Stabilizing pressure in cryogenic equipment

Abstract

A method for stabilizing pressure within a cryogenic device includes: receiving a flow rate value corresponding to an expected average mass flow rate of refrigerant through a needle probe of a cryogenic device during a cryotherapy treatment cycle; determining a target heater power to be applied to a heater associated with the cryogenic device for the treatment cycle based on the flow rate value, wherein the heater is configured to heat the refrigerant; receiving input for the treatment cycle; causing the refrigerant to flow toward the needle probe for a period of time in response to the input; and applying the target heater power to the heater during the treatment cycle so as to heat the refrigerant and stabilize the pressure within the cryogenic device.

Description

[0001] Cross-references to related application data

[0002] This application claims the benefit of U.S. Provisional Application No. 62 / 943,017, filed December 3, 2019; the entire disclosure of which is incorporated herein by reference for all purposes. Technical Field

[0003] Devices, systems and methods for cooling tissue for therapeutic purposes, including nerves for treating pain. Background Art

[0004] The present disclosure generally relates to medical devices, systems and methods for cryotherapy. More specifically, the present disclosure relates to cryogenically cooling a patient's target tissue to degenerate, inhibit, reshape or otherwise affect the target tissue to achieve a desired change in its behavior or composition. Cryogenic cooling of neural tissue has been shown to be effective in treating a variety of indications, including pain (e.g., occipital and other neuralgia, neuromas, osteoarthritis pain), spasticity, and joint stiffness, among others. For example, cooling neural tissue has been found to degenerate or inhibit nerves that contribute to these conditions. Cryogenic cooling has also been employed to address aesthetic conditions, for example, by inhibiting undesirable and / or unsightly effects on the skin (such as fine lines, wrinkles, or cellulite depressions) or on other surrounding tissues.

[0005] In view of the above, cryogenic devices with needle probes have become a mode of therapeutic cooling of target tissues for treating various indications. The needle probes of such devices are usually inserted into the skin of a patient adjacent to the target tissue. Some cryogenic devices may include a cryogen that can be injected into the target tissue via an opening in the needle of their needle probe so that the target tissue is directly cooled by the cryogen. Other cryogenic probes may include a closed needle tip, in which case the needle can be cooled (e.g., by the flow of a cryogen), and the target tissue adjacent to the cooled needle can thereby be cooled by conduction. Cryogenic probes have been proven to be effective in accurately, conveniently and reliably creating cryogenic areas at or around target tissues in the patient's body. A cryogenic area may be a volume of tissue cooled by one or more needles of a cryogenic probe (e.g., a volume of tissue near or around a distal portion of a needle). For example, a cryogenic area may be a volume of tissue as follows: the volume of the tissue is cooled so as to freeze the tissue within the volume (e.g., the cooling area may be defined by an isotherm of approximately 0°C (or other suitable temperature) that can be formed around the needle of a cryogenic probe). Summary of the invention

[0006] The present disclosure relates to improved medical devices, systems and methods.Many of the devices and systems described herein would be beneficial for cryotherapy using cryogenic devices.

[0007] In some embodiments, a method may include receiving a first flow rate value, wherein the first flow rate value corresponds to an expected average mass flow rate of a cryogen through a first needle probe of a cryogenic device during a cryotherapy treatment cycle. The method may further include determining a first target heater power to be applied to a heater associated with the cryogenic device for a first treatment cycle based on the first flow rate value. The method may further include receiving an input for the first treatment cycle. The method may include causing the cryogen to flow toward the first needle probe for a period of time in response to the input, and applying a first target heater power during the first treatment cycle so as to heat the cryogen and stabilize the pressure within the cryogenic device during or after the first treatment cycle (or in some embodiments before the first treatment cycle). This method may be used, for example, to stabilize the pressure within the cryogenic device during cryotherapy treatment.

[0008] In some embodiments, the first target heater power is defined such that an average rate of change of pressure during a cooling phase of the first treatment cycle remains within a predetermined range. In some embodiments, the first flow rate value is received by a processor of the cryogenic device from the first needle probe.

[0009] In some embodiments, the heater is coupled to a cryogen cartridge associated with the cryogen device. In some embodiments, the cryogen device includes a handpiece portion, and the cryogen cartridge and the first needle probe can be directly coupled to the handpiece portion.

[0010] In some embodiments, the method may include determining a target duty cycle (or pulse width modulation percentage (PWM%)) required to apply the first target heater power. In these embodiments, applying the first target heater power may include engaging the heater to the target duty cycle. In some embodiments, the target duty cycle is determined based on the output of the following equation: Duty Cycle = P Target x(R Heater / V Heater 2 ), where P Target is the first target heater power, R Heater is the resistance of the heater, and V Heater is the voltage across the heater. In some embodiments, the method includes: monitoring the voltage of a power supply coupled to the heater to estimate V Heater The real-time value of .

[0011] In some embodiments, applying the first target heater power includes adjusting an amount of current or voltage applied to the heater.

[0012] In some embodiments, the method includes: receiving pressure data from a pressure sensor of a cryogenic device during a first treatment cycle; calculating an average pressure change rate during a cooling phase of the first treatment cycle based on the received pressure data; and calculating a second target heater power for a second treatment cycle, wherein the second target heater power is calculated at least in part by adjusting the first target heater power up or down by an adjustment value based on the average pressure change rate. In some embodiments, the method may include determining that the average pressure change rate is negative and exceeds a predetermined range, wherein the second target heater power is calculated at least in part by adjusting the first target heater power up by the adjustment value. In some embodiments, the method may include determining that the average pressure change rate is positive and exceeds a predetermined range, wherein the second target heater power is calculated at least in part by adjusting the first target heater power down by the adjustment value. In some embodiments, the adjustment value is determined based on the magnitude of the average pressure change rate.

[0013] In some embodiments, the method may include determining that the average rate of change of pressure has an amplitude greater than a threshold amplitude. The method may further include generating a notification indicating that there is a problem with the cryogenic equipment based on the determination. In some embodiments, the average rate of change of pressure may be determined to be negative, and based on the average rate of change of pressure, the notification may identify the problem as a depleted cryogen source. In some embodiments, the average rate of change of pressure may be determined to be positive, and based on the average rate of change of pressure, the notification may identify the problem as a blocked or obstructed cryogen passage.

[0014] In some embodiments, the method may include: determining a first pressure of the cryogenic device prior to a cooling cycle of a first treatment cycle; determining a second pressure of the cryogenic device prior to a cooling cycle of a second treatment cycle; and calculating a second target heater power for the second treatment cycle. In some embodiments, the second target heater power is calculated at least in part by: adjusting the first target heater power upward when the second pressure is less than the first pressure; or adjusting the first target heater power downward when the second pressure is greater than the first pressure.

[0015] In some embodiments, the method may include: replacing the first needle probe with a second needle probe; receiving a second flow rate value, wherein the second flow rate value corresponds to an expected average mass flow rate of refrigerant through the second needle probe during a cryotherapy treatment cycle; and determining, based on the second flow rate value, a new target heater power to be applied by the heater for a treatment cycle to be performed using the second needle probe.

[0016] In some embodiments, the first treatment cycle includes a cooling phase and a recovery phase. In some embodiments, the first target heater power is applied during the cooling phase.

[0017] A cryogenic device for implementing the methods described herein is described. In some embodiments, the cryogenic device may include a cryogen source including a pressurized cryogen; a cryogen passage configured to direct the cryogen toward a needle probe including one or more needles, wherein the cryogen is configured to deliver cryotherapy to a target tissue via the one or more needles; a heater; and a processor. In some embodiments, the processor may be configured to: receive a first flow rate value, wherein the first flow rate value corresponds to an expected average mass flow rate of the cryogen through a first needle probe of the cryogenic device during a cryotherapy treatment cycle; determine a first target heater power to be applied to a heater associated with the cryogenic device for a first treatment cycle based on the first flow rate value, wherein the heater is configured to heat the cryogen; receive an input for the first treatment cycle; in response to the input, flow the cryogen toward the first needle probe for a period of time; and apply the first target heater power to the heater during the first treatment cycle to heat the cryogen and stabilize the pressure within the cryogenic device during or after the first treatment cycle. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1A-1B An example embodiment of a cryogenic apparatus is shown that includes a cartridge holder for holding a cryogen cartridge and a needle probe.

