Two-stage cryocooler

Abstract

A cryogenic ablation tool having a primary fluid circuit for cryogenically cooling or heating tissue surrounding a distal portion of the cryogenic ablation tool. The primary fluid circuit has a primary-primary heat exchanger that facilitates recuperative heat exchange between a high pressure flow of the primary fluid and a low pressure flow of the primary fluid. The cryogenic ablation tool has a secondary fluid circuit having a secondary-secondary heat exchanger that is used to allow recuperative heat exchange between a high pressure flow of the secondary fluid and a low pressure flow of the secondary fluid. The secondary fluid circuit also has a primary-secondary heat exchanger that allows heat exchange between a high pressure flow of the primary fluid and a low pressure flow of the secondary fluid.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to U.S. Patent Provisional Application No. 62 / 886,853, filed on August 14, 2019, which is incorporated herein by reference in its entirety. Technical Field

[0003] The present disclosure relates to a cryoprobe for cryoablation and a system for cryoablation. Background Art

[0004] During cryogenic surgery, surgeons can deploy one or more cryogenic probes to ablate a target area of ​​a patient's anatomical structure by freezing and thawing tissue. In one example, the cryogenic probe uses the Joule-Thomson effect to produce cooling or heating of the probe tip. In this case, the expansion of the cryogenic fluid in the cryogenic probe from a higher pressure to a lower pressure causes the tip of the device to cool to a temperature equal to or lower than the temperature corresponding to cryogenically ablated tissue near the tip. The heat transfer between the expanded cryogenic fluid and the outer wall of the cryogenic probe causes an ice ball to form in the tissue around the tip, and subsequently cryogenically ablates the tissue.

[0005] Some cryoprobes may be used to ablate lesions in human lungs or other body passages. In such cases, the cryoprobe may have to pass through tortuous and / or narrow passages and may therefore be configured such that the cryoprobe may not support cryogenic fluids pressurized to pressures typically used for cryoablation (e.g., 3500 psi). In addition, delivering cryogenic fluids at pressures below typical supply pressures for cryoablation (e.g., 3500 psi) may not result in adequate cooling or formation of ice balls of a desired size within a desired time (e.g., 35 mm ice balls within 10 minutes). Summary of the invention

[0006] Advantageous aspects of the present disclosure provide a cryoablation tool having a dual-stage cryocooler suitable for producing ice balls of a size suitable for cryoablation.

[0007] In a first aspect of a cryogenic ablation tool, a cryogenic ablation tool is provided, comprising: a primary fluid circuit, which comprises a flow of a high-pressure flow of a primary fluid and a flow of a low-pressure flow of a primary fluid, the primary fluid circuit being fluidly coupled to a distal portion of the cryogenic ablation tool for cryogenically cooling or heating tissue surrounding the distal portion of the cryogenic ablation tool, the primary fluid circuit comprising a primary-primary heat exchanger configured for performing a recuperative heat exchange between the high-pressure flow of the primary fluid and the low-pressure flow of the primary fluid; a secondary fluid circuit comprising a high-pressure region for the flow of the high-pressure flow of the secondary fluid and a low-pressure region for the flow of the low-pressure flow of the secondary fluid, the secondary fluid circuit comprising a secondary-secondary heat exchanger for performing a recuperative heat exchange between the high-pressure flow of the secondary fluid and the low-pressure flow of the secondary fluid. and a primary-secondary heat exchanger configured to perform recuperative heat exchange between a high-pressure flow of the primary fluid and a low-pressure flow of the secondary fluid, the secondary-secondary heat exchanger terminating at a secondary-secondary outlet; and a primary-secondary heat exchanger configured to perform recuperative heat exchange between a high-pressure flow of the primary fluid and a low-pressure flow of the secondary fluid, the primary-secondary heat exchanger comprising a primary-secondary inlet, the primary-secondary heat exchanger being arranged such that the primary-secondary inlet is located downstream of the secondary-secondary outlet along the flow direction of the high-pressure flow of the secondary fluid, the primary-secondary heat exchanger and the secondary-secondary heat exchanger being arranged such that the low-pressure flow of the secondary fluid first exchanges heat with the primary fluid in the primary-secondary heat exchanger and then exchanges heat with the high-pressure flow of the secondary fluid in the secondary-secondary heat exchanger.

[0008] According to an advantageous aspect, the primary-primary heat exchanger, the secondary-secondary heat exchanger and the primary-secondary heat exchanger each comprise a tube having an outer wall. The outer wall of the tube comprises an extension to increase the surface area of ​​the outer wall.

[0009] In another aspect, the primary-primary heat exchanger, the secondary-secondary heat exchanger, and the primary-secondary heat exchanger each include fin tubes.

[0010] In another aspect, the secondary-secondary heat exchanger and the primary-secondary heat exchanger each include a tube that is wound around a tubular mandrel in a series of turns. In one approach, the secondary-secondary heat exchanger and the primary-secondary heat exchanger are each wound around the same tubular mandrel. The primary-primary heat exchanger may also include a tube that is wound around a tubular mandrel in a series of turns.

[0011] According to one aspect of the present disclosure, a primary-primary heat exchanger is fluidly coupled to a primary-secondary heat exchanger such that a high pressure flow of the primary fluid flows through the primary-secondary heat exchanger first and then through the primary-primary heat exchanger.

[0012] 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 flow of the primary fluid from the primary-secondary heat exchanger.

[0013] 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 flow of the primary fluid from the secondary-secondary heat exchanger.

[0014] On the other hand, the flow of the low pressure stream of the primary fluid is isolated from the low pressure region of the secondary fluid circuit.

