Two-stage low-temperature cooler

Abstract

A cryogenic ablation tool has a primary fluid circuit for cryogenically cooling or heating tissue around a distal portion of the cryogenic ablation tool. The primary fluid circuit has a primary-primary heat exchanger that facilitates regenerative 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 with a secondary-secondary heat exchanger for allowing regenerative 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

This application is a divisional application of patent application 202080071595.3 for invention. Cross - Reference to Related Applications

[0001] This application claims priority to U.S. Provisional Patent Application No. 62 / 886,853, filed Aug. 14, 2019, which is incorporated herein by reference in its entirety. Technical Field

[0002] The present disclosure relates to cryoprobes for cryoablation and systems for cryoablation. Background Art

[0003] During cryosurgery, a surgeon may deploy one or more cryoprobes to ablate a target region of a patient's anatomy by cooling and thawing tissue. In one example, a cryoprobe uses the Joule-Thomson effect to produce cooling or heating at the tip of the probe. In this case, the expansion of a cryogenic fluid in the cryoprobe from a higher pressure to a lower pressure causes the tip of the device to cool to a temperature equal to or below the temperature corresponding to cryoablating tissue near the tip. Heat transfer between the expanded cryogenic fluid and the outer wall of the cryoprobe causes an ice ball to form in the tissue surrounding the tip and subsequent cryoablation of the tissue.

[0004] Some cryoprobes can be used to ablate lesions in the human lung or other body passages. In this case, the cryoprobe may have to pass through tortuous and / or narrow passages and may thus be configured such that the cryogenic fluid cannot be pressurized to the pressures typically used for cryoablation (e.g., 3500 psi). Additionally, delivering the cryogenic fluid at pressures below the typical supply pressures for cryoablation (e.g., 3500 psi) may not result in sufficient cooling or formation of an ice ball of the desired size within the desired time (e.g., a 35 mm ice ball within 10 minutes). Summary of the Invention

[0005] Advantageous aspects of the present disclosure provide a cryoablation tool having a two-stage cryocooler suitable for producing an ice ball sized for cryoablation.

[0006] In a first aspect of a cryoablation tool, there is provided a cryoablation tool including: a primary fluid circuit including the flow of a high-pressure stream of a primary fluid and a low-pressure stream of the primary fluid, the primary fluid circuit being 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 including a primary-primary heat exchanger configured to perform a regenerative heat exchange between the high-pressure stream of the primary fluid and the low-pressure stream of the primary fluid; a secondary fluid circuit including a high-pressure region for the flow of a high-pressure stream of a secondary fluid and a low-pressure region for the flow of a low-pressure stream of the secondary fluid, the secondary fluid circuit including a secondary-secondary heat exchanger for performing a 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 at a secondary-secondary outlet; and a primary-secondary heat exchanger configured to perform a 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 including a primary-secondary inlet, the primary-secondary heat exchanger being arranged such that the primary-secondary inlet is downstream of the secondary-secondary outlet along the flow direction of the high-pressure stream of the secondary fluid, the primary-secondary heat exchanger and the secondary-secondary heat exchanger being arranged such that the low-pressure stream 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 stream of the secondary fluid in the secondary-secondary heat exchanger.

[0007] According to an advantageous aspect, the primary-primary heat exchanger, the secondary-secondary heat exchanger, and the primary-secondary heat exchanger each include a tube having an outer wall. The outer wall of the tube includes extensions to increase the surface area of the outer wall.

[0008] In another aspect, the primary-primary heat exchanger, the secondary-secondary heat exchanger, and the primary-secondary heat exchanger each include a finned tube.

[0009] In another aspect, the secondary-secondary heat exchanger and the primary-secondary heat exchanger each include a tube wound around a tubular mandrel in a series of turns. In one method, 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 wound around a tubular mandrel in a series of turns.

[0010] According to one aspect of the present disclosure, the primary-primary heat exchanger is fluidly coupled to the primary-secondary heat exchanger such that the high-pressure stream of the primary fluid first flows through the primary-secondary heat exchanger and then through the primary-primary heat exchanger.

[0011] 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.

[0012] On the other hand, 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.

[0013] On the other hand, the flow of the low-pressure flow of the primary fluid is isolated from the low-pressure region of the secondary fluid circuit.

[0014] On the other hand, the low-pressure flow of the primary fluid can be concentrically arranged with and physically separated from the low-pressure flow of the secondary fluid.

