Patent Publication Number: US-2021161579-A1

Title: Cryogenic Devices With Venting Features

Description:
CROSS REFERENCE TO RELATED APPLICATION DATA 
     The present application claims the benefit of U.S. Provisional Appln No. 62/942,547 filed Dec. 2, 2019; the full disclosure which is incorporated herein by reference in its entirety for all purposes. 
    
    
     RELATED FIELDS 
     Devices, systems, and methods for cooling tissue for therapeutic purposes, including nerves for treating pain. 
     BACKGROUND 
     The present disclosure is generally directed to medical devices, systems, and methods for cryotherapy. More specifically, the present disclosure relates to cryogenically cooling target tissues of a patient so as to degenerate, inhibit, remodel, or otherwise affect a target tissue to achieve a desired change in its behavior or composition. Cryogenic cooling of neural tissues has been shown to be effective in treating a variety of indications including pain (e.g., occipital and other neuralgias, neuromas, osteoarthritis pain), spasticity, and joint stiffness, among others. For example, cooling neural tissues has been found to degenerate or inhibit nerves that are instrumental in causing these conditions. Cryogenic cooling has also been employed to address cosmetic conditions, for example, by inhibiting undesirable and/or unsightly effects on the skin (such as lines, wrinkles, or cellulite dimples) or on other surrounding tissue. 
     In light of the above, cryogenic devices with needle probes have emerged as a mode of therapeutically cooling target tissues for treating a variety of indications. The needle probes of such devices are typically inserted into a patient&#39;s skin adjacent to a target tissue. Some cryogenic devices may include a cryogen that may be either injected into the target tissue via openings in needles of their needle probes, such that the target tissue is cooled directly by the cryogen. Other cryogenic probes may include closed needle tips, in which case the needles may be cooled (e.g., by a flow of the cryogen), and the target tissue adjacent to the cooled needles may thereby be cooled by conduction. Cryogenic probes have proved to be effective in creating cryozones within a patient at or around target tissues with precision, convenience, and reliability. A cryozone may be a volume of tissue that is cooled by one or more needles of a cryogenic probe (e.g., a volume of tissue near or around a distal portion of the needles). For example, a cryozone may be a volume of tissue that is cooled so as to freeze the tissue within the volume (e.g., the cryozone may be defined by an approximately 0° C. (or other suitable temperature) isotherm that may form around a needle of the cryogenic probe). 
     BRIEF SUMMARY 
     This disclosure relates to improved medical devices, systems, and methods. Many of the devices and systems described herein will be beneficial for cryotherapy using a cryogenic device. Various features of such a cryogenic device are described herein. 
     In some embodiments, a cryogenic device may include a housing having a cryogen pathway configured to conduct a cryogen from a pressurized cryogen cartridge toward a needle probe with one or more needles, wherein the cryogen is configured to deliver cryotherapy to a target tissue via the one or more needles; an auxiliary pathway coupled to the cryogen pathway and exposed to a relatively low-pressure environment (e.g., an ambient-air environment in which the housing is disposed); and a movable sealing element configured to seal the cryogen pathway from the auxiliary pathway when the movable sealing element is in a closed position, and further configured to open the cryogen pathway to the auxiliary pathway so as to vent an amount of the cryogen to the relatively low-pressure environment when the movable sealing element is in an open position, wherein the movable sealing element is configured to be moved by a user-actuatable element coupled to the movable sealing element and separately configured to be moved by an automatic pressure relief mechanism. 
     In some embodiments, the automatic pressure relief mechanism includes a biasing element configured to apply a biasing force to bias the movable sealing element toward the closed position, the biasing force causing the movable sealing element to be secured against an opening of the auxiliary pathway or urged against the opening of the auxiliary pathway, wherein the movable sealing element is configured to be moved to the open position when the biasing force is overcome by a pressure in the cryogen pathway exceeding a maximum pressure value. In some embodiments, the biasing element is an elastic element (e.g., a spring) coupled to the movable sealing element. 
     In some embodiments, the user-actuatable element is coupled to a bracket element that is coupled to the movable sealing element, the user-actuatable element configured to be actuated by a user to move the bracket element along a first direction or a second direction. Moving the bracket element along the first direction may cause the movable sealing element to move to the open position and moving the bracket element along the second direction causes the movable sealing element to move to the closed position. 
     In some embodiments, the cryogenic device may include a locking mechanism, wherein the locking mechanism is configured to lock the cryogen cartridge within a cartridge holder of the housing until the movable sealing element is in the open position. In some embodiments, the locking mechanism is configured to lock the cryogen cartridge within the cartridge holder until the user-actuatable element is actuated to move the movable sealing element along a first direction, such that the cryogen cartridge is unable to be removed until the movable sealing element is moved along the first direction. In some embodiments, the locking mechanism is coupled to a bracket element coupled to the movable sealing element and the user-actuatable element, the locking mechanism being configured to lock the cryogen cartridge within the cartridge holder until the user-actuatable element is actuated to move the bracket element along a first direction, such that the cryogen cartridge is unable to be removed until the bracket element is moved along the first direction. 
