flow, in that the higher the cryogen backpressure, the higher the temperature at the ablation tip. In an exemplary configuration, the majority of heat removal may occur as a result of a phase transition (boiling) of the cryogen within or near the ablation tip 102. The temperature that the ablation tip 102 can achieve may be proportional to the boiling point (evaporation temperature) of the cryogen, which is proportional to the cryogen pressure. For example, increasing the backpressure on the cryogen increases the temperature relative to the minimum temperature that the ablation tip can achieve. Without some flow-restricting element (e.g., a valve or throttle) to slow the flow of the cryogen exhaust flow, backpressure may be a contradictory side effect of flow restriction in the exhaust path, since such flow restriction may be flow rate dependent. 20 illustrates an exemplary flow restricting element in the form of a constriction 242 located between the exhaust cryogen flow from the malleable shaft 104 and the exhaust cryogen flow that ultimately enters the exhaust line 116. If the dimensions of the constriction 242 were constant without a valve, the amount of backpressure created would be a function of flow rate, with increased flow rates resulting in higher backpressure. In some exemplary embodiments according to at least some aspects of the present disclosure, the adapter 140 may be configured such that the cross-sectional area for the cryogen exhaust flow of the constriction 242 is a fraction of the cross-sectional area for the cryogen exhaust flow of the exhaust line 116. In an exemplary embodiment, the cross-sectional area for the cryogen exhaust flow of the constriction 242 may be less than about 70% of the cross-sectional area for the cryogen exhaust flow of the exhaust line 116. In another exemplary embodiment, the cross-sectional area for the cryogen exhaust flow of the constriction 242 may be less than about 50% of the cross-sectional area for the cryogen exhaust flow of the exhaust line 116. In yet another exemplary embodiment, the cross-sectional area for the cryogen exhaust flow of the constriction 242 may be less than about 30% of the cross-sectional area for the cryogen exhaust flow of the exhaust line 116 .In yet another exemplary embodiment, the cross-sectional area for the cryogen exhaust flow of the restriction 242 may be less than about 15% of the cross-sectional area for the cryogen exhaust flow of the exhaust line 116. In another exemplary embodiment, the cross-sectional area for the cryogen exhaust flow of the restriction 242 may be about 10% of the cross-sectional area for the cryogen exhaust flow of the exhaust line 116.

[0036] 21 , the second exemplary cryogenic probe (cryoprobe) 300 may share many of the same components as the first exemplary cryoprobe 100, including the handle housing 108, the connection bundle 112, the inlet line 114, the exhaust line 116, the thermocouple leads 118, and the insulating tubing 106. However, the second exemplary cryoprobe 300 differs in the configuration of the malleable shaft and ablation tip. In this exemplary embodiment, the malleable shaft 304 may or may not be covered by the flexible insulating tubing 170. Regardless of whether the flexible insulating tubing is utilized, the malleable shaft 304 may surround the fluid exhaust tube 310 and define a path for spent cryogen to be routed to the handle housing 108. The outer periphery of the exhaust tube 310 cooperates with the inner periphery of the malleable shaft 304 to define a fluid inlet tube 312 for the cryogenic fluid. In an exemplary embodiment, the cross-sectional area ratio of the exhaust tube 310 to the inlet tube 312 may range between approximately 30:1 and 1:1. A notable difference in this exemplary cryoprobe tubing is that the exhaust tube 310 is circumferentially nested relative to the inlet tube 312 as a means to avoid inadvertent ablation of tissue that may come into contact with the malleable shaft 304, assuming the cryogenic fluid flowing through the inlet tube is not necessarily cold enough to ablate tissue (e.g., above approximately −10° C.). In an exemplary embodiment, the inlet tube 312 does not become cold enough to ablate tissue because the fluid flowing within the inlet tube 312 is under high pressure (e.g., 300-800 psi) and therefore the boiling point of the cryogenic fluid is higher than the tissue ablation temperature. The heat generated due to compressing the cryogenic fluid also helps maintain the outside of the inlet tube 312 at a temperature above the tissue ablation temperature. Additionally, any heat exchange from the discharge tube to the cryogenic fluid flowing through the inlet pipe 312 is introduced into the discharge flow through a boiler 320. The distal end of the malleable shaft 304 extends further distally than the distal end of the discharge pipe 310.This difference in the distal end forms a flanged recess that partially receives a boiler 320 having an axial cross section that matches the axial cross section of the malleable shaft 304, which in an exemplary form may be circular.