[0015] On the other hand, the high-pressure regions of the primary-secondary heat exchanger and the secondary-secondary heat exchanger are isolated from the low-pressure flow of the primary fluid.

[0016] 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.

[0017] According to one aspect, the primary fluid circuit includes a first Joule-Thomson (J-T) orifice located in the distal segment of the cryoablation tool. The first J-T orifice is fluidly coupled to the primary-primary heat exchanger via a primary supply pipe 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 J-T orifice is configured to cryogenically expand the high-pressure flow of the primary fluid into a low-pressure flow of the primary fluid.

[0018] On the other hand, the cryoablation tool further includes a primary return pipe through which the low-pressure flow of the primary fluid passes, and the first J-T orifice is disposed within the primary return pipe.

[0019] In some aspects, the secondary fluid circuit includes a second Joule-Thomson (J-T) orifice. The second JT orifice is fluidly coupled to the secondary-secondary heat exchanger via a secondary supply pipe 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. 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.

[0020] On the other hand, the cryoablation tool further includes a secondary return pipe to allow the expanded secondary fluid to pass through, wherein the secondary-secondary heat exchanger, the primary-secondary heat exchanger, and the second JT orifice are each disposed within the secondary return pipe.

[0021] According to one aspect, the secondary return pipe is fluidly isolated from the low-pressure flow of the primary fluid of the primary fluid circuit.

[0022] In addition, the low-pressure flow of the primary fluid and / or the secondary fluid can be configured to be discharged to the atmosphere. A shared exhaust pipe can be configured for discharging the low-pressure flow of the primary fluid and / or the secondary fluid to the atmosphere (via the shared exhaust pipe).

[0023] In one aspect, a cryoablation tool includes a primary inlet conduit for conveying a primary fluid to a primary fluid circuit in a primary fluid loop; and a secondary inlet conduit for conveying a secondary fluid to a secondary fluid circuit. Before discharging the primary or secondary fluid to the atmosphere, a shared discharge conduit may be arranged to pass the primary or secondary fluid through the primary inlet conduit and the secondary inlet conduit.

[0024] Another embodiment provides a cryoablation tool including: 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 convey 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 J-T orifice configured to convey 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 includes 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 includes a secondary-secondary heat exchange region upstream of the second J-T orifice; the primary return conduit is further configured to pass the primary cryogenic gas through the primary-primary heat exchange region in a direction countercurrent to the supply direction; and the secondary return conduit is further configured to pass the secondary fluid through the primary-secondary heat exchange region and the secondary-secondary heat exchange region in a direction countercurrent to the supply direction in each case.

[0025] In another aspect, the primary supply conduit is arranged in a first plurality of coils configured as a primary-secondary heat exchanger in the primary-secondary heat exchange region and in a second plurality of coils configured as a primary-primary heat exchanger in the primary-primary heat exchange region; and the secondary supply conduit is arranged in a third plurality of coils configured as a secondary-secondary heat exchanger in the secondary-secondary heat exchange region.

[0026] 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.

[0027] On the other hand, the first multiple coil includes a first coil and a second coil, the first coil being arranged upstream of the second coil with respect to the direction in which the primary fluid flows through the first coil; each coil in the second multiple coil is located downstream of the second coil with respect to the direction in which the primary fluid flows in the first coil; and each coil in the third multiple coil is located upstream of the first coil with respect to the direction in which the primary fluid flows in the first coil.

[0028] On the other hand, the secondary return conduit may be configured to first pass the expanded secondary fluid successively through the entire length of the primary-secondary heat exchange zone and then pass the secondary fluid through the entire length of the secondary-secondary heat exchange zone. The secondary return conduit may be configured to first pass the expanded secondary fluid through each coil of the primary-secondary heat exchanger and then through the secondary-secondary heat exchanger.

[0029] On the other hand, the primary-primary heat exchange zone is arranged within the primary return conduit and further arranged distally of both the primary-secondary and secondary-secondary heat exchange zones.

[0030] On the other hand, the secondary-secondary heat exchange zone is arranged within the secondary return conduit in proximity to the primary-secondary heat exchange zone.