[0019] Figure 2A An example needle probe is shown.

[0020] Figure 2B-2C An example embodiment of a port of a PCBA of a handpiece portion that receives a proximal portion of a PCBA of a needle probe is shown.

[0021] Figure 3A An example graph reflecting pressures and temperatures associated with a cryogenic device during a single treatment cycle is shown, wherein a heater heats the exterior of the cryogen box to maintain a relatively constant temperature at the exterior of the cryogen box.

[0022] Figure 3B Shown reflected in Figure 3A An example graph of pressure and temperature within a cryogenic device during a treatment cycle occurring after the treatment cycle shown.

[0023] Figure 4 A simplified cross-sectional schematic diagram of an example cryogen cartridge coupled to a needle probe via a cryogen passage is shown.

[0024] Figure 5An example high-level system schematic of a cryogenic device is shown.

[0025] Figure 6 An example pressure / temperature graph corresponding to a method of stabilizing refrigerant pressure by applying a target heater power specifically designed to compensate for the amount of pressure lost during the cooling phase of a treatment cycle is shown.

[0026] Figure 7 An example pressure / temperature graph corresponding to a method for real-time pressure monitoring and correction to stabilize pressure during a cool-down phase is shown.

[0027] Figure 8 An example pressure / temperature graph is shown for a plurality of treatment cycles including a treatment cycle indicating a problem with the cryogenic device.

[0028] Fig. 9 A simplified schematic diagram of the cryogenic apparatus in use is shown.

[0029] Fig.10 An example method for stabilizing pressure within a cryogenic device is shown. DETAILED DESCRIPTION

[0030] The present disclosure describes features of cryogenic devices that can be used to deliver cryotherapy to patients. In some embodiments, the described cryogenic devices may include a needle for delivering cryotherapy subcutaneously to a target specific tissue for treating various conditions. For example, the cryogenic device may include a needle configured for insertion near a peripheral nerve to deliver cryotherapy to the peripheral nerve to treat pain, spasticity, or other such conditions that may be improved by such treatment. More information about using cryotherapy to relieve pain or spasticity can be found in U.S. Patent No. 8,298,216, filed on November 14, 2008; U.S. Patent No. 9,610,112, filed on March 18, 2014; U.S. Patent No. 10,085,789, filed on March 13, 2017; and U.S. Patent Publication No. 20190038459, filed on September 14, 2018, the complete disclosures of which are incorporated herein by reference in their entirety for all purposes. Cryogenic devices may also be used for preventive treatments (such as destruction or prevention of neuromas), for example, as described in U.S. Patent No. 10,470,813, filed on March 14, 2016, the complete disclosure of which is incorporated herein by reference in its entirety for all purposes.

[0031] Figure 1A-1BAn example embodiment of a cryogenic device 100 is shown, which includes a box holder 140 for holding a cryogen box 130 and a needle probe 110. As shown in the example embodiment shown, the cryogenic device 100 can be a self-contained handpiece suitable for being grasped and manipulated by the operator's hand. In other embodiments, the cryogenic device may include physically separated components. For example, the cryogenic device may include a handpiece and a cryogen box separated from the handpiece, and the handpiece includes a needle probe. In some embodiments, the cryogenic device 100 may have a multi-part (e.g., two-part) housing, wherein the needle probe 110 is disposed in a separate probe housing, and the separate probe housing can be coupled to the housing of the handpiece portion. In other embodiments, the needle probe 110 may not be disposed in a separate housing, and may be configured to be directly inserted into the housing of the cryogenic device 100. As an example, the cryogenic device 100 in at least some of these embodiments may have a single housing.

[0032] In some embodiments, the cryogen box 130 can be a disposable box filled with a cryogen (e.g., nitrous oxide, fluorocarbon refrigerant, and / or carbon dioxide). The cryogen box 130 can be pressurized so that the cryogen therein is maintained at a relatively high pressure. In some embodiments, the cryogenic device 100 can include a box door 120 for accessing the cryogen box 130 (e.g., for replacing the cryogen box 130). The box door 120 can be configured to move from an open position for allowing the box holder 140 to receive the cryogen box 130 to a closed position for fixing the cryogen box 130 in the housing of the cryogenic device 100. For example, as Figure 1A-1B As shown, the box door 120 can be configured to rotate around the rotation point 125 to allow access to the cryogen box 130. In this example, the user can open the box door 120 (e.g., when the user notices that the cryogen box 130 is empty) (e.g., Figure 1A The cryogen cartridge 130 is removed from the cartridge holder 140 (as shown), a new cryogen cartridge 130 is inserted into the cartridge holder 140, and the cartridge door 120 is closed (as shown). Figure 1B shown).

[0033] In some embodiments, cryotherapy using the cryogenic device 100 can be performed in discrete treatment cycles. For example, the processor of the cryogenic device 100 can be configured to control the cryogen flow (e.g., by operating a supply valve). The processor can be configured to provide a treatment cycle in response to a treatment instruction. The treatment cycle may include a cooling phase (wherein the cryogen flows to the needle) and a recovery phase (wherein the cryogen does not flow to the needle). For example, the treatment cycle may include a cooling phase with a duration of 20-65 seconds, followed by a recovery phase with a duration of 10-60 seconds. As another example, a treatment cycle including a cooling phase with a duration of 33-60 seconds and a subsequent recovery phase with a duration of 15-45 seconds may be particularly advantageous. During the cooling phase, when the cryogen flows to the needle, a low temperature area may be formed in the tissue around the needle (e.g., at the distal tip of the needle). For example, the low temperature area can be defined by a 0°C isotherm (e.g., a cooling region) so that the low temperature area includes a frozen tissue "ice ball". In some embodiments, a cryogen can be vaporized within the needle cavity to cause the creation of a cryogenic region (e.g., by utilizing the Joule-Thomson effect). During the recovery phase, the cryogen flow is stopped so that the needle warms to the baseline temperature. More information about the healing cycle can be found in U.S. Patent Publication No. 20190038459, filed on September 14, 2018, which is incorporated herein by reference in its entirety for all purposes.

[0034] In some embodiments, the cryogenic device 100 may include a skin warmer, which may be a heating element for warming the skin, for example, to reduce collateral damage to the skin. The skin warmer may be activated for a specified heating duration before or during a treatment cycle. For example, the skin warmer may be activated for a pre-heating period of a specific duration before a treatment cycle. More information about cryogenic devices with skin warmers can be found in U.S. Pat. No. 10,470,813, filed on March 14, 2016, which is incorporated herein by reference in its entirety for all purposes.

