Cryosurgery system with pressure regulation

Abstract

A surgical cryoablation system includes a valve having a valve inlet and a valve outlet, wherein the valve inlet can be connected to a cryogenic fluid source at a pressure greater than 4000 psi, and the valve outlet can be connected to a cryoablation probe so that the valve outlet is in fluid communication with the cryoprobe and the cryogenic fluid source is in fluid communication with the valve inlet.

Description

Background Art

[0001] Cryosurgical systems can be used for cryoablation of target tissue (e.g., tumor). For example, during cryosurgical procedures, a surgeon can deploy one or more surgical tools, such as a cryoprobe, to cryoablate a target area of ​​a patient's anatomical structure by placing a cryoprobe at or near a target area of ​​the patient's anatomical structure. In one example, the cryoprobe utilizes the Joule-Thomson (JT) effect of a heat transfer medium or a fluid supplied under pressure to produce cooling. The expansion of the pressurized cryogenic fluid causes the temperature to be at or below those temperatures required for cryoablation of tissue near the top of the cryoprobe when it passes through the JT orifice. Heat transfer between the expanded cryogenic fluid and the outer wall of the cryoprobe can be used to form an ice ball, and thus cryoablate tissue.

[0002] In a cryosurgical system, cryogenic fluid may be supplied to the cryoprobe at a pressure to cause freezing of tissue during the freezing procedure and at a lower pressure for thawing tissue during the thawing procedure.There may be one or more freezing and thawing cycles during a cryoablation procedure.

[0003] The cryosurgical system includes one or more cryoprobes connected to one or more cryogenic fluid sources. Such a system is described in commonly assigned patent U.S. Patent No. 8,066,697 and published application U.S. Publication No. 2010 / 0256620A1, the contents of which are incorporated herein by reference in their entirety. Such a system provides separate supply and pressure control systems for high-pressure and low-pressure cryogenic fluids, and is therefore relatively heavy, bulky, and more expensive to produce. Summary of the invention

[0004] The systems and methods disclosed herein provide a heat transfer medium, such as a cryogenic fluid (liquid / gas), to transfer heat between surgical tools and surrounding tissue of a patient during a surgical procedure. The systems and methods disclosed herein allow for pressure regulation of the heat transfer medium during a surgical procedure.

[0005] In one embodiment, the pressure regulating system includes a pressure control valve that can be actuated to an open state to allow heat transfer medium to pass through the pressure control valve toward the surgical tool. The pressure control valve can be actuated to a closed state to restrict the passage of heat transfer medium therethrough. Preferably, the pressure regulating system includes a control system that controls the actuation of the pressure control valve according to one or more control algorithms.

[0006] Another embodiment provides a first control algorithm for actuating a pressure control valve to an open and closed state. The control algorithm can be, for example, executed by a control system. The control system can determine whether the pressure of the heat transfer medium is less than a minimum set point pressure according to the first control algorithm, and if so, output a first signal to the valve actuator to open the pressure control valve. The control system can also determine whether the pressure of the heat transfer medium is higher than a maximum set point pressure according to the first control algorithm, and if so, output a second signal to the valve actuator to close the pressure control valve.

[0007] In another alternative embodiment, after closing the pressure control valve, the pressure may not decrease, and may initially continue to increase before decreasing. In such an alternative embodiment, the control algorithm may include a second control algorithm that may perform substantially the same steps as the first control algorithm, but additionally may determine whether the pressure of the heat transfer medium reaches and / or exceeds the first pressure after closing the pressure control valve. If so, the second control algorithm may advantageously adjust the minimum pressure set point by an offset.

[0008] In further alternative embodiments, the offset may be equal to the difference between the first pressure and the maximum pressure set points, and the minimum pressure set point may be lowered by an amount substantially equal to the calculated offset.

[0009] According to the second control algorithm, it can be determined whether the pressure of the heat transfer medium is at or below a second pressure corresponding to the adjustment value of the minimum pressure set point after closing the pressure control valve and before subsequently opening the pressure control valve. If it is the second pressure, a third signal is sent to open the pressure control valve.

[0010] In another optional embodiment, the first pressure is optionally greater than the maximum pressure set point. In fact, such an embodiment can allow the opening and closing of the pressure control valve to include the effects of the control system (e.g., built-in delay, pressure blocking, etc.) and allow the pressure of the heat transfer medium to be controlled to be approximately equal to the desired nominal pressure.

[0011] In further alternative embodiments, the control system may automatically indicate a fault condition if the pressure control valve does not close in response to the second signal.

[0012] In one such alternative embodiment, the time elapsed after opening the pressure control valve may be compared to a predetermined time. If the pressure control valve remains open for more than the predetermined time, the pressure control valve may be closed and / or a fault condition may be generated. Preferably, the predetermined time may be greater than the time the pressure control valve remains open when controlled according to the first and / or second algorithm.

[0013] In another preferred embodiment, in the absence of a fault condition, the pressure control valve is in an open state for a first duration. In such an embodiment, the predetermined time is greater than the first duration.

[0014] A surgical system, such as a cryosurgical system, may include such an embodied pressure regulating system, which, in use, is connected to deliver a heat transfer medium from a source to a surgical tool.

[0015] In another embodiment, a cryosurgical system is provided, which includes a pressure regulating system for performing one or more cryosurgical procedures (cryoablation, cryogenic freezing after thawing, etc.). The cryosurgical system can have at least one cryoprobe having a distal operating tip located in a distal portion. The cryoprobe can receive a heat transfer medium to perform the cryosurgical procedure. A pressure control valve can be fluidly coupled to the cryoprobe and can regulate the pressure of the heat transfer medium supplied to the cryoprobe so as to allow uniform heat transfer between at least the distal portion of the cryoprobe.

[0016] Alternatively, pressure regulation of the heat transfer medium may be performed only during a thawing period following a freezing operation. In such an embodiment, the control system may determine, for example based on operator input, whether the cryosurgical system is performing a freezing operation, a thawing operation, or a cauterizing operation.

[0017] In further embodiments, the heat transfer medium may be in a cryogenic state at the distal tip to freeze and / or cryoablate tissue surrounding the cryoprobe during a freezing operation. The heat transfer medium may be in a non-cryogenic state at the distal tip during a thawing operation (or cauterization operation).

[0018] In an optional embodiment, the heat transfer medium can be argon. The heat transfer medium can be at a pressure of about 3500 psi (about 250 bar) upstream of one or more pressure control valves and expand from a pressure of about 3500 psi upon reaching the distal tip of the cryoprobe to create an ice ball and / or cryoablate tissue.

[0019] In another alternative embodiment, the heat transfer medium can be argon and can be adjusted from a pressure of about 1000 psi to about 4000 psi to a pressure between about 200 psi (about 14 bar) and about 1000 psi (about 70 bar). In such an embodiment, the pressure of the argon upstream of the pressure control valve can be 3500 psi, and when pressure regulation is performed using one or more control algorithms disclosed herein, it can be at a pressure between about 200 psi and about 1000 psi.

[0020] In other optional or additional embodiments, multiple cryoprobes can be connected to the pressure control valve (e.g., achieved by a manifold design). In such an embodiment, each cryoprobe can be operated independently relative to the other cryoprobes, so that the control system can determine the maximum pressure set point and the minimum pressure set point corresponding to each cryoprobe, and open and close the pressure control valve connected to each cryoprobe based on the corresponding maximum pressure set point and the minimum pressure set point.

[0021] In another optional embodiment, each pressure control valve is electrically actuatable, for example, a solenoid valve. In this case, the control system is in electrical communication with each pressure control valve.

[0022] In a further alternative embodiment, each cryoprobe comprises an electric heater for providing heat during a thawing operation. In this case, during a thawing operation, the heat transfer medium can distribute the heat generated by the electric heater.

[0023] In another optional aspect, the amount of heat transfer medium flowing through the pressure control valve in a closed state can be less than the amount of heat transfer medium flowing through the pressure control valve in an open state, and therefore, opening and closing the pressure control valve according to a control algorithm can actually change the pressure of the heat transfer medium flowing through the pressure control valve.

[0024] In further optional aspects, the pressure regulation system may include a pressure transducer to measure and / or monitor the pressure of the heat transfer medium. In an optional embodiment, the pressure transducer may be positioned at or downstream of the outlet of the pressure control valve.

[0025] In one embodiment, a surgical system includes a pressure regulating system for regulating the pressure of a heat transfer medium delivered from a heat transfer medium source to a surgical tool at a pressure for inducing freezing during a freezing process and at a lower pressure for thawing during a thawing process, the pressure regulating system comprising: a valve device, the valve device including a pressure control valve and an actuator for actuating the valve to an open and closed state, wherein in the open state, the valve allows the flow of the heat transfer medium to the surgical tool, and in the closed state, the valve prevents the flow of the heat transfer medium to the surgical tool; and a controller, which is operably connected to the valve device to cause selective actuation of the valve to the open and closed states, wherein during the thawing process, when the determined pressure is less than a lower set point pressure value, the controller responds to the determined pressure of the heat transfer medium downstream of the valve device to cause the valve to be actuated to an open state, and when the determined pressure is higher than an upper set point pressure value, causes the valve to be actuated to a closed state, thereby generating a thawing pressure, which cycles between the set point pressure values ​​to deliver a pressure over time that is less than the pressure that causes freezing.

[0026] If, for example, the pressure exceeds the range as determined by the pressure sensor, the pressure range can be adjusted by the adjustment value, and the adjustment value can then be reduced in multiple thawing pressure cycles. During thawing, when the fluid pressure is adjusted so as not to cause freezing, the heater can heat the fluid to transfer thermal energy to thaw the frozen tissue.

