Two-Stage Cryocooler

Abstract

The cryoablation tool has a primary fluid circuit for cryogenically cooling or heating tissue surrounding a distal portion of the cryoablation tool. The primary fluid circuit has a primary-primary heat exchanger that facilitates regenerative heat exchange between a high-pressure stream of primary fluid and a low-pressure stream of primary fluid. The cryoablation tool has a secondary fluid circuit with a secondary-secondary heat exchanger that allows regenerative heat exchange between a high-pressure stream of secondary fluid and a low-pressure stream of secondary fluid. The secondary fluid circuit also has a primary-secondary heat exchanger that allows heat exchange between the high-pressure stream of primary fluid and the low-pressure stream of secondary fluid.

Description

[Technical Field]

[0001] The present disclosure relates to cryoprobes for use in cryoablation and systems for cryoablation. [Background technology]

[0002] In cryosurgery, surgeons may utilize one or more cryoprobes to ablate targeted areas within a patient's body by freezing and thawing tissue. In one example, a cryoprobes utilizes the Joule-Thomson effect to cool or heat the probe tip. In such cases, the expansion of the cryogenic fluid within the cryoprobes from a higher pressure to a lower pressure causes the tip of the instrument to cool to a temperature below that corresponding to cryoablation of the tissue adjacent to the tip. Heat transfer between the expanding cryogenic fluid and the outer wall of the cryoprobes creates a frozen area within the tissue surrounding the tip, which then undergoes cryoablation necrosis.

[0003] Some cryoprobes may be useful for ablating lesions in a person's lungs or other body passageways. In such cases, the cryoprobes may need to navigate tortuous and / or narrow passageways. Therefore, the cryoprobes' configuration may not be able to support cryogenic fluid pressurized to pressures typical for cryoablation (e.g., 3500 psi). Furthermore, delivering cryogenic fluid at pressures lower than typical delivery pressures for cryoablation (e.g., 3500 psi) may not provide sufficient cooling or may not produce a desired size frozen area within a desired time frame (e.g., a 35 mm frozen area in 10 minutes). Summary of the Invention

[0004] Advantageous aspects of the present disclosure provide a cryoablation tool with a two-stage cryocooler suitable for producing frozen lesions of suitable size for cryoablation. In a first aspect of the cryo-ablation tool, a cryo-ablation tool is provided, the cryo-ablation tool comprising a primary fluid circuit with a flow of a high-pressure stream of a primary fluid and a low-pressure stream of the primary fluid, the primary fluid circuit fluidly coupled to a distal portion of the cryo-ablation tool for cryogenically cooling or heating tissue surrounding the distal portion of the cryo-ablation tool, the primary fluid circuit comprising a primary-primary heat exchanger configured for regenerative heat exchange between the high-pressure stream of the primary fluid and the low-pressure stream of the primary fluid, the cryo-ablation tool comprising a secondary fluid circuit with a high-pressure region for the flow of the high-pressure stream of the secondary fluid and a low-pressure region for the flow of the low-pressure stream of the secondary fluid, the secondary fluid circuit comprising a secondary-secondary heat exchanger for regenerative heat exchange between the high-pressure stream of the secondary fluid and the low-pressure stream of the secondary fluid, the secondary-secondary heat exchanger terminating in a secondary-secondary outlet. The cryo-ablation tool includes a primary-secondary heat exchanger configured to perform regenerative heat exchange between a high-pressure stream of a primary fluid and a low-pressure stream of a secondary fluid, the primary-secondary heat exchanger including a primary-secondary inlet, the primary-secondary heat exchanger arranged such that the primary-secondary inlet is positioned downstream of the secondary-secondary outlet along a flow direction of the high-pressure stream of the secondary fluid, and the primary-secondary heat exchanger and the secondary-secondary heat exchanger are arranged such that the low-pressure stream of the secondary fluid exchanges heat with the primary fluid in the primary-secondary heat exchanger prior to exchanging heat with the high-pressure stream of the secondary fluid in the secondary-secondary heat exchanger.

[0005] According to an advantageous embodiment, the primary-to-primary heat exchanger, the secondary-to-secondary heat exchanger, and the primary-to-secondary heat exchanger each comprise a tube having an outer wall, the outer wall of the tube comprising an extension for increasing the surface area of ​​the outer wall.

[0006] In another embodiment, the primary-to-primary heat exchanger, the secondary-to-secondary heat exchanger, and the primary-to-secondary heat exchanger each comprise finned tubes. In other embodiments, the secondary-secondary heat exchanger and the primary-secondary heat exchanger each comprise a tube wound in a continuous series of wraps around a tubular mandrel. In one version, the secondary-secondary heat exchanger and the primary-secondary heat exchanger each are wound around the same tubular mandrel. The primary-primary heat exchanger may also comprise a tube wound in a continuous series of wraps around a tubular mandrel.

[0007] According to one aspect of the present disclosure, the primary-primary heat exchanger is fluidly coupled to the primary-secondary heat exchanger, whereby a high-pressure stream of the primary fluid flows through the primary-secondary heat exchanger prior to flowing through the primary-primary heat exchanger.

[0008] In another aspect, the fluid coupling between the primary-primary heat exchanger and the primary-secondary heat exchanger is configured to fluidly isolate the low pressure stream of the primary fluid from the primary-secondary heat exchanger.

[0009] In an additional aspect, the fluid coupling between the primary-primary heat exchanger and the primary-secondary heat exchanger is configured to fluidly isolate the low pressure stream of the primary fluid from the secondary-secondary heat exchanger.

[0010] In another aspect, the flow of the low pressure stream of primary fluid is isolated from the low pressure region of the secondary fluid circuit. In another aspect, the low pressure stream of the primary fluid may be arranged so as to be concentric with and physically separated from the low pressure stream of the secondary fluid.

[0011] In another embodiment, the high pressure region of the primary-secondary heat exchanger and the high pressure region of the secondary-secondary heat exchanger are isolated from the low pressure stream of the primary fluid. In another embodiment, both the secondary-secondary heat exchanger and the primary-secondary heat exchanger are isolated from the low pressure region of the primary fluid circuit.