[0037] 21 and 22 , the proximal end of the boiler 320 may include a nipple 324 configured to be received within the discharge pipe 310 and form a fluid seal between a central bore 328 extending through the boiler 320 and the interior of the discharge pipe 310. In a further exemplary form, the nipple 324 may include an external raised circumferential ring 329 configured to form a friction fit and fluid seal between the nipple 324 and the discharge pipe 310 to maintain the relative longitudinal position of the boiler 320 with respect to the discharge pipe 310. To prevent over-insertion of the boiler 320 into the discharge pipe 310, the nipple 324 includes a circumferential lip 330 against which the distal end of the discharge pipe 310 may abut. In an exemplary form, the nipple 324 may extend axially and terminate distally in a proximal flange 332 configured to fill an internal gap formed by the flared distal end of the malleable shaft 304. Despite filling this internal gap, the boiler 320 may include one or more flow channels 334 that provide fluid communication between the lead-in tube 312 and the interior of the distal ablation portion 302, which may include an ablation tip 336 that includes a closed distal end 303 and / or the boiler 320. In an exemplary form, the boiler 320 may be fabricated from a polymeric material and injection molded over one or more existing lines, such as hypotubes 335, to define and enable fluid communication through the flow channels 334. As an example, the flow channels 334 may not extend substantially beyond the distal end of the boiler 320 body, thereby forming a nozzle that is substantially flush with the boiler 320 body. Alternatively, the hypotube 335 may extend substantially beyond the distal end of the boiler 320 body in a spiral or other configuration to allow the cryogen fluid within the ablation tip 336 to expand and pre-cool the cryogen fluid before it exits the flow path inside the ablation tip (see FIG. 23).

[0038] As an example, to fluidly seal the ablation tip 336 and the service pipe 312 around the boiler 320, the boiler 320 may include two or more external circumferential trenches 340, each receiving a respective O-ring 342. Interposed between each trench 340 on the circumference of the boiler 320 is a raised rib 343 with a corresponding groove 344. In this exemplary embodiment, the height of the raised rib 343 may be selected to be slightly less than the material thickness of at least one of the malleable shaft 304 and the ablation tip 336, so that joining the boiler 320, the malleable shaft 304, and the ablation tip 336 does not result in significant irregularities in the resulting outer surfaces of the joined components. The boiler 320, malleable shaft 304, and ablation tip 336 are joined together by crimping one of them onto the distal end of the malleable shaft 304 so that its end is located within the proximal one of the grooves 344, while the proximal end of the ablation tip 336 is similarly crimped to be received within the distal end of groove 344. Note that this crimping process is performed on the malleable shaft 304, and the ablation tip 336 is also operable to form a complete fluid-tight seal via the O-ring 342.

[0039] Forming a fluid-tight seal allows the cryogen to flow from the inlet pipe 312 through the flow passage 334 of the boiler 320 to the interior of the ablation tip 336. Upon reaching the ablation tip 336, the cryogen is allowed to expand at significantly lower pressures within the ablation tip 336, resulting in Joule-Thomson expansion and significantly reducing the temperature of the cryogen and the ablation tip. By way of example, the cryogen may include any number of cryogens, such as, without limitation, nitrous oxide, argon, and carbon dioxide. As a further example, the cryogen may be a phase-change fluid that reaches equilibrium (or saturation point) at room temperature (approximately 15°C-25°C) and a pressure of less than 2000 psi. As a further example, in the case of nitrous oxide, the cryogen may be supplied as a liquid at a temperature of approximately 80°F and a pressure of approximately 800 psi upstream of the boiler 320 and exit as a gas phase or a mixed gas-liquid phase at approximately -68°C and 45 psi. As Joule-Thomson expansion continues within the ablation tip 336, the exterior of the ablation tip may cool to a temperature low enough for use in an ablation procedure, thereby bringing the ablation tip into contact with the tissue to be ablated. By way of example, depending on the cryogenic fluid utilized, exemplary flow rates for the cryogenic fluid through the flow passage 334 range from approximately 15 cubic centimeters per minute to over 100 cubic centimeters per minute.