[0015] In another aspect, the low pressure flow of the primary fluid may be arranged concentrically with and physically separated from the low pressure flow of the secondary fluid.

[0016] On the other hand, 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 flow of the primary fluid.

[0017] On the other hand, both the secondary-secondary heat exchanger and the primary-secondary heat exchanger are isolated from the low pressure region of the primary fluid circuit.

[0018] According to one aspect, the primary fluid circuit includes a first Joule-Thomson (JT) orifice located in a distal segment of a cryogenic ablation tool, the first JT orifice being fluidly coupled to the primary-primary heat exchanger via a primary supply conduit to receive a high-pressure flow of the primary fluid after the high-pressure flow of the primary fluid passes through the primary-primary heat exchanger, the first JT orifice being configured to cryogenically expand the high-pressure flow of the primary fluid into a low-pressure flow of the primary fluid.

[0019] In another aspect, the cryoablation tool further comprises a primary return conduit for passing a low pressure flow of a primary fluid therethrough, the first JT orifice being disposed within the primary return conduit.

[0020] In certain aspects, the secondary fluid circuit includes a second Joule-Thomson (JT) orifice, which is fluidly coupled to the secondary-secondary heat exchanger via a secondary supply conduit to receive the high-pressure flow of the secondary fluid after the high-pressure flow of the secondary fluid passes through the secondary-secondary heat exchanger, and the second JT orifice is configured to cryogenically expand the high-pressure flow of the secondary fluid into a low-pressure flow of the secondary fluid.

[0021] In another aspect, the cryoablation tool further comprises a secondary return conduit to allow the expanded secondary fluid to pass therethrough, wherein the secondary-secondary heat exchanger, the primary-secondary heat exchanger and the second JT orifice are each disposed within the secondary return conduit.

[0022] According to one aspect, the secondary return conduit is fluidly isolated from the low pressure flow of primary fluid of the primary fluid circuit.

[0023] Furthermore, the low pressure flow of the primary fluid and / or the secondary fluid may be configured to be exhausted to atmosphere.The shared exhaust conduit may be configured for exhaustion of the low pressure flow of the primary fluid and / or the secondary fluid to atmosphere (via the shared exhaust conduit).

[0024] In one aspect, the cryoablation tool includes a primary inlet conduit for a primary fluid circuit to deliver a primary fluid to the primary fluid circuit; and a secondary inlet conduit for delivering a secondary fluid to the secondary fluid circuit. Before the primary fluid or the secondary fluid is discharged to the atmosphere, the shared exhaust conduit can be arranged to pass the primary fluid or the secondary fluid through the primary inlet conduit and the secondary inlet conduit.

[0025] Another embodiment provides a cryogenic ablation tool, comprising: a shaft having a proximal end and a distal end; a primary supply conduit configured to supply a primary fluid from a high-pressure cryogenic gas source to the 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; a primary return conduit configured to carry the primary fluid away from the distal expansion chamber; 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; and a secondary return conduit configured to The secondary fluid is carried away 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 is located downstream of the primary-secondary heat exchange area; and the secondary supply conduit includes a secondary-secondary heat exchange area located upstream of the second JT orifice; the primary return conduit is also configured to allow the primary low-temperature gas to pass through the primary-primary heat exchange area in a countercurrent manner to the supply direction; the secondary return conduit is also configured to allow the secondary fluid to pass through the primary-secondary heat exchange area and the secondary-secondary heat exchange area in sequence in a countercurrent manner to the supply direction in each case.

[0026] On the other hand, the primary supply pipe is arranged in a first plurality of coils, configured as a primary-secondary heat exchanger in a primary-secondary heat exchange area, and is arranged in a second plurality of coils, configured as a primary-primary heat exchanger in a primary-primary heat exchange area; and the secondary supply pipe is arranged in a third plurality of coils, configured as a secondary-secondary heat exchanger in a secondary-secondary heat exchange area.

[0027] In another aspect, the primary return conduit is configured to pass the expanded primary fluid through the primary-primary heat exchanger; and the secondary return conduit is configured to first pass the expanded secondary fluid through the primary-secondary heat exchanger and then pass the expanded secondary fluid through the secondary-secondary heat exchanger.

[0028] On the other hand, the first multiple coils include a first coil and a second coil, the first coil is arranged upstream of the second coil relative to the direction in which the primary fluid flows through the first coil; each coil in the second multiple coils is located downstream of the second coil relative to the direction in which the primary fluid flows in the first coil; and each coil in the third multiple coils is located upstream of the first coil relative to the direction in which the primary fluid flows in the first coil.

[0029] On the other hand, the secondary return pipe can be configured to first pass the expanded secondary fluid through the entire length of the primary-secondary heat exchange area in sequence, and then pass the secondary fluid through the entire length of the secondary-secondary heat exchange area. The secondary return pipe can be configured to first pass the expanded secondary fluid through each coil of the primary-secondary heat exchanger, and then pass it through the secondary-secondary heat exchanger.

[0030] On the other hand, the primary-primary heat exchange region is arranged within the primary return conduit and is further arranged distally from both the primary-secondary and secondary-secondary heat exchange regions.

[0031] In another aspect, the secondary-secondary heat exchange region is arranged adjacent to the primary-secondary heat exchange region within the secondary return conduit.

[0032] In another aspect, the primary supply conduit includes a tubular region that is wound around a mandrel in a series of turns to form a primary-secondary heat exchanger. The secondary supply conduit may include a tubular region that is wound around a mandrel in a series of turns to form a secondary-secondary heat exchanger. In addition, the primary supply conduit may include a tubular region that is wound around a mandrel in a series of turns to form a primary-secondary heat exchanger, and the secondary supply conduit may include a tubular region that is wound around the same mandrel in a series of turns to form a secondary-secondary heat exchanger. The primary supply conduit may include a tubular region that is wound around a mandrel in a series of turns to form a primary-primary heat exchanger.

