Devices and methods for targeted vaporization of cryogen

Abstract

Embodiments of the present disclosure relate to devices and methods for targeted vaporization of cryogen. A cryoablation device includes a Dewar flask configured to hold a volume of cryogen and a heater assembly positioned in the Dewar flask. The heater assembly includes at least one heater configured to heat a targeted portion of the cryogen when a volume of the cryogen in the Dewar bottle changes. The targeting portion of the cryogen is located at or near a top surface of the liquid level of the liquid cryogen.

Description

Technical Field

[0001] The present disclosure relates to devices and methods for targeted vaporization of cryogens. More specifically, the present disclosure relates to devices and methods for targeted vaporization of cryogens in a dewar to pressurize the dewar for efficient transfer of liquid cryogen for cryoablation procedures. Background Art

[0002] This section provides background information related to the present disclosure, which is not necessarily prior art.

[0003] Systems and methods for providing cryoablation treatment can include a cryoablation probe introduced at or near a target tissue within a patient. The cryoablation system can include a cryogen that is extremely cold (liquid, gas, or mixed-phase nitrogen, argon, helium, etc.) and that can pass through the probe in thermal contact with the target tissue. Heat from the tissue is transferred from the tissue, through the probe, and into the cryogen that removes heat from the targeted tissue. This removal of heat causes the tissue to freeze, thereby destroying the targeted tissue. When the tissue freezes, ice typically forms in an ice ball. The ice ball can be spherical, ellipsoidal, or other circular shapes. It is desirable to perform cryoablation treatment such that the target tissue is completely frozen and freezing of surrounding tissue and / or body structures is minimized.

[0004] Traditional or existing systems typically include a cryogen source and a delivery system that operates to deliver the cryogen to the probe to produce a satisfactory and predictable temperature at the target tissue. However, existing systems may include multiple separate systems, separate controls, independent measurement devices, and separate user interfaces, which can lead to inefficiencies and reduced treatment effectiveness. Accordingly, there is a need for improved devices and systems to improve efficiency, reduce treatment costs, and improve treatment effectiveness. Summary of the Invention

[0005] This section provides a general overview of the present disclosure and is not a full disclosure of its entire scope or all of its features.

[0006] In some embodiments of the present disclosure, a cryoablation device can include a dewar configured to hold a volume of cryogen and a heater assembly positioned within the dewar. The heater assembly can include at least one heater configured to heat a targeted portion of the cryogen when the volume of cryogen within the dewar changes.

[0007] In one aspect, the targeted portion of the cryogen can include the portion of the cryogen that is at or near the cryogen liquid level.

[0008] In another aspect, the targeted portion of the cryogen can include the portion within a predetermined distance from the cryogen liquid level.

[0009] In another aspect, the heater can convert a liquid refrigerant into refrigerant vapor.

[0010] In another aspect, the heater assembly can be connected to a transfer conduit inside the Dewar flask.

[0011] In another aspect, the heater assembly can be coupled to the wall of the Dewar flask.

[0012] In another aspect, the heater assembly can be coupled to a support rod in the Dewar flask.

[0013] In another aspect, the heater assembly can include a plurality of heaters, each of the plurality of heaters being positioned at a different height relative to the base of the Dewar flask.

[0014] In another aspect, the plurality of heaters can be positioned inside a thermal insulation enclosure in the Dewar flask.

[0015] In another aspect, at least one heater can be positioned at the top of the Dewar flask.

[0016] In another aspect, at least one heater can be configured to move within the Dewar flask.

[0017] In another aspect, at least one heater can be slidably positioned on a shaft in the Dewar flask, and at least one heater can be configured to slide along the shaft when the level of the refrigerant in the Dewar flask changes.

[0018] In another aspect, at least one heater includes a float having a predetermined buoyancy, the float being configured to hold at least one heater at a predetermined position relative to the level of the refrigerant in the Dewar flask.

[0019] In another aspect, the refrigerant can be nitrogen.

[0020] In some embodiments of the present disclosure, a method of heating a targeted portion of a refrigerant is provided. The method can include obtaining refrigerant level information characterizing the position of the level of the refrigerant in the Dewar flask, obtaining pressure information characterizing the internal pressure of the Dewar flask, and energizing a heater in the Dewar flask to heat a targeted portion of the refrigerant in the Dewar flask when the pressure information indicates that the internal pressure of the Dewar flask is less than a predetermined pressure value.