     In some embodiments, the cryogenic device may include a pressure sensor and a locking mechanism, wherein the locking mechanism is configured to lock the cryogen cartridge within a cartridge holder of the housing until a pressure level detected at the pressure sensor within the cryogen pathway is below a threshold pressure value. In some embodiments, the threshold pressure value is less than a maximum pressure value beyond which the automatic pressure relief mechanism is configured to cause the movable sealing element to move to the open position. 
     In some embodiments, the movable sealing element may include a conical structure that is configured to fit within the auxiliary pathway. The movable sealing element may include a cylindrical portion, a spherical portion, or a semi-spherical portion that is configured to fit within the auxiliary pathway. 
     In some embodiments, the cryogenic device may include a housing having a cryogen pathway configured to conduct a cryogen from a pressurized cryogen cartridge toward a needle probe with one or more needles, wherein the cryogen is configured to deliver cryotherapy to a target tissue via the one or more needles; an auxiliary pathway coupled to the cryogen pathway and exposed to a relatively low-pressure environment; and a movable sealing element configured to seal the cryogen pathway from the auxiliary pathway when the movable sealing element is in a closed position, and further configured to open the cryogen pathway to the auxiliary pathway so as to vent an amount of the cryogen to the relatively low-pressure environment when the movable sealing element is in an open position. The movable sealing element may be biased toward the closed position by an elastic element, the elastic element configured to exert an elastic force causing the movable sealing element to be secured against an opening of the auxiliary pathway or urged against an opening of the auxiliary pathway, wherein the movable sealing element is configured to be moved to the open position when the elastic force is overcome by a pressure in the cryogen pathway exceeding a maximum pressure value. The movable sealing element may be coupled to a bracket element that is coupled to a user-actuatable element, the user-actuatable element configured to be actuated by a user to move the bracket element along a first direction or a second direction, wherein moving the bracket element along the first direction causes the movable sealing element to move to the open position and moving the bracket element along the second direction causes the movable sealing element to move to the closed position. 
     In some embodiments, a method for replacing a cartridge of the cryogenic device may include actuating a user-actuatable element of the cryogenic device having a cryogen pathway configured to deliver a cryogen from a first cryogen cartridge to a needle probe, wherein the user-actuatable element is coupled to a movable sealing element adapted for sealing the cryogen pathway from an auxiliary pathway when the movable sealing element is in a closed position, wherein the auxiliary pathway is coupled to the cryogen pathway and exposed to a relatively low-pressure environment. The method may include, in response to actuation of the user-actuatable element, moving the movable sealing element from the closed position to an open position, wherein the movable sealing element is configured to open the cryogen pathway to the auxiliary pathway so as to vent an amount of the cryogen to the relatively low-pressure environment when the movable sealing element is in the open position; and causing a locking mechanism to unlock the first cryogen cartridge within a cartridge holder of the cryogenic device. The first cryogen cartridge may then be removed. In some embodiments, the first cryogen cartridge may be replaced with a second cryogen cartridge. 
     In some embodiments, a method for relieving pressure in a cryogenic device may include actuating a user-actuatable element of the cryogenic device having a cryogen pathway configured to deliver a cryogen from a first cryogen cartridge to a needle probe, wherein the user-actuatable element is coupled to a movable sealing element adapted for sealing the cryogen pathway from an auxiliary pathway when the movable sealing element is in a closed position, wherein the auxiliary pathway is coupled to the cryogen pathway and exposed to a relatively low-pressure environment. The method may include, in response to actuation of the user-actuatable element, moving the movable sealing element from the closed position to an open position, wherein the movable sealing element is configured to open the cryogen pathway to the auxiliary pathway so as to vent an amount of the cryogen to the relatively low-pressure environment when the movable sealing element is in the open position. The method may include causing the movable sealing element to be automatically moved when pressure within the cryogen pathway exceeds a maximum pressure value, wherein the movable sealing element is biased toward the closed position by an elastic element, the elastic element configured to exert an elastic force urging the movable sealing element against the auxiliary pathway when the pressure within the cryogen pathway is below the maximum pressure value, and wherein the movable sealing element is configured to be moved to the open position when the elastic force is overcome by the pressure in the cryogen pathway exceeding a maximum pressure value. The method may further include causing a locking mechanism to lock or unlock the cryogen cartridge within a cartridge holder of the cryogenic device. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIGS. 1A-1B  illustrate an example embodiment of a cryogenic device including a cartridge holder for holding a cryogen cartridge and a needle probe. 
         FIG. 2  illustrates an internal view of an assembly of an example cryogenic device including the cryogen cartridge coupled to the chassis. 
         FIG. 3A  illustrates a simplified cross-section schematic of the cryogen cartridge coupled to the chassis of an example cryogenic device. 
         FIG. 3B  illustrates a cross-section of the sub-portion AA denoted in  FIG. 2 . 
         FIG. 3C  illustrates an internal view of the sub-portion AA denoted in  FIG. 2 , showing portions of the cryogen pathway and the auxiliary pathway. 