[0012] According to one aspect, the primary fluid circuit comprises a first Joule-Thomson (JT) orifice positioned within the distal section of the cryo-ablation tool, the first JT orifice fluidly coupled to the primary-primary heat exchanger via a primary supply conduit to receive the high-pressure stream of primary fluid after it passes through the primary-primary heat exchanger, the first JT orifice configured to cryogenically expand the high-pressure stream of primary fluid into a low-pressure stream of primary fluid.

[0013] According to another aspect, the cryo-ablation tool further includes a primary return conduit through which the low pressure stream of the primary fluid passes, the first JT orifice being disposed in the primary return conduit.

[0014] In certain embodiments, the secondary fluid circuit comprises a second Joule-Thomson (JT) orifice fluidly coupled to the secondary-secondary heat exchanger via a secondary supply conduit to receive the high-pressure stream of secondary fluid after it passes through the secondary-secondary heat exchanger, the second JT orifice configured to cryogenically expand the high-pressure stream of secondary fluid into a low-pressure stream of secondary fluid.

[0015] In an additional aspect, the cryo-ablation tool further comprises a second return conduit through which the expanded secondary fluid can pass, and the secondary-secondary heat exchanger, the primary-secondary heat exchanger, and the second JT orifice are each disposed within the second return conduit.

[0016] According to one embodiment, the second return conduit is fluidly isolated from the low pressure stream of primary fluid in the primary fluid circuit. Further, the low pressure streams of the primary fluid and / or the secondary fluid may be configured to be discharged to atmosphere. The common discharge conduit may be configured to discharge the low pressure streams of the primary fluid and / or the secondary fluid (via the common discharge conduit) to atmosphere.

[0017] According to one aspect, a cryo-ablation tool includes a primary inlet conduit for a primary fluid circuit for delivering a primary fluid to the primary fluid circuit and a secondary inlet conduit for delivering a secondary fluid to the secondary fluid circuit, and a common exhaust conduit may be configured such that the primary fluid or the secondary fluid passes through the primary inlet conduit and the secondary inlet conduit before exhausting the primary fluid or the secondary fluid to atmosphere.

[0018] Another embodiment provides a cryo-ablation tool. The cryo-ablation tool includes a shaft having a proximal end and a distal end. The cryo-ablation tool includes a primary supply conduit configured to supply a primary fluid from a high-pressure cryogenic gas source to a distal end of the shaft, the primary supply conduit having a first Joule-Thomson orifice at its distal end configured to deliver the primary fluid to a first expansion chamber. The cryo-ablation tool includes a primary return conduit configured to convey the primary fluid from the distal expansion chamber. The cryo-ablation tool includes a secondary supply conduit configured to supply a secondary fluid to a second Joule-Thomson orifice, the second JT orifice configured to deliver the secondary fluid to a second expansion chamber. The cryo-ablation tool includes a secondary return conduit configured to convey the secondary fluid from the second expansion chamber. The primary supply conduit includes a primary-secondary heat exchange area and a primary-primary heat exchange area, the primary-primary heat exchange area being downstream of the primary-secondary heat exchange area. The secondary supply conduit includes a secondary-secondary heat exchange area upstream of the second JT orifice. The primary fluid return conduit is further configured for passing the primary cryogenic gas through the primary-primary heat exchange area countercurrent to the supply direction. The secondary return conduit is further configured for passing the secondary fluid antegrade through the primary-secondary heat exchange area and the secondary-secondary heat exchange area countercurrent to the supply direction.

[0019] In another aspect, the primary supply conduit is disposed in a first plurality of coils configured as a primary-secondary heat exchanger in the primary-secondary heat exchange area and in a second plurality of coils configured as a primary-primary heat exchanger in the primary-primary heat exchange area, and the secondary supply conduit is disposed in a third plurality of coils configured as a secondary-secondary heat exchanger in the secondary-secondary heat exchange area.

[0020] In another aspect, the primary return conduit is configured to pass the expanded primary fluid through a primary-primary heat exchanger, and the secondary return conduit is configured to pass the expanded secondary fluid through a primary-secondary heat exchanger prior to the expanded secondary fluid passing through the secondary-secondary heat exchanger.

[0021] In another aspect, the first plurality of coils comprises a first coil and a second coil, the first coil being disposed upstream of the second coil with respect to the flow direction of the primary fluid through the first coil, each coil of the second plurality of coils being positioned downstream of the second coil with respect to the flow direction of the primary fluid in the first coil, and each coil of the third plurality of coils being positioned upstream of the first coil with respect to the flow direction of the primary fluid in the first coil.

[0022] In another aspect, the secondary return conduit may be configured to pass the expanded secondary fluid forward through the entire length of the primary-secondary heat exchange area before the secondary fluid passes through the entire length of the secondary-secondary heat exchange area. The secondary return conduit may be configured to pass the expanded secondary fluid through each coil of the primary-secondary heat exchanger before it passes through the secondary-secondary heat exchanger.

[0023] In another embodiment, the primary-primary heat exchange zone is disposed within the primary return conduit and is further disposed distally of both the primary-secondary heat exchange zone and the secondary-secondary heat exchange zone. In another embodiment, the secondary-secondary heat exchange area is located proximal to the primary-secondary heat exchange area within the secondary return conduit.

[0024] In another aspect, the primary supply conduit comprises a tubular region wound in a continuous winding around a mandrel to form a primary-secondary heat exchanger. The secondary supply conduit may comprise a tubular region wound in a continuous winding around a mandrel to form a secondary-secondary heat exchanger. Further, the primary supply conduit may comprise a tubular region wound in a continuous winding around a mandrel to form a primary-secondary heat exchanger, and the secondary supply conduit may comprise a tubular region wound in a continuous winding around the same mandrel to form a secondary-secondary heat exchanger. The primary supply conduit may comprise a tubular region wound in a continuous winding around a mandrel to form a primary-primary heat exchanger.

[0025] In another aspect, the primary return conduit is configured so that the primary fluid passes through the primary-primary heat exchange zone but not through the primary-secondary or secondary-secondary heat exchange zones. In another embodiment, the primary-secondary heat exchange zone and the secondary-secondary heat exchange zone are each disposed within a secondary return conduit, which may then fluidly isolate the primary return conduit from the primary-secondary heat exchange zone and the secondary-secondary heat exchange zone.