[0033] In another aspect, the primary return conduit is configured to allow the primary fluid to pass through the primary-primary heat exchange region without passing through the primary-secondary heat exchange region or the secondary-secondary heat exchange region.

[0034] On the other hand, the primary-secondary heat exchange area and the secondary-secondary heat exchange area are each disposed in a secondary return conduit. The secondary return conduit can then fluidically isolate the primary return conduit from the primary-secondary heat exchange area and the secondary-secondary heat exchange area.

[0035] In another aspect, the primary return conduit includes a portion disposed concentrically around the secondary return conduit. The portion may be located downstream of the primary-primary heat exchange region relative to the direction of flow of the expanded primary fluid.

[0036] 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 DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 is an exemplary schematic diagram of a cryoablation tool;

[0038] Figure 2 It describes the internal details Figure 1 Another exemplary schematic diagram of a cryoablation tool;

[0039] Figure 3 yes Figure 1 Schematic diagram of an exemplary pre-cooler for a cryoablation tool;

[0040] Figure 4 yes Figure 1 Schematic diagram of an exemplary primary-primary heat exchanger of a cryoablation tool;

[0041] Figure 5 Is the description and Figure 1 A thermodynamic schematic diagram of primary-primary, primary-secondary, and secondary-secondary heat exchangers associated with a cryoablation tool of FIG. 1 ; and

[0042] Figure 6 Is the description and Figure 1 Exemplary thermodynamic characteristic diagrams of thermodynamic states associated with primary-primary, primary-secondary, and secondary-secondary heat exchangers are shown. DETAILED DESCRIPTION

[0043] Figure 1 A schematic diagram of a cryoablation tool 100 according to one embodiment is shown. According to some embodiments, the cryoablation tool 100 may include a catheter 102. In an advantageous aspect, the catheter 102 may be inserted into a working channel of a bronchoscope and may therefore generally be flexible. The cryoablation tool 100 may include a distal portion 104 and a proximal portion 106. The distal portion 104 may terminate at a distal operating tip 108. In some cases, the distal operating tip 108 may have to puncture tissue and may therefore be configured as a rigid tip. Alternatively, the distal operating tip 108 may not be a rigid tip.

[0044] Reference Figure 1 and 2, the cryoablation tool 100 includes a primary fluid circuit 110 (shown in solid lines) 110. The primary fluid circuit 110 may be associated with a primary fluid. The primary fluid circuit 110 may be in fluid communication with a distal portion 104 of the cryoablation tool 100. The primary fluid may cool (e.g., cryogenically) or heat tissue surrounding the distal portion of the cryoablation tool 100. The primary fluid circuit 110 may include a primary supply conduit 112 for carrying a high-pressure flow of the primary fluid. The primary fluid circuit 110 may also include a primary return conduit 114 for carrying a low-pressure flow of the primary fluid.

[0045] The primary fluid circuit 110 may also include a primary-primary heat exchanger 120 configured to exchange heat (e.g., recuperative heat exchange) between a high pressure flow of primary fluid and a low pressure flow 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 to receive the high pressure flow of primary fluid. The primary-primary outlet 124 may be fluidly coupled to a primary conduit 128 (e.g., a primary capillary) to deliver the primary fluid toward the distal operating tip 108.

[0046] In an advantageous aspect, a high pressure flow of the primary fluid (from the primary supply conduit 112) can flow through the first cryocooler 130. In such an embodiment, the high pressure flow of the primary fluid can be located upstream of the first cryocooler 130 (relative to the direction 166). In addition, the low pressure flow of the primary fluid can be located downstream of the first cryocooler 130 (relative to the direction 166). Figure 2 As shown, the primary supply conduit 128 (eg, primary capillary tube) includes a first Joule-Thomson ("JT") orifice 130 at the 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.

[0047] In such an embodiment, the high-pressure flow of primary fluid can undergo expansion at or downstream of the first JT orifice 130 in the first expansion chamber 132. The first expansion chamber 132 can be fluidly connected to the primary return conduit 114 to carry (the expanded low-pressure flow of) primary fluid away from the expansion chamber toward the proximal portion 106 (e.g., to the atmosphere if the primary fluid circuit 110 is an open circuit, or back to the primary fluid source if the primary fluid circuit 110 is a closed circuit).

[0048] In an embodiment, the primary fluid may be a cooling fluid (e.g., nitrogen, air, argon, krypton, xenon, N 2 O、CO 2 CF 4). In this case, the high pressure flow of the primary fluid may be at a pressure such that expansion through the first JT orifice 130 may cause the primary fluid to cool to a temperature for cryogenically ablating tissue surrounding the distal operating fluid. In certain aspects, the pressure of the high pressure flow of the primary fluid upstream of the first JT orifice 130 may be between about 1000 psi and about 2000 psi (e.g., about 1800 psi). Thus, in embodiments where the primary fluid is a cooling fluid, the temperature of the primary fluid after expansion from the first JT orifice 130 may be less than about 190 Kelvin.

[0049] Alternatively, the primary fluid may be a heating fluid (e.g., helium, hydrogen). In this case, the high pressure flow of the primary fluid may be at a pressure such that expansion through the first JT orifice 130 may result in an increase in the temperature of the primary fluid, which in turn results in heating of the tissue surrounding the distal operating fluid. Such an embodiment may be used to thaw cryogenic tissue.