[0027] The details of one or more examples are set forth in the accompanying claims and the description below. Other features, objects, and advantages will be apparent from the detailed description and drawings, and from the claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 is a schematic diagram illustrating a surgical system according to one non-limiting exemplary embodiment;

[0029] Figure 2 is a schematic diagram illustrating a cryosurgery system according to one non-limiting exemplary embodiment;

[0030] Figure 3 is a front cross-sectional view showing a cryoprobe according to one non-limiting exemplary embodiment;

[0031] Figure 4 is a schematic diagram illustrating a pressure regulation system according to one non-limiting exemplary embodiment;

[0032] Figure 5 It is shown Figure 4 A schematic diagram of the downstream connection of the pressure regulating system;

[0033] Figure 6 is a schematic diagram illustrating various components of a control system according to one non-limiting exemplary embodiment;

[0034] Figure 7 is a flow chart illustrating a control algorithm for regulating pressure according to one non-limiting exemplary embodiment;

[0035] Figure 8 is a flow chart illustrating another control algorithm for regulating pressure according to one non-limiting exemplary embodiment;

[0036] Fig. 9 When it is realized Figure 7 and Figure 8 A graphical representation of the pressure of the heat transfer medium as measured by a pressure transducer when the control algorithm is used;

[0037] Fig.10 is a flow chart illustrating another control algorithm for regulating pressure according to one non-limiting exemplary embodiment; and

[0038] Fig.11is a flow chart illustrating another control algorithm for regulating pressure according to one non-limiting exemplary embodiment. DETAILED DESCRIPTION

[0039] refer to Figure 1 , which shows an example of a surgical system 50 that includes a pressure regulating system 52 for regulating the pressure of a heat transfer medium or fluid supplied from a fluid source 54 to a surgical tool 56. In a cryoablation surgical system, the surgical tool is a cryoablation probe that is used to receive fluid at a pressure to induce freezing during a freezing procedure and at a lower pressure for thawing during a thawing operation.

[0040] The fluid source may be a pressurized container for containing fluid at a desired pressure, or a supply line in a hospital for supplying fluid at a desired pressure from a remote source. A pressure regulator is arranged to be connected to the fluid source and the surgical tool via fluid lines 58, 60 to regulate the pressure at which the fluid is delivered from the source to the surgical tool. The pressure regulator includes a valve device, which includes a valve 62 and a valve actuator 64, the valve actuator 64 being used to actuate the valve to an open state that allows the flow of fluid to the surgical tool and a closed state that restricts the flow of fluid. A pressure transducer or sensor 66 is arranged to determine or measure the pressure of the fluid flowing to the surgical tool downstream of the valve, and is operably connected to the controller to output a signal corresponding to the determined pressure.

[0041] The controller 68 of the pressure regulating system is connected to the pressure regulator by a control line 70. During the cryogenic or freezing process, the controller causes the valve to be actuated to an open state, thereby allowing fluid flow at a pressure suitable for generating cryogenic temperatures in the surgical tool (the pressure generated by the cryogenic temperature). This pressure can generally be the same as the pressure at which the fluid stored in the system is subject to pressure loss. During the thawing process, the controller controls the pressure regulator so that the fluid flow to the surgical tool is at a reduced pressure below the pressure generated by the cryogenic temperature. The lower pressure reduces the temperature applied by the surgical probe.

[0042] The controller is connected to the pressure transducer by a control line 72 and is arranged to receive an output from the pressure transducer 66 corresponding to the pressure determined by the transducer. The controller causes selective actuation of the valve 62 in response to the determined pressure.

[0043] In order to reduce the pressure during the thawing process, the controller 68 causes the valve 62 to be actuated to the open and closed states at the corresponding lower and upper set point pressure values ​​to generate a thawing pressure that is less than the pressure for causing freezing (the pressure generated by the low temperature) and is used to deliver the pressure over time. The target pressure that changes over time is the mean effective pressure and is between the lower and upper set point pressure values. The set point pressure value is predetermined so that the flow pressure is lower than the pressure generated by the low temperature and depends on the selected heat transfer medium and other characteristics of the system. At least the lower set point value is less than the pressure generated by the low temperature, and preferably, both the lower and upper set point pressure values ​​are less than the pressure generated by the low temperature.

[0044] In the event that the pressure exceeds the set point pressure value (or acceptable range of pressure values) during operation, particularly during thawing, the set point pressure value may be adjusted by the controller if the flow pressure is higher than desired. If during the thawing pressure cycle, the pressure exceeds the upper set point pressure value, adjustments are made to compensate. There are multiple reasons for this overpressure, as will be explained in more detail below.

[0045] In one example, the controller is arranged to adjust the lower set point pressure value by an adjustment value if the pressure exceeds the upper set point pressure value during the thawing pressure cycle, and cause the valve to actuate to an open state at the adjusted lower set point pressure value. The adjustment allows the pressure to decrease to a pressure less than the lower set point pressure value during the thawing pressure cycle to compensate for the pressure exceeding the upper set point pressure value. The adjustment between the lower set point pressure value and the adjusted set point pressure value may be equal to the difference between the excess pressure and the upper set point pressure value.

[0046] In another example, the controller is arranged to adjust the upper set point pressure value for the defrost pressure cycle by an adjustment value if the pressure exceeded the upper set point pressure value in the previous defrost pressure cycle, and cause the valve to actuate to the closed state at the adjusted upper set point pressure value. The adjustment to the upper set point pressure value may be equal to the difference between the excess pressure and the upper set point pressure value.

[0047] The adjustment values ​​are reduced over multiple defrost pressure cycles so that over time, the adjusted upper and lower set point pressure values ​​are consistent with the upper and lower set point pressure values ​​that generate the target defrost pressure, with the effective average between the upper and lower set point pressure values ​​serving as the target defrost pressure. Preferably, one or both adjustment values ​​are reduced from one cycle to the previous consecutive cycle. Fig. 9 The graph in shows an example of a pressure cycle during regulation, where the effective average pressure gradually becomes consistent with the desired or target nominal pressure.

[0048] The surgical tool 56 includes a supply tube 74. The pressurized fluid in the supply tube undergoes Joule-Thomson expansion into the expansion area 76 of the tool, causing cooling. When the fluid pressure is high enough, the expansion results in a temperature suitable for frozen tissue. The surgical tool includes a heater 78, which is used to heat the fluid in the supply tube during the thawing process. During thawing, the fluid is adjusted to a lower pressure, and the fluid does not cause significant cooling that would otherwise offset the heat supplied by the heater. The controller 68 is operably connected to the heater via a control line 80. When thawing is required, the controller outputs a signal to the heater to cause heating.

[0049] Supply tube 74 is spaced from the inner housing wall of the surgical tool to define a fluid passageway 82 for conveying fluid away from the expansion region to exhaust port 84 for recirculation to the fluid source, or exhaust to atmosphere, or control.

[0050] In the following description, an example of a surgical system, such as a cryosurgery system, is described, including a more detailed explanation and many modifications that may be included in the above examples or other examples. For example, any aspect of the present disclosure related to the pressure regulating system 200 described below also applies to the pressure regulating system 52 described above, and similarly applies to the control systems 68 and 310.

[0051] refer to Figure 2 , a pressure regulating system 200 for a surgical system is shown. The surgical system may be a cryosurgical system. However, it should be understood that the pressure regulating system 200 is not limited to a cryosurgical system.

[0052] The whole system

[0053] Figure 2 1 is a schematic diagram of a cryosurgery system 10. The components of the system can be compactly packaged inside a system housing 12. The cryosurgery system includes one or more fluid sources 14. During cryosurgery, the fluid source 14 can supply a heat transfer medium or fluid. For example, the heat transfer medium can be a fluid such as argon, nitrogen, air, krypton, CO2, CF4, xenon, and various other gases. In one example, the fluid source 14 can simply be a pressurized container or tank. In certain advantageous aspects, the cryosurgery system 10 can take the form of a portable desktop console. In some such advantageous aspects, the system can have a weight of less than about 50 pounds (e.g., about 44 pounds). Therefore, such a system can be compactly positioned in an operating room, thereby reducing space requirements.

[0054] Figure 2 The cryosurgical system 10 shown includes a pressure regulating system 200 that can regulate the pressure supplied from the fluid source 14 to the surgical tool ( Figure 3 As shown in Figure 2As can be seen, the pressure regulating system 200 includes one or more pressure control valves in fluid communication with the fluid source 14. The pressure regulating system 200 includes a control system 310 for controlling the pressure control valves S1, S2, S3, S4, S5, S6, S7, S8, S9, S10, S11, S12, S13, S14, S15, S16, S17, S18, S19, S20, S21, S3, S40, S51, S52, S53, S54, S65, S76, S77, S78, S79, S80, S81, S82, S83, S84, S85, S86, S87, S88, S89, S90, S91, S92, S93, S94, S95, S96, S97, S98, S99, S9 n actuation, as will be further described below.

[0055] continue Figure 2 , the heat transfer medium can be transported from the fluid source 14 via the fluid source outlet 16 toward the pressure regulating system 200, as will be further described below. The heat transfer medium in the fluid source 14 can be at a pressure much higher than the desired pressure. For example, the pressure of the heat transfer medium at the fluid source outlet 16 can be about 3500psi (about 240bar) or in a range between about 1000psi (about 69bar) ​​to about 4000psi (about 275bar). The fluid source 14 can be a pressurized container or container (e.g., a gas cylinder) that contains a heat transfer medium at a pressure much higher than the pressure at the fluid source outlet 16, for example, between about 5000psi (about 350bar) and about 7000psi (about 480bar). Therefore, the pressure of the heat transfer medium is reduced to a desired level by including a pressure regulator. The heat transfer medium just downstream of the pressure regulator (e.g., when the fluid is traveling toward the cryoprobe) can be at a pressure lower than the pressure at the fluid source outlet 16. For example, in some cases, the pressure regulator can reduce the pressure of the heat transfer medium to less than about 4000 psi (about 275 bar) (eg, about 3500 psi or 240 bar). Optionally, a pressure transducer can be fluidly coupled to the pressure regulator to measure the pressure of the heat transfer medium of the fluid source 14.