[0026] In another embodiment, the primary return conduit includes a portion concentrically disposed around the secondary return conduit, which portion may be downstream of the primary-primary heat exchange zone with respect to the flow direction of the expanded primary fluid.

[0027] In another aspect, the primary return conduit is configured to discharge the primary fluid to atmosphere, and / or the secondary return conduit is configured to discharge the secondary fluid to atmosphere. [Brief explanation of the drawings]

[0028] [Figure 1] 1 is an exemplary schematic diagram of a cryoablation tool. [Figure 2] 2 is another exemplary schematic diagram of the cryo-ablation tool of FIG. 1 showing its internal details. [Figure 3] 2 is a perspective view of an exemplary precooler of the cryoablation tool of FIG. 1; [Figure 4] 2 is a perspective view of an exemplary primary-primary heat exchanger of the cryo-ablation tool of FIG. 1; [Figure 5] 2 is a thermodynamic diagram showing primary-primary, primary-secondary, and secondary-secondary heat exchangers associated with the cryoablation tool of FIG. 1. [Figure 6] 2 is an exemplary thermodynamic diagram illustrating the thermodynamic conditions associated with the primary-primary, primary-secondary, and secondary-secondary heat exchangers shown in FIG. 1; DETAILED DESCRIPTION OF THE INVENTION

[0029] FIG. 1 shows a schematic diagram of a cryoablation tool 100 according to one embodiment. According to some embodiments, the cryoablation tool 100 may include a catheter 102. Advantageously, the catheter 102 may be inserted into a working channel of a bronchoscope and therefore may be generally flexible. The cryoablation tool 100 may include a distal section 104 and a proximal section 106. The distal section 104 may terminate in a distal working tip 108. In some instances, the distal working tip 108 may be required to pierce tissue and therefore may be configured as a rigid tip. Alternatively, the distal working tip 108 may not be a rigid tip.

[0030] 1 and 2, the cryo-ablation tool 100 includes a primary fluid circuit 110 (shown by a solid line). The primary fluid circuit 110 may be associated with a primary fluid. The primary fluid circuit 110 may be in fluid communication with the distal section 104 of the cryo-ablation tool 100. The primary fluid may cool (e.g., cryogenically) or heat tissue surrounding the distal portion of the cryo-ablation tool 100. The primary fluid circuit 110 may include a primary supply conduit 112 for carrying a high-pressure stream of the primary fluid. The primary fluid circuit 110 may also include a primary return conduit 114 for carrying a low-pressure stream of the primary fluid.

[0031] The primary fluid circuit 110 may also include a primary-primary heat exchanger 120 configured to exchange heat (e.g., regenerative heat) between a high-pressure stream of primary fluid and a low-pressure stream of primary fluid. The primary-primary heat exchanger 120 includes a primary-primary inlet 122 and a primary-primary outlet 124. The primary-primary inlet 122 may be fluidly coupled to the primary supply conduit 112 that receives the high-pressure stream of primary fluid. The primary-primary outlet 124 may be fluidly coupled to a primary conduit 128 (e.g., a primary capillary) that delivers the primary fluid to the distal working tip 108.

[0032] Advantageously, a high-pressure stream of primary fluid (from the primary supply conduit 112) may flow through the first cryocooler 130. In such an embodiment, the high-pressure stream of primary fluid may be upstream (with respect to direction 166) of the first cryocooler 130. Additionally, a low-pressure stream of primary fluid may be downstream (with respect to direction 166) of the first cryocooler 130. As shown in FIG. 2 , the primary supply conduit 128 (e.g., a primary capillary tube) includes a first Joule-Thomson (“JT”) orifice 130 at an end of the primary supply conduit downstream of the primary-primary outlet. Thus, the first cryocooler 130 may be an open-loop cryocooler, such as the first JT orifice 130.

[0033] In such an embodiment, the high-pressure stream of primary fluid may expand within a first expansion chamber 132 at or downstream of the first JT orifice 130. The first expansion chamber 132 may be in fluid communication with a primary return conduit 114 for conveying (the expanded low-pressure stream of) the primary fluid from the expansion chamber towards the proximal section 106 (e.g., to exhaust to atmosphere if the primary fluid circuit 110 is an open circuit, or to return to the primary fluid source if the primary fluid circuit 110 is a closed circuit).

[0034] The primary fluid, in embodiments, can be a cooling fluid (e.g., nitrogen, air, argon, krypton, xenon, NO, CO, CF). In such cases, the high-pressure stream of primary fluid can be at a pressure that, as a result of expansion through the first JT orifice 130, can result in the primary fluid being cooled to a temperature for cryoablation of tissue surrounding the distal working fluid. In certain aspects, the pressure of the high-pressure stream of primary fluid upstream of the first JT orifice 130 can be from about 1000 psi to about 2000 psi (e.g., about 1800 psi). Thus, in one embodiment where the primary fluid is a cooling fluid, the temperature of the primary fluid after expansion from the first JT orifice 130 can be less than about 190 Kelvin.

[0035] Alternatively, the primary fluid can be a heated fluid (e.g., helium, hydrogen). In such a case, the high-pressure stream of primary fluid can be at a pressure that can increase the temperature of the primary fluid as a result of expansion through the first JT orifice 130 and correspondingly heat the tissue surrounding the distal working fluid. Such an embodiment can be useful for melting frozen tissue.

[0036] In some embodiments, the primary fluid circuit 110 may be arranged such that the flow of the high-pressure stream of primary fluid is countercurrent to the flow of the low-pressure stream of primary fluid in at least certain portions of the primary fluid circuit 110. For example, as previously described, in one embodiment, the high-pressure stream of primary fluid passes through the first JT orifice 130. As shown in FIGS. 1 and 2 , the flow direction of the primary fluid reverses as it expands through the first JT orifice 130, thereby resulting in a countercurrent flow between the high-pressure stream of primary fluid and the low-pressure stream of primary fluid near the first JT orifice 130. Furthermore, because the high-pressure stream of primary fluid and the low-pressure stream of primary fluid may be countercurrent near the primary-primary inlet 122 of the primary-primary heat exchanger 120, the primary return conduit is configured to pass the primary cryogenic gas through the primary-primary heat exchange area in a countercurrent flow to the feed direction.