[0031] On the other hand, the primary supply conduit includes a tubular region that is wound around a mandrel in a series of turns to form the primary-secondary heat exchanger. The secondary supply conduit may include a tubular region that is wound around the mandrel in a series of turns to form the secondary-secondary heat exchanger. Additionally, the primary supply conduit may include a tubular region that is wound around the mandrel in a series of turns to form the 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 the secondary-secondary heat exchanger. The primary supply conduit may include a tubular region that is wound around the mandrel in a series of turns to form the primary-primary heat exchanger.

[0032] On the other hand, the primary return conduit is configured to pass the primary fluid through the primary-primary heat exchange zone without passing through the primary-secondary heat exchange zone or the secondary-secondary heat exchange zone.

[0033] On the other hand, the primary-secondary heat exchange zone and the secondary-secondary heat exchange zone are each disposed within the secondary return conduit. Then, the secondary return conduit may fluidly isolate the primary return conduit from the primary-secondary heat exchange zone and the secondary-secondary heat exchange zone.

[0034] On the other hand, the primary return conduit includes a portion that is concentrically disposed around the secondary return conduit. This portion may be located downstream of the primary-primary heat exchange zone with respect to the direction of flow of the expanded primary fluid.

[0035] On the other hand, the primary return conduit is configured to discharge the primary fluid to the atmosphere and / or the secondary return conduit is configured to discharge the secondary fluid to the atmosphere. Description of the Drawings

[0036] Figure 1 is an exemplary schematic diagram of a cryoablation tool;

[0037] Figure 2 is to illustrate its internal details Figure 1 Another exemplary schematic diagram of the cryoablation tool;

[0038] Figure 3 is Figure 1 Schematic diagram of an exemplary pre-cooler of the cryoablation tool;

[0039] Figure 4 is Figure 1 Schematic diagram of an exemplary primary-primary heat exchanger of the cryoablation tool;

[0040] Figure 5 is to illustrate the Figure 1 Thermodynamic schematic diagram of the primary-primary, primary-secondary, and secondary-secondary heat exchangers associated with the cryoablation tool; and

[0041] Figure 6 is to illustrate the Figure 1 Exemplary thermodynamic property diagram of the thermodynamic states associated with the primary-primary, primary-secondary, and secondary-secondary heat exchangers shown. Detailed Description

[0042] Figure 1 A schematic diagram showing a cryoablation tool 100 according to one embodiment. According to some embodiments, the cryoablation tool 100 may include a catheter 102. In an advantageous aspect, the catheter 102 may be inserted into the working channel of a bronchoscope and may thus 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 thus be configured as a rigid tip. Alternatively, the distal operating tip 108 may not be a rigid tip.

[0043] Referring to 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 the distal portion 104 of the cryoablation tool 100. The primary fluid may cool (e.g., cryogenically) or heat the 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.

[0044] The primary fluid circuit 110 may further include a primary-primary heat exchanger 120 configured to effect heat exchange (e.g., regenerative heat exchange) between the high-pressure flow of the primary fluid and the low-pressure flow of the 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 the primary fluid. The primary-primary outlet 124 may be fluidly coupled to a primary conduit 128 (e.g., a primary capillary) to convey the primary fluid toward the distal operating tip 108.

[0045] In an advantageous aspect, the high-pressure flow of the primary fluid (from the primary supply conduit 112) may flow through a first cryocooler 130. In such an embodiment, the high-pressure flow of the primary fluid may be upstream of the first cryocooler 130 (relative to direction 166). Additionally, the low-pressure flow of the primary fluid may be downstream of the first cryocooler 130 (relative to direction 166). As Figure 2 shown, the primary supply conduit 128 (e.g., a primary capillary) includes a first Joule-Thomson (“JT”) orifice 130 at the end of the primary supply conduit downstream of the primary-primary outlet. Accordingly, the first cryocooler 130 may be an open-loop cryocooler, such as the first J-T orifice 130.

[0046] In such an embodiment, the high-pressure flow of the primary fluid may undergo expansion at or downstream of the first JT orifice 130 in the first expansion chamber 132. The first expansion chamber 132 may be in fluid communication with the primary return conduit 114 to carry away the (expanded low-pressure flow of the) primary fluid from the expansion chamber, toward the proximal portion 106 (e.g., discharged to the atmosphere if the primary fluid circuit 110 is open-loop, or returned to the primary fluid source if the primary fluid circuit 110 is a closed circuit).