[0040] As previously mentioned, the temperature that the ablation tip 336 can achieve is directly proportional to the backpressure of the cryogen exhaust flow. Accordingly, the second exemplary cryoprobe 300 may (or may not) include a flow-restricting element in the form of a pressure valve (e.g., a safety valve) 350 proximate the ablation tip 336 that maintains a predetermined backpressure within the ablation tip 336 by regulating the flow of used cryogen through the exhaust conduit 310. In an exemplary form, the safety valve 350 may include a frusto-conical plug 352 operably coupled to a spring 354 having a predetermined tension (i.e., spring constant). In this exemplary embodiment, the spring 354 may comprise a coil spring having an enlarged portion 356 that is prevented proximally from extending beyond a distal frusto-conical end 358 of the central bore 328. This distal frusto-conical end 358 may be operable to perform a funnel function for the cryogenic fluid moving within the central bore 328 and exiting the ablation tip 336. The spring 354 is pretensioned (i.e., spring biased) to maintain a substantially fluid-tight seal between the plug 352 and the frusto-conical proximal end 359 of the central bore 328 (which acts as a valve seat for the valve disc) until a predetermined pressure is reached. Once the fluid pressure in the central bore 328 reaches the predetermined pressure, the cryogen pressure exerts a force on the plug 352 sufficient to overcome the biasing action of the spring 354, thereby allowing the plug 352 and the frusto-conical proximal end 359 of the central bore 328 to separate. As a further example, those skilled in the art will understand that the spring 354 may be selected or manipulated to set a backpressure maintained within the ablation tip 336. As a further example, the spring 354 may be selected or manipulated to set a backpressure maintained within the ablation tip 336 between 15 psi and 100 psi, including between 30 psi and 50 psi. In the exemplary embodiment, with the central bore 328 having a diameter of 0.125 inches at its narrowest point, a spring force of 0.6 pounds is operable to maintain a back pressure of 50 psi within the ablation tip 336 .Although the exemplary safety valve 350 is described as extending into the boiler 320 and to a position proximate to the ablation tip 336, one skilled in the art will understand that one or more safety valves may be located proximate to the boiler and / or may not be located proximate to the ablation tip 336.

[0041] With or without relief valve 350, counterflow is established by the expanded cryogenic fluid flowing through central bore 328 and into exhaust conduit 310, providing pre-cooling to the cryogenic fluid flowing through inlet conduit 312 and flow passage 334 as Joule-Thomson expansion within ablation tip 336 continues. Gap 321 between the outer radial surface at the distal end of boiler 320 and the inner radial surface of ablation tip 336 may act as a nozzle, similar to nozzle 206 of cryoprobe 100. Similarly, flow passage 334 may act as a fluid flow constriction, similar to fluid flow element 208 of cryoprobe 100. In some exemplary embodiments, the cross-section of gap (nozzle) 321 may be substantially smaller than the cross-section of inlet conduit 312 upstream of boiler 320. Similarly, in some exemplary embodiments, the cross-section of flow passage 334 may be substantially smaller than the cross-section of inlet conduit 312 upstream of boiler 320. In some exemplary embodiments, the cross section of gap (nozzle) 321 may be smaller than the cross section of flow path 334. Although not required, a vacuum or low pressure purge may be applied on exhaust line 116 (see FIG. 1 ) to rapidly force the flow of low pressure cryogenic fluid through exhaust pipe 310 and into the exhaust line.

[0042] In this exemplary embodiment, the ablation tip 336 may comprise a spherical profile having a diameter ranging from approximately 3.0 millimeters to 18.0 millimeters. However, other geometries may be utilized for the ablation tip 336, such as, without limitation, a domed cylindrical shape as shown in FIG. 18 and a rounded conical shape as shown in FIG. 19. As a further example, the ablation tip 336 may comprise any spherical profile (e.g., as shown in FIG. 15). Those skilled in the art will appreciate that the geometry of the ablation tip 336 may be suitable for any number of geometries specifically designed to perform a particular ablation of an anatomical feature.