[0037] According to an advantageous aspect, the counterflow arrangement of the high-pressure stream of primary fluid and the low-pressure stream of primary fluid may enable regenerative heat exchange therebetween. In examples where the primary fluid circuit 110 conveys a cooling gas, the regenerative heat exchange may include heat removal from the high-pressure stream of primary fluid, such that the primary fluid is pre-cooled before expanding through the first JT orifice 130. In examples where the primary fluid circuit 110 conveys a heating gas, the regenerative heat exchange may include heating from the high-pressure stream of primary fluid, such that the primary fluid is pre-heated before expanding through the first JT orifice 130. The regenerative heat exchange may advantageously achieve a desired temperature at the distal working tip 108.

[0038] As mentioned above, in some embodiments, the cryoablation tool 100 may include a catheter 102 that is sufficiently flexible to be manipulated within a bronchoscope. In such embodiments, the catheter 102 may be fabricated from a material that may not be able to withstand typical pressures at which a primary fluid may be supplied in other cryoablation tools (e.g., greater than about 2000 psi, e.g., about 3500 psi). In such situations, it may be advantageous to supply the primary fluid at a pressure lower than typical pressures for cryoablation. The primary fluid may be supplied at less than about 2000 psi, e.g., about 1800 psi. However, to facilitate reaching a temperature suitable for cryoablation at the distal working tip 108, a secondary fluid circuit 140 may be provided to pre-cool the primary fluid, as described further below.

[0039] 1 and 2, the cryo-ablation tool 100 includes a secondary fluid circuit 140 (shown in dotted lines). The secondary fluid circuit 140 may include a secondary supply conduit 142 that carries a high-pressure stream of secondary fluid. The secondary supply conduit is configured to supply the secondary fluid to a second cryocooler (JT orifice). The second cryocooler may be configured to deliver the secondary fluid to a second expansion chamber. The secondary fluid circuit 140 may also include a secondary return conduit 144 that carries a low-pressure stream of secondary fluid. The secondary return conduit may be configured to carry the secondary fluid away from the second expansion chamber.

[0040] In advantageous aspects, the secondary fluid circuit 140 can facilitate heat exchange between the primary fluid and the secondary fluid. In some such advantageous aspects, the secondary fluid circuit 140 can be used to pre-cool a high-pressure stream of primary fluid in embodiments in which the primary fluid is cooled upon expansion to cryoablate tissue surrounding the distal working tip 108. In such advantageous aspects, and referring to FIG. 2 , the secondary fluid circuit 140 can also include a primary-secondary heat exchanger 150. In certain aspects, the primary-secondary heat exchanger 150 can facilitate heat exchange between a high-pressure stream of primary fluid and a low-pressure stream of secondary fluid. The primary-secondary heat exchanger 150 can include a primary-secondary inlet 152 and a primary-secondary outlet 154.

[0041] 2, the secondary fluid circuit 140 may include a secondary-secondary heat exchanger 160, which allows for heat exchange (e.g., regenerative heat exchange) between a high-pressure stream of the secondary fluid and a low-pressure stream of the secondary fluid. In some advantageous aspects, the secondary fluid may also be a cooling fluid. In such embodiments, heat may be removed from the high-pressure stream of the secondary fluid by regenerative heat exchange between the high-pressure stream of the secondary fluid and the low-pressure stream of the secondary fluid. Thus, the secondary-secondary heat exchanger 160 may facilitate pre-cooling the high-pressure stream of the secondary fluid.

[0042] 2 , secondary-secondary heat exchanger 160 may include a secondary-secondary inlet 162 and a secondary-secondary outlet 164. Secondary-secondary inlet 162 may be upstream of secondary-secondary outlet 164 along direction 166. Further, secondary-secondary inlet 162 may be upstream of each of primary-primary inlet 122 and primary-primary outlet 124. In addition, secondary-secondary outlet 164 may also be upstream of each of primary-primary inlet 122 and primary-primary outlet 124.

[0043] The secondary-secondary inlet 162 may be fluidly coupled to the secondary supply conduit 142 that receives a high-pressure stream of the secondary fluid. The secondary-secondary outlet 164 may be fluidly coupled to a secondary conduit 168 (e.g., a secondary capillary 168) that receives the secondary fluid from the secondary-secondary outlet 164. The secondary fluid may thus pass through the secondary-secondary heat exchanger 160 by entering the secondary-secondary inlet 162 and exiting the secondary-secondary outlet 164.

[0044] Advantageously, the high-pressure stream of secondary fluid exiting the secondary-secondary outlet 164 may enter a secondary capillary 168 and flow through a second cryocooler 170. In such an embodiment, the high-pressure stream of secondary fluid may be upstream (with respect to direction 166) of the second cryocooler 170. Additionally, a low-pressure stream of secondary fluid may be downstream (with respect to direction 166) of the second cryocooler 170. In the embodiment shown in FIG. 2 , a second Joule-Thomson (“JT”) orifice 170 is located at the end of the secondary conduit 168 (e.g., secondary capillary 168) downstream of the secondary-secondary outlet 164. Thus, the second cryocooler 170 may be a second JT orifice 170. In such an embodiment, the high-pressure stream of secondary fluid may expand in a second expansion chamber 172 at or downstream of the second JT orifice 170. The second expansion chamber 172 may be in fluid communication with a secondary return conduit 144 for conveying the expanded low-pressure stream of secondary fluid (e.g., to exhaust to atmosphere if the secondary fluid circuit 140 is an open circuit, or to return to a secondary fluid source if the secondary fluid circuit 140 is a closed circuit).