[0056] Figure 2 The system shown may be of the "closed loop" type. One such system is described in commonly assigned application entitled "Closed Loop System for Cryosurgery" and issued U.S. Patent No. 9,078,733 B2, the entire contents of which are incorporated herein by reference. In one embodiment of the closed loop system, after the surgical procedure is completed, the heat transfer medium is not discharged to the surrounding environment. Instead, the heat transfer medium is discharged from the flow channel ( Figure 5 Channel 1, channel 2, channel 3, channel 4, etc. shown) returns (e.g., via a return path) to fluid source 14. Directional control valves (e.g., check valves) can be used to reduce and / or prevent the flow of heat transfer medium in a direction other than the intended direction (e.g., toward or back from cryoprobe 100).

[0057] Cryoprobe

[0058] As previously described, the surgical tool may be a cryoprobe 100, such as Figure 31. The cryoprobe 100 shown. The cryoprobe 100 includes an elongated, generally cylindrical, hollow body or probe shaft 102. The shaft is shown in cross-section to show internal components (e.g., a trocar). The probe shaft 102 is formed with an operating tip 104 at a portion 106 distal to a fluid or control connection to pass through the patient's tissue during deployment. A coupler 108 is located at a proximal portion 110 opposite the distal portion 106. The coupler 108 includes a pin 111 for connecting to a control system 310 and / or a source, as will be further described below.

[0059] The probe shaft 102 can have a substantially small cross section to allow deployment in the tissue of the patient. In one example, the probe shaft 102 has an outer diameter of approximately 2.1 millimeters. Other sizes of the probe shaft 102 can also be considered. For example, the probe shaft 102 can have an outer diameter between approximately 1.5 millimeters and approximately 2.4 millimeters. In addition, the operating tip 104 can be made of a soft material so as to be flexible (e.g., relative to the proximal portion of the cryoprobe 100) to penetrate soft tissue.

[0060] like Figure 3 As seen in , the cryoprobe 100 includes a supply tube 112 that extends substantially along its length to provide a high-pressure heat transfer medium to the operating tip 104. The supply tube 112 can be coaxially / concentrically positioned within the probe shaft 102. The supply tube 112 can be configured to supply a heat transfer medium (e.g., a cryogenic fluid) for forming an ice ball on the outer surface of the probe shaft 102 above the distal portion 106. In some cases, the supply tube 112 can be a capillary tube.

[0061] The cryoprobe 100 may include a cryocooler, such as Figure 3 . For example, the supply tube 112 can terminate in a Joule-Thomson orifice 114. The Joule-Thomson orifice 114 can be positioned near the operating tip 104 so as to allow the heat transfer medium to exit the Joule-Thomson orifice 114 to expand into the expansion chamber to cool the distal portion 106 and, in particular, the operating tip. When the heat transfer medium expands in the expansion chamber, it cools rapidly and forms ice balls of different shapes and / or sizes on the outer surfaces of the distal portion and the operating tip 104. The heat transfer medium that expands in the expansion chamber is colder than the heat transfer medium that enters. The ice balls formed due to the rapid expansion of the heat transfer medium can freeze and / or ablate tissue (e.g., a tumor).

[0062] Although an exemplary cryocooler is shown, such as a Joule-Thomson orifice 114, it should be understood that other types of cryocoolers, such as cryogenic Dewar flasks, Stirling-type coolers, pulse refrigerators (PTRs), Gifford-McMahon (GM) coolers, can be considered within the scope of the present invention. In addition, as briefly described above, cryogenic fluids that can be used for cooling include argon, liquid nitrogen, air, krypton, CF4, xenon, or N2O.

[0063] The outer surface of the operating tip 104 can be made of a material with high thermal conductivity, such as a metal or metal alloy for effectively conducting heat away from the patient's tissue. Stainless steel is a suitable example of such a material.

[0064] Reference again Figure 3 , a heater 116 may optionally be disposed within the probe shaft 102 to thaw and / or cauterize tissue. The heater 116 may be operated after cooling and ice ball formation to thaw frozen tissue. Optionally, the heater 116 may be operated after the surgical procedure is completed to facilitate the detachment of the cryoprobe 110 therefrom. As referred to herein, thawing / thawing interchangeably refers to either of the two processes of thawing the ice ball between freezing operations or operating the heater 116 to facilitate the detachment of the cryoprobe 100.

[0065] Heater 116 is arranged to heat the heat transfer fluid when it is transported by supply pipe 112 during the thawing portion of the process. The heat transfer medium can be under conditions (pressure, temperature, etc.) so that when expanded from orifice 114, the heat transfer medium may not reach cryogenic temperatures (as described below) in some cases. Instead, the heat transfer medium under these conditions serves to transfer heat to distal portion 108 and operating top to thaw tissue. The heat transfer medium itself can be at a temperature sufficient to thaw, or, as shown, can be heated by heater 116 to increase the temperature.

[0066] The electric heater 116 can be disposed coaxially with the supply tube 112 and the probe shaft 102 to facilitate heating the distal portion 106 of the cryoprobe 100. Alternatively, the electric heater 116 can be positioned elsewhere in the cryoprobe 100 to heat the distal portion 106 of the cryoprobe 100. The electric heater 116 can be a resistive heater 116, wherein the electric heater 116 generates heat proportional to the current flowing through it and the resistance of the electric heater 116. In this case, the probe is arranged to be connected to a power source to deliver current to the heater 116.

[0067] like Figure 3As seen in the example of FIG. 1 , the annular area between the supply tube 112 and the inner wall of the probe shaft 102 defines a return chamber 118 in fluid communication with the expansion chamber for conveying the expanded heat transfer medium from the expansion chamber. In the example of a closed loop system, the heat transfer medium is returned to the fluid source after each surgical procedure. Alternatively, the system can be operated in an "open loop" configuration and can be discharged to the surrounding environment after use.

[0068] Properties of the heat transfer medium

[0069] In some examples of the system, the heat transfer medium may be in an initial state when entering the pressure regulating system 200. The initial state may be defined by an initial pressure and an initial temperature. The initial pressure and initial temperature may be such that when the heat transfer medium undergoes expansion (e.g., Joule-Thomson expansion through the orifice 114), both the pressure and temperature of the heat transfer medium may be reduced. However, when the heat transfer medium undergoes expansion from a pressure significantly less than the initial pressure, the reduction in pressure may not be accompanied by a reduction in temperature (e.g., to a cryogenic temperature). Therefore, if it is desired to provide the heat transfer medium to the distal portion 108 at a cryogenic state, the pressure of the heat transfer medium entering the pressure regulating system 200 may not need to be further reduced from the initial pressure. However, if a heat transfer medium in a non-cryogenic state is provided to the distal portion 108, the pressure of the heat transfer medium may be greatly reduced from the initial pressure by the pressure regulating system 200.

[0070] In an example of a system, as described above, if the initial pressure of the heat transfer medium is high enough, the heat transfer medium undergoes expansion and is cooled. The expansion of the heat transfer medium can sufficiently cool the heat transfer medium so that the temperature of the heat transfer medium is reduced to a cryogenic temperature. For simplicity, this sufficiently high initial pressure is called a cryogenic pressure and will vary depending on the medium (the type of heat transfer medium, such as gas or liquid, the temperature of the heat transfer medium before expansion, etc.) and other characteristics of the system. Therefore, during the freezing process, the pressure regulator is arranged to supply the heat transfer medium at a cryogenic pressure, taking into account that there are some inherent pressure losses in the system (e.g., between the pressure regulator and the surgical tool).

[0071] During thawing, the pressure of the heat transfer medium is adjusted so that it is less than the cryogenic pressure. Preferably, the pressure is adjusted so that it is less than the cryogenic pressure by a safety margin. For simplicity, this pressure is referred to as the non-cryogenic pressure. Expansion of the heat transfer medium from the non-cryogenic pressure (e.g., the same medium and under the same characteristics as the freezing process) may not sufficiently reduce the temperature of the heat transfer medium to reach the cryogenic temperature.

[0072] In one example, the cryogenic pressure may be about 3500 psi (about 240 bar), and the heat transfer medium may be argon. The cryogenic temperature generated may be less than about 150 Kelvin, and preferably in the range of 120 to 150 Kelvin. During the freezing process, when the argon leaves the supply tube 112, it expands from the cryogenic pressure, causing cooling, and reaches a cryogenic state. During the thawing process, the supply pressure of argon is adjusted to a non-cryogenic pressure of less than about 1000 psi (about 70 bar), and preferably less than about 700 psi (about 48 bar). When the argon undergoes expansion from this pressure, its temperature does not drop significantly to reach the cryogenic temperature (or generally remains constant). The argon can be maintained at a temperature above 150K, and preferably above 273K, and can continue to increase, especially when heated by the heater 116.

[0073] At this point, the cryoprobe 100 can receive a heat transfer medium during the thawing process (or cauterization). At this point, the heater 116 supplies heat to the probe shaft 102 to facilitate the removal of the probe shaft 102 from the frozen tissue. Therefore, in such an embodiment, the heat transfer medium can evenly distribute the heat generated by the heater 116 over the surface area of ​​the probe shaft 102 to allow a uniform heat transfer rate between various points of the probe shaft 102 and the surrounding tissue. Such an embodiment allows the probe shaft 102 to be easily removed from the tissue.

[0074] Reference again Figure 2 , the heat transfer medium is delivered from the fluid source 14 to the pressure regulating system 200 to regulate the pressure of the heat transfer medium. One or more cryoprobes can be fluidly connected to the pressure regulating system 200 and positioned downstream of the pressure regulating system 200 (e.g., when the fluid travels toward the cryoprobe) so that the heat transfer medium at a desired pressure can be supplied to the supply tube 112. The pressure regulating system 200 can adjust the pressure of the heat transfer medium so that the heat transfer medium is in a cryogenic state during certain portions of the cryosurgical procedure and in a non-cryogenic state during certain other portions of the cryosurgical procedure.