[0043] 24 and 25, those skilled in the art will similarly appreciate that various configurations may be utilized within the malleable shaft 304 to supply cryogenic fluid to and remove expanded / cooled cryogenic fluid from the ablation tip 336. By way of example, and with particular reference to FIG. 24, the malleable shaft 304 may contain an insert 400 that defines an insulating air pocket (e.g., stagnant fluid pocket) 410, one or more cryogenic inlet tubes 420, and one or more cryogenic outlet tubes 430. The inlet tubes 420 may be separate from the outlet tubes 430. The exemplary insert 400 may comprise an extruded polymer such as, without limitation, polypropylene, polyvinylidene fluoride, and low-density polyethylene. The insert 400 may have a triangular shape (e.g., cross-section) to provide three contact points within the malleable shaft 304, reducing the number of contact points between the insert and the malleable shaft, thereby reducing conductive heat transfer between the cryogenic exhaust pipe 430 and the surface of the malleable shaft 304. As a further example, a triangular shape may be selected to fit within the diameter of the malleable shaft 304 and provide three contact points between the insert and the shaft, realizing that an equilateral triangle may minimize dead air volume, while a right-angled triangle may maximize dead air volume. In some exemplary embodiments, the dead air volume may be sealed and vented, thereby providing an enhanced barrier to heat transfer to the exterior surface. As an alternative to a triangular shape, a shape with additional sides (e.g., a shape with a cross-section having four or more sides) may be used. In exemplary configurations, the inlet pipe 420 and the exhaust pipe 430 may comprise nothing more than longitudinal channels formed in the insert 400, or may comprise dedicated tubes (e.g., hypotubes) from which the inserts are extruded. It is also within the scope of this exemplary insert 400 to include one or more conduits for routing thermocouple leads (not shown) or sensor leads (not shown) to provide real-time information regarding the temperature and / or pressure within one or more of the conduits 420, 430 and the air pocket 410.

[0044] FIG. 25 illustrates a further exemplary insert 450 that may be disposed within the malleable shaft 304 and may define an insulating air pocket (e.g., stagnant fluid pocket) 460, one or more cryogenic inlet tubes 470, and one or more cryogenic outlet tubes 480. The exemplary insert 450 may comprise an extruded polymer such as, without limitation, polypropylene, polyvinylidene fluoride, and low-density polyethylene. The insert 450 may comprise a hexagonal shape to provide six contact points within the malleable shaft 304, reducing the number of contact points between the insert and the malleable shaft, thereby reducing conductive heat transfer between the relatively cryogenic outlet tubes 480 and the surface of the malleable shaft. As a further example, by utilizing an object with sharp (low surface area contact) contact points with the malleable shaft, the surface area for conductive heat transfer is reduced compared to an arcuate surface that matches the internal curvature of the malleable shaft. In exemplary forms, inlet conduit 470 and outlet conduit 480 may comprise nothing more than longitudinal channels formed within insert 450, or may comprise dedicated tubing into which the insert is extruded. It is also within the scope of this exemplary insert 450 to include one or more conduits for routing thermocouple leads (not shown) or sensor leads (not shown) to provide real-time information regarding the temperature and / or pressure within one or more of conduits 470, 480 and air pocket 460.

[0045] One or more of the components disclosed herein may include an echogenic coating to provide ultrasound visibility during surgical procedures where a direct line of sight may be obstructed. Those skilled in the art will appreciate the use of ultrasound in non-line-of-sight surgical procedures. Therefore, details regarding ultrasound have been omitted to promote brevity. As an alternative to ultrasound, other visualization methods known in the art may be used.

[0046] The cryogenic probes 100, 300 described above may include electrical sensing to indicate that the ablation sequence is complete. As an example, one may apply a pulse signal (i.e., send an electrical signal through the nerve or tissue) to a nerve or other tissue distal to the ablation, such as in the intercostal space, during a cryoanalgesia procedure, and attempt to measure the electrical signal at a location proximal to the ablation; the ablation should cause the electrical signal to dissipate, or the electrical signal should become unmeasurable due to being interrupted by the ablation. Continuous or discontinuous pulsing may be used to determine when the ablation procedure is complete.

[0047] 26, an exemplary process 500 for using any of the previously described cryoprobes 100, 300 is described below. First, a draw of cryogenic fluid must be established (502) from a static location or a portable fluid holding vessel. By way of example, in an exemplary situation where nitrous oxide is used as the cryogenic fluid, a portable fluid holding vessel (e.g., a 20 pound tank) of liquefied nitrous oxide may be fluidly connected to an AtriCure Cryo Module (ACM), which is itself fluidly connected to the cryoprobe 100.