[0045] In some embodiments, the secondary fluid circuit 140 can be arranged such that the flow of the high-pressure stream of secondary fluid is countercurrent to the flow of the low-pressure stream of secondary fluid across at least a portion of the secondary fluid circuit 140. For example, as previously described, in one embodiment, the high-pressure stream of secondary fluid passes through the second JT orifice 170. As shown in FIGS. 1 and 2 , the flow direction of the secondary fluid reverses upon expansion through the second JT orifice 170, thereby resulting in a countercurrent flow between the high-pressure stream of secondary fluid and the low-pressure stream of secondary fluid near the second JT orifice 170. Furthermore, the high-pressure stream of secondary fluid and the low-pressure stream of secondary fluid can be countercurrent flow between the high-pressure stream of secondary fluid and the low-pressure stream of secondary fluid near the secondary-secondary inlet 162 of the secondary-secondary heat exchanger 160. Thus, in an advantageous embodiment, the secondary return conduit 144 can be configured to pass the secondary fluid antegrade through the primary-secondary heat exchange area 182 and the secondary-secondary heat exchange area 212, respectively, in a countercurrent flow relative to the feed direction.

[0046] 2, primary-secondary heat exchanger 150 may be antegradely positioned relative to secondary-secondary heat exchanger 160. Such a antegrade positioning may facilitate a low-pressure stream of secondary fluid exchanging heat with the primary fluid in primary-secondary heat exchanger 150 before exchanging heat with a high-pressure stream of secondary fluid in secondary-secondary heat exchanger 160. In such a antegrade positioning, primary-secondary inlet 152 may be positioned downstream (with respect to direction 166) of secondary-secondary outlet 164. Furthermore, primary-secondary outlet 154 may also be positioned downstream (with respect to direction 166) of secondary-secondary outlet 164.

[0047] In certain aspects, the expanded low-pressure stream of secondary fluid may first exchange heat with the high-pressure stream of primary fluid. For example, in one embodiment (described further below), the secondary stream may flow through primary-secondary heat exchanger 150 before flowing through secondary-secondary heat exchanger 160. In this manner, the secondary return conduit may be configured to pass the expanded secondary fluid antegrade through the entire primary-secondary heat exchange zone (i.e., each coil of the primary-secondary heat exchange coil) before the secondary fluid passes through the secondary-secondary heat exchange coil.

[0048] 1 and 2, in certain embodiments in which the cryo-ablation tool 100 includes a flexible catheter 102, the secondary-secondary heat exchanger 160 and the primary-secondary heat exchanger 150 may each be positioned outside the catheter 102, for example, near the proximal section 106 of the cryo-ablation tool 100. Additionally, the primary-primary heat exchanger 120 may be positioned within the flexible catheter 102. This arrangement may further facilitate providing the secondary fluid at a higher pressure than the high-pressure stream of primary fluid.

[0049] As mentioned above, in embodiments in which the cryoablation tool 100 includes a flexible catheter 102, it may be advantageous to supply the primary fluid at a pressure lower than typical cryoablation pressures. For example, the primary fluid may be supplied at a pressure lower than approximately 2000 psi, e.g., approximately 1800 psi, which may not provide sufficient cooling for cryoablation without the secondary fluid circuit 140 if the primary fluid is a cooling fluid. However, passing the primary fluid through the primary-secondary heat exchanger 150 can enable regenerative heat exchange between the primary and secondary fluids to pre-cool the primary fluid, achieving temperatures suitable for cryoablation even when the primary fluid is supplied at a pressure lower than typical cryoablation supply pressures.

[0050] Advantageously, the high-pressure stream of secondary fluid may be at a higher pressure than the high-pressure stream of primary fluid. The secondary fluid may be supplied at a pressure greater than about 2000 psi (e.g., 3500 psi). When the secondary fluid passes through the second cryocooler 170 (e.g., the second JT orifice 170), if the secondary fluid is a cooling fluid, it may reach a cryogenic temperature (e.g., less than about 190 Kelvin). The expanded low-pressure stream of secondary fluid may remove heat from the high-pressure stream of primary fluid in the primary-secondary heat exchanger 150, thereby precooling the primary fluid before it passes through the primary-primary heat exchanger 120.

[0051] Figure 3 shows a perspective view of a primary-to-secondary and secondary-to-secondary heat exchanger according to one embodiment. Figure 4 shows a perspective view of a primary-to-primary heat exchanger 120 according to one embodiment. 3 , the primary supply conduit 112 may be a metal tube and may be fluidly coupled to a primary-secondary heat exchanger 150. The primary-secondary heat exchanger 150 may include a plurality of first heat exchange coils 180 between a primary-secondary inlet 152 and a primary-secondary outlet 154.

[0052] 2 and 3 , the plurality of first heat exchanger coils may define a first heat exchange area 182. The plurality of coils may include a first coil 184 and a second coil 186. The first coil 184 may be upstream of the second coil 186 (with respect to the direction 166). The first coil 184 may be closer to the primary-secondary inlet 152 than the primary-secondary outlet 154. The second coil 186 may be closer to the primary-secondary outlet 154 than the primary-secondary inlet 152. The primary-secondary heat exchange area may extend between the first coil 184 and the second coil 186 and / or between the primary-secondary inlet 152 and the primary-secondary outlet 154.

[0053] According to certain embodiments, the plurality of first heat exchanger coils 180 (primary-secondary heat exchangers) may be formed from metal tubing (tubular regions of the plurality of supply conduits) wound around a mandrel 188. The metal tubing may include an outer wall. The outer wall may include extensions to increase the surface area of ​​the outer wall. For example, in one embodiment, the first heat exchange coils 180 may include fins 190 to enhance heat exchange in the first heat exchange region 182. The primary fluid may flow through the interior of the metal tube. With reference to FIGS. 2 and 3 , an expanded, low-pressure stream of the primary fluid may flow through a finned portion of the metal tube. The fins 190 may facilitate heat exchange between the high-pressure stream of the primary fluid flowing inside the metal tube and the low-pressure stream of the secondary fluid flowing outside the finned portion of the metal tube.

[0054] Referring to Figure 2, the primary fluid may exchange heat with the secondary fluid in the primary-secondary exchanger before continuing to the primary-primary heat exchanger 120. Referring to Figure 4, the primary-primary heat exchanger 120 may include a plurality of second heat exchange coils 200. Referring to Figures 2 and 4, the primary-secondary heat exchanger 150 and the primary-primary heat exchanger 120 may be in a antegrade arrangement. As such, each coil of the plurality of second heat exchange coils 200 may be downstream (with respect to direction 166) of a first coil 184 of the plurality of first heat exchange coils 180.