[0050] In some embodiments, the primary fluid circuit 110 can be arranged such that the high pressure flow of the primary fluid is countercurrent to the low pressure flow of the primary fluid over at least some portions of the primary fluid circuit 110. For example, as described above, in one embodiment, the high pressure flow of the primary fluid passes through the first JT orifice 130. Figure 1 and 2 As shown, the flow direction of the primary fluid is reversed when expanding at the first JT orifice 130, thereby causing the high-pressure flow of the primary fluid and the low-pressure flow of the primary fluid to flow in countercurrent near the first JT orifice 130. In addition, the high-pressure flow of the primary fluid and the low-pressure flow of the primary fluid may flow in countercurrent near the primary-primary inlet 122 of the primary-primary heat exchanger 120, so the primary return conduit is configured to allow the primary low-temperature gas to pass through the primary-primary heat exchange region in a countercurrent manner to the supply direction.

[0051] According to an advantageous aspect, the counter-flow arrangement of the high pressure flow of the primary fluid and the low pressure flow of the primary fluid may allow for a recuperative heat exchange therebetween. In the case where the primary fluid circuit 110 carries a cooling gas, the recuperative heat exchange may include removing heat from the high pressure flow of the primary fluid, resulting in pre-cooling of the primary fluid prior to expansion through the first JT orifice 130. In the case where the primary fluid circuit 110 carries a heating gas, the recuperative heat exchange may include adding heat from the high pressure flow of the primary fluid, resulting in pre-heating of the primary fluid prior to expansion through the first JT orifice 130. The recuperative heat exchange may advantageously result in a desired temperature being achieved at the distal operative tip 108.

[0052] As previously described, in some embodiments, the cryogenic ablation tool 100 may include a catheter 102 that is flexible enough to be manipulated within a bronchoscope. In such an embodiment, the catheter 102 may be made of a material that cannot withstand the typical pressure (e.g., greater than about 2000 psi, such as about 3500 psi) at which the primary fluid is supplied in other cryogenic ablation tools. In this case, it may be advantageous to supply the primary fluid at a pressure lower than the typical pressure used for cryogenic ablation. The primary fluid can be supplied at a pressure of less than about 2000 psi, such as about 1800 psi. However, in order to help reach a temperature suitable for cryogenic ablation at the distal operating tip 108, a secondary fluid circuit 140 may be provided to pre-cool the primary fluid, as will be further described below.

[0053] Reference Figure 1 and 2 , the cryoablation tool 100 includes a secondary fluid circuit 140 (shown in dashed lines). The secondary fluid circuit 140 may include a secondary supply conduit 142 that carries a high pressure flow 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 the second expansion chamber. The secondary fluid circuit 140 may also include a secondary return conduit 144 that carries a low pressure flow of secondary fluid. The secondary return conduit may be configured to carry the secondary fluid away from the second expansion chamber.

[0054] 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, in embodiments where the primary fluid cools upon expansion to cryoablate tissue surrounding the distal operative tip 108, the secondary fluid circuit 140 can be used to pre-cool the high pressure flow of the primary fluid. Figure 2 As shown, the secondary fluid circuit 140 may also include a primary-secondary heat exchanger 150. In certain aspects, the primary-secondary heat exchanger 150 may facilitate heat exchange between the high pressure flow of the primary fluid and the low pressure flow of the secondary fluid. The primary-secondary heat exchanger 150 may include a primary-secondary inlet 152 and a primary-secondary outlet 154.

[0055] Continue to refer to Figure 2 , the secondary fluid circuit 140 can include a secondary-secondary heat exchanger 160 that allows heat exchange (e.g., recuperative heat exchange) between the high pressure flow of the secondary fluid and the low pressure flow of the secondary fluid. In some advantageous aspects, the secondary fluid can also be a cooling fluid. In such an embodiment, the recuperative heat exchange between the high pressure flow of the secondary fluid and the low pressure flow of the secondary fluid can remove heat from the high pressure flow of the secondary fluid. Therefore, the secondary-secondary heat exchanger 160 can help pre-cool the high pressure flow of the secondary fluid.

[0056] Refer again Figure 2 , the secondary-secondary heat exchanger 160 may include a secondary-secondary inlet 162 and a secondary-secondary outlet 164. The secondary-secondary inlet 162 may be located upstream of the secondary-secondary outlet 164 along the direction 166. In addition, the secondary-secondary inlet 162 may be located upstream of each of the primary-primary inlet 122 and the primary-primary outlet 124. In addition, the secondary-secondary outlet 164 may also be located upstream of each of the primary-primary inlet 122 and the primary-primary outlet 124.

[0057] The secondary-secondary inlet 162 may be fluidly coupled to the secondary supply conduit 142 to receive the high pressure flow of the secondary fluid. The secondary-secondary outlet 164 may be fluidly coupled to a secondary conduit 168 (e.g., a secondary capillary tube 168) to receive the secondary fluid from the secondary-secondary outlet 164. The secondary fluid may thus enter at the secondary-secondary inlet 162 and exit at the secondary-secondary outlet 164 thereby passing through the secondary-secondary heat exchanger 160.

[0058] In an advantageous aspect, the high pressure flow of the secondary fluid exiting the secondary-secondary outlet 164 may enter the secondary capillary tube 168 and may flow through the second cryocooler 170. In such an embodiment, the high pressure flow of the secondary fluid may be located upstream (relative to the direction 166) of the second cryocooler 170. Additionally, the low pressure flow of the secondary fluid may be located downstream (relative to the direction 166) of the second cryocooler 170. Figure 2 In the illustrated embodiment, a secondary conduit 168 (e.g., a secondary capillary tube 168) downstream of the secondary-secondary outlet 164 terminates at a second Joule-Thomson ("JT") orifice 170. Thus, the second cryocooler 170 may be a second JT orifice 170. In such an embodiment, the high-pressure flow of the secondary fluid may undergo expansion at or downstream of the second JT orifice 170 in the second expansion chamber 172. The second expansion chamber 172 may be in fluid communication with the secondary return conduit 144 to carry the expanded, low-pressure flow of the secondary fluid (e.g., to atmosphere if the secondary fluid circuit 140 is open circuit, or back to the secondary fluid source if the secondary fluid circuit 140 is closed circuit).