[0021] In one aspect, the targeted portion of the refrigerant can include the portion of the refrigerant that is at or near the level of the refrigerant.

[0022] In another aspect, the targeted portion of the refrigerant can include the portion within a predetermined distance from the level of the refrigerant.

[0023] In another aspect, the heater is a first heater, and the method further includes de-energizing the first heater when the liquid level moves below the first heater and energizing a second heater, where the second heater is at a predetermined distance below the first heater.

[0024] In another aspect, the method may further include de-energizing the heater when pressure information indicates that the internal pressure of the Dewar flask is greater than a predetermined threshold.

[0025] In another aspect, the heater may be slidably positioned on a shaft in the Dewar flask, and the heater is configured to slide along the shaft when the liquid level of the refrigerant in the Dewar flask changes.

[0026] From the description provided herein, further applicable fields will become apparent. The description and specific examples in this summary are intended for illustrative purposes only and are not intended to limit the scope of the present disclosure. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The drawings described herein are only for illustration of selected embodiments and not all possible implementations, and are not intended to limit the scope of the present disclosure.

[0028] Figure 1 is a diagram of an exemplary cryoablation device according to some embodiments of the present disclosure.

[0029] Figure 2 is Figure 1 a diagram of the cryoablation device shown, where the liquid refrigerant is at different levels.

[0030] Figure 3 is a diagram of another exemplary cryoablation device according to some embodiments of the present disclosure.

[0031] Figure 4 is a diagram of another exemplary cryoablation device according to some embodiments of the present disclosure.

[0032] Figure 5 is a diagram of another exemplary cryoablation device according to some embodiments of the present disclosure.

[0033] Figure 6 is a diagram of another exemplary cryoablation device according to some embodiments of the present disclosure.

[0034] Figure 7 is a diagram of aspects of a cryoablation device according to some embodiments of the present disclosure, which may include a movable heater assembly.

[0035] Figure 8 is a diagram of an exemplary heater assembly that can be used in various cryoablation devices of the present disclosure.

[0036] Figure 9 FIG. is an illustration of another exemplary cryoablation device in accordance with some embodiments of the present disclosure.

[0037] Figure 10 FIG. is a flow chart showing an exemplary method of pressurizing a cryoablation device in accordance with some embodiments of the present disclosure.

[0038] Corresponding reference numerals indicate corresponding parts throughout the several views of the drawings. DETAILED DESCRIPTION

[0039] Example embodiments will now be described more fully with reference to the accompanying drawings.

[0040] The example embodiments are provided so that this disclosure will be thorough, and will fully convey the scope to those skilled in the art. Numerous specific details are set forth such as examples of specific components, devices, and methods, to provide a thorough understanding of embodiments of the present disclosure. Those skilled in the art will appreciate that specific details are not required, and that the example embodiments may be embodied in many different forms and should not be construed as limiting the scope of the present disclosure. In some example embodiments, well-known processes, well-known device structures, and well-known technologies are not described in detail.

[0041] The terminology used herein is for the purpose of describing particular example embodiments only and is not intended to be limiting. As used herein, unless the context clearly dictates otherwise, the singular forms "a", "an", and "the" may also be intended to include the plural forms. The terms "comprises", "comprising", "including", "has" include, and thus specify the presence of stated features, integers, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof. The method steps, processes, and operations described herein should not be construed as necessarily being performed in the particular order discussed or illustrated, unless specifically identified as an order of performance. It should also be understood that additional or alternative steps may be employed.

[0042] When an element or layer is referred to as being “on,” “engaged to,” “connected to,” or “coupled to” another element or layer, it can be directly on, engaged, connected, or coupled to the other element or layer, or intervening elements or layers may be present. In contrast, when an element is referred to as being “directly on,” “directly engaged to,” “directly connected to,” or “directly coupled to” another element or layer, there may be no intervening elements or layers present. Other words used to describe the relationship between elements should be interpreted in a similar manner (e.g., “between” versus “directly between,” “adjacent” versus “directly adjacent,” etc.). As used herein, the term “and / or” includes any and all combinations of one or more of the associated listed items.