         FIG. 4A  illustrates an external view of the sub-portion AA denoted in  FIG. 2 , showing the movable sealing element in its closed position. 
         FIG. 4B  illustrates the movable sealing element in its open position. 
         FIGS. 5A-5C  illustrate example embodiments of a movable sealing element. 
         FIG. 6  illustrates an example method for replacing a cartridge of a cryogenic device. 
         FIG. 7  illustrates a simplified schematic diagram of a cryogenic device while in use. 
     
    
    
     DETAILED DESCRIPTION 
     The present disclosure describes cryogenic devices that may be used to deliver a cryotherapy to patients. In some embodiments, the described cryogenic devices may include needles for delivering cryotherapy subcutaneously to target particular tissues for treating a variety of conditions. For example, the cryogenic devices may include needles that are configured to be inserted near peripheral nerves to deliver cryotherapy to the peripheral nerves to treat pain, spasticity, or other such conditions that may be improved by such therapy. More information about the use of cryotherapy for alleviation of pain or spasticity may be found in U.S. Pat. No. 8,298,216 filed Nov. 14, 2008; U.S. Pat. No. 9,610,112 filed Mar. 18, 2014; U.S. Pat. No. 10,085,789 filed Mar. 13, 2017; and U.S. Patent Publn No. 2019/0038459 filed Sep. 14, 2018, the full disclosures which are incorporated herein by reference in their entirety for all purposes. The cryogenic devices may also be used for prophylactic treatment such as disruption or prevention of neuromas, for example, as described in U.S. Pat. No. 10,470,813 filed Mar. 14, 2016, the full disclosure of which is incorporated herein by reference in its entirety for all purposes. 
       FIGS. 1A-1B  illustrate an example embodiment of a cryogenic device  100  including a cartridge holder  140  for holding a cryogen cartridge  130  and a needle probe  110 . As shown in the illustrated example embodiment, the cryogenic device  100  may be a self-contained handpiece suitable for being grasped and manipulated by an operator&#39;s hand. In other embodiments, the cryogenic device may include physically separated components. For example, the cryogenic device may include a handpiece including a needle probe and a cryogen cartridge that is separated from the handpiece. In some embodiments, the cryogenic device  100  may have a multi-part (e.g., a two-part) housing, with the needle probe  110  disposed within a separate probe housing that may be coupled to a housing of a handpiece portion. In other embodiments, the needle probe  110  may not be disposed within a separate housing and may be configured to be inserted directly 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. 
     In some embodiments, the cryogen cartridge  130  may be a disposable cartridge filled with a cryogen (e.g., nitrous oxide, fluorocarbon refrigerants, and/or carbon dioxide). The cryogen cartridge  130  may be pressurized, such that the cryogen within is maintained at a relatively high pressure. In some embodiments, the cryogenic device  100  may include a cartridge door  120  for accessing the cryogen cartridge  130  (e.g., to replace it). The cartridge door  120  may be configured to move from an open position for allowing the cartridge holder  140  to receive a cryogen cartridge  130  to a closed position for securing the cryogen cartridge  130  within the housing of the cryogenic device  100 . For example, as illustrated in  FIG. 1A-1B , the cartridge door  120  may be configured to swivel around swivel point  125  to allow access to the cryogen cartridge  130 . In this example, a user may open the cartridge door  120  (e.g., when the user notices that the cryogen cartridge  130  is empty) as shown in  FIG. 1A , remove the cryogen cartridge  130  from the cartridge holder  140 , insert a new cryogen cartridge  130  into the cartridge holder  140 , and close the cartridge door  120  as shown in  FIG. 1B . In some embodiments, the cryogenic device  100  may include a valve between the cryogen cartridge  130  and a cryogen pathway (through which the cryogen is to flow toward an attached needle probe  110  during a treatment cycle to cool down the needle probe  110 ) for sealing off the cryogen from the cryogen pathway (e.g., when a treatment cycle is not occurring). 
       FIG. 2  illustrates an internal view of an assembly  200  of an example cryogenic device  100  including the cryogen cartridge  130  coupled to the chassis  105 . In some embodiments, the cryogenic device  100  may include a probe receptacle  170  configured to receive the needle probe  110 . In some embodiments, the probe receptacle  170  may be configured to couple the needle probe  110  to the cryogen cartridge  130  via the cryogen pathway within the chassis  105  (not shown in  FIG. 2 ). In some embodiments, the probe receptacle  170  may be bored into a chassis  105  of the cryogenic device, wherein the chassis  105  includes at least a portion of the cryogen pathway. For example, the chassis  105  may include one or more lumens therein that are coupled to an outlet of the cryogen cartridge  130 , and the one or more lumens of the chassis  105  may be coupled to the probe receptacle  170 . In some embodiments, the chassis may include the entire cryogen pathway within the handpiece portion of the cryogenic device  100  (e.g. from the outlet of the cryogen cartridge  130  to the probe receptacle  170 ). A sub-portion AA of the assembly  200  is denoted in dashed lines, and will be further referenced in the disclosure below. 