[0059] In some embodiments, the secondary fluid circuit 140 may be arranged such that the high pressure flow of the secondary fluid is countercurrent to the flow of the low pressure flow of the secondary fluid over at least some portions of the secondary fluid circuit 140. For example, as described above, in one embodiment, the high pressure flow of the secondary fluid passes through the second JT orifice 170. Figure 1 and 2As shown, the flow direction of the secondary fluid is reversed when expanding at the second JT orifice 170, resulting in countercurrent flow of the high-pressure flow of the secondary fluid and the low-pressure flow of the secondary fluid near the second JT orifice 170. In addition, the high-pressure flow of the secondary fluid and the low-pressure flow of the secondary fluid may flow in countercurrent near the secondary-secondary inlet 162 of the secondary-secondary heat exchanger 160. Therefore, in an advantageous aspect, the secondary return conduit 144 may be configured to sequentially pass the secondary fluid through the primary-secondary heat exchange region 182 and the secondary-secondary heat exchange region 212 in a countercurrent manner to the supply direction in each case.

[0060] like Figure 2 As shown, the primary-secondary heat exchanger 150 can be arranged in series with respect to the secondary-secondary heat exchanger 160. Such a series arrangement can help the low-pressure flow of the secondary fluid to first exchange heat with the primary fluid in the primary-secondary heat exchanger 150, and then exchange heat with the high-pressure flow of the secondary fluid in the secondary-secondary heat exchanger 160. In such a series arrangement, the primary-secondary inlet 152 can be located downstream (relative to the direction 166) of the secondary-secondary outlet 164. In addition, the primary-secondary outlet 154 can also be located downstream (relative to the direction 166) of the secondary-secondary outlet 164.

[0061] In certain aspects, the low pressure flow of the expanded secondary fluid may first be heat exchanged with the high pressure flow of the primary fluid. For example, in one embodiment (described further below), the secondary flow may be completely passed through the primary-secondary heat exchanger 150 before passing through the secondary-secondary heat exchanger 160. Thus, the secondary return conduit may be configured to first pass the expanded secondary fluid through the entire primary-secondary heat exchange area or each coil of the primary-secondary heat exchange coil in sequence, and then pass the secondary fluid through the secondary-secondary heat exchange coil.

[0062] Come back for reference Figure 1 and Figure 2 In certain embodiments where the cryogenic ablation tool 100 includes a flexible catheter 102, the secondary-secondary heat exchanger 160 and the primary-secondary heat exchanger 150 can each be located outside the catheter 102, for example, near the proximal portion 106 of the cryogenic ablation tool 100. In addition, the primary-primary heat exchanger 120 can be located within the flexible catheter 102. This arrangement can further facilitate supplying the secondary fluid at a pressure greater than the high pressure flow of the primary fluid.

[0063] As previously described, in embodiments where the cryoablation tool 100 includes a flexible catheter 102, it may be advantageous to supply the primary fluid at a pressure lower than a typical pressure for cryoablation. For example, the primary fluid may be supplied at a pressure less than about 2000 psi, such as about 1800 psi, which, in the absence of the secondary fluid circuit 140, may not result in sufficient cooling for cryoablation if the primary fluid is a cooling fluid. However, by passing the primary fluid through the primary-secondary heat exchanger 150, even when the primary fluid is supplied at a pressure lower than a typical supply pressure for cryoablation, regenerative heat exchange between the secondary fluids may be allowed to pre-cool the primary fluid and reach a temperature suitable for cryoablation.

[0064] Advantageously, the pressure of the high pressure flow of the secondary fluid can be greater than the pressure of the high pressure flow of the primary fluid. For example, the secondary fluid can 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, the secondary fluid can reach a cryogenic temperature (e.g., less than about 190 Kelvin). The expanded low pressure flow of the secondary fluid can remove heat from the high pressure flow of the primary fluid in the primary-secondary heat exchanger 150, thereby pre-cooling the primary fluid before the primary fluid passes through the primary-primary heat exchanger 120.

[0065] Figure 3 Schematic diagram showing primary-secondary and secondary-secondary heat exchangers according to one embodiment. Figure 4 A schematic diagram of a primary-primary heat exchanger 120 is shown according to one embodiment.

[0066] Reference Figure 3 The primary supply conduit 112 may be a metal tube capable of being fluidly coupled to the primary-secondary heat exchanger 150. The primary-secondary heat exchanger 150 may include a plurality of first heat exchange coils 180 between the primary-secondary inlet 152 and the primary-secondary outlet 154.

[0067] Reference Figure 2 and 3 , the plurality of first heat exchange coils may define a first heat exchange region 182. The plurality of coils may include a first coil 184 and a second coil 186. The first coil 184 may be located upstream (relative to direction 166) of the second coil 186. The first coil 184 may be closer to the primary-secondary inlet 152 than to the primary-secondary outlet 154. The second coil 186 may be closer to the primary-secondary outlet 154 than to the primary-secondary inlet 152. The primary-secondary heat exchange region 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.