[0048] In an exemplary embodiment, the ACM is intended for use in cryosurgical treatment of cardiac arrhythmias. The ACM may comprise a non-sterile reusable cryoablation probe and / or a sterile disposable cryoablation probe. The ACM may further include an electromechanical cryosurgery unit (which may include controls, displays, indicators, and associated programmed logic or circuitry) that supplies cryofluid (e.g., nitrous oxide (NO)) to the cryoablation probe under conditions that cool an active area of the probe operable to ablate tissue contacting the active area while the cryofluid flows through the probe, which in an exemplary embodiment allows an operator to form ablation lines through tissue, such as cardiac tissue, without restriction. The ACM may further include a cryofluid holding container, a cryofluid inlet line in fluid communication (or selectively in fluid communication) with the holding container and the cryoablation probe, a cryofluid outlet line in fluid communication with the cryoablation probe, a holding container heater, a manual switch that allows for controlling the supply of cryofluid from the holding container to the cryoprobe, and the cryoprobe itself. In an exemplary embodiment, the ACM provides controlled delivery of cryogenic fluid to the cryoprobe, enabling tissue lesion formation at temperatures below -40°C, with a typical operating range of -50°C to -70°C.

[0049] In operation 504, cryogen conditions may be adjusted and / or verified. In an exemplary form, the portable fluid holding vessel may have a heater blanket covering the tank, which is operable to apply heat to the vessel to control the internal pressure. The internal pressure, in an exemplary form, may range between approximately 700 psi (approximately 17°C) and 850 psi (approximately 23°C). As an example, the ACM may provide visual feedback regarding the vessel pressure and temperature, with the feedback updated in real time. To the extent that heat is needed to reach the proper pressure, a green light may be illuminated as part of the ACM, indicating that the cryotank pressure is within a predetermined operating range.

[0050] In operation 506, a user activates the ACM to supply pressurized cryogenic fluid to the cryoprobe via the inlet line. As an example, the ACM supplies pressurized cryogenic fluid at approximately 725 psi to the inlet connection of the cryoprobe, such that the pressure of the cryogenic fluid is between 500 psi and 725 psi just before it reaches the ablation tip.

[0051] In operation 508, cryogen may be supplied to the cryoprobe 100, 300. When the cryogen is initially supplied to the ablation tip, it expands to approximately atmospheric pressure (14.7 psi). In operation 510, the backpressure of the used cryogen may be monitored and / or adjusted. In an exemplary embodiment, as more cryogen enters the ablation tip and used cryogen accumulates, backpressure begins to build and may be adjusted to reach a steady-state backpressure of approximately 52 psi, which corresponds to an ablation tip temperature of approximately -65°C. However, it should be noted that ablation of tissue using the ablation tip may begin after the ablation tip temperature reaches a predetermined value. The predetermined value may be higher than the steady-state temperature and may include, without limitation, -40°C.

[0052] An ablation cycle may be initiated in operation 512. Once the ablation tip reaches a predetermined ablation temperature, the ACM may perform an ablation cycle in which the ablation tip is maintained at or below the predetermined ablation temperature for a predetermined period of time, such as, without limitation, 120 seconds.

[0053] In operation 514, a defrost (e.g., heating) cycle may be initiated. In an exemplary embodiment, the ACM may activate the defrost cycle upon completion of the ablation cycle. As an example, the defrost cycle may include shutting off the cryogenic fluid exhausted from the cryoprobe while continuing to supply cryogenic fluid to the cryoprobe. Ultimately, the cryogenic fluid within the probe will all be at the same pressure and temperature, such as approximately 800 psi (corresponding to an ablation tip temperature of approximately 10°C) without restriction. Notably, various exemplary cryoprobes according to at least some aspects of the present disclosure may be configured to withstand pressures expected during a defrost cycle, which are higher than those expected during a freeze cycle. The ACM monitors the temperature at the ablation tip using a thermocouple, and upon reaching a predetermined defrost temperature, discontinues the inlet flow of cryogenic fluid to the cryoprobe while allowing the exhausted cryogenic fluid to vent, ultimately raising the temperature and reducing the pressure of the cryoprobe to atmospheric conditions.

[0054] After the defrost cycle is complete, the ACM may be reactivated (operation 506) to resume the freeze and defrost cycle. Alternatively, a treatment termination sequence (operation 516) may be initiated, in which the connection between the cryoprobe and the tank is severed and the ACM is deactivated.