       FIG. 3A  illustrates a simplified cross-section schematic of the cryogen cartridge  130  coupled to the chassis  105  of an example cryogenic device  100 . A sub-portion corresponding to the sub-portion AA denoted in  FIG. 2  is illustrated. In the example illustrated in  FIG. 3A , the cryogen cartridge  130  is coupled to the cryogen pathway  360 , which includes, for example, cryogen pathway portions  360   a ,  360   b , and  360   c . A valve  305  may be positioned (e.g., along the cryogen pathway  360 ) between the cryogen in the cartridge  130  and the probe receptacle  170 , such that cryogen flow to a needle probe  110  coupled to the probe receptacle  170  may be controlled by opening and closing the valve  305 . In the illustrated example, when the valve  305  is opened, the cryogen is allowed to flow from through the cryogen pathway (e.g., the cryogen pathway portion  360   c ) toward the probe receptacle  170 . In some embodiments, the cryogenic device  100  may include one or more filtration devices along the cryogen pathway for filtering out impurities in the cryogen. For example, as illustrated in  FIG. 3A , a filter  350  may be disposed along the cryogen pathway  360 , such that the cryogen is made to pass through the filter  350  before it can proceed. The filtration devices may be used to filter out impurities (e.g., impurities that may have been introduced to the cryogen during manufacturing, as a result of puncturing the cartridge to access the refrigerant, or from the environment in which the cryogenic device  100  is used). Solid impurities can compromise the performance of the cryogenic device by occluding passageways and/or creating leak paths in sealing mechanisms. Fluid impurities, both liquids and gasses, such as oil, water, oxygen, nitrogen, and carbon dioxide can also be present within the cryogen cartridge. These impurities may also occlude or restrict cryogen pathways, and/or chemically alter properties of the refrigerant. The filtration device may include an element for capturing solids, as well as or alternatively an element for capturing fluids. The filtration device may include any suitable combination of particulate filters and/or molecular filters. More information about filters in cryogenic devices may be found in U.S. Pat. No. 9,155,584 filed Jan. 14, 2013, which is incorporated by reference herein in its entirety for all purposes. In some embodiments, the filter  139  may be replaceable (e.g., by replacing the piercing element  135 , or by simply replacing the filter  139 ). 
     Referencing the example in  FIG. 3A , the cryogen may flow through the filter  350  through pathway portion  360   b , and continue toward the probe receptacle  170  via the cryogen pathway portion  360   c . This flow is illustrated by the arrow  365 . 
     In some embodiments, as illustrated in  FIG. 3A , cryogenic device  100  may also include an auxiliary pathway  330 . In some embodiments, the auxiliary pathway  330  may be used to vent an amount of the cryogen from the cryogenic device  100 . The auxiliary pathway  330  may be exposed to a relatively low-pressure environment (as compared to the cryogen pathway) such that cryogen within the auxiliary pathway is automatically vented when it is unobstructed. For example, referencing  FIG. 3A , the auxiliary pathway  330  may be open at the distal end to an ambient-air environment (e.g., the environment in which the housing of the cryogenic device  100  is disposed). In some embodiments, as illustrated in  FIG. 3A , a movable sealing element  310  may be disposed within or near the auxiliary pathway  330  such that the movable sealing element  310  is configured to seal the cryogen pathway from the auxiliary pathway  330  when the movable sealing element  310  is in a closed position. The movable sealing element  310  may be further configured to be moved to an open position. Moving the movable sealing element  310  to the open position may open the cryogen pathway to the auxiliary pathway  330 , which may vent an amount of cryogen from the cryogenic device  100  to the relatively low-pressure environment via the auxiliary pathway  330 . Although this disclosure illustrates and describes the movable sealing element  310  as sealing the entire auxiliary pathway  330  from the cryogen pathway  360 , the disclosure contemplates that the movable sealing element  310  may be disposed at a location external to the auxiliary pathway  330  or further up the auxiliary pathway  330  such that the movable sealing element  310  still serves to seal cryogen within the cryogenic device  100  when it is in a closed position and vent cryogen from the cryogenic device  100  when it is in an open position. 
       FIG. 3B  illustrates a cross-section of the sub-portion AA denoted in  FIG. 2 . As illustrated, the cryogen cartridge  130  is coupled to the cryogen pathway portion  360   a . In the illustrated example, the cryogen pathway portion  360   a  includes a lumen bored through a piercing element  370  of the cryogenic device  100 . The piercing element  370  may have a sharp piercing point that is configured to pierce through a portion (e.g., a membrane) of the cryogen cartridge  130  to allow cryogen from the cryogen cartridge  130  to flow out of the cryogenic cartridge  130  and into the cryogen pathway  360 . For example, the cryogen may flow into the cryogen pathway portion  360   a  illustrated in  FIG. 3B . In this example, the cryogen may then flow through the filter  350  and into the cryogen pathway portion  360   b . During ordinary use, the cryogen may then flow through the cryogen pathway portion  360   c  and out to an attached needle probe  110  via the probe receptacle  170 . (The cross-section view of  FIG. 3B  does not allow for the illustration of the connection between the cryogen pathway portion  360   b  and the cryogen pathway portion  360   c  in the example cryogenic device  100 .) In the illustrated example of  FIG. 3B , the movable sealing element  310  is in the closed position, thereby sealing the auxiliary pathway  330  from the cryogen pathway portion  360   b . In this example, the movable sealing element  310  is coupled to a bracket element  340 , which is coupled to a spring  320  that provides a biasing force toward the proximal direction so as to bias the movable sealing element  310  toward the closed position. 