[0068] According to certain embodiments, the plurality of first heat exchange coils 180 (primary-secondary heat exchangers) may be formed of a metal tube (a tubular region of the primary supply conduit) wound around a mandrel 188. 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 first heat exchange coils 180 may include fins 190 to increase heat exchange on the first heat exchange region 182. The primary fluid may flow through the interior of the metal tube. Figure 2 and 3 The expanded low-pressure flow of the primary fluid can flow through the finned portion of the metal tube. The fins 190 can enhance the heat exchange between the high-pressure flow of the primary fluid flowing through the inside of the metal tube and the low-pressure flow of the secondary fluid flowing through the outside of the finned portion of the metal tube.

[0069] Reference Figure 2 After exchanging heat with the secondary fluid in the primary-secondary exchanger, the primary fluid may continue toward the primary-primary heat exchanger 120. Figure 4 , the primary-primary heat exchanger 120 may include a plurality of second heat exchange coils 200. Figure 2 and Figure 4 , the primary-secondary heat exchanger 150 and the primary-primary heat exchanger 120 may be arranged in series. Therefore, each coil of the plurality of second heat exchange coils 200 may be located downstream (with respect to direction 166) of the first coil 184 of the plurality of first heat exchange coils 180.

[0070] According to certain embodiments, the plurality of second heat exchange coils 200 (primary-primary heat exchangers) may be formed by winding around a mandrel (e.g., similar to Figure 3 The metal tube (the tubular region of the primary supply duct) is formed around the mandrel 188. Figure 4 , the metal tube may include an outer wall. The outer wall may include an extension 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 increase heat exchange on the second heat exchange region 204. The primary fluid may flow through the interior of the metal tube. Figure 2 and 3 The expanded low-pressure flow of the primary fluid can flow through the finned portion of the metal tube. The fins 202 can enhance the heat exchange between the high-pressure flow of the primary fluid flowing through the inside of the metal tube and the low-pressure flow of the primary fluid flowing through the outside of the finned portion of the metal tube.

[0071] As previously described, the primary fluid exiting the primary-primary heat exchanger 120 may enter a primary conduit 128 (e.g., a primary capillary tube) and flow toward a first cryocooler 130. In some cases, the first cryocooler 130 may be a first JT orifice 130. The primary fluid may expand in a primary expansion chamber located downstream of the primary-primary heat exchange region near the distal operating tip 108 to expand the primary fluid. The expanded low-pressure primary fluid may be carried by the primary return conduit 114.

[0072] Refer again Figure 2 and Figure 4 , the second heat exchange region (primary-primary heat exchange region) 204 may be arranged within the primary return conduit 114. The primary return conduit 114 may thus generally surround the plurality of second heat exchange coils (second heat exchange regions) 200. The primary return conduit 114 may thus allow the expanded low-pressure primary fluid to pass through the second heat exchange region and thereby exchange heat (e.g., recuperative heat exchange) with the high-pressure flow of the primary fluid flowing inside the metal tubes of the plurality of second heat exchange coils 200 (primary-primary heat exchangers).

[0073] Advantageously, if Figure 2 As shown, the primary return conduit 114 is configured to allow the primary fluid to pass through the primary-primary heat exchange area 204 without passing 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, and the secondary return conduit fluidically isolates the expanded primary fluid flowing in 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 disposed concentrically around the secondary return conduit 144. This enables the flow or primary fluid to bypass 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, the portion is located downstream of the primary-primary heat exchange area 204 relative to the flow of the primary fluid.

[0074] Reference Figure 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 third heat exchange coils 210, which may define a secondary-secondary heat exchange region 212.

[0075] According to certain illustrated embodiments, the plurality of third heat exchange coils (secondary-secondary heat exchangers) may be formed of a metal tube (a tubular portion of the second supply conduit) wound around a mandrel. In some cases, the mandrel around which the third heat exchange coils may be wound may be the same as the mandrel 188 around which the first heat exchange coils may be wound, or alternatively, may be coextensive with the mandrel 188 around which the first heat exchange coils may be wound. Alternatively, the mandrel around which the third heat exchange coils may be wound may be separate from the mandrel 188 around which the first heat exchange coils may be wound.

[0076] Back to Figure 3 , the metal tube of the third heat exchange coil 210 may include an outer wall. The outer wall may include an extension 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 increase heat exchange on the third heat exchange area. The secondary fluid entering the secondary-secondary inlet 162 may flow through the interior of the metal tube. Figure 2 and 3 The expanded low pressure flow of the secondary fluid (leaving the second JT orifice 170) can flow through the finned portion of the metal tube. The fins 214 can enhance the heat exchange between the high pressure flow of the secondary fluid flowing inside the metal tube and the low pressure flow of the secondary fluid flowing outside the finned portion of the metal tube.

[0077] As previously described, the low-pressure flow of the secondary fluid may first be heat exchanged with the high-pressure flow of the primary fluid in the primary-secondary heat exchanger 150, and then heat exchanged with the high-pressure flow of the secondary fluid in the secondary-secondary heat exchanger 160. Therefore, each coil of the plurality of third heat exchange coils 210 may be located upstream of the first coil 184 of the plurality of first heat exchange coils 180. Therefore, with respect to the flow direction in the secondary return duct 144, the secondary-secondary heat exchange area 212 and the primary-secondary heat exchange area 182 may be arranged in the secondary return duct 144, and the secondary-secondary heat exchange area 212 may be arranged downstream of the primary-secondary heat exchange area 182.

[0078] As previously described, 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 to a second cryocooler 170. In some cases, the second cryocooler 170 may be a second JT orifice 170. The secondary fluid may expand in a secondary expansion chamber located downstream of the primary-secondary heat exchange region. While expanding, the low-pressure stream of the secondary fluid flows through the finned portion of the primary-secondary heat exchange region for recuperative heat exchange with the high-pressure stream of the primary fluid. The low-pressure stream of the secondary fluid then flows through the finned portion of the secondary-secondary heat exchange region 212 for recuperative heat exchange with the high-pressure stream of the secondary fluid.