[0055] As can be seen with reference to FIG. 28 , the exemplary cryoprobes 100, 300 may be used in the application of cryoanalgesia. Cryoanalgesia, or nerve cryolysis 700, uses extreme cold to cauterize peripheral nerves, resulting in a temporary but fully reversible loss of sensory nerve function. Cryoanalgesia produces axonotmesis, a degree of nerve damage according to Seddon's classification. In this case, the axon 702 and myelin are sever- ed, but at least some of the surrounding tubular structures, such as the endoneurium 704, perineurium 706, fascicles 710, and / or epineurium 708, remain intact. The subsequent Wallerian degeneration, a process in which the entire length of the nerve segment distal to the cryoanalgesia site (cryoinjury) is removed, takes approximately one week. Nerve regeneration begins at the proximal segment and continues at an average rate of 1–3 mm / day along undamaged structural components until the tissue is reinnervated. This process can take weeks to months, depending on the extent of the cryoinjury on the tissue. Cryoanalgesia preserves nerve structures and is not associated with the development of nerve tumors.

[0056] Localized analgesia to nerves (e.g., intercostal nerves) targets discomfort from pain resulting from incisions, any surgical muscle tears, nerve damage from surgical instruments (e.g., retractors) and surgical retainers (e.g., sutures), and any openings created by tubes or trocar sites. In an exemplary form, one exemplary process involves cryoanalgesia for post-thoracotomy pain, involving cryoablation of the intercostal nerves. Attempting cryoablation at temperatures that are not low enough, e.g., above −20° C., results in only a transient nerve conduction block with a return of sensation upon tissue thawing, while temperatures that are too low, e.g., below −100° C., can result in permanent nerve damage. When the cryoprobe 100, 300 is placed in contact with tissue, such as the pleura or intercostal nerves, an iceball forms around the tip of the cryoprobe 100, 300, and heat extraction penetrates the tissue several millimeters, creating a cryolession. The extent of the cryoinjury may depend on several other factors in addition to the probe temperature, including the size and material of the cryoprobe, the duration of freezing, the rate of freezing, the rate of thawing, and the number of freeze-thaw cycles. Below is described an exemplary procedure for performing cryoanalgesia following thoracotomy, which is effective for pain management and may be applied to any nerve within an animal's body.

[0057] 27, it may be recommended to perform the cryoablation procedure as early in the procedure as possible, such as before or immediately after creating the thoracotomy. The target nerve, such as the intercostal nerve 602, may be located within the incised intercostal space 604 (e.g., between the ribs 606, 608), preferably at the edge of the innermost intercostal muscle 610 and the membranous portion 612 of the internal intercostal muscle. The location may be selected to be proximal to the lateral cutaneous branch, but at least 2 cm from the ganglion 614 and 4 cm from the spine.

[0058] Approximately 2-3 cm of the cryoprobe 100, 300 (including the ablation tip 102) may be exposed, and the elongated shaft may be shaped to follow the curve of the costal groove. A hockey stick or C-shape may be used. The ablation tip 102 of the cryoprobe 100, 300 may be positioned directly above the nerve 602 at a slight angle so that the nerve is located directly below the ablation tip. The insulating tube of the cryoprobe 100, 300 may be placed over the ribs 606, 608 and carefully slid along the ribs until the cryoprobe falls off the rib and enters the costal groove.

[0059] Prior to ablation, the ablation tip 102 may be pressed into the rib groove with sufficient pressure to compress and stabilize the tissue and reduce local perfusion. Suitable pressure may be sufficient to cause blanching when applied to the skin. After the ablation tip 102 is placed in contact with or adjacent to the nerve 602, cryogenic fluid flowing through the cryoprobe 100, 300 is operable to cool the ablation tip (to approximately −65°C) and initiate or continue a freeze duration to freeze the nerve. By way of example, the freeze duration may be 120 seconds when the cryoprobe tip 102 is positioned adjacent to the nerve 602, while it may be shorter (e.g., 90 seconds) when the ablation tip is in direct contact with the nerve. The cryoprobe 100, 300 may be defrosted after the freeze duration to allow for detachment between the ablation tip and the animal tissue. In exemplary embodiments, once the cryoprobe 100, 300 is defrosted, the ablation tip 102 may become bright and shiny and may be moved without resistance. To prevent tissue or nerve damage, the cryoprobe should not be forcibly moved while attached to tissue. After defrosting, the freeze duration process and defrost sequence may be repeated at another location on the same nerve (or at a different location on a different nerve) and may be repeated as necessary to achieve appropriate pain management results. Generally, several exemplary cryoanalgesia procedures, such as those described above, may be repeated for the intercostal nerves located in each of the third through ninth intercostal spaces.