[0047] In an embodiment, the primary fluid may be a cooling fluid (e.g., nitrogen, air, argon, krypton, xenon, N2O, CO2, CF4). In this case, the high-pressure flow of the primary fluid may be at a pressure such that expansion through the first J-T orifice 130 may cause the primary fluid to cool to a temperature for cryoablating tissue around the distal operating fluid. In some aspects, the pressure of the high-pressure flow of the primary fluid upstream of the first J-T 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 J-T orifice 130 may be less than about 190 Kelvin.

[0048] 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 J-T orifice 130 may cause the temperature of the primary fluid to increase, correspondingly causing heating of the tissue around the distal operating fluid. Such embodiments may be used to thaw cryogenic tissue.

[0049] In some embodiments, the primary fluid circuit 110 may be arranged such that the flow of the high-pressure flow of the primary fluid and the flow of the low-pressure flow of the primary fluid are countercurrent on 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. As Figure 1 and 2 shown, the flow direction of the primary fluid is reversed when expanding at the first JT orifice 130, resulting in countercurrent flow of the high-pressure flow of the primary fluid and the low-pressure flow of the primary fluid 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 be countercurrent near the primary-primary inlet 122 of the primary-primary heat exchanger 120, so the primary return pipe is configured to pass the primary cryogenic gas through the primary-primary heat exchange area in a direction countercurrent to the supply direction.

[0050] According to an advantageous aspect, the countercurrent arrangement of the high-pressure flow of the primary fluid and the low-pressure flow of the primary fluid may allow regenerative heat exchange between them. In the case where the primary fluid circuit 110 carries a cooling gas, the regenerative heat exchange may include removing heat from the high-pressure flow of the primary fluid, causing pre-cooling of the primary fluid before expansion through the first JT orifice 130. In the case where the primary fluid circuit 110 carries a heating gas, the regenerative heat exchange may include adding heat from the high-pressure flow of the primary fluid, causing pre-heating of the primary fluid before expansion through the first JT orifice 130. The regenerative heat exchange may advantageously result in achieving the desired temperature at the distal operating tip 108.

[0051] As previously described, in some embodiments, the cryoablation tool 100 may include a catheter 102 that is flexible enough to be manipulated within a bronchoscope. In such embodiments, the catheter 102 may be made of a material that cannot withstand the typical pressures (e.g., greater than about 2000 psi, such as about 3500 psi) for supplying the primary fluid in other cryoablation tools. In such cases, it may be advantageous to supply the primary fluid at a pressure lower than the typical pressure for cryoablation. The primary fluid can be supplied at a pressure less than about 2000 psi, such as about 1800 psi. However, to help achieve a temperature suitable for cryoablation 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.

[0052] Referring 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 the secondary fluid. The secondary supply conduit is configured to supply the secondary fluid to a second cryocooler (J-T 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 flow of the secondary fluid. The secondary return conduit may be configured to carry the secondary fluid away from the second expansion chamber.

[0053] In an advantageous aspect, the secondary fluid circuit 140 may facilitate heat exchange between the primary fluid and the secondary fluid. In some such advantageous aspects, in embodiments where the primary fluid is cooled upon expansion to freeze and ablate tissue around the distal operating tip 108, the secondary fluid circuit 140 may be used to pre-cool the high-pressure flow of the primary fluid. In an advantageous aspect, as Figure 2 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.

[0054] Continuing to refer Figure 2 , the secondary fluid circuit 140 may include a secondary-secondary heat exchanger 160 that allows heat exchange between the high-pressure flow of the secondary fluid and the low-pressure flow of the secondary fluid (e.g., regenerative heat exchange). In some advantageous aspects, the secondary fluid may also be a cooling fluid. In such embodiments, the regenerative heat exchange between the high-pressure flow of the secondary fluid and the low-pressure flow of the secondary fluid may remove heat from the high-pressure flow of the secondary fluid. Thus, the secondary-secondary heat exchanger 160 may facilitate pre-cooling the high-pressure flow of the secondary fluid.

[0055] Referring again to 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 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. Additionally, the secondary-secondary outlet 164 may also be located upstream of each of the primary-primary inlet 122 and the primary-primary outlet 124.

[0056] The secondary-secondary inlet 162 may be fluidly coupled to a secondary supply conduit 142 to receive a high-pressure flow of secondary fluid. The secondary-secondary outlet 164 may be fluidly coupled to a secondary conduit 168 (such as a secondary capillary 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 and thereby pass through the secondary-secondary heat exchanger 160.