       FIG. 3C  illustrates an internal view of the sub-portion AA denoted in  FIG. 2 , showing portions of the cryogen pathway  360  and the auxiliary pathway  330 . As illustrated by the arrow  365  in the example of  FIG. 3C , during ordinary use where cryogen is caused to flow to an attached needle probe  110 , cryogen flows through cryogen pathway portions  360   b  and  360   c  ( 360   a  is not shown in this figure). As mentioned above, the valve  305  (e.g., disposed along cryogen pathway portion  360   b ) may be operated to control cryogen flow within the cryogen pathway  360 . In this example, the cryogen exits the chassis  105  via the probe receptacle  170  and into the attached needle probe  110  (not shown). 
       FIG. 4A  illustrates an external view of the sub-portion AA denoted in  FIG. 2 , showing the movable sealing element  310  in its closed position.  FIG. 4B  illustrates the movable sealing element  310  in its open position. As illustrated, the movable sealing element  310  in its closed position ( FIG. 4A ) serves to prevent cryogen flow out of the auxiliary pathway  330 , and the movable sealing element  310  in its open position ( FIG. 4B ) allows cryogen flow out of the auxiliary pathway  330 . In some embodiments, the movable sealing element  310  may be configured to be moved by an automatic pressure relief system. The movable sealing element  310  may be biased toward the closed position by a biasing force that causes the movable sealing element  310  to be secured against an opening of the auxiliary pathway  330  or urged against the opening of the auxiliary pathway  330 . The biasing force may be provided by an elastic element such as a spring. For example, as illustrated in  FIG. 4A , a spring  320  that is configured to engage the movable sealing element  310  may provide a biasing force so as to urge the movable sealing element  310  against the auxiliary pathway  330 . In some embodiments, alternatively or additionally, the movable sealing element  310  may itself be an elastic, resilient component (e.g., a shape-memory component such as a flat spring) that is, for example, fixed to the chassis  105  and biased toward the closed position. In some embodiments, the movable sealing element  310  may be configured to be moved to an open position when the biasing force is overcome by a pressure exerted by pressurized cryogen within the cryogenic device  100 . For example, referencing  FIGS. 4A-4B , the biasing force provided by the spring  320  may be overcome when pressure in the cryogen pathway  360  exceeds a maximum pressure value. This maximum pressure value may be, for example, 1700 psi. In this example, following Hooke&#39;s law F=−kx, the spring constant k of the spring  320  may be set such that the force F provided by pressure at the maximum pressure value causes the spring to compress by a prescribed distance x so as to vent cryogen. When pressure in the cryogen pathway  360  is sufficiently decreased from the venting, the biasing force may no longer be overcome, and the movable sealing element  310  may return to the closed position. There are many instances where the described automatic pressure relief system would be advantageous. For example, pressure within the cryogenic device  100  may build up above the maximum pressure value if the cryogenic device  100  is left in an extremely hot environment. As another example, the cryogenic device  100  may include a cartridge heater for heating the cryogen cartridge  130 , for example, to stabilize cryogen pressure and thereby help create uniform coolant conditions to allow for consistent cryozone formation during a cryotherapy treatment. In this example, a heater malfunction (e.g., one that causes the cartridge heater to apply an excess amount of heat) could cause pressure to build up above the maximum pressure value. More information about cryogenic devices with cartridge heaters for heating cryogen cartridges may be found in U.S. Pat. No. 9,066,712 (Atty. Docket No. 002310US) filed Dec. 22, 2009, which is incorporated herein by reference in its entirety for all purposes. As another example, a valve malfunction may cause a buildup of cryogen within the cryogen pathway  360  (e.g., referencing  FIG. 3A , preventing or reducing the advance of cryogen distally beyond the valve  305 ), which, in combination with otherwise acceptable amounts of heat being added by a cartridge heater, may result in a pressure buildup above the maximum pressure value. In these examples, allowing pressure to build up to the maximum pressure value may be unsafe and/or may damage the cryogenic device  100 . As such, an automatic pressure relief system may be an important feature for the cryogenic device  100 . 