[0035] Figure 2A An example needle probe 110 is shown. In some embodiments, the illustrated needle probe 110 can have an outer housing (not shown). In some embodiments, the needle probe 110 can include one or more needles 115 adapted to penetrate into the patient's skin adjacent to target tissue (e.g., neural tissue). For example, Figure 2AAs shown in , the needle probe 110 may include three needles 115. Each of the needles of the needle probe 110 may have a needle cavity (not shown) disposed therein. In some embodiments, the needles 115 may have closed tips without any distal openings so that they do not allow the cryogen to be ejected from the distal end of the needles 115. In these embodiments, the needles 115 themselves are cooled, and the adjacent target tissue is thereby cooled by conduction. For example, the needle may have a needle cavity into which the cryogen may flow, thereby cooling the needle. In other embodiments, the needle 115 may have an open tip, in which case the target tissue may be cooled by injecting the cryogen into or near the target tissue in the patient's body. In some embodiments, the needle probe 110 may include a probe extension 119, which is configured to be fixed to the probe container 170. When the needle probe is fixed to the probe container 170, the probe extension 119 extends proximally toward the proximal end of the cryogenic device (for illustrative purposes, Figure 1A The proximal and distal directions are indicated in ). Figure 2A , the probe extension 119 can have a probe cavity (not shown) disposed therein, which extends from the proximal end to the distal end. When the needle probe is fixed to the probe container, the probe cavity can be fluidically coupled to a cryogen passage extending from the cryogen box 130 toward the probe container 170 for delivering cryogen to the needle. The probe cavity can be coupled to the needle cavity of the needle 115 at the distal end of the cryogenic device so that cryogen can be allowed to pass through the probe cavity and enter the needle cavity (e.g., to cool the needle tip). In some embodiments, cryogen can be discharged (e.g., on the proximal side) after cooling the needle. In some embodiments, cryogen can flow into and be discharged from the needle cavity repeatedly and sequentially (e.g., during one or more treatment cycles).

[0036] In some embodiments, the cryogenic device 100 can be a smart device that includes a first processor (e.g., located in the handpiece and separate from the needle probe 110) to assist the operator in performing the treatment. In some embodiments, the needle probe 110 can be a smart probe. In these embodiments, the needle probe 110 can include a printed circuit board assembly (PCBA). Figure 2A As shown, the PCBA may include a second processor 118a. In some embodiments, the PCBA may also include a memory component. The PCBA may further include one or more connectors 118b (e.g., a card edge connector) that electrically couple the needle probe 110 to the remainder of the cryogenic device 100 (e.g., a handpiece portion). For example, when the needle probe is received by the probe receptacle 170, a portion of the PCBA 118 (including the connector 118b) may be received by a port in the handpiece portion.

[0037] Figure 2B-2C An example embodiment of a port 178 of the PCBA 175 of the handpiece portion is shown, which receives the proximal portion of the PCBA 118 of the needle probe 110. Figure 2B-2C As shown in the example embodiment of FIG. 1 , the connector 118 b of the PCBA 118 may be configured to slide into an opening of the port 178 of the PCBA 175 of the handpiece portion.

[0038] Once the PCBA 118 of the needle probe 110 is connected to the PCBA 175 of the hand piece portion, the needle probe 110 may be able to transmit information to the hand piece portion and / or receive information from the hand piece portion (e.g., via the second processor 118a). In some embodiments, the needle probe 110 may transmit (to the first processor) a probe descriptor that may identify, among other things, a corresponding probe type of the needle probe. For example, the probe descriptor may identify the number of needles (e.g., a single needle probe, a three needle probe, a five needle probe), the length of the needles, the configuration of the needles (e.g., a rectangular array, a square array, an elliptical shape, a circular shape, a triangle, a three-dimensional shape such as an inverted pyramid), the average mass flow rate of the cryogen through the needle probe, the duration of the preheating period during which the skin warmer of the cryogenic device 100 is activated, the duration of the cooling phase during which cryogen is delivered to the needle probe 110, the duration of the recovery phase during which a valve is closed to prevent further delivery of cryogen to the needle probe 110, or any other suitable feature or parameter that may be specified for the operation of the needle probe 110. Probe descriptors and specific types of parameters that may be included therein are discussed further below. More information about smart cryogenic devices and smart tips may be found in U.S. Patent No. 10,130,409, filed on November 20, 2018, which is incorporated herein by reference in its entirety for all purposes.

[0039] Figure 3A An example pressure / temperature curve reflecting the pressure and temperature associated with the cryogenic device 110 during a single treatment cycle is shown, wherein the heater heats the exterior of the cryogen cartridge 130 to maintain a relatively constant temperature at the exterior of the cryogen cartridge 130. Figure 3A , the healing cycle may begin with a cooling phase 310 , which may be followed by a recovery phase 320 . Figure 3AThe line labeled "Tprobe" indicates the temperature at the needle probe 110. The line labeled "Pressure" indicates the pressure of the cryogen within the cryogenic device 100. For example, the pressure can be measured by one or more pressure sensors upstream or downstream of a supply valve through which the cryogen flows. The line labeled "TCrtg(Ext)" indicates the temperature at the exterior of the cryogen box 130, which can be measured, for example, by one or more temperature sensors positioned near or adjacent to the cryogen box 130. As shown, during the cooling stage 310, as more and more cryogen flows into the cavity of the needle probe 110, the temperature at the needle probe 110 decreases. Figure 3A In the "T probe" line and the "TCrtg (Ext)" line in the present disclosure (and subsequent figures showing pressure / temperature curves), the "T probe" line and the "TCrtg (Ext)" line will be read with reference to the "temperature (°C)" axis, while the "pressure" line will be read with reference to the "pressure (pounds per square inch absolute (psia))" axis. In some embodiments, the cryogen in the cryogen box 130 can be pressurized to be at a baseline pressure value. For example, Figure 3A As shown, the baseline pressure value can be about 910 pounds per square inch absolute (psia). When the cryogen is released from the pressurized cryogen box 130 during the cooling stage 310 and is caused to flow along the cryogen path, the reduction of the cryogen in the cryogen box 130 can cause the pressure in the cryogen box 130 to decrease relative to the baseline pressure. Incidentally, this pressure reduction may also be accompanied by a temperature reduction. This temperature drop may be due to a cryogen phase change. The cryogen can be pressurized in the cryogen box 130 so that it is mainly maintained in the liquid phase. When the cryogen is released from the cryogen box 130 and the pressure is therefore reduced, a certain amount of liquid cryogen may undergo a phase change from liquid to gas (e.g., liquid N 2 O can boil and evaporate into gaseous N due to the reduced pressure. 2 O), which is an endothermic phase transition that absorbs heat from the surroundings and ultimately causes the remaining liquid cryogen to cool. Figure 3A The "Pressure" line in the example of FIG. 1 shows the decrease in pressure during a treatment cycle. Figure 3A As shown in brackets 312-1 in FIG. 1 , when the cooling phase 310 of the treatment cycle begins, the pressure initially drops by approximately 10 psia when the cryogen is released from the cryogen cartridge 130 (e.g., when the supply valve opens). Figure 3A In the example shown, the pressure continues to drop during the remainder of the cooling phase, with the pressure dropping by approximately 20 psia. This continued pressure drop is represented by bracket 312-2. The result is an overall pressure drop of approximately 30 psia (10 psia + 20 psia).

[0040] The pressure of the cryogen in cryogen cartridge 130 may be important because the pressure of the cryogen affects the flow rate of the cryogen to needle probe 110. A significant reduction in pressure may result in a reduction in the amount of cryogen delivered to the needle of needle probe 110 and / or the amount of cryogen evaporated within the needle of needle probe 110 during a treatment cycle, which ultimately affects the characteristics of the cryogenic region formed due to the cooling thereby produced. A reduction in pressure may result in the formation of a cryogenic region having a volume that is less than, for example, an optimal value.

[0041] In some embodiments, the cryogenic device 100 can actively increase the temperature of the cryogen within the cryogen box 130 in order to increase the pressure of the cryogen to compensate for any pressure drop. In some embodiments, the cryogenic device 100 can include a heater for actively increasing the temperature of the cryogen. By increasing the cryogen temperature, the cryogen pressure increases, where the exact amount of pressure increase is based on the inherent properties of the cryogen, as can be determined by its corresponding liquid-gas phase transition curve (e.g., for N 2 O, through N 2 O is characterized by the liquid-vapor phase transition curve (which is well known). For example, as discussed below, one or more heaters can be placed along the exterior of the cryogen cartridge 130 to apply heat to the cryogen cartridge 130. Figure 3A A method of increasing pressure by the following manner is shown: a relatively small amount of heat is applied to the cryogen box 130, so that the outside of the cryogen box 130 is maintained at a relatively constant temperature during the entire use period of the cryogenic device 100 (e.g., in the process of multiple treatment cycles). In this illustrated example, the "TCrtg (Ext)" line indicates that the temperature at the outside of the cryogen box 130 is maintained at about 30°C by, for example, turning on or off the heater with a relatively constant duty cycle whether the cooling phase or the recovery phase is occurring. The duty cycle (or pulse width modulation percentage (PWM%)) can be expressed as a fraction or percentage of a period, during which the heater is turned on (or when a power greater than a threshold power is applied to the heater) during the fraction or percentage of a period. For example, the duty cycle can be defined by the equation duty cycle = PW / T x 100%, where PW is a pulse width (e.g., the time when the heater is turned on), and T is the period of the entire open / close cycle.