[0057] In an advantageous aspect, the high-pressure flow of the secondary fluid leaving the secondary-secondary outlet 164 may enter the secondary capillary 168 and may flow through the second cryocooler 170. In such an embodiment, the high-pressure flow of the secondary fluid may be upstream of the second cryocooler 170 (relative to direction 166). Additionally, the low-pressure flow of the secondary fluid may be downstream of the second cryocooler 170 (relative to direction 166). Figure 2 In the illustrated embodiment, the secondary conduit 168 (such as a secondary capillary 168) downstream of the secondary-secondary outlet 164 terminates at a second Joule-Thomson (“JT”) orifice 170. Thus, the second cryocooler 170 may be the 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 fluidly in communication with a secondary return conduit 144 to carry the expanded low-pressure flow of the secondary fluid (e.g., discharged to the atmosphere if the secondary fluid circuit 140 is open or returned to the secondary fluid source if the secondary fluid circuit 140 is closed).

[0058] In some embodiments, the secondary fluid circuit 140 may be arranged such that the flow of the high-pressure flow of the secondary fluid is countercurrent to the flow of the low-pressure flow of the secondary fluid on 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. As Figure 1 and 2As shown, the flow direction of the secondary fluid reverses when expanding at the second JT orifice 170, resulting in a 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 exhibit a countercurrent flow near the secondary-secondary inlet 162 of the secondary-secondary heat exchanger 160. Thus, in an advantageous aspect, the secondary return conduit 144 may be configured to cause the secondary fluid to sequentially pass through the primary-secondary heat exchange region 182 and the secondary-secondary heat exchange region 212 in a manner countercurrent to the supply direction in each case.

[0059] As Figure 2 shown, the primary-secondary heat exchanger 150 may be arranged sequentially relative to the secondary-secondary heat exchanger 160. Such a sequential arrangement may facilitate 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 with the high-pressure flow of the secondary fluid in the secondary-secondary heat exchanger 160. In such a sequential arrangement, the primary-secondary inlet 152 may be located downstream (with respect to direction 166) of the secondary-secondary outlet 164. In addition, the primary-secondary outlet 154 may also be located downstream (with respect to direction 166) of the secondary-secondary outlet 164.

[0060] In some aspects, the low-pressure flow of the expanded secondary fluid may first exchange heat with the high-pressure flow of the primary fluid. For example, in one embodiment (described further below), the secondary flow may completely flow through the primary-secondary heat exchanger 150 before flowing through the secondary-secondary heat exchanger 160. Thus, the secondary return conduit may be configured to first cause the expanded secondary fluid to sequentially pass through the entire primary-secondary heat exchange region or each coil of the primary-secondary heat exchange coil, and then cause the secondary fluid to pass through the secondary-secondary heat exchange coil.

[0061] Referring back to Figure 1 and Figure 2 , in certain embodiments where the cryoablation tool 100 includes a flexible catheter 102, the secondary-secondary heat exchanger 160 and the primary-secondary heat exchanger 150 may each be located outside the catheter 102, for example, near the proximal portion 106 of the cryoablation tool 100. In addition, the primary-primary heat exchanger 120 may be located within the flexible catheter 102. Such an arrangement may further facilitate supplying the secondary fluid at a pressure greater than the high-pressure flow of the primary fluid.

[0062] As described above, 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 the typical pressure used for cryoablation. For example, the primary fluid can be supplied at a pressure less than about 2000 psi, such as about 1800 psi. In the absence of the secondary fluid circuit 140, if the primary fluid is a cooling fluid, it may not result in sufficient cooling for cryoablation. 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 the typical supply pressure for cryoablation, regenerative heat exchange between the secondary fluids can be allowed to pre-cool the primary fluid and reach a temperature suitable for cryoablation.

[0063] 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 (such as 3500 psi). When the secondary fluid passes through the second cryocooler 170 (such as the second J-T orifice 170), if the secondary fluid is a cooling fluid, the secondary fluid can reach cryogenic temperatures (such as 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 it passes through the primary-primary heat exchanger 120.

[0064] Figure 3 Schematic diagrams of a primary-secondary and secondary-secondary heat exchanger according to one embodiment are shown. Figure 4 Schematic diagram of a primary-primary heat exchanger 120 according to one embodiment is shown.