[0079] Advantageously, in the case where both the primary fluid and the secondary fluid are cooling fluids, the secondary fluid may reach a cryogenic temperature after flowing through the second cryocooler 170. As the secondary fluid flows through the finned tubes of the first heat exchange coil 180, the temperature of the secondary fluid may gradually increase. The secondary fluid flowing through 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 temperature of the secondary fluid flowing just near the primary-secondary outlet 154. Therefore, by passing the secondary fluid first through the primary-secondary heat exchanger 150, the secondary fluid at its coldest temperature may exchange heat with the primary fluid, thereby allowing optimal removal of heat from the primary fluid to effectively pre-cool it.

[0080] Refer again Figure 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 so as to fluidly isolate the low pressure flow of the primary fluid from the low pressure flow of the secondary fluid. Therefore, the low pressure flow of the primary fluid may not flow through the secondary-secondary heat exchanger 160 or the primary-secondary heat exchanger 150.

[0081] According to an advantageous embodiment, the primary-secondary heat exchange region, the primary-primary heat exchange region, and the secondary-secondary heat exchange region 212 may be separated from each other longitudinally (eg, along direction 166). Figures 2 to 4 , each coil of the secondary-secondary heat exchange area 212 may be located upstream of the primary-secondary heat exchange area and the primary-primary heat exchange area. In addition, the distance between adjacent coils of the plurality of third heat exchange coils 210 may be substantially smaller than the distance between the coils of the secondary-secondary heat exchange area 212 and the coils of the primary-secondary heat exchange area or the coils of the primary-primary heat exchange area.

[0082] Continue to refer to Figures 2 to 4 , each coil of the plurality of third heat exchange coils 210 (forming the secondary-secondary heat exchanger 160) may be located upstream (with respect to the direction 166) of each of the primary-secondary inlet 152 and the primary-primary inlet 122. In addition, each coil of the plurality of first coils (forming the primary-secondary heat exchanger 150) may be located upstream (with respect to the direction 166) of the primary-primary inlet 122.

[0083] As previously mentioned, arrangements such as those disclosed above may facilitate effective regenerative heat exchange, thereby allowing desired cryogenic (or thawing) characteristics to be achieved at the distal operative tip 108 .

[0084] Figure 5 and Figure 6A thermodynamic diagram and a thermodynamic characteristic diagram are shown to illustrate an example of a two-stage cryocooler. According to this example, the primary fluid may be argon. The secondary fluid may also be argon. Figure 5 , the primary fluid circuit 110 is shown in solid lines, while the secondary fluid circuit 140 is shown in dashed lines.

[0085] Reference Figure 5 and 6 , when the secondary fluid enters the secondary-secondary heat exchanger 160, the secondary fluid is in thermodynamic state 1 at the secondary-secondary inlet 162. The secondary fluid is in thermodynamic state 2 at the secondary-secondary outlet 164. The secondary fluid undergoes expansion and reaches thermodynamic state 3. The secondary fluid in thermodynamic state 3 exchanges heat through the primary-secondary heat exchanger 150. The secondary fluid is in thermodynamic state 4 after heat exchange through the primary-secondary heat exchanger 150. The secondary fluid in thermodynamic state 4 flows through the secondary-secondary heat exchanger 160 and reaches thermodynamic state 5 after heat exchange with the secondary fluid that entered the secondary-secondary heat exchanger 160 in thermodynamic state 1 as the secondary fluid flows through the secondary-secondary heat exchanger 160.

[0086] Reference Figure 5 and 6 , when the primary fluid enters the primary-secondary heat exchanger 150, the primary fluid is at thermodynamic state 6 at the primary-secondary inlet 152. The primary fluid is at thermodynamic state 7 at the primary-secondary outlet 154. The primary fluid enters the primary-primary inlet 122 at thermodynamic state 7 and leaves the primary-primary outlet 124 at thermodynamic state 8. The primary fluid undergoes expansion and reaches thermodynamic state 9. The primary fluid at thermodynamic state 9 exchanges heat with the tissue. The primary fluid reaches thermodynamic state 10 after exchanging heat with the tissue. The primary fluid at thermodynamic state 10 flows through the primary-primary heat exchanger 120 and reaches thermodynamic state 11 after exchanging heat with the primary fluid entering the secondary-secondary heat exchanger 160 at thermodynamic state 7.

[0087] exist Figure 5 and 6 In the example of , both the primary fluid and the secondary fluid can be cooling fluids. Thus, the expansion of the primary fluid between states 8 and 9 and the expansion of the secondary fluid between states 2 and 3 each result in cooling. Figure 6It can be seen that the pressure of the primary fluid entering the primary-secondary heat exchanger 150 at thermodynamic state 6 may be lower than the secondary fluid entering the secondary-secondary heat exchanger 160 at thermodynamic state 1. However, the temperature of the expanded primary fluid at thermodynamic state 9 may be lower than the temperature of the expanded secondary fluid at thermodynamic state 3. Therefore, despite the supply of the primary fluid at a lower pressure, a low temperature suitable for cryoablation (e.g., less than 190K, for example, about 120K) can be achieved due to the dual-stage cryogenic cooling.