     In some embodiments, the movable sealing element may separately be configured to be moved manually. For example, as illustrated in  FIGS. 4A-4B , the cryogenic device  100  may include a bracket element  340  that is coupled to the movable sealing element  310 , such that moving the bracket element  340  causes the movable sealing element  310  to also move. In some embodiments, the bracket element  340  may be configured to move in a first direction and a second direction. These directions may be along an axis (e.g., the longitudinal axis) of the cryogenic device  100 . In this example, moving the bracket element  340  in the first direction (e.g., the distal direction) causes the movable sealing element  310  to move in the first direction (e.g., the distal direction), and moving the bracket element  340  in the second direction (e.g., the proximal direction) causes the movable sealing element  310  to move in the second direction (e.g., the proximal direction). As such, the bracket element  340  may be used to move the movable sealing element  310  between open and closed positions. For example, referencing  FIGS. 4A-4B , moving the bracket element  340  (and correspondingly, the movable sealing element  310 ) in a distal direction may cause the movable sealing element  310  to move to the open position, thereby allowing cryogen within the cryogen pathway  360  to vent via the auxiliary pathway  330 . Similarly, moving the bracket element  340  (and correspondingly, the movable sealing element  310 ) in a proximal direction may cause the movable sealing element  310  to move to the closed position, thereby sealing the auxiliary pathway  330 . In some embodiments, as illustrated in  FIGS. 4A-4B , the bracket element  340  may be coupled to a user-actuatable element  345  (or the user-actuatable element  345  and the bracket element  340  may be a single integral component) that allows a user to manually move the bracket element  340  as described above. The user-actuatable element  345  may be, for example, a slider element that is configured to move in the first direction (e.g., distally) and the second direction (e.g., proximally) as illustrated in  FIGS. 4A-4B , or may be any other suitable element for receiving a user input (e.g., a mechanical button disposed on an exterior housing of the cryogenic device  100 , a virtual button disposed on an LCD screen coupled to or associated with the cryogenic device  100 , etc.). In some embodiments, the user-actuatable element  345  may be biased (e.g., with an elastic element) toward a position corresponding to movable sealing element  310  being in the closed position. For example, referencing  FIGS. 4A-4B , when a user slides and applies a force to hold the user-actuatable element  345  at a distal position, the movable sealing element  310  is moved to the open position, and may remain there so long as the user continues to hold the user-actuatable element  345  at the distal position. In this example, when the user releases the user-actuatable element  345 , the user-actuatable element  345  may automatically revert back to a proximal position, thereby moving the movable sealing element  310  to the closed position. In other embodiments, the user-actuatable element  345  may not be biased, in which case the user having actuatable element  345  (and correspondingly, the movable sealing element  310 ) maintains its position (proximal or distal) until further actuation by the user. Although the disclosure focuses on a user-actuatable element  345  and a movable sealing element  310  that are configured to move in distal and proximal directions, these elements may move in any suitable direction so long as they achieve the purpose of moving the movable sealing element  310  between open and closed positions. 
     A manual means of moving the movable sealing element  310  may be useful in a number of different scenarios. For example, a user may manually move the movable sealing element  310  prior to removing a cryogen cartridge  130  so as to vent cryogen within the cryogen pathway  360 . This may enhance device safety by reducing risks associated with removing the cryogen cartridge  130  while there is still pressurized cryogen within the cryogen pathway  360 . Referencing the example cryogen device  100  illustrated in  FIG. 3A , prior to removing the cartridge  130 , a user may manually move the movable sealing element  310  to the open position to allow cryogen within the cryogen pathway  360  (e.g., cryogen in the cryogen pathway  360  proximal to the valve  305 ) to be vented via the auxiliary pathway  330 . This may ensure that pressure in the cryogen pathway  360  leading up to the cryogen cartridge  310  is reduced and/or brought to an ambient temperature to allow for safe removal of the cryogen cartridge  130 . In some embodiments, as in the illustrated example of  FIG. 3A , the auxiliary pathway  330  may be positioned upstream from the valve  305  to ensure that all cryogen within the cryogen pathway (leading up to the cryogen cartridge  330  at least) has an opportunity to be vented from the cryogenic device via the auxiliary pathway  330 . As another example of a scenario in which a manual means of moving the movable sealing element  310  may be useful, a user may manually move the movable sealing element  310  after having determined (e.g., based on data from a pressure sensor) that pressure within the cryogen pathway  360  is above a desired pressure value (e.g., if the pressure value is not high enough to overcome the biasing force for automatic pressure relief, if there is a malfunction with the automatic pressure relief mechanism, etc.). 
     Although the disclosure focuses on particular example mechanisms for moving the movable sealing element  310 , other suitable means of moving the movable sealing element  310  are also contemplated. For example, the movable sealing element  310  may be moved by an electronic component such as a rotational motor or a linear actuator. The electronic component may receive pressure data from pressure sensors within the cryogen pathway  360 , and may automatically be operated to move the movable sealing element  310 . Additionally or alternatively, the electronic component may receive a signal (e.g., an electrical signal) when a user actuates the user-actuatable element  345  (e.g., a mechanical or virtual button on the exterior of the cryogenic device), in response to which the electronic component may be operated to move the movable sealing element  310 . 