[0065] Referring Figure 3 , the primary supply conduit 112 can be a metal tube capable of being fluidly coupled to the primary-secondary heat exchanger 150. The primary-secondary heat exchanger 150 can include a plurality of first heat exchange coils 180 between a primary-secondary inlet 152 and a primary-secondary outlet 154.

[0066] Referring Figure 2 and 3 , the plurality of first heat exchange coils can define a first heat exchange area 182. The plurality of coils can include a first coil 184 and a second coil 186. The first coil 184 can be upstream (with respect to direction 166) of the second coil 186. The first coil 184 can be closer to the primary-secondary inlet 152 than the primary-secondary outlet 154. The second coil 186 can be closer to the primary-secondary outlet 154 than the primary-secondary inlet 152. The primary-secondary heat exchange area can 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.

[0067] According to certain embodiments, a plurality of first heat exchange coils 180 (primary-secondary heat exchanger) may be formed by a metal tube (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 coil 180 may include fins 190 to increase heat exchange on the first heat exchange area 182. The primary fluid may flow through the interior of the metal tube. Refer to Figure 2 and 3 , the expanded low-pressure flow of the primary fluid may flow through the fin portion of the metal tube. The fins 190 may enhance the heat exchange between the high-pressure flow of the primary fluid flowing through the interior of the metal tube and the low-pressure flow of the secondary fluid flowing outside the fin portion of the metal tube.

[0068] Refer to Figure 2 , after heat exchange with the secondary fluid in the primary-secondary exchanger, the primary fluid may continue towards the primary-primary heat exchanger 120. Refer to Figure 4 , the primary-primary heat exchanger 120 may include a plurality of second heat exchange coils 200. Refer to Figure 2 and Figure 4 , the primary-secondary heat exchanger 150 and the primary-primary heat exchanger 120 may be arranged in sequence. Thus, 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.

[0069] According to certain embodiments, a plurality of second heat exchange coils 200 (primary-primary heat exchanger) may be formed by a metal tube (tubular region of the primary supply conduit) wound around a mandrel (e.g., similar to Figure 3 the mandrel 188). Returning to Figure 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 increase heat exchange on the second heat exchange area 204. The primary fluid may flow through the interior of the metal tube. Refer to Figure 2 and 3 , the expanded low-pressure flow of the primary fluid may flow through the fin portion of the metal tube. The fins 202 may enhance the heat exchange between the high-pressure flow of the primary fluid flowing through the interior of the metal tube and the low-pressure flow of the primary fluid flowing outside the fin portion of the metal tube.

[0070] As described above, the primary fluid exiting the primary-primary heat exchanger 120 can enter a primary conduit 128 (e.g., a primary capillary) and flow towards the first cryocooler 130. In some cases, the first cryocooler 130 can be a first J-T orifice 130. The primary fluid can expand in a primary expansion chamber downstream of the primary-primary heat exchange region located near the distal operating tip 108 to expand the primary fluid. The expanded low-pressure primary fluid can be carried by a primary return conduit 114.

[0071] Referring again to Figure 2 and Figure 4 , a second heat exchange region (primary-primary heat exchange region) 204 can be disposed within the primary return conduit 114. Thus, the primary return conduit 114 can generally surround a plurality of second heat exchange coils (second heat exchange region) 200. The primary return conduit 114 can thus pass the expanded low-pressure primary fluid through the second heat exchange region and thereby effect heat exchange (e.g., regenerative 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 exchanger).

[0072] Advantageously, as Figure 2 shown, the primary return conduit 114 is configured to pass the primary fluid through the primary-primary heat exchange region 204 without passing through the primary-secondary heat exchange region 182 or the secondary-secondary heat exchange region 212. Advantageously, the primary-secondary heat exchange region 182 and the secondary-secondary heat exchange region 212 are each disposed within a secondary return conduit 144 that fluidly isolates the expanded primary fluid flowing in the primary return conduit 114 from the primary-secondary heat exchange region 182 and the secondary-secondary heat exchange region 212. Advantageously, the primary return conduit 114 can include a portion concentrically disposed around the secondary return conduit 144. This allows the flow or primary fluid to bypass the secondary return conduit 144 without passing through either the primary-secondary heat exchange region 182 or the secondary-secondary heat exchange region 212 disposed within the secondary return conduit 144. Advantageously, this portion is downstream of the primary-primary heat exchange region 204 with respect to the primary fluid flow.