[0043] Although the terms first, second, third, etc. may be used herein to describe various elements, components, regions, layers, and / or sections, these elements, components, regions, layers, and / or sections should not be limited by these terms. These terms may be used only to distinguish one element, component, region, layer, or section from another. Unless the context clearly indicates otherwise, terms such as “first,” “second,” and other numerical terms when used herein do not imply a sequence or order. Thus, the first element, component, region, layer, or section discussed below may be referred to as the second element, component, region, layer, or section without departing from the teachings of the example embodiments.

[0044] For ease of description, spatial relative terms, such as “inner,” “outer,” “beneath,” “below,” “lower,” “above,” “upper,” etc., may be used herein to describe the relationship of one element or feature to another as illustrated. In addition to the orientation depicted in the figures, the spatial relative terms may be intended to encompass different orientations of the device in use or operation. For example, if the device in the figures is turned over, an element described as “beneath” or “below” other elements or features would then be oriented “above” the other elements or features. Thus, the example term “below” can encompass both an orientation of above and below. The device may be otherwise oriented (rotated 90 degrees or at other orientations), and the spatial relative descriptors used herein are to be interpreted accordingly.

[0045] The present disclosure relates to devices and methods for delivering a liquid cryogen to a cryoablation probe. In some examples, the methods and devices can deliver a liquid cryogen to a cryoablation probe during cryoablation therapy. The methods and devices of the present disclosure are improvements over known or existing devices and methods. Compared to existing devices and methods, the methods and devices of the present disclosure can deliver the liquid in a more efficient manner, in a shorter time, at a lower cost, and with lower energy consumption.

[0046] In various embodiments further described below, the apparatus and method of the present disclosure include a heating assembly positioned inside a Dewar flask and configured to heat a targeted portion of the cryogen. Heating of the targeted portion of the cryogen causes some of the cryogen in the cryogen to change from liquid cryogen to cryogen vapor. The density of the cryogen vapor is less than that of the liquid cryogen and may cause an increase in the internal pressure of the Dewar flask. The increased internal pressure in the Dewar flask can help move the liquid cryogen from the Dewar flask through one or more transfer conduits to a cryoprobe or other element.

[0047] The apparatus and method of the present disclosure are improvements over existing or known systems because the heating assembly heats the targeted portion of the cryogen at or near the level of the cryogen in the Dewar flask. Targeting the portion of the liquid cryogen at the level (e.g., targeted at the top surface of the liquid cryogen) allows the formed cryogen vapor to leave a volume of the liquid cryogen and fill the top portion above the liquid cryogen in the Dewar flask. This targeting allows for a reduction in the amount of energy used to pressurize the Dewar flask because the vaporized cryogen does not need to travel through a long distance in the liquid cryogen where it may revert back to liquid cryogen before leaving the liquid cryogen and filling the top portion of the Dewar flask. Additionally, the temperature of the liquid cryogen can be maintained at a lower overall temperature than would be the case if the vaporized cryogen traveled through the liquid cryogen.

[0048] Now referring Figure 1 and Figure 2 , an example cryoablation device 100 is shown. The cryoablation device 100 can be used, for example, to deliver a liquid cryogen to one or more cryoablation probes (not shown). The cryoablation device 100 can include a container or Dewar flask 102, a transfer conduit 104, a pump assembly 106, and a supply conduit 108. The Dewar flask 102 can be a container for holding a volume of cryogen. The Dewar flask 102 can be insulated and / or made of a suitable material to keep the cryogen at a low temperature for cryoablation treatment. In some examples, the Dewar flask can be sized to perform multiple cryoablation cycles. In some examples, the Dewar flask 102 can be sized to accommodate approximately 25 to approximately 50 liters of cryogen. Various cryogens can be used, such as helium, argon, nitrogen, etc. In a preferred example, liquid nitrogen can be used as the cryogen for cryoablation treatment.

[0049] The Dewar flask 102 can be filled with a volume of cryogen. When the Dewar flask 102 is in the filled or near-filled condition as Figure 1 shown, this volume of cryogen can position the level L1 of the cryogen at or near the top of the Dewar flask 102. After performing multiple cryoablation cycles, the cryogen may be depleted such that the level L1 drops from the filled condition to the depleted level L2, as Figure 2As shown. When the refrigerant reaches a predetermined threshold, the Dewar bottle 102 may need to be refilled to restore the Dewar bottle 102 to the filling condition as Figure 1 shown.