[0075] For example, the cryoprobe 100 can receive a heat transfer medium in a cryogenic state during a freezing cycle. Thus, as will be described below, the pressure regulating system 200 can be configured to ensure that the heat transfer medium leaving the supply tube 112 is at a cryogenic pressure (e.g., 3500 psi for argon) during the freezing cycle. In addition, during a thawing operation (and / or a cauterization operation), the cryoprobe 100 can receive a heat transfer medium in a non-cryogenic state to allow heat exchange between the cryoprobe 100 and the tissue surrounding the cryoprobe 100. Thus, as will be further described below, the pressure regulating system 200 can be configured to ensure that the pressure of the heat transfer medium is less than the non-cryogenic pressure (e.g., less than 1000 psi for argon) downstream of the pressure regulating system 200 (e.g., when the fluid travels toward the cryoprobe) and / or when the heat transfer medium leaves the supply tube 112. Advantageously, as described above, providing a heat transfer medium in a non-cryogenic state during a thawing operation (or cauterization operation) allows for even distribution of heat generated by the heater 116 during the thawing operation (or cauterization operation), such that heat transfer between the probe shaft 102 and surrounding tissue (e.g., as characterized by the temperature of the probe shaft over the length of the probe shaft) is even during the thawing cycle (and / or cauterization). Such an embodiment can improve the ease of removing the cryoprobe 100 once cryoablation is complete.

[0076] Pressure regulation system

[0077] Common inlet of pressure control valve

[0078] Figure 4 is a schematic diagram showing details of the pressure regulation system 200. Figure 4 , the solid lines connecting the various components may be fluid lines or conduits 204 (eg, tubes) that are coupled to the components of the pressure regulating system 200 by fluid couplings (eg, mechanical connectors).

[0079] like Figure 4 As can be seen in FIG. 2 , the pressure regulating system 200 includes a plurality of pressure control valves (S1, S2, S3, S4, ... S n ). The valve controller can be integrated into the pressure control valve (S1, S2, S3, S4, ... S n ). The valve controller may include an electrical / electronic circuit (e.g., a diode, a field programmable gate array, a printed circuit board (PCB), a processor, etc.) that can receive electrical signals and / or instructions. The valve controller may optionally include an electromagnetic actuator that can be energized (e.g., by voltage or current) or de-energized to adjust the pressure control valve (S1, S2, S3, S4, ... S n ) to move between the on and off states.

[0080] In one embodiment, the pressure control valves (S1, S2, S3, S4, ... S n ) may be configured and arranged in the form of a manifold design and may be referred to as a distribution manifold 210. Return to Reference Figure 2 According to one example, the distribution manifold 210 may be housed within the system housing 12 .

[0081] In one example, if Figure 4 As shown in FIG. 1 , the distribution manifold 210 may optionally have a common manifold inlet 212 upstream of each pressure control valve S1, S2, S3, S4 and a plurality of valve outlets 214a, 214b, 214c, 214d, ... 214n. Each valve outlet (214a, 214b, 214c, 214d, ... 214n) is connected to a corresponding pressure control valve (S1, S2, S3, S4, ... S n ) downstream (e.g., as fluid travels toward the cryoprobe) one or more cryoprobes can be fluidly coupled to each valve outlet (214a, 214b, 214c, 214d, ... 214n) via corresponding flow channels (216a, 216b, 216c, 216d ... 216n). Although four pressure control valves are shown, it should be understood that additional or fewer valves are contemplated within the scope of the present disclosure. In addition, configurations other than manifold designs for arranging and positioning the pressure control valves are also contemplated within the present disclosure.

[0082] like Figure 4 As shown in , the common manifold inlet 212 can be fluidly coupled to the fluid line 16 supplying the heat transfer medium. The fluid connection of the manifold inlet can allow the manifold inlet to be in direct or indirect fluid communication with the fluid source 14 and thus directly or indirectly receive the heat transfer medium therefrom.

[0083] Flow and return to cryoprobe

[0084] Figure 5 An example of a system for connecting to multiple cryosurgical tools so that a procedure can be performed using more than one tool is shown. Figure 5 The connections (214a, 214b, 214c, and 214d) of each of the valve outlets are shown. In the illustrated embodiment, each flow channel (216a, 216b, 216c, 216d, ... 216n) is connected to two sub-channels (216a-1, 216a-2, 216b-1, 216b-2, 216c-1, 216c-2, 216d-1, 216d-2), each of which can be fluidically connected to the cryoprobe 100. Thus, according to the illustrated embodiment, a single pressure control valve ( Figure 3S1, S2, S3, S4, ... S shown in n ) can be fluidly connected to the two cryoprobes. It is conceivable within the scope of the present disclosure that each pressure control valve (S1, S2, S3, S4, ... S n ) with additional or fewer cryoprobes. The subchannels can be configured in the shape of fluid ports or connectors to connect the distribution manifold 210 and its components to the proximal connector 108 of the cryoprobe 100. For example, the subchannels can terminate in a connector that can engage and connect to the proximal pin 111 of the proximal connector 108. Advantageously, in addition to being fluidly connected to the subchannels, the proximal connector 108 can also electrically connect the cryoprobe 100 to the control system 310 (e.g., via a BNC-type electrical connector and / or cable) to allow the control system 310 to electrically communicate with the cryoprobe 100 before or during cryosurgery.

[0085] The pressure regulation system may include various optional flow regulation components, such as reference e.g. Figure 4 As explained, to ensure the properties of the heat transfer medium entering the pressure control valve for various purposes, such as releasing excessive pressure in the fluid line 204, the fluid line 204 conveys the heat transfer medium if the pressure in the fluid line 204 reaches and / or exceeds the limit value of the pressure. The authority value of the pressure can be selected based on operating conditions and safety considerations. The pressure regulation system 200 can also optionally include a pressure transducer fluidly coupled to the fluid line 204 to monitor the pressure of the heat transfer medium entering the pressure regulation system 200 and conveyed by the fluid line 204. In addition, optionally, the pressure regulation system 200 can include a dryer, which can be fluidly coupled to the pressure transducer and positioned downstream thereof (for example, when the fluid is proceeding toward the cryoprobe). Optionally, each flow channel 216a, 216b, 216c, 216d (in Figure 3 The subchannels 214a, 214b, 214c, 214d (shown as fluidly coupled to valve outlets 214a, 214b, 214c, 214d) may be fluidly coupled to one or more desiccators (e.g., silica gel or other desiccants or desiccators). Additionally, in some cases, each subchannel may have a directional control valve to reduce or prevent the chance of heat transfer medium flowing in an unintended direction (e.g., downstream of the cryoprobe 100, or backflow from the cryoprobe 100 toward the fluid source 14 via a return path).

[0086] As mentioned previously, the system may be a closed loop system whereby the heat transfer medium is not exhausted after use, but rather is returned to the fluid source 14 . Figure 5 One such reflow section 300 is shown according to one embodiment. Figure 5As seen in FIG. 1 , the return portion 300 may also be configured as a manifold, and in some embodiments may be referred to as a return manifold 304. The return manifold 304 may have return sub-channels (302a-1, 302a-2, 302b-1, 302b-2, 302c-1, 302c-2, 302d-1, 302d-2). In certain non-limiting embodiments, the number of return sub-channels (302a-1, 302a-2, 302b-1, 302b-2, 302c-1, 302c-2, 302d-1, 302d-2) may be equal to the number of flow sub-channels (216a-1, 216a-2, 216b-1, 216b-2, 216c-1, 216c-2, 216d-1, 216d-2). Each return sub-channel may be in the form of a fluid connection port and may be in fluid communication with the return lumen 118 of the cryoprobe 100 .

[0087] Solenoid / Valve Controls

[0088] For example, Figure 1 , Figure 2 and Figure 4 The pressure control valve shown in is associated with a valve control or actuator to cause actuation of the valve in response to an output from a system control (e.g., controller 68 or system control 310). The valve control may include a solenoid that causes or allows movement of a valve member to selectively engage with a valve seat. When the valve member engages with the valve seat, flow through the valve is restricted (closed state), and when disengaged, flow is allowed (open state). In one example, the valve controller may include an electrical control circuit that communicates with a control system (e.g., receives signals and / or instructions from the control system) to energize the solenoid in response to an output signal from the control system. Other types of valves are contemplated within the scope of the present disclosure.

[0089] Can actuate pressure control valves (S1, S2, S3, S4, ... S n ) to move the pressure control valve (S1, S2, S3, S4, ... S n In the open state, the heat transfer medium received from the common manifold inlet can flow through the pressure control valves (S1, S2, S3, S4, ... S n ) and exits the pressure control valve via the valve outlet (214a, 214b, 214c, 214d, ... 214n), and flows toward the cryoprobe 100 fluidly coupled to the valve outlet (214a, 214b, 214c, 214d, ... 214n). The pressure control valve (S1, S2, S3, S4, ... S n) is typically in the closed state until it is actively powered on (e.g., by an electrical signal or command sent from the control system 310) to move from the closed state to the open state.

[0090] In some aspects, in the open state and the closed state, respectively, the pressure control valve may be in a fully open and fully closed state, respectively, or may be partially open and partially closed. As used herein, the terms "closed", "closed", "closed" (or variations thereof) or "closed state" may include a partially closed state and / or a fully closed state. In addition, the terms "open", "open", "open" (or variations thereof) or "open state" may include a partially open state and / or a fully open state. In some embodiments, the amount of heat transfer medium flowing through the pressure control valve in the closed state may be less than the amount (e.g., flow rate) of the heat transfer medium flowing through the pressure control valve when the pressure control valve is open. When the pressure control valve is closed, the amount (e.g., flow rate) of the heat transfer medium flowing through the pressure control valve may correspond to approximately zero. When the pressure control valve is open, the amount (e.g., flow rate) of the heat transfer medium may be greater than zero.