[0042] refer to Figure 3A, the cryogenic device 100 may attempt to maintain a relatively constant temperature (e.g., 30°C) on the outside of the cryogen box 130. Over the entire period of use, a relatively constant, relatively small amount of heat is added (e.g., by adopting a constant, relatively low duty cycle). This method will work if the temperature at the outside of the cryogen box 130 reflects the temperature of the internal cryogen. However, the temperature applied to the outside of the cryogen box 130 is not transferred to the internal cryogen quickly enough, so that the temperature of the outside of the cryogen box 130 does not fully estimate the temperature of the internal cryogen. As experimentally confirmed, there is a significant lag between the heating of the outside of the cryogen box 130 and the heating of the internal cryogen. Therefore, although adding a constant, relatively small amount of heat will increase the temperature and pressure over time, this increase occurs at a relatively slow rate. As Figure 3A , this rate of increase may not be sufficient to offset the decrease in temperature and pressure caused by the release of cryogen during the cooling phase 310. Therefore, in addition to the initial pressure drop corresponding to bracket 312-1, a continued decrease in pressure may be observed during the cooling phase 310, as shown by the downward sloping pressure curve corresponding to bracket 312-2. Figure 3A The continuous decrease shown in may be problematic because such continuous changes in pressure during the cooling stage 310 may translate into changes in the cryogen flow rate within the cooling stage 310 and may result in suboptimal low temperature region formation. For example, the cryogen flow rate may continue to decrease as the pressure continues to decrease during the cooling stage 310, resulting in a reduced level of cooling within the cooling stage 310. Therefore, a method of maintaining a constant pressure during the cooling stage 310 may be desirable to achieve consistent cooling during the cooling stage 310, thereby forming a low temperature region with desired characteristics (e.g., with a desired volume and temperature profile). This article describes an example method that can be used to maintain a constant pressure during the cooling stage 310.

[0043] Furthermore, in some embodiments, many cryotherapeutic treatments may require multiple treatment cycles, for example, to apply an optimal amount of cryotherapy to a target tissue (e.g., a nerve) while minimizing collateral damage (e.g., to surrounding tissue). Alternatively or additionally, multiple treatment cycles may be used to create a "treatment line," which may, for example, be a treatment spot line that is transverse to the intended location of the target nerve. More information regarding treatment lines may be found in U.S. Patent No. 9,295,512, filed September 12, 2013, the entire disclosure of which is incorporated herein by reference in its entirety for all purposes. A further requirement for multiple treatment cycles is that, after a first treatment cycle, the refrigerant pressure must be restored to a baseline pressure value before initiating a second treatment cycle. In some embodiments, this pressure recovery may occur during a recovery phase that is separate from the cooling phase (e.g., see U.S. Pat. No. 9,295,512, filed September 12, 2013). Figure 3A , recovery phase 320, which occurs immediately after cooling phase 310). Pressure recovery is critical to ensuring consistent treatment during repeated treatment cycles. As discussed above, pressure changes can affect the characteristics of the cryogenic zone formed during a treatment cycle, and starting a second treatment cycle at a pressure value different from the baseline pressure value will result in the creation of a cryogenic zone during the second treatment cycle that is different from the cryogenic zone created during the first treatment cycle. For example, the second treatment cycle may have started at a pressure value lower than the baseline pressure value, in which case the flow rate may have been reduced, ultimately resulting in a cryogenic zone that is smaller than the cryogenic zone formed in the first treatment cycle. This lack of consistency may cause the cryotherapy to be suboptimal in some cases. The continued lack of proper pressure recovery during repeated cycles may exacerbate the problem. For example, if the pressure keeps dropping between cycles, the cryogenic zone may become smaller and smaller with each treatment cycle. Therefore, the cryogenic device 100 may use the recovery phase 320 to establish the internal pressure back to the baseline pressure value. For example, as Figure 3A As shown, when the cryogen flow stops at the end of the cooling phase 310, the pressure begins to increase and continues to increase during the recovery phase 320. Figure 3A In the example of , if a relatively constant low level of heat is added (e.g., just enough heat to maintain the exterior of the cryogen box 130 at a temperature of approximately 30°C), this increase in pressure occurs at a relatively slow rate for over 300 seconds. The pressure increase is limited by the rate of heat diffusion through the cryogen, which depends on the heat differential between relatively hot and relatively cold areas. Other things being equal, a high heat differential translates into a faster rate of heat diffusion. Figure 3A In the example of , the relatively low level of heat applied to the exterior of the cryogen box 130 can result in a relatively low heat differential, which in turn translates into a relatively low rate of thermal diffusion, causing the temperature (and pressure) to increase relatively slowly. In order to allow full pressure recovery, it is necessary to extend the recovery phase 320 to a relatively long period, thereby placing a limit on the rate at which multiple cycles can be performed.

[0044] Figure 3B An example pressure / temperature curve is shown, which reflects the Figure 3A The pressure and temperature within the cryogenic device 100 during the treatment cycle that occurs after the treatment cycle shown. Figure 3A Same, Figure 3B A method is shown that attempts to maintain a relatively constant temperature (e.g., 30°C) on the exterior of the cryogen box 130 by applying a relatively constant, relatively small amount of heat (e.g., by employing a constant, relatively low duty cycle) throughout the period of use. Figure 3B and Figure 3A The difference is that, as discussed above, the initial pressure cannot be restored back to the original baseline pressure value. This is because the heat added to maintain the temperature of the exterior of the cryogen box 130 at approximately 30°C may not be sufficient to compensate for the pressure loss of the previous cycle. Although the pressure may have recovered given enough time (when the cryogen temperature matches the temperature of the exterior of the cryogen box 130, e.g., 30°C), the treatment cycles that occur in relatively rapid succession may not allow sufficient time. Therefore, Figure 3B The flow rate during the treatment cycle depicted in may be suboptimal. In addition, since the starting pressure is already relatively low, the gap between the actual pressure value during the cooling phase and the target pressure value is expected to further increase during the next treatment cycle, because more heat will be required in the next treatment cycle to bring the refrigerant pressure to the target pressure value.

[0045] Figure 4 A simplified cross-sectional schematic diagram of an example cryogen cartridge 130 coupled to a needle probe 110 via a cryogen passage is shown. In some embodiments, a heater may be coupled to the cryogen cartridge 130 to heat the cryogen within the cryogen cartridge 130. Figure 4 In the example shown, the heater 430 is disposed adjacent to or near the cryogen box 130. In some embodiments, one or more temperature sensors (e.g., temperature sensors 440 and 442) may be disposed adjacent to or near the cryogen box 130 to measure the temperature at the exterior of the cryogen box 130 to approximate the temperature within the cryogen box 130. In some embodiments, a supply valve 405 may be disposed along the cryogen passage to control the flow of the cryogen. For example, the supply valve 405 may alternate between an open position and a closed position to allow or prevent the cryogen from flowing downstream toward the needle probe 110. In some embodiments, the cryogen flow may be regulated by opening the supply valve to a position between the open position and the closed position. In some embodiments, one or more pressure sensors (e.g., an upstream pressure sensor 410 and a downstream pressure sensor 412) may be disposed along the cryogen passage to monitor the cryogen pressure. Although Figure 4 The simplified schematic diagram of shows a specific configuration and quantity of specific elements (e.g., heater 430, temperature sensors 440 and 442, pressure sensors 410 and 412) disposed in a specific location, but the present disclosure contemplates that any number and configuration of these elements can be disposed in any suitable location. For example, heater 430 can be positioned near the cryogen box, but not adjacent to the cryogen box. As another example, a second heater can be positioned adjacent to cryogen box 130. As another example, cryogenic device 100 can include only a single pressure sensor (e.g., upstream pressure sensor 410).