[0055] According to certain embodiments, the plurality of second heat exchange coils 200 (primary-primary heat exchangers) may be formed from a metal tube (a tubular region of a primary supply conduit) wound around a mandrel (e.g., similar to mandrel 188 in FIG. 3 ). Referring to FIG. 4 , the metal tube may include an outer wall. The outer wall may include extensions to increase the surface area of ​​the outer wall. For example, in one embodiment, the second heat exchange coil 200 may include fins 202 to enhance heat exchange in the second heat exchange region 204. The primary fluid may flow through the interior of the metal tube. Referring to FIGS. 2 and 3 , an expanded low-pressure stream of the primary fluid may flow over a finned portion of the metal tube. The fins 202 may facilitate heat exchange between the high-pressure stream of primary fluid flowing inside the metal tube and the low-pressure stream of primary fluid flowing outside the finned portion of the metal tube.

[0056] The primary fluid exiting the primary-primary heat exchanger 120 may enter a primary conduit 128 (e.g., a primary capillary) and flow toward a first cryocooler 130, as previously described. The first cryocooler 130 may, in some examples, be a first JT orifice 130. The primary fluid may be expanded in a primary expansion chamber for expanding the primary fluid, located downstream of the primary-primary heat exchange region near the distal working tip 108. The expanded, low-pressure primary fluid may be conveyed by a primary return conduit 114.

[0057] 2 and 4, the second heat exchange area (primary-primary heat exchange area) 204 may be disposed within the primary return conduit 114. In this manner, the primary return conduit 114 may generally surround the plurality of second heat exchange coils (second heat exchange area) 200. The primary return conduit 114 may thus allow the expanded, low-pressure primary fluid to pass through the second heat exchange area, thereby exchanging heat (e.g., regenerative heat) with the high-pressure stream of primary fluid flowing inside the metal tubes of the plurality of second heat exchange coils 200 (primary-primary heat exchangers).

[0058] Advantageously, as shown in FIG. 2 , the primary return conduit 114 is configured so that the primary fluid passes through the primary-primary heat exchange area 204 but not through the primary-secondary heat exchange area 182 or the secondary-secondary heat exchange area 212. Advantageously, the primary-secondary heat exchange area 182 and the secondary-secondary heat exchange area 212 are each disposed within the secondary return conduit 144, which fluidly isolates the expanded primary fluid flowing within the primary return conduit 114 from the primary-secondary heat exchange area 182 and the secondary-secondary heat exchange area 212. Advantageously, the primary return conduit 114 may include a portion that is concentrically disposed around the secondary return conduit 144. This allows the flow of the primary fluid to pass around the secondary return conduit 144 without passing through either the primary-secondary heat exchange area 182 or the secondary-secondary heat exchange area 212 disposed within the secondary return conduit 144. Advantageously, this section is downstream of the primary-primary heat exchange area 204 with respect to the flow of the primary fluid.

[0059] 2 and 3, the secondary supply conduit 142 may supply the secondary fluid to the secondary-secondary heat exchanger 160. The secondary-secondary heat exchanger 160 may include a plurality of tertiary heat exchange coils 210, which may define a secondary-secondary heat exchange area 212.

[0060] According to the particular embodiment of the figures, the plurality of third heat exchanger coils (secondary-secondary heat exchangers) may be formed from metal tubing (the tubular portion of the second supply conduit) wound around a mandrel. In some cases, the mandrel around which the third heat exchanger coils may be wound may be the same as, or alternatively have the same extent as, the mandrel 188 around which the first heat exchanger coils may be wound. Alternatively, the mandrel around which the third heat exchanger coils may be wound may be separate from the mandrel 188 around which the first heat exchanger coils may be wound.

[0061] Referring to FIG. 3 , the metal tube of the third heat exchange coil 210 may include an outer wall. The outer wall may include extensions to increase the surface area of ​​the outer wall. For example, in one embodiment, the third heat exchange coil 210 may include fins 214 to enhance heat exchange in the third heat exchange zone. The secondary fluid entering the secondary-secondary inlet 162 may flow inside the metal tube. Referring to FIGS. 2 and 3 , the expanded low-pressure stream of secondary fluid (exiting the second JT orifice 170) may flow over the finned portion of the metal tube. The fins 214 may facilitate heat exchange between the high-pressure stream of secondary fluid flowing inside the metal tube and the low-pressure stream of secondary fluid flowing outside the finned portion of the metal tube.

[0062] As previously mentioned, the low-pressure stream of secondary fluid may first exchange heat with the high-pressure stream of primary fluid in primary-secondary heat exchanger 150 and then with the high-pressure stream of secondary fluid in secondary-secondary heat exchanger 160. Accordingly, each coil of the plurality of third heat exchange coils 210 may be positioned upstream of a first coil 184 of the plurality of first heat exchange coils 180. Thus, with respect to the flow direction within secondary return conduit 144, secondary-secondary heat exchange area 212 and primary-secondary heat exchange area 182 may be disposed within secondary return conduit 144, and secondary-secondary heat exchange area 212 may be disposed downstream of primary-secondary heat exchange area 182.

[0063] The secondary fluid exiting the secondary-secondary heat exchanger 160 may enter a secondary conduit 168 (e.g., a secondary capillary tube 168) and flow toward a second cryocooler 170, as previously described. The second cryocooler 170 may, in some instances, be a second JT orifice 170. The secondary fluid may expand in a secondary expansion chamber positioned downstream of the primary-secondary heat exchange area. Upon expansion, the low-pressure stream of the secondary fluid flows over the finned portion of the primary-secondary heat exchange area for regenerative heat exchange with the high-pressure stream of the primary fluid. The low-pressure stream of the secondary fluid then flows over the finned portion of the secondary-secondary heat exchange area 212 for regenerative heat exchange with the high-pressure stream of the secondary fluid.