[0091] Pressure transducer

[0092] Reference again Figure 1 , Figure 2 and Figure 4 The pressure regulation system 52, 200 may include one or more pressure transducers or sensors for determining the flow pressure. The control system is arranged to receive outputs from the transducers to control the operation of the pressure regulation system. For simplicity, in the following more detailed description of the transducers, reference is made to Figure 2 and Figure 4 The transducer shown in FIG. 1 is shown in FIG. 1 , but any aspect of the description is equally applicable to Figure 1 Sensor 66 in. Each pressure transducer (PT1, PT2, PT3, PT4, ... PT n ) can be fluidly connected to corresponding or associated pressure control valves (S1, S2, S3, S4, ... S n In some embodiments, the pressure transducers (PT1, PT2, PT3, PT4, ... PT n ) can be arranged at the outlet of each pressure control valve. In other embodiments, the pressure transducer (PT1, PT2, PT3, PT4, ... PT n ) can be set on each pressure control valve (S1, S2, S3, S4, ... S n) further downstream of the outlet of the cryoprobe. In some cases, the pressure may not vary significantly between the valve outlet (214a, 214b, 214c, 214d, ... 214n) and downstream near the body of the cryoprobe. Therefore, the pressure transducers (PT1, PT2, PT3, PT4, ... PT n ) can be customized to be located at the pressure control valve (S1, S2, S3, S4, ... S n ) at a suitable location downstream of the

[0093] Pressure transducer (PT1, PT2, PT3, PT4, ... PT n ) can measure the corresponding pressure control valve (S1, S2, S3, S4, ... S n ) downstream (e.g., when the fluid is moving toward the cryoprobe). n ) can measure the instantaneous pressure of the heat transfer medium. Alternatively, the pressure transducer (PT1, PT2, PT3, PT4, ... PT n ) can provide a pressure reading indicating the pressure of the heat transfer medium averaged over time within a predefined interval, such as by sampling the pressure of the heat transfer medium within a predefined interval at a predefined sampling frequency. In this case, the pressure transducers (PT1, PT2, PT3, PT4, ... PT n ) the time interval at which pressure data is collected, and the sampling rate at which data is collected (as will be further described below). Although the following description relates to the use of pressure transducers (PT1, PT2, PT3, PT4, ... PT n ) to provide pressure feedback to control performance, as can be appreciated, the pressure transducer can provide pressure feedback to control performance during the freezing cycle, as well as (e.g., adjust the size and shape of the ice ball, etc.). In addition, the pressure transducers (PT1, PT2, PT3, PT4, ... PT n ) can provide an output in the form of a pressure of the heat transfer medium and / or an output indicating the pressure of the heat transfer medium (e.g., an electrical signal, a voltage, etc.). One or more signal conditioning circuits (e.g., an analog-to-digital converter, a filter 324, etc.) can optionally be provided to condition the pressure generated by the pressure transducers (PT1, PT2, PT3, PT4, ... PT n ) signal provided by the

[0094] Control systems and circuits

[0095] The control system is arranged to control the flow of a heat transfer medium supplied to a cryosurgical tool so as to operate the tool in one of a frozen condition or a thawed condition. As described herein, the control controls actuation of a pressure valve device and, at least in the thawed condition, responds to output from an associated pressure transducer to control actuation. Figure 2 and Figure 4 Further details of the control system are described, but the details apply more generally to other embodiments.

[0096] As described above, each pressure control valve (S1, S2, S3, S4, ... S n ) can be fluidly connected to at least one cryoprobe 100 so as to allow the heat transfer medium to selectively flow through the cryoprobe 100. Therefore, some embodiments of the system further include a pressure control valve (S1, S2, S3, S4, ... S n ) of the valve controller. The control system 310 may be a controller in the form of a processor, a gate array (e.g., a field programmable gate array, FPGA), an application specific integrated circuit (ASIC), or a microcontroller that is in electrical communication with the various components of the system (in Figure 1 The control system 310 may include electrical and / or electronic circuits that may be configured or programmable to control the pressure control valves (S1, S2, S3, S4, ... S n ) of the valve controller. The control system 310 can be connected to the pressure transducers (PT1, PT2, PT3, PT4, ... PT n ) operates in communication and can receive pressure (or a signal indicative of pressure) measured therefrom.

[0097] Return to reference Figure 2 In certain advantageous aspects, the control system 310 can be housed within the system housing 12 and in electrical communication with the pressure regulating system 200. In addition, the control system 310 can also be in electrical communication with a cryoprobe connected to a valve outlet (214a, 214b, 214c, 214d, ... 214n). In addition, the control system 310 can include and / or be in electrical communication with a sensor, a timer, an analog-to-digital converter, a wired or wireless communication circuit, etc. In addition, the control system 310 can be operably connected to an external display and an input device (e.g., a keyboard, a mouse, a touch screen, etc.) to receive input from an operator. Alternatively, the control system 310 can be an external computer that can be connected to the system. In this case, the external computer can have computer-readable instructions and / or be programmed with computer-readable instructions to perform one or more control and / or surgical steps, as will be further described below.

[0098] Figure 6 2 is a schematic diagram showing various components of a pressure regulating system according to one embodiment. In this explanation, reference is made to a pressure regulating system 200, which includes one or more pressure transducers (PT1, PT2, PT3, PT4, ... PT2) in electrical communication with one or more signal conditioning components 320. n In one example, the signal conditioning component 320 may include an analog-to-digital converter 322 that converts the pressure transducers (PT1, PT2, PT3, PT4, ... PT n ) The analog electrical signal measured by the pressure sensor is converted into a digital signal. The measurement parameters, such as the sampling rate and the duration of the pressure measurement (e.g., the duration of the freezing, thawing or cauterization cycle), can be appropriately set.

[0099] Continue to refer Figure 6 , one or more filters 324 may optionally be provided as part of the signal conditioning component 320. The filters 324 may advantageously reduce measurement noise and / or provide anti-aliasing of the pressure measurement.

[0100] As mentioned above and reference Figure 4 The control system 310 can be connected with the pressure control valves (S1, S2, S3, S4, ... S n ) electrical communication. Therefore, the control system 310 can send electrical signals to the pressure control valves (S1, S2, S3, S4, ... S n ) to switch it from an open state to a closed state, and vice versa. The control system 310 may send electrical signals to the pressure control valves (S1, S2, S3, S4, ... S2) based on the operating conditions. n ).

[0101] In one example, if the control system 310 determines (e.g., based on operator input) that a freezing operation is to be performed, the control system 310 may send a signal to the pressure control valves (S1, S2, S3, S4, ... Sn) to move them to an open state and / or to close the pressure control valves (S1, S2, S3, S4, ... Sn) for a predefined duration (e.g., corresponding to the duration of the freezing operation). n ) is maintained in an open state. This allows the heat transfer medium from the fluid source 14 to flow through the valve outlets (214a, 214b, 214c, 214d, ... 214n) and enter the cryoprobe 100.

[0102] In another example, if the control system (e.g., based on operator input) determines that a thawing (or cauterizing) operation is to be performed, the control system (e.g., system 310) may send a signal to the pressure controller valves (S1, S2, S3, S4, ... S n ) to repeatedly move between an open state and / or a closed state according to a predetermined algorithm. This can allow the heat transfer medium to be distributed from the fluid source 14 to the cryoprobe at a lower pressure (eg, relative to a cryo operation).

[0103] Continue to refer Figure 4 and Figure 5 In some illustrative embodiments, each cryoprobe 100 can be operated independently of other cryoprobes. Therefore, the control system 310 can actuate each pressure control valve independently of other pressure control valves. Therefore, the control system 310 can selectively actuate each pressure control valve to selectively control the flow of the heat transfer medium corresponding to each pressure control valve to the cryoprobe 100. Additionally, the control system 310 can actuate each valve within a certain duration to supply a heat transfer medium in a low temperature or non-low temperature state, as will be further described below. Such embodiments can advantageously allow different types of cryoprobes (e.g., having different outer diameters of probe shafts and / or different freezing / thawing properties) to be connected to the same cryoablation system and still be controlled independently of each other.

[0104] As previously described, the control system 310 provides a control signal to each pressure control valve (S1, S2, S3, S4, ... S n ) sends an electrical signal to the pressure control valve (S1, S2, S3, S4, ... S n ) to an open state or a closed state. During the defrost cycle, the control system 310 switches the pressure control valves (S1, S2, S3, S4, ... S5) to an open state or a closed state according to one of the disclosed control algorithms. n ) sends an electrical signal to repeatedly switch between the open state and the closed state. In another advantageous embodiment, the control system 310 can selectively and independently actuate each pressure control valve (S1, S2, S3, S4, ... S n ), so that each cryoprobe 100 can be operated independently of the other cryoprobes.

[0105] In one example, reference Figure 2 and Figure 5, when the first cryoprobe 100a performs a freezing operation, the second cryoprobe 100b may not perform any operation, while the third cryoprobe 100c performs a thawing operation. The control system 310 may send a first signal to a first pressure control valve S1 in fluid communication with the first cryoprobe 100a to maintain an open state for the duration of the freezing operation. The control system 310 may send a second signal to a second pressure control valve S2 in fluid communication with the second cryoprobe 100b to remain closed, and send a third signal to the third pressure control valve S3 so as to repeatedly switch between an open state and a closed state if the pressure (or data indicating the pressure) measured by the pressure transducer PT3 is not within a predetermined pressure range.

[0106] As previously described, in certain embodiments, the heat transfer medium may be in a cryogenic state when exiting the supply tube 112 of the cryoprobe 100 for certain cryosurgical procedures (e.g., freezing), and may be in a non-cryogenic state for certain other cryosurgical procedures (e.g., thawing / cauterization). In an advantageous aspect of the present disclosure, the pressure control valves (S1, S2, S3, S4, ... S5) are in a state of being ... n ) remains in an open state. However, during the duration of the thawing cycle, the pressure control valve may be repeatedly opened and closed. Obviously, repeated opening and closing of the pressure control valve may result in a decrease in pressure downstream of the valve outlet (214a, 214b, 214c, 214d, ... 214n) (e.g., when the fluid travels toward the cryoprobe), as will be described below.

[0107] In some such embodiments, during thawing (or cauterization), the pressure control valves (S1, S2, S3, S4, ... S n ), until the pressure of the heat transfer medium is the desired pressure set point (e.g., less than the second pressure). When expanding from a pressure less than the second pressure, the heat transfer medium can advantageously be in a non-cryogenic state so that ice ball formation may not occur during the thawing operation.