[0046] In some embodiments, the probe descriptor may be transmitted by a first needle probe 110, the first needle probe 110 including a first flow rate value corresponding to an expected average mass flow rate of the refrigerant through the first needle probe 110 of the cryogenic device 100 during a cryotherapy treatment cycle. A processor of the cryogenic device 100 (e.g., a first processor located on a handpiece portion of the cryogenic device 100) may receive the first flow rate value. In some embodiments, the processor of the cryogenic device 100 may use the first flow rate value to determine the amount of refrigerant flowing to the needle of the needle probe 110 during a particular treatment cycle. For example, the first flow rate value may correspond to an expected average mass flow rate of n. In this example, if a particular treatment cycle includes a cooling phase having a duration of 20 seconds, the processor may calculate that 20n units of refrigerant have flowed to the needle of the needle probe 110 during the particular treatment cycle. In some embodiments, each individual needle probe 110 may include (e.g., as part of an associated probe descriptor) information about its corresponding flow rate value, and may communicate that flow rate value (e.g., as part of its probe descriptor) to a processor of the cryogenic device 100. For example, a first needle probe 110 may be replaced by a second needle probe 110. At some point (e.g., immediately after inserting the second needle probe 110 into the probe receptacle 170, after receiving an input for starting a treatment cycle, etc.), the second needle probe 110 may communicate its own flow rate value to a processor of the cryogenic device 100 for processing. In some embodiments, each needle probe 110 may have a probe descriptor that includes information about specified parameters related to the timing of a delivery cycle. For example, a probe descriptor for a particular needle probe 110 may include information about a preheat time (e.g., during which the skin warmer of the cryogenic device 100 may be heated to reduce collateral damage to the skin, as described above), a cool-down phase duration (e.g., during which the valve remains open), a recovery phase duration (e.g., during which the valve is closed), and / or any other suitable parameters. In this example, each of these parameters may be uniquely customized for the specific circumstances of the needle probe 110. For example, the cool-down phase duration for a five-needle probe may be less than the cool-down phase duration for a three-needle probe.

[0047] In some embodiments, the processor of the cryogenic device 100 can use the flow rate value of the needle probe 110 to calculate the amount of cryogen that has been used and / or the amount remaining in the cryogen box 130. The processor of the cryogenic device 100 can calculate these amounts based on the average mass flow rate and the amount of time that the supply valve for releasing the cryogen has been opened. In some embodiments, the flow rate value can be derived from the needle size, the number of needles and / or other suitable parameters associated with the needle probe 110. In some embodiments, the flow rate value can be determined empirically by testing. For example, a specific probe type can be tested to determine the average flow rate value of each probe type. As another example, each specific needle probe 110 can be tested separately, and a personalized flow rate value can be determined and assigned to a specific needle probe 110, so that the probe descriptor transmitted by the specific needle probe 110 includes a personalized flow rate value. In the case where it is not feasible to have strict tolerances in manufacturing, such personalized flow rate values ​​may be particularly useful (for example, two different needle probes of a single type may have different flow rates, for example, due to different sizes of their corresponding cavities (due to differences in manufacturing)).

[0048] Figure 5 An example high-level system schematic diagram of a cryogenic device 100 is shown. Figure 5 The PCBA 175 of the cryogenic device 100 and other components that interface with the PCBA 175 are shown. Figure 5, the puncture element 540 can be contained in the cryogenic device, and its position can use the puncture point to puncture the cryogen box 130. Once the cryogen box 130 is punctured, the pressurized cryogen in it can be coupled with the cryogen passage fluid leading to the needle probe 110 via the cryogen passage extending through the puncture element 540 and toward the supply valve 405, and the supply valve 405 can control the cryogen to flow from the cryogen box 130 to the needle probe 110. In some embodiments, the cryogenic device 100 may include an upstream pressure sensor 410 for measuring the upstream pressure of the supply valve 405 and a downstream pressure sensor 412 for measuring the downstream pressure of the supply valve 405. The supply valve 405 can be opened or closed by any suitable means. For example, a stepper motor 407 (for example, controllable via a microcontroller unit 510) can be used to move the valve between an open position and a closed position or a position between the two. Typically, when the supply valve 405 is fully opened in the cooling phase of the treatment cycle, the upstream pressure is approximately equal to the downstream pressure. Thus, some embodiments of the cryogenic device 100 may include only an upstream pressure sensor 410 that approximates the pressure within the cryogen cartridge 130 when the cryogen cartridge 130 is fluidically coupled to the cryogen passage (e.g., after the cryogen cartridge 130 is punctured through the puncture point 540). Other embodiments of the cryogenic device 100 may include both an upstream pressure sensor 410 and a downstream pressure sensor 412, for example, to diagnose delivery problems (e.g., to determine whether the valve 405 fails to open or close, or to determine whether there is an obstruction between the two pressure sensors 410 and 412).

[0049] refer to Figure 5In some embodiments, the cryogenic device 100 may include a microcontroller unit 510 for monitoring and operating the cryogenic device 100. In some embodiments, the cryogenic device 100 may include one or more processors, such as a processor 515. The one or more processors 515 may be part of the microcontroller unit 510 disposed on the PCBA 175. In some embodiments, the processor 515 (or any other suitable circuit system) may determine a first target heater power to be applied to a heater 430 associated with the cryogenic device 100 for a first treatment cycle. In some embodiments, the target heater power may be a heater power value configured to generate heat via the heater 430 to compensate for the pressure / heat loss that occurs during the cooling phase of the treatment cycle so as to stabilize the pressure within the cryogenic device 100 during the cooling phase. Such pressure stabilization is also optimal for allowing rapid recovery during the recovery phase following the cooling phase, as it can prevent the pressure from dropping too low during the cooling phase. The processor of the cryogenic device 100 may transmit a signal that instructs the circuit system associated with the heater 430 to apply the first target heater power to the heater in order to heat the cryogen. In some embodiments, processor 515 can determine the first target heater power based on the first flow rate value. In some embodiments, as described above, cryogenic device 100 can theoretically derive the amount of cryogenic agent expected to be released from cryogenic box 130 when first needle probe 110 is in use. For example, it can calculate the amount of expected cryogenic agent released in the following manner: the average mass flow rate associated with the first flow rate value is multiplied by the duration of cryogenic flow (for example, as can be determined based on the duration of supply valve 405 being opened). In the case where the amount of cryogenic agent released can be regulated at supply valve 405 (for example, valve is opened 30%, 50%, etc.), calculation can be appropriately weighted to consider this regulation. Cryogenic device 100 can then use the amount of cryogenic agent released to estimate the target energy required for compensating for the heat lost due to cryogenic release. Target heating power can be derived subsequently (for example, by dividing the target energy by the amount of time expected to be spent in the cooling stage). The derived heating power can be applied to the heater 430 to increase the pressure of the cryogen in the cryogenic device 100, so as to stabilize the pressure during the cooling stage and / or allow the pressure to recover during the recovery stage. In some embodiments, the target heating power (or the required amount of heat) can be derived alternatively or additionally based on experience. For example, the flow rate value can be related to the amount of the expected cryogen release, or to the target heating power (or the required amount of heat). In this example, the processor of the cryogenic device 100 can access a lookup table to determine the target heating power, or alternatively can use a mathematical model or function derived from experience to determine the target heating power.The cryogenic device 100 may also include one or more temperature sensors (eg, thermistors) 440 and 442, which may be used to measure the temperature of the exterior of the cartridge (eg, a reference). Figure 3A-3B , as reflected by the curve labeled “TCrtg(Ext)”). A temperature signal corresponding to the measured temperature may be transmitted to the microcontroller unit 510.