[0060] It can be difficult to place the ablation tip of conventional cryoprobes known in the art in the cardiac space. With the exemplary ablation tip 102, ablation of nerves in the thoracic space may be easily achieved by providing better contact to the nerve. Furthermore, fewer ablations may be required due to the size of the tip.

[0061] From the foregoing description, it will be apparent to those skilled in the art that, while the methods and apparatus described herein constitute exemplary embodiments of the present invention, the invention described herein is not limited to any precise embodiment and modifications may be made to such embodiments without departing from the scope of the invention as defined by the claims. It is further understood that the invention is defined by the claims and that any limitations or elements described in connection with the exemplary embodiments described herein should be incorporated into the interpretation of any claim element unless such limitations or elements are expressly recited. Similarly, it is understood that fulfilling each and every recognized advantage or objective of the invention as disclosed herein is not required to be within the scope of a claim. This is because the invention is defined by the claims and because inherent and / or unexpected advantages of the invention may exist despite the fact that they may not be explicitly described herein. [Explanation of symbols]

[0062] 100 Cryogenic probe, Cryoprobe 101 Distal ablation site 102 Ablation Tip 104 Long and thin shaft 105 Fluid drain pipe 106 Insulating Tube 107 spherical distal outer surface 108 Handle housing 110 Pistol Grip 112 connection bundles 113 Braided Sleeve 114 Service line 116 Discharge Line 118 Thermocouple lead wire 120 Quick Connect Adapter 130 Proximal Opening 132 bands 134 Adapter, lead-in adapter 136 Inlet hypotube, hypotube, fluid inlet pipe 138 Crimp ring, distal opening 140 Discharge adapter, adapter 141 ribbed male proximal end 142 Crimp Ring 143 Female distal end 144 frustum tapered 145 Distal Shoulder 146 Conical Compression Fitting 148 Nut 150 Helical screw 160 Thermocouple 170 Insulating tube 174 Spacer 174a, 174b, 174c, 174d spiral 175 proximal end 176 Flexible Cover 180 Proximal Shoulder 184 Distal Shoulder 190 Flexible covering material 192 Internal protrusion 193 Air Gap 194 Circumferential continuous cover 196 Distal end 198 Welds 200 internal cavity 202 Terminal 204 Distal point 206 Nozzle 208 Fluid Flow Elements 240 adapter 242 Stenosis 300 Cryogenic probe, Cryoprobe 303 Distal end 304 Malleable Shaft 310 Fluid discharge pipe, discharge pipe 312 Fluid intake pipes, intake pipes 320 Boiler 321 Gap 324 Nipple 328 central bore 329 External raised circumferential ring 330 Circumferential Lip 332 Proximal flange 334 Channel 335 Hypotube 336 Ablation Tip 340 Trench 342 O-ring 343 Raised Rib 344 Groove 350 Pressure relief valve 352 truncated cone plug 354 Spring 356 Enlarged section 358 Distal frustoconical end 359 Frustrated cone proximal end 400 inserts 410 Insulated Air Pocket 420 Cryogenic service pipe 430 Cryogenic discharge pipe 450 insert 460 Air Pocket 470 Cryogenic service pipe 480 Relatively low temperature discharge pipe 602 Intercostal nerve 604 Incisional intercostal space 606, 608 ribs 610 innermost intercostal muscle 612 Membranous part 614 Ganglia 700 nerves 702 axons 704 Endoneurium 706 Perineurium 708 Epineurium 710 Fiber bundle