[0108] In one example, if the heat transfer medium is argon, based on the size of the cryoprobe and / or the freezing / thawing properties, the pressure set point can be between about 200 psi (about 15 bar) and about 1000 psi (about 70 bar), for example, about 500 psi (about 35 bar). Thus, the pressure control valves (S1, S2, S3, S4, ... S5) can be opened and closed during the thawing / cauterization process. n ) to effectively achieve the desired pressure within the pressure set point range (e.g., approximately 200-1000 psi or 15-70 bar).

[0109] As described above, the pressure control valves may be opened and closed to achieve a desired pressure of the heat transfer medium. One or more control algorithms (described further below) may be used to control the pressure control valves (S1, S2, S3, S4, ... S n ) on and off.

[0110] Control Algorithm

[0111] Algorithm 1: On-off control

[0112] As described below, a control system (e.g., system 68 or 310) includes a computer readable storage medium that includes a control algorithm that, when executed by the control system, causes the control system to perform, for example, Figure 7 and Figure 8 The steps shown in and described in this article. Figure 7 A control algorithm 600 for regulating the pressure of a heat transfer medium during a thawing cycle (or cauterization) is shown according to a non-limiting exemplary embodiment. The steps described herein (e.g., for algorithms 600, 700, 900, and 1000) can be used to adjust the pressure in at least one of the flow channels via at least one of the pressure control valves (e.g., S1) based on the pressure measured by at least one of the pressure transducers (e.g., PT1). Optionally, the pressure can be adjusted based on the pressure measured by the pressure transducers (PT1, PT2, PT3, PT4, ... PT n ) simultaneously and / or sequentially controls the pressure control valves (S1, S2, S3, S4, ... S n ) to adjust the pressure in all flow channels.

[0113] At step 602, a pressure transducer (e.g., PT1) measures pressure and sends the measured pressure (or an electrical signal representing it) to the control system 310. At step 604, the control system 310 receives the measured pressure (or an electrical signal representing it) and compares it to a minimum or lower pressure set point. If the measured pressure is less than the minimum pressure set point value, at step 606, the control system 310 sends a signal to the valve controller to open the pressure control valve. While the valve is open, the control system 310 may continue to monitor the pressure (via the pressure received from the pressure transducer) to determine at step 608 whether the pressure reaches and / or exceeds the maximum or upper pressure set point. If the control system 310 determines that the measured pressure reaches and / or exceeds the maximum pressure set point value, at step 610, the control system 310 sends a signal (or instruction) to the valve controller to close the pressure control valve.

[0114] In an example implementation of the control algorithm 600, the pressure regulation system 200 may receive pressure from the pressure transducer at periodic intervals. For example, the pressure transducer may sample the pressure at a predetermined sampling rate (e.g., 2 kHz) and may send the measured pressure to the control system 310. The sampling rate may be selected to minimize (or eliminate) aliasing and generate a sufficient number of pressure readings.

[0115] The control system 310 can compare the measured pressure to the minimum and maximum pressure set points. If the measured pressure is at or less than the pressure set point, the control system 310 sends a signal or instruction to the valve controller to open the pressure control valve. At the same time, the pressure transducer continues to generate pressure measurements at its predetermined sampling rate and sends them to the control system 310. The control system 310 then continues to monitor the measured pressure and determines whether the measured pressure is within the range of the pressure set points (e.g., above the minimum pressure set point and less than the maximum pressure set point).

[0116] The minimum and maximum pressure set points can be set to values ​​based on the type of cryoprobe and its freeze / thaw performance. Both the minimum and maximum pressure set points can be the same value or different values. As the pressure cycles between the set points, it will generate an effective mean flow pressure between the set points, and the values ​​of the set points are predetermined so that the expansion from the effective mean flow pressure will result in the temperature of the heat transfer medium being non-cryogenic and suitable for the thawing process.

[0117] In an optional embodiment, the control algorithm 600 may include an optional step 612, whereby the control system 310 tracks the time that has passed after the pressure control valve has been opened, and compares the elapsed time with a predetermined time at step 614. If the elapsed time exceeds the predetermined time, at optional step 616, if the predetermined time has passed, the control system 310 may generate a fault signal to indicate that the flow channel has failed (one or more of 216a, 216b, 216c, 216d). At optional step 618, the control system 310 may then send a signal (or instruction) to close the pressure control valve.

[0118] In an example implementation of the control algorithm 600, the pressure control valve can be opened and closed based on the measured pressure. The valve can remain open for a first duration (e.g., 30 milliseconds), at which point the pressure measured by the pressure transducer can reach the maximum pressure set point. The control system 310 can typically send a signal to close the valve. However, if there is a fault in the pressure regulation system 200 and the control system 310 cannot close the pressure control valve, the control system 310 can continue to monitor the time elapsed since the valve was opened. If the elapsed time exceeds a predetermined time (e.g., two seconds), the control system 310 can close the pressure control valve and / or send a fault signal. This embodiment can provide additional safety in the event that the control system 310 cannot regulate the pressure.

[0119] Algorithm 2: On-off control with changing set point

[0120] Figure 8 A control algorithm 700 for regulating the pressure of a heat transfer medium during a thaw / cauterize cycle is shown according to another non-limiting exemplary embodiment.

[0121] The control algorithm 700 can be substantially similar to the control algorithm 600. In one example, the control algorithm 700 can be implemented when the pressure (as measured by the pressure transducer) may not always respond instantaneously to the opening and closing of the valve. Thus, in some such examples, when the pressure set point is reached, the pressure (as measured by the pressure transducer) may continue to rise even after the valve is closed. The control algorithm 700 can account for this effect to provide a consistent and stable pressure.

[0122] At step 702, the pressure transducer measures the pressure and sends the measured pressure (or an electrical signal representing it) to the control system 310. At step 704, the control system 310 receives the measured pressure (or an electrical signal representing it) and compares it to the minimum pressure set point. If the measured pressure is at or less than the minimum pressure set point value, at step 706, the control system 310 sends a signal to the valve controller to open the pressure control valve. When the valve is open, the control system 310 can continue to monitor the pressure (via the pressure received from the pressure transducer) to determine whether the pressure reaches and / or exceeds the maximum pressure set point at step 708. If the control system 310 determines that the measured pressure reaches and / or exceeds the maximum pressure set point, at step 710, the control system 310 sends a signal (or instruction) to the valve controller to close the pressure control valve. At this point, the pressure (as measured by the pressure transducer) may continue to rise before starting to decrease. At optional step 712, the control system 310 can compare the pressure value before the pressure begins to decrease with the first pressure. If the pressure (as measured by the pressure transducer) reaches and / or exceeds the first pressure (after the pressure control valve is closed), at optional step 714, the control system 310 may determine that the minimum pressure set point may have to be offset or adjusted to result in a smaller deviation from the desired nominal pressure (e.g., by adjusting the pressure of the pressure control valve). Fig. 9 described).

[0123] At step 714, the control system 310 may calculate an offset and adjust the minimum pressure set point by an amount corresponding to the offset. In one example, the offset may be the difference between the first pressure and the maximum pressure set point. In this example, the minimum pressure set point may be adjusted (lowered) by the offset. Thus, for subsequent cycles, the pressure control valve may not open until the new lowered or adjusted minimum pressure set point is reached. Subsequently, the offset from the maximum set point may also be adjusted for subsequent cycles so that the pressure range between the adjusted set points is smaller than the initial set point value.

[0124] In some advantageous embodiments, the first pressure may be greater than the maximum pressure set point, and the second pressure may be less than the minimum pressure set point. In additional and alternative embodiments, the first and second pressures may not be constant throughout the thawing (or cauterizing) cycle, and may be adjusted each time the pressure control valve is opened and closed. In further additional and alternative embodiments, over time, the first and second pressures may eventually be equal to the maximum pressure set point and the minimum pressure set point, respectively. In such an advantageous embodiment, after closing the pressure control valve, the pressure (as measured by the pressure transducer) may eventually decrease monotonically (rather than initially increasing and then decreasing). In this way, in a pressure cycle, one cycle reduces the adjustment of one or both of the set points compared to subsequent cycles, so that the adjustment tends to zero and the effective pressure is aligned with the target nominal pressure.

[0125] In an example implementation of the control algorithm 700, the pressure control valve may be opened and closed based on the measured pressure and the pressure set point. If the pressure is below the minimum pressure set point, the control system 310 may send a signal to open the pressure control valve. The pressure may continue to increase and eventually reach the maximum pressure set point. The control system 310 may send a signal to close the pressure control valve. Due to the effects of delays, blockages, etc. in the valve opening and closing in response to the signal from the control system 310, the pressure measured by the pressure sensor may continue to increase, for example, until the first pressure before starting to decrease again. The first pressure may be greater than the maximum pressure set point. Therefore, if the pressure reaches and / or exceeds the first pressure, the control system 310 may not open the pressure control valve when the minimum pressure set point is reached. Before the pressure control valve is opened again, the control system 310 may wait until the pressure reaches the second pressure. When the pressure reaches the second pressure, the pressure control valve is opened.

[0126] In one example involving argon as a heat transfer medium, the minimum pressure set point may be, for example, about 450 psi (about 30 bar). In this example, the maximum pressure set point may be, for example, about 500 psi (about 35 bar). The first pressure may be, for example, about 550 psi (about 38 bar). Therefore, if the pressure reaches and / or exceeds the first pressure of about 550 psi, the control system 310 may not open the pressure control valve when the minimum pressure set point of about 450 psi is reached. In this example, the pressure continues to decrease until a second pressure of about 400 psi (about 28 bar) is reached. When the pressure reaches the second pressure, the pressure control valve is opened.

[0127] The control system 310 can adjust the values ​​of the first pressure and the second pressure corresponding to valve opening and closing based on the measured pressure in subsequent cycles of valve opening and closing based on the offset between the measured pressure and the minimum and maximum pressure set points shortly before or after the valve opens and closes, respectively. In addition, as will be further described below, the control system can also determine the minimum and maximum pressure set points based on the type of cryoprobe with which it is in operative communication.