     The configuration illustrated in the example embodiments of  FIGS. 4A-4B  is advantageous in that it integrates two separate means of relieving excess pressure from the cryogenic device  100  into a single combined mechanism. Such integration affords both reduced complexity to the cryogenic device  100  and a reduced footprint (e.g., due to the lack of redundancies that would otherwise exist in having two separate mechanisms). 
       FIGS. 5A-5C  illustrate example embodiments of movable sealing element  310 . The movable sealing element  310  may be dimensioned so as to efficiently seal the auxiliary pathway  330  and also couple efficiently with one or more mechanisms for moving the movable sealing element  310  (e.g., the bracket  340 , the spring  320 ).  FIG. 5A  illustrates a movable sealing element  310  with a conical first portion  510 , a cylindrical second portion  520 , and a coupling portion  530  (e.g., for coupling with the bracket  340  and the spring  320  of  FIGS. 4A-4B ).  FIG. 5B  illustrates a movable sealing element  310  with a cylindrical first portion  510  and a coupling portion  530 .  FIG. 5C  illustrates a semispherical first portion  520 , a cylindrical second portion, and a coupling portion  530 . Although  FIGS. 5A-5C  illustrate movable sealing elements  310  with a particular number of portions, the disclosure contemplates any number of portions. Additionally, although  FIGS. 5A-5C  illustrate the different portions as being separate, the disclosure contemplates that one or more of the portions may be integrated (e.g., referencing  FIG. 5A , portions  510 ,  520 , and  530  may be one integral component). Additionally, although  FIGS. 5A-5C  illustrate particular shapes for portions of the movable sealing element  310 , any suitable shapes may be used (e.g., spherical, cuboidal, pyramidal). 
     In some embodiments, the cryogenic device  100  may include a locking mechanism, wherein the locking mechanism is configured to lock the cryogen cartridge  130  within the cartridge holder  140  until the movable sealing element  310  is in the open position. Having such a locking mechanism may provide additional safety for users of the cryogenic device  100 , by preventing users from removing the cryogen cartridge  130  until there is an exit path for any pressurized cryogen that may in the cryogen pathway  360 . Removing the cryogen cartridge  130  when there is a buildup of high-pressure cryogen within the cryogen pathway  360  may result in cryogen being propelled out of the cryogen pathway  360  (e.g., proximally) in an unsafe manner. A locking mechanism may force the user to move the movable sealing element  310  (e.g., by actuating the user-actuatable element  345 ) to the open position, such that any cryogen within the cryogen pathway  360  may at least begin venting via the auxiliary pathway  330  before the cryogen cartridge  130  is removed (and also have a second exit path via the auxiliary pathway  330 ). In some embodiments, the locking mechanism may require that the movable sealing element  310  be held in the open position for a predetermined period of time (e.g., as a safety measure to ensure that an amount of built-up cryogen is vented). For example, a timer may be initiated when the user actuates the user-actuatable element  345 , and the cryogen cartridge  130  may only be unlocked from the cartridge holder  140  after a predetermined period of time has elapsed. 
     Any suitable means may be used to ensure that the movable sealing element  310  is in the open position (or that it has been in the open position for a predetermined period of time). In some embodiments, the locking mechanism may be configured to unlock the cryogen cartridge  130  when an element coupled to the movable sealing element  310  is moved. For example, the locking mechanism may include a retaining element coupled to (or part of) the movable sealing element  310  that may act as a barrier (e.g., mechanical barrier) that prevents the removal of a cryogen cartridge  130 . In this example, moving the movable sealing element  310  to the open position may cause the retaining element to be moved such that the cryogen cartridge  130  may be unlocked from the cartridge holder  140 . In some embodiments, cryogen cartridge may be unable to be removed until an input element (e.g., an unlock button) is actuated to unlock the cryogen cartridge  130 . In some embodiments, the input element may be the user-actuatable element  345 , in which case the user-actuatable element  345  may be actuated (e.g., referencing  FIGS. 4A-4B , by sliding the user-actuatable element  345  in the distal direction to move the movable sealing element  310  to the open position). In some of these embodiments, a retaining element coupled to (or part of) the user-actuatable element  345  may act as a barrier (e.g., mechanical barrier) that prevents the removal of a cryogen cartridge  130 . Actuating the user-actuatable element  345  may cause the retaining element to be moved so as to unlock the cryogen cartridge  130  from the cartridge holder  140 . In some embodiments, the locking mechanism may be coupled to an element such as the bracket element  340  in  FIGS. 4A-4B  that is coupled to the movable sealing element  310 . The locking mechanism may be configured to lock the cryogen cartridge within the cartridge holder until the bracket element  340  is moved. In some of these embodiments, a retaining element coupled to (or part of) the bracket element  340  may act as a barrier (e.g., mechanical barrier) that prevents the removal of a cryogen cartridge  130 . Moving the bracket element  340  (e.g., referencing  FIGS. 4A-4B , moving the bracket element  340  distally by sliding the user-actuatable element  345 ) may cause the retaining element to be moved so as to unlock the cryogen cartridge  130  from the cartridge holder  140 . 