[0064] Advantageously, in instances where the primary and secondary fluids are each cooling fluids, the secondary fluid may reach a cryogenic temperature after flowing through the second cryocooler 170. As the secondary fluid flows over the finned tubes of the first heat exchange coil 180, the temperature of the secondary fluid may gradually increase. The secondary fluid flowing over the finned tubes of the third heat exchange coil 210 (e.g., near the secondary-secondary outlet 164) may therefore be at a higher temperature than the secondary fluid flowing immediately proximal to the primary-secondary outlet 154. In this way, by first flowing the secondary fluid over the primary-secondary heat exchanger 150, the coldest secondary fluid may exchange heat with the primary fluid, thereby enabling optimal heat removal from the primary fluid for its effective pre-cooling.

[0065] 2 , the secondary return conduit 144 may generally surround the plurality of third heat exchange coils 210. Advantageously, the secondary return conduit 144 may be fluidly isolated from the primary return conduit 114 to fluidly isolate the low-pressure stream of primary fluid from the low-pressure stream of secondary fluid. In this manner, the low-pressure stream of primary fluid may not flow through the secondary-secondary heat exchanger 160 or the primary-secondary heat exchanger 150.

[0066] According to an advantageous embodiment, the primary-secondary heat exchange zone, the primary-primary heat exchange zone, and the secondary-secondary heat exchange zone 212 may be separated from one another longitudinally (e.g., along direction 166). Referring to FIGS. 2-4, each coil of the secondary-secondary heat exchange zone 212 may be upstream of the primary-secondary heat exchange zone and the primary-primary heat exchange zone. Furthermore, the distance between adjacent coils of the plurality of third heat exchange coils 210 may be substantially shorter than the distance between a coil in the secondary-secondary heat exchange zone 212 and a coil in the primary-secondary heat exchange zone or a coil in the primary-primary heat exchange zone.

[0067] 2-4, each coil of the plurality of third heat exchange coils 210 (forming the secondary-secondary heat exchanger 160) may be upstream (with respect to direction 166) of each of the primary-secondary inlet 152 and the primary-primary inlet 122. Additionally, each coil of the plurality of first coils (forming the primary-secondary heat exchanger 150) may be upstream (with respect to direction 166) of the primary-primary inlet 122.

[0068] Arrangements such as those disclosed above can facilitate effective regenerative heat exchange, as previously mentioned, thereby enabling desired cryoablation (or melting) characteristics at the distal working tip 108. [Example]

[0069] 5 and 6 show a thermodynamic diagram and a thermodynamic property diagram for illustrating an example of a two-stage cryocooler. According to this example, the primary fluid may be argon. The secondary fluid may also be argon. Referring to FIG. 5, the primary fluid circuit 110 is shown in solid lines and the secondary fluid circuit 140 is shown in dotted lines.

[0070] 5 and 6, the secondary fluid is at thermodynamic state 1 at secondary-secondary inlet 162 as the secondary fluid enters secondary-secondary heat exchanger 160. The secondary fluid is at thermodynamic state 2 at secondary-secondary outlet 164. The secondary fluid expands to reach thermodynamic state 3. The secondary fluid at thermodynamic state 3 exchanges heat in primary-secondary heat exchanger 150. The secondary fluid is at thermodynamic state 4 after heat exchange in primary-secondary heat exchanger 150. The secondary fluid at thermodynamic state 4 flows through secondary-secondary heat exchanger 160 and reaches thermodynamic state 5 as the secondary fluid passes through secondary-secondary heat exchanger 160 after heat exchange with the secondary fluid that entered secondary-secondary heat exchanger 160 at thermodynamic state 1.

[0071] 5 and 6, the primary fluid is at thermodynamic state 6 at primary-secondary inlet 152 when the primary fluid enters primary-secondary heat exchanger 150. The primary fluid is at thermodynamic state 7 at primary-secondary outlet 154. The primary fluid enters primary-primary inlet 122 at thermodynamic state 7 and exits primary-primary outlet 124 at thermodynamic state 8. The primary fluid expands and reaches thermodynamic state 9. The primary fluid at thermodynamic state 9 exchanges heat with tissue. After exchanging heat with tissue, the primary fluid reaches thermodynamic state 10. The primary fluid at thermodynamic state 10 flows through primary-primary heat exchanger 120 and reaches thermodynamic state 11 after exchanging heat with primary fluid entering secondary-secondary heat exchanger 160 at thermodynamic state 7.

[0072] In the examples of FIGS. 5 and 6 , each of the primary fluid and the secondary fluid may be a cooling fluid. Thus, cooling occurs as a result of the expansion of the primary fluid between states 8 and 9 and the expansion of the secondary fluid between states 2 and 3, respectively. As can be seen from FIG. 6 , the primary fluid entering primary-secondary heat exchanger 150 at thermodynamic state 6 may be at a lower pressure than the secondary fluid entering secondary-secondary heat exchanger 160 at thermodynamic state 1. However, the temperature of the primary fluid after expansion to thermodynamic state 9 may be lower than the temperature of the secondary fluid after expansion to thermodynamic state 3. Thus, even with the primary fluid provided at a lower pressure, two-stage cryocooling may result in low temperatures suitable for cryoablation (e.g., below −83.15° C. (190 K), e.g., about −153.15° C. (120 K)).

Claims

1. 1. A cryoablation tool comprising: the cryo-ablation tool comprising a primary fluid circuit, the primary fluid circuit comprising a high pressure region for flow of a high pressure stream of a primary fluid and a low pressure region for flow of a low pressure stream of the primary fluid; the primary fluid circuit is fluidly coupled to a distal portion of the cryoablation tool for cryogenically cooling or heating tissue surrounding the distal portion of the cryoablation tool; the primary fluid circuit comprising a primary-primary heat exchanger configured to provide regenerative heat exchange between the high-pressure stream of the primary fluid and the low-pressure stream of the primary fluid; the cryo-ablation tool includes a secondary fluid circuit, the secondary fluid circuit including a high pressure region for flow of a high pressure stream of a secondary fluid and a low pressure region for flow of a low pressure stream of the secondary fluid; the secondary fluid circuit includes a secondary-secondary heat exchanger configured to provide regenerative heat exchange between the high-pressure stream of the secondary fluid and the low-pressure stream of the secondary fluid; the secondary-secondary heat exchanger terminating in a secondary-secondary outlet for a high pressure stream of secondary fluid located at a downstream end of the secondary-secondary heat exchanger; the cryo-ablation tool includes a primary-secondary heat exchanger configured to provide regenerative heat exchange between the high-pressure stream of the primary fluid and the low-pressure stream of the secondary fluid; the primary-secondary heat exchanger includes a primary-secondary inlet for a high-pressure stream of a primary fluid located at an upstream end of the primary-secondary heat exchanger; the primary-secondary heat exchanger is positioned such that the primary-secondary inlet is located downstream of the secondary-secondary outlet along a flow direction of the high-pressure stream of the secondary fluid; The primary-secondary heat exchanger is disposed in the cryoablation tool proximal to the primary-primary heat exchanger and distal to the secondary-secondary heat exchanger. Cryoablation tools.