[0128] In another example, during a subsequent cycle after a pressure regulation cycle according to the control algorithm 700, the pressure may not reach as high as the first pressure. After the pressure control valve is closed, the pressure may, for example, reach a lower value of the third pressure. Therefore, in the next subsequent cycle, before the pressure control valve is opened, the control system 310 can wait until the pressure reaches, for example, the fourth pressure. In some optional advantageous embodiments, the pressures at opening and closing can eventually converge to a minimum pressure set point and a maximum pressure set point, respectively. The control system 310 can dynamically adjust the values ​​of the first pressure, the second pressure, the third pressure, and the fourth pressure (and subsequent pressures) corresponding to the opening and closing of the valve based on the measured pressure at various points in the cycle and the offset between the measured pressure and the minimum and maximum pressure set points. In addition, as will be further described below, the control system can also determine the minimum and maximum pressure set points based on the type of cryoprobe with which it is operationally communicated.

[0129] In some such examples involving argon as the heat transfer medium, if the maximum pressure set point is about 500 psi, the first pressure is about 550 psi, the minimum pressure set point is about 450 psi, and the second pressure is about 400 psi, the third pressure can be about 525 psi (about 36 bar), and the fourth pressure can be about 475 psi (about 33 bar).

[0130] The control system 310 may typically send a signal to close the valve. However, if there is a fault in the pressure regulation system 200 and the control system 310 is unable to close the pressure control valve, the control system 310 may continue to monitor the time that has passed since the valve was opened. If the time that has passed exceeds a predetermined time (e.g., two seconds), the control system 310 may close the pressure control valve and / or send a fault signal. This embodiment may provide additional safety in the event that the control system 310 is unable to regulate pressure.

[0131] Fig. 9 6 and 700, respectively. At time t0, the pressure transducer begins collecting pressure data (e.g., as shown by steps 602 and 702 of control algorithms 600 and 700, respectively). At time 1, the pressure measured by the pressure transducer (at Fig. 9600 and 700, respectively), and the control system 310 sends a signal (or instruction) to open the pressure control valve (e.g., as shown in steps 606 and 706 of the control algorithms 600 and 700, respectively). The pressure measured by the pressure transducer begins to increase. At time t2, the pressure measured by the pressure transducer reaches the maximum pressure set point (e.g., as shown in steps 608 and 708 of the control algorithms 600 and 700, respectively). At this point, the control system 310 sends a signal (or instruction, such as shown in steps 610 and 710 of the control algorithms 600 and 700, respectively) to close the pressure control valve.

[0132] In some optional embodiments, after the pressure control valve is closed, the pressure measured by the pressure sensor may begin to decrease monotonically until the pressure control valve is opened again. Alternatively, in other optional embodiments, the pressure measured by the pressure transducer may continue to increase (as indicated by the pressure sensor) even after the pressure control valve has been closed until time t3 before the decrease. Fig. 9 denoted by the dotted line in the figure).

[0133] In some such optional embodiments, at time t3, the pressure measured by the pressure transducer may reach and / or exceed the first pressure. In such optional embodiments, as described above, the control system 310 may allow the pressure to continue to decrease further below the minimum pressure set point to reduce the chance of the pressure overshooting the maximum pressure set point in the next opening of the pressure control valve. Therefore, at time t4, the pressure (as measured by the pressure transducer) is allowed to decrease to a second pressure (less than the minimum pressure set point), at which point the pressure control valve is opened again.

[0134] Fig. 9 A desired nominal pressure is also shown in solid line. The desired nominal pressure may be a cycle average pressure and may be the pressure of the heat transfer medium downstream of the pressure control valve (e.g., when in the supply pipe of the cryoprobe or downstream thereof). The desired nominal pressure may remain substantially constant over time.

[0135] Fig. 9 The dashed line in FIG. 4 also shows the effective average pressure. The effective average pressure may be a cycle average representing the cycle average over a single cycle. As previously described, due to effects such as delays in valve opening and closing, physical obstructions, etc., the pressure measured by the transducer may not respond instantaneously to the opening and closing of the valve and may continue to rise even after the valve is closed.

[0136] Thus, the effective average pressure may oscillate around the desired normal pressure. Over time, as the control system adjusts the opening and closing of the valve to ensure that the measured pressure corresponds to the minimum and maximum pressure set points, respectively (e.g., Figure 8 ), the effective average pressure may converge (within a few cycles of valve opening and valve closing) to the desired nominal pressure, as described in algorithm 700. Fig. 9 shown.

[0137] Algorithm 3: Pressure set point level based on needle type

[0138] Fig.10 A method 900 of controlling the flow of a heat transfer medium during a thawing cycle according to a non-limiting exemplary embodiment is shown. The method 900 can advantageously allow for independent control of different types of cryoprobes (e.g., having different probe shaft outer diameters and / or different freeze / thaw properties). In such cases, the pressure set points described above can be different. Thus, the method 900 can determine that it may be necessary to supply a heat transfer medium to provide effective heat distribution during thawing (or cauterization) without having a pressure set point at which freezing and / or ice ball formation occurs for a particular probe type.

[0139] At step 902, a control system, such as control system 310, can read (e.g., via a processor) information about the cryoprobe connected to each flow channel (216a, 216b, 216c, 216d, ... 216n). The information can be stored in an electronic circuit (e.g., a chip) on the cryoprobe. At step 904, control system 310 can determine a pressure set point for each of the channels based on the information about the cryoprobe. In one example, optionally, the pressure set points for different types of cryoprobes can be determined in advance (e.g., experimentally) and stored in a memory or storage device that is in operational communication with control system 310 (e.g., wired or wirelessly). Alternatively, in another example, as another option, the pressure set point can be determined empirically.

[0140] At step 906, the control system 310 actuates the pressure control valves (S1, S2, S3, S4, ... S2) according to the control algorithm (described above, for example, the control algorithm 600 or the control algorithm 700 or a variation thereof). n ) and use the pressure set point determined at step 904. For example, the values ​​of the maximum and minimum pressure set points can be determined by the control system 310 at step 904 and used in conjunction with the control algorithm 600 or 700. Optionally, as described above with respect to Figure 8 As described, Fig.10The algorithm can also dynamically adjust the pressure set point during operation so that over time, the measured pressure roughly corresponds to the desired effective pressure.

[0141] In an optional embodiment, when method 900 is used in conjunction with control algorithm 700, control system 310 can determine and set one or more of a maximum pressure set point, a minimum pressure set point, a first pressure, and a second pressure for each flow channel (one or more of 216a, 216b, 216c, 216d) based on the type of cryoprobe connected to the corresponding flow channel and / or its freezing / thawing properties.

[0142] An example implementation of method 900 is as follows. A first cryoprobe 100a and a second cryoprobe 100b may be connected to a first flow channel 216a and a second flow channel 216b. The control system 310 may determine (e.g., based on previous data, experiments, empirical methods) that the pressure set point for the first cryoprobe 100a is approximately 500psi and the pressure for the second cryoprobe 100b is approximately 450psi. In such a case, the control system 310 may actuate the first pressure control valve S1 that is fluidically coupled to the first flow channel 216a according to a control algorithm (600, 700, or 1000) so that the pressure in the first flow channel 216a is approximately 500psi. The control system 310 may also actuate the second pressure control valve S2 (independent of the first pressure control valve) so that the pressure in the second flow channel 216b is approximately 450psi. Additional or alternative implementations of method 900 may also be envisioned.

[0143] Algorithm 3: Duty Cycle (described earlier)

[0144] Fig.10 A control algorithm 1000 for adjusting the pressure of a heat transfer medium according to a non-limiting exemplary embodiment is shown. The method can be performed with a cryosurgical system according to any of the disclosed embodiments. The method can be in the form of machine-readable (or computer-executable) instructions and provided to the control system 310 (e.g., programmed in a memory of the control system 310). At step 1002, the control system 310 can determine (e.g., based on user input received in step 1001) whether the cryosurgical system is performing a thawing (or cauterization) operation or a freezing operation. The control system 310 can make such a determination, for example, based on operator input. If the control system 310 determines that the system is about to perform a freezing cycle, optionally, the control system 310 can determine (based on operator input or stored program settings) which of the freezing probes will perform the freezing operation. At step 1006, the control system 310 can communicate with the pressure control valves (S1, S2, S3, S4, ... S n) electrical communication and sends an electrical signal, which controls the pressure of the valve (S1, S2, S3, S4, ... S n ) switches from its closed state to an open state. Advantageously, at this point, the control system 310 can determine that the pressure control valves (S1, S2, S3, S4, ... S n ) corresponds to the cryoprobe that performs the cryo operation, and selectively actuates those pressure control valves (S1, S2, S3, S4, ... S n Alternatively, the control system 310 may actuate all the pressure control valves (S1, S2, S3, S4, ... S n In another advantageous aspect, the control system 310 can monitor the pressure transducers (PT1, PT2, PT3, PT4, ... PT n ) to control and adjust the refrigeration performance. For example, once the desired refrigeration performance (e.g., as indicated by the size of the ice ball) is achieved, the control system 310 can close (and / or repeatedly open and close) the pressure control valves (S1, S2, S3, S4, ... S n ).

[0145] If the control system 310 determines that the cryosurgical system is performing thawing (or cauterization), the control system 310 then, at step 1008, receives a signal from a pressure transducer (PT1, PT2, PT3, PT4, PT5, PT6, PT7, PT8, PT9, PT10, PT11, PT12, PT23, PT34, PT5, PT6, PT7 n ) receives pressure measurement data. At step 1010, the control system 310 determines whether the pressure measured downstream of the pressure control valve (e.g., when the fluid is traveling toward the cryoprobe) is within a predetermined pressure range. As previously described, the predetermined range can be less than the second pressure (e.g., less than the pressure of the heat transfer medium in a non-cryogenic state). If the control system 310 determines that the pressure is not within the predetermined pressure range, at step 1012, the control system 310 repeatedly actuates (e.g., by sending an electrical signal) the pressure control valve to switch between an open state and a closed state of the pressure control valve. The control system 310 can perform this step until the pressure downstream of the pressure control valve (e.g., when the fluid is traveling toward the cryoprobe) is within the predetermined pressure range.