[0073] Referring to Figure 2 and 3 , a secondary supply conduit 142 can supply secondary fluid to the secondary-secondary heat exchanger 160. The secondary-secondary heat exchanger 160 can include a plurality of third heat exchange coils 210 that can define a secondary-secondary heat exchange region 212.

[0074] According to certain illustrated embodiments, a plurality of third heat exchange coils (secondary-secondary heat exchangers) may be formed by a metal tube (tubular portion of the second supply conduit) wound around a mandrel. In some cases, the mandrel around which the third heat exchange coil may be wound can be the same as the mandrel 188 around which the first heat exchange coil may be wound, or alternatively, coextensive with the mandrel 188 around which the first heat exchange coil may be wound. Or, the mandrel around which the third heat exchange coil may be wound can be separate from the mandrel 188 around which the first heat exchange coil may be wound.

[0075] Returning to Figure 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 increase heat exchange over the third heat exchange area. The secondary fluid entering the secondary-secondary inlet 162 may flow through the interior of the metal tube. Referring to Figure 2 and 3 , the expanded low-pressure flow of the secondary fluid (exiting the second J-T orifice 170) may flow through the finned portion of the metal tube. The fins 214 may enhance heat exchange between the high-pressure flow of the secondary fluid flowing through the interior of the metal tube and the low-pressure flow of the secondary fluid flowing outside the finned portion of the metal tube. As previously described, the low-pressure flow of the secondary fluid may first exchange heat with the high-pressure flow of the primary fluid in the primary-secondary heat exchanger 150, and then with the high-pressure flow of the secondary fluid in the secondary-secondary heat exchanger 160. Thus, each 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. Thus, relative to the flow direction within the secondary return conduit 144, the secondary-secondary heat exchange region 212 and the primary-secondary heat exchange region 182 may be arranged within the secondary return conduit 144, and the secondary-secondary heat exchange region 212 may be arranged downstream of the primary-secondary heat exchange region 182.

[0076] As previously described, the secondary fluid exiting the secondary-secondary heat exchanger 160 may enter the secondary conduit 168 (e.g., secondary capillary 168) and flow towards the second cryocooler 170. In some cases, the second cryocooler 170 may be the second J-T orifice 170. The secondary fluid may expand in a secondary expansion chamber located downstream of the primary-secondary heat exchange region. Upon expansion, the low-pressure flow of the secondary fluid flows through the finned portion of the primary-secondary heat exchange region for regenerative heat exchange with the high-pressure flow of the primary fluid. The low-pressure flow of the secondary fluid then flows through the finned portion of the secondary-secondary heat exchange region 212 for regenerative heat exchange with the high-pressure flow of the secondary fluid.

[0077] Advantageously, in the case where both the primary fluid and the secondary fluid are cooling fluids, the secondary fluid can 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) can thus be at a higher temperature than the secondary fluid flowing just near the primary-secondary outlet 154. Therefore, by passing the secondary fluid through the primary-secondary heat exchanger 150 first, the secondary fluid at its coldest temperature can exchange heat with the primary fluid, thereby allowing optimal heat removal from the primary fluid for its effective pre-cooling.

[0078] Referring again to Figure 2 , the secondary return pipe 144 can generally surround a plurality of third heat exchange coils 210. Advantageously, the secondary return pipe 144 can be fluidly isolated from the primary return pipe 114 so as to fluidly isolate the low-pressure flow of the primary fluid from the low-pressure flow of the secondary fluid. Thus, 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.

[0079] 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 can be longitudinally separated from each other (e.g., along direction 166). Referring to Figures 2 to 4 , each coil of the secondary-secondary heat exchange region 212 can be located upstream of the primary-secondary heat exchange region and the primary-primary heat exchange region. Additionally, the distance between adjacent coils of the plurality of third heat exchange coils 210 can be substantially less than the distance between the coils of the secondary-secondary heat exchange region 212 and the coils of the primary-secondary heat exchange region or the primary-primary heat exchange region.

[0080] Continuing 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) can be located 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) can be located upstream (with respect to direction 166) of the primary-primary inlet 122.

[0081] As previously mentioned, arrangements such as those disclosed above can contribute to effective regenerative heat exchange, thereby allowing the desired cryogenic (or thawing) characteristics to be obtained at the distal operating tip 108.