[0050] In some embodiments, the processor 515 of the cryogenic device 100 may receive input for the first treatment cycle. For example, a user may activate an input button that causes an input signal to be transmitted to the processor 515 of the cryogenic device 100. In response to the input, the processor 515 of the cryogenic device 100 may cause the cryogen to flow toward the first needle probe 110 for a period of time (e.g., by causing the supply valve 405 to open) that corresponds to the cooling phase of the treatment cycle.

[0051] Figure 6 An example pressure / temperature graph corresponding to a method of stabilizing refrigerant pressure by applying a target heater power specifically designed to compensate for the amount of pressure lost during the cooling phase of a treatment cycle is shown. Figure 6 A priming cycle is shown, followed by four treatment cycles with cool-down phases 1 to 4 . Figure 6 The method shown can be used to maintain a relatively constant pressure during the cooling phase when the cryogen is delivered. As described in further detail below, this method has several advantages. In some embodiments, the processor 515 of the cryogenic device 100 can cause the heater to apply a first target heater power during the first treatment cycle so as to heat the cryogen and stabilize the pressure in the cryogenic device before, during or after the first treatment cycle. The first target heater power can be applied by any suitable means within a time period (e.g., during the cooling phase of the first treatment cycle). In some embodiments, the circuit system associated with the heater can be made to change the voltage or current applied to the heater. In other embodiments, a constant voltage and current can be supplied to the heater, but the heater power ultimately applied by the heater within a time period can be changed by changing the duty cycle of the heater. In these embodiments, the following equation can be used to determine the appropriate duty cycle for applying the target heater power: Duty Cycle = P Target x(R Heater / V Heater 2 ), where P Target is the first target heater power, R Heater is the resistance of the heater, and V Heateris the voltage across the heater. Pressure stabilization may involve maintaining the average rate of change of pressure within a predetermined range (or maintaining the pressure relatively constant) during the cool-down phase of a treatment cycle. Figure 6 , a target heater power is applied to the box in order to keep the pressure relatively constant within each cooling stage. Figure 6 As shown in the "TCrtg (Ext)" line in the example of , heater power is no longer applied to maintain the temperature at the outside of the box at a constant 30°C. Instead, in this example, a relatively high heater power can be applied to quickly increase the cryogen temperature during the cooling phase to specifically compensate for the estimated pressure loss during the cooling phase. For example, the heater can be operated at a duty cycle of approximately 23%, wherein the heater is turned on during the cooling phase to compensate for the estimated pressure loss. When compared to a lower duty cycle that will be used to maintain the outside of the box at a constant temperature (e.g., approximately 30°C), a relatively high heater power can transfer heat to the cryogen in the cryogen box 130 more quickly (and therefore increase the pressure of the cryogen in the cryogen box 130).

[0052] By applying a target heater power specifically tailored to compensate for pressure losses during the cool-down phase, the cryogen pressure can be stabilized during the cool-down phase to allow for consistent cryogen flow during the cool-down phase. Figure 6 The pressure remains relatively constant during the cooling stages, as shown by the relatively flat pressure lines during cooling stages 1 to 4. This constant pressure during the cooling stages, in turn, allows for consistent application of cooling energy during the cooling stages, ultimately leading to optimal low temperature region formation.

[0053] Another advantage of this customized approach (compared to the more conventional approach of simply maintaining a constant temperature of the exterior of the cryogen box 130) is that the recovery phase is shortened, thereby allowing multiple treatment cycles to be performed in a shorter period of time. This shortened recovery phase may be due to the fact that no continuous drop in pressure occurs during the cooling phase. For example, referring to Figure 3A (where the heater is activated to maintain a constant temperature at the exterior of the reference junction 130), after an initial pressure drop at the beginning of the cooling phase, the pressure continues to drop during the cooling phase. Figure 6 (where the heater applies a relatively high target heater power specifically tailored to compensate for the pressure loss), after an initial pressure drop at the beginning of the cool-down phase, the pressure is stable during the remainder of the cool-down phase. Thus, at the end of the cool-down phase, Figure 6 The total pressure drop compared to its baseline pressure value in the method shown is less than Figure 3AThe total pressure drop in the method shown is compared to its baseline pressure value. A smaller pressure difference (i.e., the pressure difference between the pressure at the end of the cooling phase and the baseline pressure value) means that, other things being equal, it takes less time to restore the pressure to the baseline pressure value. Additionally, Figure 6 The method shown is relative to Figure 3A The method shown applies a higher heater power, thus, as discussed above, allowing faster transfer of heat to the cryogen. Thus, when the cryogen is heated faster, the pressure can be restored back to the baseline pressure value at a faster rate.

[0054] Figure 7 An example pressure / temperature diagram corresponding to a real-time pressure monitoring and correction method for stabilizing pressure during the cooling phase is shown. By using pressure measurement to directly determine the pressure of the cryogen in the cryogen box 130, an accurate real-time pressure can be determined. This is in contrast to the more conventional method of using the temperature measurement performed at the outside of the cryogen box 130. Therefore, the pressure can be monitored and adjusted in real time to adjust any deviation from the expected pressure value when applying the target heater power initially determined. For example, although the first target heater power may be a good theoretical estimate of the heat that needs to be added to compensate for the pressure drop during the cooling phase, practical factors may cause the estimate to be inaccurate. For example, manufacturing deviations can lead to changes in heater resistance (thereby causing deviations in the heat applied when applying a specified heater power), supply pipe size (thereby causing deviations in the cryogen flow rate from the expected flow rate estimated using the associated flow rate value). Some of these manufacturing deviations can be mitigated by personalized testing of the cryogenic device 100 (e.g., testing each needle probe individually, and then specifying personalized flow rate values ​​for the needle probe as described above) and / or running a calibration routine to consider manufacturing deviations. However, such testing and / or calibration may not always be possible, and there may be factors that are not easily tested or calibrated. Therefore, real-time monitoring and correction may be advantageous. Figure 7An example is shown in which, after the startup cycle, a first target heater power is applied during cooling stage 1 in an attempt to stabilize the pressure during cooling stage 1. However, the cryogenic device 100 may determine that the first target heater power is insufficient to maintain a constant average pressure during cooling stage 1, for example, as evidenced by a negative slope during cooling stage 1 (which indicates that the pressure continues to drop during cooling stage 1). For example, the processor 515 of the cryogenic device 100 may receive pressure data from a pressure sensor of the cryogenic device during cooling stage 1, and may calculate the average pressure change rate during cooling stage 1. In order to try to stabilize the pressure so that the average pressure remains constant during the next cooling stage (i.e., cooling stage 2), the cryogenic device 100 may adjust the target heater power upward. The processor 515 may determine that the average pressure change rate is negative, and may calculate an adjusted target heater power for cooling stage 2, wherein the adjusted target heater power is calculated at least in part by adjusting the first target heater power upward by an adjustment value based on the average pressure change rate during cooling stage 1. Processor 515 may then cause heater 430 to apply the adjusted target heater power during Cooling Phase 2 (eg, by increasing the duty cycle, by increasing the voltage supplied to heater 430, etc.). This increase in heater power is caused by Figure 7 The "TCrtg" line in FIG. 2 shows a sharp increase in the temperature around the outside of the cryogen box during cooling stage 2, demonstrating the increase in heater power. Figure 7 The increased heater power allows the average pressure to remain constant during Cooling Stage 2, as shown by the relatively flat pressure curve during Cooling Stage 2.