Claims

1. 1. A cryogenic probe comprising: an elongate shaft at least partially housing or defining a fluid inlet conduit and a fluid outlet conduit, the elongate shaft including a distal ablation portion terminating at a closed distal end; a housing at least partially surrounding at least a portion of the proximal end of the elongate shaft and receiving or defining at least a portion of the fluid inlet tube and at least a portion of the fluid outlet tube; a boiler comprising one or more flow channels providing fluid communication from the fluid inlet tube to an interior of the distal ablation portion, and a central bore providing fluid communication from the interior of the distal ablation portion to the fluid outlet tube, the central bore being fluidically sealed to the interior of the fluid outlet tube; a valve extending into the boiler in fluid communication with the fluid outlet and downstream from the distal ablation portion, the valve configured to regulate fluid flow through at least a portion of the fluid outlet; Equipped with the valve includes a valve disc configured to engage a valve seat to form a seal between the valve seat and the valve disc; The valve disc is spring biased into engagement with the valve seat of the cryogenic probe.

2. The cryogenic probe of claim 1 , wherein the valve comprises a restriction fluidly interposed between the fluid discharge pipe and a central bore of the boiler.

3. 3. The cryogenic probe of claim 2, wherein a cross-sectional area for fluid flow of the constriction is less than about 70% of a cross-sectional area for fluid flow of a fluid exhaust conduit.

4. 3. The cryogenic probe of claim 2, wherein a cross-sectional area for fluid flow of the constriction is less than about 30% of a cross-sectional area for fluid flow of a fluid exhaust conduit.

5. 3. The cryogenic probe of claim 2, wherein a cross-sectional area for fluid flow of the constriction is less than about 15% of a cross-sectional area for fluid flow of a fluid exhaust conduit.

6. The cryogenic probe of claim 1 , wherein the valve comprises a pressure valve.

7. The cryogenic probe of claim 6 , wherein at least a portion of the spring is located within the distal ablation portion.

8. The cryogenic probe of claim 1 , wherein the distal ablation portion includes a spherical outer surface.

9. The cryogenic probe of claim 8 , wherein the spherical outer surface comprises a hemisphere.

10. 10. The cryogenic probe of claim 1, wherein the fluid inlet tube includes a fluid flow constriction before reaching a nozzle in the distal ablation section.

11. The cryogenic probe of claim 1 , wherein the elongate shaft can bend through an angle of more than 180 degrees without breaking.

12. The cryogenic probe of claim 1 , wherein an interior of the elongate shaft and an exterior of the fluid outlet tube define the fluid inlet tube.

13. 1. A cryogenic probe comprising: a malleable elongate shaft that at least partially houses or defines a fluid inlet conduit and a fluid outlet conduit; a flexible insulating tube surrounding the malleable elongate shaft along its longitudinal length and extending distally beyond the malleable elongate shaft; a housing at least partially surrounding at least a portion of the proximal end of the elongate shaft and receiving or defining at least a portion of the fluid inlet tube and at least a portion of the fluid outlet tube; a flow restricting element in fluid communication with the fluid outlet conduit, the flow restricting element regulating fluid flow through at least a portion of the fluid outlet conduit; a distal ablation portion including a closed distal end in fluid communication with the fluid inlet tube and the flow restricting element and in selective fluid communication with the fluid outlet tube, the distal ablation portion extending distally beyond the flexible insulating tube; a boiler comprising one or more flow channels providing fluid communication from the fluid inlet tube to an interior of the distal ablation portion, and a central bore providing fluid communication from the interior of the distal ablation portion to the fluid outlet tube, the central bore being fluidically sealed to the interior of the fluid outlet tube; Equipped with the flow restricting element comprises a valve extending into the boiler and downstream from the distal ablation portion, the valve comprising a valve disc configured to engage a valve seat to form a seal between the valve seat and the valve disc, the valve disc being spring biased into engagement with the valve seat; A cryogenic probe, wherein a portion of the distal ablation section is surrounded by the flexible insulating tube.

14. The cryogenic probe of claim 13 , wherein the flexible insulating tube includes at least one of a foam spacer and a spiral spacer.

15. The cryogenic probe of claim 14 , wherein at least one of the foam spacer and the spiral spacer terminates before reaching a distal end of the flexible insulating tube.

16. 14. The cryogenic probe of claim 13, wherein the flexible insulating tube is formed with a radial dimension that increases from distal to proximal adjacent a distal end of the flexible insulating tube.

17. 15. The cryogenic probe of claim 14, wherein the flexible insulating tube has a radial dimension at its distal end that is less than a radial dimension of at least one of the foam spacer and the helical spacer.

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