[0082] Figure 5 and Figure 6A thermodynamic schematic diagram and a thermodynamic property diagram are shown to illustrate an example of a two-stage cryogenic cooler. According to this example, the primary fluid may be argon. The secondary fluid may also be argon. Referring to Figure 5 , the primary fluid circuit 110 is shown by a solid line, while the secondary fluid circuit 140 is shown by a dashed line.

[0083] Referring to 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 exchanging heat through the primary-secondary heat exchanger 150. The secondary fluid in thermodynamic state 4 flows through the secondary-secondary heat exchanger 160, and as the secondary fluid flows through the secondary-secondary heat exchanger 160, after exchanging heat with the secondary fluid entering the secondary-secondary heat exchanger 160 in thermodynamic state 1, it reaches thermodynamic state 5.

[0084] Referring to Figure 5 and 6 , when the primary fluid enters the primary-secondary heat exchanger 150, the primary fluid is in thermodynamic state 6 at the primary-secondary inlet 152. The primary fluid is in thermodynamic state 7 at the primary-secondary outlet 154. The primary fluid enters the primary-primary inlet 122 in thermodynamic state 7 and leaves the primary-primary outlet 124 in thermodynamic state 8. The primary fluid undergoes expansion and reaches thermodynamic state 9. The primary fluid in thermodynamic state 9 exchanges heat with the tissue. The primary fluid reaches thermodynamic state 10 after exchanging heat with the tissue. The primary fluid in 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 in thermodynamic state 7.

[0085] In [[ID= fifty - one]]Figure 5 and 6 's example, both the primary fluid and the secondary fluid may be cooling fluids. Therefore, 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. From Figure 6It can be seen that the pressure of the primary fluid entering the primary-secondary heat exchanger 150 in the thermodynamic state 6 may be lower than that of the secondary fluid entering the secondary-secondary heat exchanger 160 in the thermodynamic state 1. However, the temperature of the expanded primary fluid in the thermodynamic state 9 may be lower than that of the expanded secondary fluid in the thermodynamic state 3. Therefore, despite supplying the primary fluid at a lower pressure, a low temperature suitable for cryoablation (e.g., less than 190 K, for example, about 120 K) can still be achieved due to the two-stage cryogenic cooling.

Claims

1. A cryoablation tool, comprising: A primary fluid circuit including a high-pressure region for the flow of a high-pressure stream of a primary fluid and a low-pressure region for the 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 includes 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; A secondary fluid circuit including a high-pressure region for the flow of a high-pressure stream of a secondary fluid and a low-pressure region for the flow of a low-pressure stream of the secondary fluid, The secondary fluid circuit includes a secondary-secondary heat exchanger configured 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 terminates at a secondary-secondary outlet; And A primary-secondary heat exchanger configured for 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, The primary-secondary heat exchanger is arranged such that the primary-secondary inlet is located downstream of the secondary-secondary outlet along the direction of flow of the high-pressure stream of the secondary fluid.

2. The cryoablation tool according to 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 first exchanges heat with the primary fluid in the primary-secondary heat exchanger and then exchanges heat with the high-pressure stream of the secondary fluid in the secondary-secondary heat exchanger.

3. The cryoablation 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 include a tube having an outer wall, and the outer wall of the tube includes extensions to increase the surface area of the outer wall.

4. The cryoablation tool according to any one of the preceding claims, wherein the secondary-secondary heat exchanger and the primary-secondary heat exchanger each include a tube wound around a tubular mandrel a number of turns.

5. The cryoablation tool according to any one of the preceding claims, 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 first flows through the primary-secondary heat exchanger and then through the primary-primary heat exchanger.

6. The cryoablation tool according to claim 5, wherein the fluid coupled 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.

7. The cryoablation tool according to claim 5 or 6, wherein the 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 cryoablation tool according to any one of the preceding claims, 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 cryoablation tool according to any one of the preceding claims, wherein both the secondary-secondary heat exchanger and the primary-secondary heat exchanger are isolated from the low-pressure region of the primary fluid circuit.

10. The cryoablation tool according to any one of the preceding claims, wherein the primary fluid circuit includes a first Joule-Thomson (J-T) orifice located in the distal segment of the cryoablation tool, the first J-T orifice is 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 J-T orifice is configured to cryogenically expand the high-pressure flow of the primary fluid into the low-pressure flow of the primary fluid.

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