[0055] Similarly, the cryogenic device 100 can adjust heater power in response to a positive rate of pressure change. For example, Figure 7 Cooling stage 3 in FIG. 4 shows a positive pressure change, which may be caused by a heater power that may have been too high. In some embodiments, the processor 515 of the cryogenic device 100 has determined that the average rate of change of pressure during cooling stage 3 is positively outside of a predetermined range, and an adjusted target heater power for the next cooling stage (i.e., cooling stage 4) can be calculated. The adjusted target heater power can be calculated, for example, at least in part by adjusting the target heater power applied during cooling stage 3 downward by an adjustment value. The adjustment value can be based on the average rate of change of pressure that occurred during cooling stage 3. The processor 515 can then cause the heater 430 to apply the adjusted target heater power during cooling stage 4, which can result in a relatively constant average pressure during cooling stage 4, as shown in FIG. Figure 7 The relatively flat pressure curve during cooling stage 4 is shown in the table below. Figure 7Example heater power adjustments made during each of the cooling phases shown in , such as by adjusting the duty cycle of the heater:

[0056] Cooling phase Duty Cycle % start up 0 1 10 2 20 3 30 4 20

[0057] In some embodiments, the adjustment value can be determined based on the amplitude of the average pressure change rate. For example, a relatively high adjustment value can be determined for a relatively high amplitude, and a relatively low adjustment value can be determined for a relatively low amplitude. In some embodiments, the processor 515 can access a lookup table, or alternatively can use a mathematical model or function derived from experience to determine an appropriate adjustment value. In some embodiments, the effect of the heater power adjustment on the pressure slope during delivery can be characterized for each probe type, and the cryogenic device 100 can adjust the heater power based on this characteristic, thereby allowing a fairly accurate estimate of the appropriate correction to be made to any probe type and the measured slope. For example, under all other conditions being the same, a cryogenic device 100 receiving a probe descriptor indicating that the attached probe is a three-needle probe can calculate a first adjustment value, while a cryogenic device 100 receiving a probe descriptor indicating that the attached probe is a five-needle probe can calculate a second adjustment value different from the first adjustment value (for example, a higher adjustment value can be calculated for a five-needle probe, because the five-needle probe may have a higher average mass flow rate, so that a higher heater power adjustment may be required to achieve the same desired pressure change). As another example, all other things being equal, a first adjustment value may be calculated for a single needle probe having a 90 mm needle, and a second adjustment value may be calculated for a triple needle probe having a 9 mm needle (e.g., a higher adjustment value may be calculated for a single needle 90 mm probe because the single needle 90 mm probe may have a higher average mass flow rate than the triple needle 9 mm probe). In other embodiments, the cryogenic device 100 may apply a coarse adjustment (e.g., a 10% duty cycle increment) if the average rate of change of pressure during the cooling phase exceeds some predetermined threshold, and apply a finer increment (e.g., a 2% duty cycle increment) for average rates of change of pressure less than the predetermined threshold. This approach may be extended to multiple thresholds with additional adjustment increments (e.g., a higher threshold above which the pressure is adjusted in 20% duty cycle increments).

[0058] In some embodiments, the target heater power can be adjusted based on the pressure value before the cooling stage. For example, if it is determined that the pressure value before a specific cooling stage is lower than the optimal baseline pressure value, the cryogenic device 100 can correspondingly adjust the target heater power to be delivered during the specific cooling stage upward. As another example, if it is determined that the pressure value before a specific cooling stage is higher than the optimal baseline pressure value, the cryogenic device 100 can correspondingly adjust the target heater power to be delivered during the specific cooling stage downward. This type of monitoring and adjustment may be desirable because it provides macro-level stability that can address declining baseline levels that may be compounded over the course of multiple treatment cycles.

[0059] In some embodiments, the target heater power can be adjusted based on a comparison of pressure values ​​before and after the cooling phase. For example, the cryogenic device may determine a first pressure of the cryogenic device 100 immediately before a cooling cycle of a first treatment cycle, and determine a second pressure of the cryogenic device 100 immediately before a cooling cycle of a subsequent second treatment cycle. In this example, the cryogenic device 100 can then calculate a second target heater power for the second treatment cycle, wherein the second target heater power is calculated at least in part by adjusting the first target heater power upward or downward based on the determined difference between the first pressure and the second pressure. For example, when the second pressure is lower than the first pressure, the target heater power can be adjusted upward. As another example, when the second pressure is greater than the first pressure, the target heater power can be adjusted downward.

[0060] In some embodiments, the cryogenic device 100 may also monitor the voltage of the power supply of the cryogenic device 100 during use. In some embodiments, this voltage may be used as an estimate of the voltage across the heater 430 and may therefore be used to ensure that the heater 430 is accurately delivering the specified target heater power. For example, referring to Figure 5 , the microcontroller unit 510 of the cryogenic device 100 may receive a voltage (V Battery ) signal. In this example, V Battery Can be used as V Heater Inserted into the equation used to calculate the duty cycle above (ie, duty cycle = P Target x(R Heater / V Heater 2 )). The battery voltage can vary over time due to a variety of factors, such as the amount of charge remaining in the battery. For example, the battery voltage can vary between 4.2V and 3.2V, depending on the remaining charge. Even small changes in battery voltage can have a significant effect on the duty cycle calculation because V Heateris squared. Therefore, using V Heater Calculating the duty cycle using an updated estimate of V can help ensure that the appropriate duty cycle is employed and thereby reduce the likelihood of pressure fluctuations due to incorrect duty cycle calculations. In some embodiments, the cryogenic device 100 may alternatively monitor the current of the power supply, which can be used to derive V Heater .

[0061] Figure 8 Example pressure / temperature graphs are shown for multiple treatment cycles, including treatment cycles that indicate a problem with the cryogenic device 100. In some embodiments, the cryogenic device 100 may use pressure measurements as a means for discovering that there is a problem with the cryogenic device 100. In some embodiments, an average rate of pressure change (or an overall rate of pressure change) that is greater than an expected average rate of pressure change (or an expected overall pressure change) may indicate that there is a problem with the cryogenic device 100 that may require action more than simply adjusting heater power as described above. For example, if the pressure change exceeds an expected pressure change threshold magnitude (or if the rate of pressure change exceeds an expected rate of pressure change), the cryogenic device 100 may determine that there is a problem with the cryogenic device 100. Reference Figure 8 For example, when the average rate of change of pressure (e.g., during the cooling phase) negatively exceeds a threshold magnitude rate (e.g., as shown by a large negative slope during cooling phase 3), the cryogenic device 100 can determine that the amount of cryogen within the cryogen box 130 may be severely depleted. Such a pressure change rate exceeding the threshold magnitude rate may reflect a lack of cryogen in the system to allow sufficient pressure to accumulate. Additionally or alternatively, if during a recovery phase after the cooling phase (e.g., reference Figure 8 , the recovery phase after cooling phase 3) does not recover back to the baseline pressure value, the cryogenic device 100 can determine that the same problem may exist. As another example, when the average pressure change rate exceeds the threshold amplitude rate in the positive direction compared to the expected pressure change rate, the cryogenic device 100 can determine that there may be a problem with the cryogenic delivery (e.g., the cryogenic passage is blocked or obstructed, and there is a problem with the supply valve 405). In these cases, the processor of the cryogenic device 100 (e.g., the processor 515) can generate a notification indicating that the cryogenic device has a problem in some embodiments. In some embodiments, the notification can identify a specific problem that the cryogenic device 100 determines to be possible. In some embodiments, the notification can be displayed on a display device (e.g., a screen set on the cryogenic device 100, a screen of an external device, etc.).