[0146] In an advantageous aspect of the control algorithm 1000, the control system 310 can actuate the pressure control valve in several repeated cycles during the thawing process (or cauterization), wherein for each cycle, the pressure control valve is in an open state during a first time interval and in a closed state during a second time interval. The first and second time intervals can be selected to produce a desired pressure at the downstream of the pressure control valve. In certain additional embodiments, the pressure control valve can be in an open state for a duration corresponding to the freezing operation. In some embodiments, the ratio of the time that the pressure control valve in one or more pressure control valves remains open to the time that the pressure control valve in one or more pressure control valves remains closed can be between about 5% and about 80%.

[0147] Several advantages are provided according to embodiments of the present disclosure. Embodiments provide the ability to use a single heat transfer medium for both freezing and thawing (or cauterization) operations, thereby eliminating an additional source of fluid. In addition, by using a heat transfer medium to distribute heat during the thawing cycle (cauterization), the heat generated by the heater within the cryoprobe can be more evenly distributed so that the temperature measured at various points along the length of the cryoprobe may not change dramatically. Certain embodiments allow the pressure of the heat transfer medium to be adjusted over a wide range without the use of additional pressure regulators or solenoids. Several of the disclosed embodiments provide a cryoablation system that is compact and efficiently packaged.

[0148] Non-limiting embodiments have been described. These and additional embodiments are within the scope of the following claims.

Claims

1. A pressure regulating system for a surgical system, for regulating the pressure of a heat transfer medium supplied from a heat transfer medium source to a surgical tool, the surgical tool being connectable to the surgical system, the pressure regulating system comprising: A pressure control valve comprising an inlet fluidly connectable to the heat transfer medium source and an outlet fluidly connectable to the surgical tool, the pressure control valve being actuatable to In the open state, the heat transfer medium is allowed to pass therethrough; as well as In a closed state, reducing the heat transfer medium passing therethrough, wherein the amount of heat transfer medium flowing through the pressure control valve in the closed state is less than the amount of heat transfer medium flowing through the pressure control valve in the open state; and a control system operably coupled to the pressure control valve, the control system being configured to: receiving a signal corresponding to the pressure of the heat transfer medium at the outlet of the pressure control valve or downstream thereof, determining whether the pressure is at or below a minimum pressure set point, If the control system determines that the pressure is at or below the minimum pressure set point, sending a first signal to actuate the pressure control valve to the open state, determining whether the pressure is above a maximum pressure set point, and If the control system determines that the pressure is greater than the maximum pressure set point, sending a second signal to actuate the pressure control valve to the closed state, wherein the control system is configured to determine whether the pressure increases to a first pressure exceeding the maximum pressure set point after actuating the pressure control valve to a closed state, and to adjust the minimum pressure set point by an offset equal to the difference between the first pressure and the maximum pressure set point.

2. A pressure regulating system according to claim 1, wherein the control system is configured to send a third signal to actuate the pressure control valve to an open state if the control system determines that the pressure is at or less than the minimum pressure set point after actuating the pressure control valve to a closed state. 3 . The pressure regulating system of claim 1 , wherein the control system is configured to measure an elapsed time after the pressure control valve is actuated to an open state, and compare the elapsed time with a predetermined time. 4 . The pressure regulating system of claim 3 , wherein the control system is configured to send the second signal to actuate the pressure control valve to a closed state if the elapsed time exceeds the predetermined time. 5 . The pressure regulating system of claim 3 , wherein the control system is configured to send a fourth signal indicating a fault condition if the elapsed time exceeds the predetermined time.

6. The pressure regulating system of claim 1, wherein the pressure control valve is cooperable with a valve actuator, and the valve actuator responds to a control signal from the control system to actuate the valve to an open state and a closed state.

7. The pressure regulating system of claim 6, wherein the actuator comprises a solenoid.

8. The pressure regulating system according to claim 1, further comprising a pressure transducer configured to measure the pressure of the heat transfer medium at the outlet of the pressure control valve or downstream of the outlet of the pressure control valve.

9. A cryosurgery system, comprising: one or more cryoprobes for insertion into a patient to perform a cryosurgery procedure, each cryoprobe configured to receive a heat transfer medium delivered from a heat transfer medium source; A pressure regulating system for regulating the pressure of a heat transfer medium delivered to the or each cryoprobe, the pressure regulating system comprising: one or more pressure control valves, each pressure control valve operable to place the source of heat transfer medium in fluid communication with at least one cryoprobe, Each pressure control valve can be actuated In the open state, the heat transfer medium is allowed to pass therethrough, or In the closed state, the heat transfer medium is reduced through the wherein the amount of heat transfer medium flowing through the pressure control valve in the closed state is less than the amount of heat transfer medium flowing through the pressure control valve in the open state, and one or more pressure transducers, each pressure transducer configured to measure the pressure of the heat transfer medium at or downstream of an associated pressure control valve; and a control system operably connected to the one or more pressure control valves and the one or more pressure transducers and configured to: determining whether the pressure received from the pressure transducer is at or below a minimum pressure set point, If the pressure is at or below the minimum pressure set point, sending a first signal to actuate an associated pressure control valve to an open state, determining whether the pressure received from the pressure transducer is at or above a maximum pressure set point, and If the pressure is greater than the maximum pressure set point, sending a second signal to actuate the associated pressure control valve to a closed state, wherein the control system is configured to determine whether the pressure increases to a first pressure exceeding the maximum pressure set point after actuating the pressure control valve to a closed state, and to adjust the minimum pressure set point by an offset equal to the difference between the first pressure and the maximum pressure set point.

10. The cryosurgery system of claim 9, comprising a plurality of the cryoprobes, each of the cryoprobes being operable independently of the other cryoprobes, such that the control system is arranged to determine the maximum pressure set point and the minimum pressure set point corresponding to each cryoprobe, and to actuate the pressure control valve connected to the corresponding cryoprobe to an open state and a closed state based on the corresponding maximum pressure set point and the minimum pressure set point.

11. The cryosurgical system of claim 9, wherein each pressure control valve comprises a valve actuator for actuating the valve to a closed state and an open state, and the actuator controls actuation in response to a control signal from the control system.

12. The cryosurgical system of claim 9, wherein each cryoprobe includes an electric heater that is responsive to a control signal from the control system to heat a heat transfer medium in the cryoprobe during a thawing operation.

13. A cryosurgery system according to claim 12, wherein the control system is arranged to regulate the pressure of the heat transfer medium delivered to the or each cryoprobe during a thawing operation so that the pressure is at or below the maximum pressure set point, at which the heat transfer medium is in a non-cryogenic state to distribute the heat generated by the electric heater for transfer to the patient.

14. A cryosurgery system according to claim 9, wherein the control system is arranged to regulate the pressure of the heat transfer medium delivered to the or each cryoprobe so that the pressure is greater than the maximum pressure set point, at which the heat transfer medium is in a cryogenic state to freeze and / or cryoablate tissue surrounding the cryoprobe during a cryooperation.

15. The cryosurgical system of claim 14, wherein the control system is arranged to cause each pressure control valve to be actuated to an open state for the duration of the cryooperation.

16. The cryosurgery system of claim 9, wherein the heat transfer medium is argon.

17. The cryosurgical system of claim 16, arranged in fluid communication with a heat source to supply a heat transfer medium at a pressure between 1000 psi and 4000 psi upstream of the pressure regulating system.

18. The cryosurgery system of claim 17, wherein the minimum pressure set point is at least 200 psi.

19. The cryosurgical system of claim 18, wherein the maximum pressure set point is at or below 1000 psi.

20. The cryosurgery system of claim 9, wherein when the pressure received from the pressure transducer in the one or more pressure transducers is at or greater than a maximum pressure set point, the control system sends a signal to reduce the ratio of the time that the pressure control valve in the one or more pressure control valves remains open relative to the time that the pressure control valve in the one or more pressure control valves remains closed.

21. A cryosurgery system comprising: one or more cryoprobes; one or more pressure control valves, each pressure control valve being fluidly coupled to at least one cryoprobe, each pressure control valve being independently actuatable relative to the other pressure control valves, In the open state, a heat transfer medium is allowed to pass therethrough; as well as In a closed state, reducing the heat transfer medium passing therethrough, wherein the amount of heat transfer medium flowing through the pressure control valve in the closed state is less than the amount of heat transfer medium flowing through the pressure control valve in the open state; one or more pressure transducers, each pressure transducer fluidly coupled to a corresponding pressure control valve; and a control system in operative communication with each pressure control valve, the control system being configured to: determining whether at least one cryoprobe is performing a freezing operation or a thawing operation; If the control system determines that the at least one cryoprobe is performing the freezing operation, opening the pressure control valve fluidly coupled to the at least one cryoprobe so that a heat transfer medium is supplied to the at least one cryoprobe through the pressure control valve to cause cryogenic expansion and / or freezing, and If the control system determines that the at least one cryoprobe is performing the thawing operation, actuating the pressure control valve to repeatedly open and close the pressure control valve fluidly coupled to the at least one cryoprobe based on the pressure measured by the pressure transducer, making the pressure of the heat transfer medium supplied through the pressure control valve lower than the pressure corresponding to the low temperature expansion and / or freezing generated from the heat transfer medium, wherein the control system is configured to actuate each pressure control valve independently of the other pressure control valves based on a pressure measured by each of the pressure transducers fluidly coupled to the corresponding pressure control valve, wherein the control system is configured to determine whether the pressure increases to a first pressure exceeding a maximum pressure set point after actuating the pressure control valve to a closed state, and to adjust the minimum pressure set point by an offset equal to the difference between the first pressure and the maximum pressure set point.

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