Claims

1. A cryogenic ablation tool, comprising: a primary fluid circuit comprising a high pressure region for the flow of a high pressure stream of the primary fluid and a low pressure region for the flow of a low pressure stream of said primary fluid, The primary fluid circuit is fluidly coupled to the distal portion of the cryogenic ablation tool for cryogenically cooling or heating tissue surrounding the distal portion of the cryogenic ablation tool. the primary fluid circuit comprising a primary-primary heat exchanger configured for recuperative heat exchange between the high pressure stream of the primary fluid and the low pressure stream of the primary fluid; a secondary fluid circuit comprising a high pressure region for the flow of a high pressure stream of the secondary fluid and a low pressure region for the flow of a low pressure stream of said secondary fluid, the secondary fluid circuit comprising a secondary-secondary heat exchanger configured for recuperative heat exchange between the high pressure flow of the secondary fluid and the low pressure flow of the secondary fluid, The secondary-secondary heat exchanger terminates at a secondary-secondary outlet; and a primary-secondary heat exchanger configured for recuperative heat exchange between the high pressure flow of the primary fluid and the low pressure flow of the secondary fluid, The primary-secondary heat exchanger comprises a primary-secondary inlet, The primary-secondary heat exchanger is arranged such that the primary-secondary inlet is located downstream of the secondary-secondary outlet along the direction in which the high pressure stream of the secondary fluid flows.

2. A low-temperature ablation tool according to claim 1, wherein the primary-secondary heat exchanger and the secondary-secondary heat exchanger are arranged so that the low-pressure flow of the secondary fluid first exchanges heat with the primary fluid in the primary-secondary heat exchanger, and then exchanges heat with the high-pressure flow of the secondary fluid in the secondary-secondary heat exchanger.

3. A cryogenic ablation tool according to claim 1 or 2, wherein the primary-primary heat exchanger, the secondary-secondary heat exchanger and the primary-secondary heat exchanger each comprise a tube having an outer wall, the outer wall of the tube comprising an extension to increase the surface area of ​​the outer wall.

4. The cryogenic ablation tool of claim 1 or 2, wherein the secondary-secondary heat exchanger and the primary-secondary heat exchanger each comprise a tube wound a series of turns around a tubular mandrel.

5. A low-temperature ablation tool according to claim 1 or 2, wherein the primary-primary heat exchanger is fluidly coupled to the primary-secondary heat exchanger so that the high-pressure flow of the primary fluid first flows through the primary-secondary heat exchanger and then flows through the primary-primary heat exchanger.

6. The cryogenic ablation tool of claim 5, wherein a fluid coupled between the primary-primary heat exchanger and the primary-secondary heat exchanger is configured to fluidly isolate the low-pressure flow of the primary fluid from the primary-secondary heat exchanger.

7. The cryogenic ablation tool of claim 5, wherein a fluid coupled between the primary-primary heat exchanger and the primary-secondary heat exchanger is configured to fluidly isolate the low-pressure flow of the primary fluid from the secondary-secondary heat exchanger.

8. The cryogenic ablation tool of claim 1 or 2, wherein the flow of the low-pressure flow of the primary fluid is isolated from the low-pressure region of the secondary fluid circuit.

9. The cryogenic ablation tool of claim 1 or 2, wherein the secondary-secondary heat exchanger and the primary-secondary heat exchanger are both isolated from the low-pressure region of the primary fluid circuit.

10. The cryogenic ablation tool according to claim 1 or 2, wherein the primary fluid circuit comprises a first Joule-Thomson (JT) orifice located in a distal section of the cryogenic ablation tool, the first Joule-Thomson orifice being fluidly coupled to the primary-primary heat exchanger via a primary supply conduit to receive the high pressure flow of the primary fluid after the high pressure flow of the primary fluid passes through the primary-primary heat exchanger, The first Joule-Thomson orifice is configured to cryogenically expand the high pressure flow of the primary fluid into the low pressure flow of the primary fluid.

11. A cryogenic ablation tool, comprising: a shaft having a proximal end and a distal end; 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 orifice configured to deliver the primary fluid to a first expansion chamber; a primary return conduit configured to carry the primary fluid away from the first expansion chamber; a secondary supply conduit configured to supply a secondary fluid to a second Joule-Thomson orifice configured to deliver the secondary fluid to a second expansion chamber; a secondary return conduit configured to carry the secondary fluid away from the second expansion chamber; the primary supply conduit including a primary-secondary heat exchange region and a primary-primary heat exchange region, the primary-primary heat exchange region being downstream of the primary-secondary heat exchange region, and the secondary supply conduit including a secondary-secondary heat exchange region upstream of the second Joule-Thomson orifice; The primary return pipe is also configured to allow the primary fluid to pass through the primary-primary heat exchange area in a countercurrent manner to the supply direction, and the secondary return pipe is also configured to allow the secondary fluid to pass through the primary-secondary heat exchange area and the secondary-secondary heat exchange area in sequence in a countercurrent manner to the supply direction.

12. The cryogenic ablation tool according to claim 11, wherein the secondary return conduit is configured to first allow the expanded secondary fluid to pass through the entire length of the primary-secondary heat exchange region in sequence, and then allow the secondary fluid to pass through the entire length of the secondary-secondary heat exchange region.

13. A low-temperature ablation tool according to claim 11 or 12, wherein the secondary-secondary heat exchange region and the primary-secondary heat exchange region are arranged in the secondary return pipe, and the secondary-secondary heat exchange region is arranged to be downstream of the primary-secondary heat exchange region relative to the flow direction in the secondary return pipe.

14. A cryogenic ablation tool according to claim 11 or 12, wherein the primary supply conduit includes a tubular region, which is wound a series of times around a core shaft to form a primary-secondary heat exchanger, and the secondary supply conduit includes a tubular region, which is wound a series of times around the same core shaft to form a secondary-secondary heat exchanger.

15. The cryoablation tool according to claim 11 or 12, wherein the primary return conduit is configured to allow the primary fluid to pass through the primary-primary heat exchange region without passing through the primary-secondary heat exchange region or the secondary-secondary heat exchange region.

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