[0062] Fig. 9A simplified schematic diagram of the cryogenic device 100 when in use is shown. As shown, the needle 115 of the needle probe can be inserted into the patient's skin 810 and extend beyond the skin 810 so that the distal portion of the needle 115 is adjacent to the target tissue (e.g., neural tissue). In some embodiments, the operator can select the needle probe so that the size of the needle 115 is designed to extend distally beyond the non-target tissue and adjacent to the target tissue when the tissue engaging surface 920 contacts the skin 910. In some embodiments, once the needle 115 is positioned, the operator can submit an input to the cryogenic device 100 (e.g., by starting a button, tapping a user interface element on a touch screen, etc.) to cause the controller to open the supply valve 405, thereby allowing the refrigerant to flow from the box 130 to the cavity of the needle 115 via the refrigerant passage. The needle 115 can be configured so that the distal portion of the needle 115 is cooled more than the proximal portion of the needle 115. Therefore, the distal portion of the needle 115 can be cooled more than the proximal portion of the needle 115. Fig. 9 A cooling zone is shown formed around the target tissue.

[0063] Fig.10 An example method 1000 for stabilizing pressure within a cryogenic device is shown. The method may include, at step 1010, receiving a first flow rate value, wherein the first flow rate value corresponds to an expected average mass flow rate of cryogen through a first needle probe of a cryogenic device during a cryotherapeutic treatment cycle. At step 1020, the method may include: determining a first target heater power to be applied to a heater associated with the cryogenic device for a first treatment cycle based on the first flow rate value, wherein the heater is configured to heat the cryogen. At step 1030, the method may include receiving an input for the first treatment cycle. At step 1040, the method may include: causing the cryogen to flow toward the first needle probe for a period of time in response to the input. At step 1050, the method may include: applying the first target heater power to the heater during the first treatment cycle to heat the cryogen and stabilize the pressure within the cryogenic device during or after the first treatment cycle. Where appropriate, particular embodiments may be repeated. Fig.10 The method of claim 1 may include one or more steps of the method of claim 2, and may include additional or modified steps as appropriate. For example, as described in further detail above, the heater power may be adjusted for successive treatment cycles and the adjusted heater power may be applied during a subsequent second treatment cycle (e.g., if it is determined that the first heater power results in a negative average rate of change of pressure below a predetermined range during the cool-down phase of the first treatment cycle, a second target heater power for the second treatment cycle may be calculated by adjusting the first heater power upward). Although the present disclosure will Fig.10 The specific steps of the method are described and shown as occurring in a specific order, but the present disclosure contemplates Fig.10Any suitable steps of the method may occur in any suitable order. In addition, although the present disclosure describes and illustrates an example method for stabilizing pressure within a cryogenic device, including Fig.10 The specific steps of the method, however, where appropriate, the present disclosure contemplates any suitable method for stabilizing pressure within a cryogenic device, including any suitable steps, which may include Fig.10 All, some, or none of the steps of the method Fig.10 Furthermore, although the present disclosure describes and illustrates the implementation of Fig.10 specific components, devices or systems for specific steps of the method, but the present disclosure contemplates performing Fig.10 Any suitable combination of any suitable components, devices, or systems of any suitable steps of the method.

[0064] Although exemplary embodiments have been described in some detail for purposes of clarity of understanding and illustration, many modifications, changes, and adaptations may be implemented and / or will be apparent to those skilled in the art.

Claims

1. A cryogenic device comprising: a cryogen source, the cryogen source comprising a pressurized cryogen; a cryogen passage configured to direct the cryogen toward a needle probe including one or more needles, wherein the cryogen is configured to deliver cryotherapy to a target tissue via the one or more needles; Heater; as well as A processor configured to: receiving a first flow rate value, wherein the first flow rate value corresponds to an expected average mass flow rate of cryogen through a first needle probe of the cryogenic device during a cryotherapeutic treatment cycle; determining a first target heater power to be applied to a heater associated with the cryogenic device for a first treatment cycle based on the first flow rate value, wherein the heater is configured to heat the cryogen; receiving input for the first treatment cycle; flowing the cryogen toward the first needle probe for a period of time in response to the input; and applying the first target heater power to the heater during the first treatment cycle to heat the cryogen and stabilize pressure within the cryogenic device during or after the first treatment cycle; receiving pressure data from a pressure sensor of the cryogenic device during the first treatment cycle; calculating, based on the received pressure data, an average rate of change of pressure during a cooling phase of the first treatment cycle; and A second target heater power is calculated for a second treatment cycle, wherein the second target heater power is calculated at least in part by adjusting the first target heater power up or down by an adjustment value based on the average rate of change of pressure.

2. The cryogenic device according to claim 1, characterized in that The first target heater power is defined such that an average rate of pressure change during a cooling period of the first treatment cycle remains within a predefined range.

3. The cryogenic device according to claim 1, characterized in that The processor is further configured to determine that the average rate of change of pressure is negative, wherein the second target heater power is calculated at least in part by adjusting the first target heater power upward by the adjustment value.

4. The cryogenic device according to claim 1, characterized in that The processor is further configured to determine that the average rate of change of pressure is positive, wherein the second target heater power is calculated at least in part by adjusting the first target heater power downward by the adjustment value.

5. The cryogenic device according to claim 1 or 2, characterized in that: The heater is coupled to a cryogen source associated with the cryogenic device.

6. The cryogenic device according to claim 5, characterized in that The cryogenic device includes a handpiece portion, and wherein the cryogen source and the first needle probe are directly coupled to the handpiece portion, the cryogen passage extending between the cryogen source and the first needle probe.

7. The cryogenic device according to claim 1 or 2, characterized in that: The processor is further configured to: determining a target duty cycle required to apply the first target heater power; Wherein application of the first target heater power enables the heater to the target duty cycle.

8. The cryogenic device according to claim 7, characterized in that The target duty cycle is determined based on the output of the following equation: Duty Cycle = P Target x(R Heater / V Heater 2 ), where P Target is the first target heater power, R Heater is the resistance of the heater, and V Heater is the voltage across the heater.

9. The cryogenic device according to claim 8, characterized in that The processor is further configured to monitor the voltage of a power source coupled to the heater to estimate V Heater The real-time value of .

10. The cryogenic device according to claim 1 or 2, characterized in that: The processor is configured to apply the first target heater power by adjusting an amount of current or voltage applied to the heater.

11. The cryogenic device according to claim 1, characterized in that The adjustment value is determined based on the magnitude of the average rate of change of pressure.

12. The cryogenic device of claim 1, wherein the processor is further configured to: determining that the average rate of change of pressure has a magnitude greater than a threshold magnitude; Based on the determination, a notification is generated indicating a problem with the cryogenic equipment.

13. The cryogenic device according to claim 12, characterized in that The average rate of change of pressure is negative, and wherein the notification identifies the problem as a depleted refrigerant source based on the average rate of change of pressure.

14. The cryogenic device according to claim 12, characterized in that The average rate of change of pressure is positive, and wherein the notification identifies the problem as a clogged or blocked refrigerant path based on the average rate of change of pressure.

15. The cryogenic device according to claim 1 or 2, characterized in that: The processor is further configured to: determining a first pressure of the cryogenic device prior to a cooling cycle of the first treatment cycle; determining a second pressure of the cryogenic device prior to a cooling cycle of a second treatment cycle; Wherein the second target heater power is calculated at least in part by: When the second pressure is lower than the first pressure, adjusting the first target heater power upward; or When the second pressure is greater than the first pressure, the first target heater power is adjusted downward.

16. The cryogenic device according to claim 1 or 2, characterized in that replacing the first needle probe with a second needle probe, and the processor is further configured to: receiving a second flow rate value, wherein the second flow rate value corresponds to an expected average mass flow rate of cryogen through the second needle probe during a cooling phase of a cryotherapeutic treatment cycle; and Based on the second flow rate value, a new target heater power to be applied by the heater for a treatment cycle to be performed using the second needle probe is determined.

17. The cryogenic device according to claim 1 or 2, characterized in that: The first treatment cycle includes a cool down phase and a recovery phase, and wherein the first target heater power is applied during the cool down phase.

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