     In some embodiments, the locking mechanism is configured to lock the cryogen cartridge  130  within the cartridge holder  140  until a pressure level in the cryogen pathway  360  is below a threshold pressure value. For example, the locking mechanism may be electronically operated such that it may receive pressure signals from a pressure sensor within the cryogen pathway  360 . In this example, the locking mechanism may lock the cryogen cartridge  130  when it receives pressure signals indicating that pressure in the cryogen pathway  360  is at or above the threshold pressure value. As another example, the locking mechanism may be mechanically operated such that it locks the cryogen cartridge  130  when the pressure level in the cryogen pathway  360  is at or above the threshold pressure value. One example means of achieving this may be an elastic element such as a spring that is configured to push a retaining element against the cryogen cartridge  130  when pressure is at or above the threshold pressure value (similar to, but in direct opposition to, the way the movable sealing element  310  and spring  320  configuration operate as illustrated in  FIGS. 4A-4B ). In some embodiments, the threshold pressure level may be equal to the maximum pressure value (i.e., the value at which the movable sealing element  310  is configured to move to the open position). In other embodiments, the threshold pressure level may be less than the maximum pressure value. In these embodiments, the threshold pressure level may functionally set a higher safety standard (as compared to the maximum pressure value) for the removal of a cryogen cartridge  130 . In yet other embodiments, the opposite may be true, in which case the threshold pressure level may be more than the maximum pressure value. 
       FIG. 6  illustrates an example method  600  for replacing a cartridge of a cryogenic device. The method may include, at step  610 , actuating a user-actuatable element of the cryogenic device having a cryogen pathway configured to deliver a cryogen from a first cryogen cartridge to a needle probe, wherein the user-actuatable element is coupled to a movable sealing element adapted for sealing the cryogen pathway from an auxiliary pathway when the movable sealing element is in a closed position, wherein the auxiliary pathway is coupled to the cryogen pathway and exposed to a relatively low-pressure environment. At step  620 , the method may include, in response to actuation of the user-actuatable element, moving the movable sealing element from the closed position to an open position, wherein the movable sealing element is configured to open the cryogen pathway to the auxiliary pathway so as to vent an amount of the cryogen to the relatively low-pressure environment when the movable sealing element is in the open position. At step  630 , the method may include in response to actuation of the user-actuatable element, causing a locking mechanism to unlock the first cryogen cartridge within a cartridge holder of the cryogenic device. At step  640 , the method may include removing the first cryogen cartridge. In some embodiments, the method may include positioning a second cryogen cartridge within the cartridge holder to cause the locking mechanism to automatically secure the second cryogen cartridge in place. For example, the locking mechanism may snap into place when the second cryogen cartridge is positioned appropriately. In other embodiments, the method may include positioning the second cryogen cartridge within the cartridge holder, and actuating an input element (e.g., the user-actuatable element  345 ) to cause the locking mechanism to secure the second cryogen cartridge in place. 
     Particular embodiments may repeat one or more steps of the method of  FIG. 6 , where appropriate. Although this disclosure describes and illustrates particular steps of the method of  FIG. 6  as occurring in a particular order, this disclosure contemplates any suitable steps of the method of  FIG. 6  occurring in any suitable order. Moreover, although this disclosure describes and illustrates an example method for replacing a cartridge of a cryogenic device, including the particular steps of the method of  FIG. 6 , this disclosure contemplates any suitable method for replacing a cartridge of a cryogenic device, including any suitable steps, which may include all, some, or none of the steps of the method of  FIG. 6 , where appropriate. Furthermore, although this disclosure describes and illustrates particular components, devices, or systems carrying out particular steps of the method of  FIG. 6 , this disclosure contemplates any suitable combination of any suitable components, devices, or systems carrying out any suitable steps of the method of  FIG. 6 . 
       FIG. 7  illustrates a simplified schematic diagram of a cryogenic device  100  while in use. As illustrated, the needles  115  may be inserted into and beyond the skin  710  of the patient such that distal portions of the needles  115  are adjacent to a target tissue (e.g., nerve tissue). In some embodiments, an operator may select a needle probe such that the needles  115  are sized so as to extend distally beyond non-target tissue and adjacent to a target tissue when a tissue-engaging surface  720  is made to contact the skin  710 . In some embodiments, once the needles  115  are positioned, an operator may submit an input to the cryogenic device  100  (e.g., by actuating a button, tapping a user interface element on a touchscreen, etc.) to cause a controller to open a supply valve  122 , thereby enabling a cryogen to flow from the cartridge  130  to the lumens of the needles  115  via a cryogen pathway. The needles  115  may be configured such that distal portions of the needles  115  are cooled more than proximal portions of the needles  115 . As such, the distal portions of the needles  115  may create a cooling zone around the target tissue as illustrated in  FIG. 7 . 
     While the exemplary embodiments have been described in some detail for clarity of understanding and by way of example, a number of modifications, changes, and adaptations may be implemented and/or will be obvious to those as skilled in the art. Hence, the scope of the present invention is limited solely by the claims as follows.