2. 2. The cryo-ablation tool of claim 1, wherein the primary-secondary heat exchanger and the secondary-secondary heat exchanger are arranged such that the low pressure stream of the secondary fluid exchanges heat with the primary fluid in the primary-secondary heat exchanger prior to exchanging heat with the high pressure stream of the secondary fluid in the secondary-secondary heat exchanger.

3. 3. The cryoablation tool of claim 1, wherein the primary-to-primary heat exchanger, the secondary-to-secondary heat exchanger, and the primary-to-secondary heat exchanger each comprise a tube having an outer wall, the outer wall of the tube comprising fins to increase a surface area of ​​the outer wall.

4. 4. The cryoablation tool of claim 1, wherein the secondary-secondary heat exchanger and the primary-secondary heat exchanger each comprise a tube wound in a continuous winding around a tubular mandrel.

5. 5. The cryoablation tool of claim 1, wherein the primary-primary heat exchanger is fluidly coupled to the primary-secondary heat exchanger such that the high-pressure stream of the primary fluid flows through the primary-secondary heat exchanger prior to flowing through the primary-primary heat exchanger.

6. 6. The cryo-ablation tool of claim 5, wherein the fluid coupling between the primary-to-primary heat exchanger and the primary-to-secondary heat exchanger is configured to fluidly isolate the low-pressure stream of the primary fluid from the primary-to-secondary heat exchanger.

7. 7. The cryo-ablation tool of claim 5 or 6, wherein the fluid coupling between the primary-to-primary heat exchanger and the primary-to-secondary heat exchanger is configured to fluidly isolate the low-pressure stream of the primary fluid from the secondary-to-secondary heat exchanger.

8. A cryo-ablation tool according to any preceding claim, wherein the flow of the low pressure stream of the primary fluid is isolated from the low pressure region of the secondary fluid circuit.

9. 9. The cryoablation tool of claim 1, further comprising a flexible catheter, wherein the secondary-secondary heat exchanger and the primary-secondary heat exchanger are disposed outside the flexible catheter, and the primary-primary heat exchanger is disposed inside the flexible catheter.

10. the primary fluid circuit includes a first Joule-Thomson (JT) orifice positioned in a distal section of the cryo-ablation tool; the first JT orifice is fluidly coupled to the primary-to-primary heat exchanger via a primary supply conduit to receive the high-pressure stream of the primary fluid after it passes through the primary-to-primary heat exchanger; the first JT orifice is configured to cryogenically expand the high-pressure stream of the primary fluid into the low-pressure stream of the primary fluid. A cryoablation tool according to any one of claims 1 to 9.

11. 1. A cryoablation tool comprising: The cryoablation tool comprises a shaft having a proximal end and a distal end; the cryo-ablation tool comprising a primary supply conduit configured to supply a primary fluid from a high-pressure cryogenic gas source to a distal end of the shaft, the primary supply conduit comprising a first Joule-Thomson (JT) orifice configured to deliver the primary fluid to a first expansion chamber; the cryo-ablation tool comprising a primary return conduit configured to convey the primary fluid away from the first expansion chamber; the cryo-ablation tool comprising a secondary supply conduit configured to supply a secondary fluid to a second JT orifice configured to deliver the secondary fluid to a second expansion chamber; the cryo-ablation tool comprising a secondary return conduit configured to convey the secondary fluid away from the second expansion chamber; the primary supply conduit comprises a primary-secondary heat exchange area and a primary-primary heat exchange area, the primary-primary heat exchange area being downstream of the primary-secondary heat exchange area; the secondary supply conduit comprises a secondary-secondary heat exchange area upstream of the second JT orifice; the primary-secondary heat exchange region is disposed within the cryo-ablation tool proximal to the primary-primary heat exchange region and distal to the secondary-secondary heat exchange region; the primary return conduit is further configured to pass the primary fluid through the primary-primary heat exchange area in countercurrent to a feed direction; The cryoablation tool, wherein the secondary return conduit is further configured to pass the secondary fluid through the primary-secondary heat exchange area and the secondary-secondary heat exchange area antegrade and countercurrent to the supply direction.

12. 12. The cryo-ablation tool of claim 11, wherein the secondary return conduit is configured to pass the expanded secondary fluid antegrade through the entire length of the primary-secondary heat exchange region before the secondary fluid passes through the entire length of the secondary-secondary heat exchange region.

13. 13. The cryoablation tool of claim 11 or 12, wherein the secondary-secondary heat exchange area and the primary-secondary heat exchange area are disposed in the secondary return conduit, and the secondary-secondary heat exchange area is disposed downstream of the primary-secondary heat exchange area with respect to a flow direction within the secondary return conduit.

14. 14. A cryoablation tool according to any one of claims 11 to 13, wherein the primary supply conduit comprises a tubular region wound in a continuous turn around a mandrel to form the primary-secondary heat exchanger, and the secondary supply conduit comprises a tubular region wound in a continuous turn around the same mandrel to form the secondary-secondary heat exchanger.

15. 15. The cryoablation tool of claim 11, wherein the primary return conduit is configured such that the primary fluid passes through the primary-primary heat exchange area but not through the primary-secondary heat exchange area or the secondary-secondary heat exchange area.

16. 16. The cryoablation tool of claim 11, further comprising a flexible catheter, wherein the secondary-secondary heat exchange area and the primary-secondary heat exchange area are disposed on the outside of the flexible catheter, and the primary-primary heat exchange area is disposed on the inside of the flexible catheter.

Images