[0050] The transfer conduit 104 can extend from the pump assembly 106 into the liquid refrigerant 110. The transfer conduit 104 can be a tube or other lumen that fluidly connects the interior volume of the Dewar bottle 102 to the pump assembly 106. The liquid refrigerant can flow from the Dewar bottle 102 through the transfer conduit 104. The pump assembly 106 can include a pump, a motor, and / or other elements to cause the liquid refrigerant to flow from the transfer conduit 104 to the supply conduit 108. The supply conduit 108 can be fluidly coupled to a manifold, a valve, and / or other elements to provide the liquid refrigerant from the Dewar bottle 102 to one or more cryoablation probes.

[0051] In other examples, the cryoablation device 100 can include Figure 1 and Figure 2 other elements that may not be shown in

[0052] and / or can include alternative configurations. In other examples, the cryoablation device 100 can include a pump located within the Dewar bottle and / or at other locations coupled to the transfer conduit 104. As can be understood, the features of the present disclosure can be included on such alternative configurations of the cryoablation device 100. The following description is for illustrative purposes and describes various elements used in conjunction with the cryoablation device 100 and should not be construed as limiting the use of such elements.

[0053] Each heater among heaters 120a to 120f in the heater array may include a suitable heating element to heat the liquid refrigerant 110 positioned at or near the heater. For example, the heating element may be a resistive heating element coupled to a suitable power source and controller. The controller may energize the heating element and may control the delivered power, including controlling power signal, amplitude, frequency, duty cycle, pulse width, or other characteristics, such that a desired amount of energy is supplied to heat the liquid refrigerant as desired. In other examples, heater 120 and / or the included heating element may have other configurations, such as an infrared heater or a laser heater. The heater may also include a power or energy conversion heater, such as a wireless power, transmitted power, radio frequency (RF) or microwave heater, a pressure heater, or other heaters capable of transferring heat or power to the dewar and effecting vaporization of the liquid refrigerant.

[0054] Each heater among heaters 120a to 120f may be energized as desired to heat the liquid refrigerant 110, thereby vaporizing the liquid refrigerant 110 into refrigerant gas. The refrigerant gas may rise and occupy the top portion of the dewar 102, which may have a pressure P, as Figure 1 shown. As more liquid refrigerant is heated and converted into refrigerant gas, the pressure P in the dewar may increase. The pressure P may exert a force on the liquid refrigerant 110. This force may push the liquid refrigerant into the transfer conduit 104. This force may also push the liquid refrigerant 110 into a pump located in the cryoablation device 100. Thus, generating refrigerant gas from the liquid refrigerant 110 may charge the pump of the cryoablation device 100. The pressure required to charge the pump of the cryoablation device 100 may have a predetermined pressure range or a predetermined pressure threshold. For example, it may be desirable to heat enough liquid refrigerant to convert the liquid refrigerant into refrigerant gas and pressurize the dewar to an internal pressure in the range of about 10 psi to about 15 psi. In other examples, a predetermined pressure threshold of about 10 psi may be used. In other examples, other pressure ranges may be used, which may depend on pump design, pressure tolerance, heater efficiency, and / or other factors. For example, if the dewar is configured as a pressure vessel, a pressure range or pressure threshold exceeding 15 psi may be used.

[0055] Pressurizing the dewar to a predetermined pressure threshold or a predetermined pressure range is also used for additional purposes. The increase in pressure in the dewar may raise the boiling point of the liquid refrigerant (such as liquid nitrogen) in the dewar. This elevated boiling point may help prevent refrigerant gas from entering the pump. It is desirable to prevent refrigerant gas from entering the pump because the refrigerant gas may generate heat when pressurized and inhibit the normal operation of the pump.

[0056] During a cryoablation cycle, liquid cryogen 110 can move from the dewar 102 to the cryoablation probe. The cryogen can return to the dewar and / or be vented to the environment. The cryogen can be depleted during the cryoablation cycle such that the level L1 of the liquid cryogen 110 moves downward in the dewar 102. Such conditions are shown in Figure 2 During treatment, different heaters 102a to 102f can be alternately and / or continuously powered such that the desired heater heats a targeted portion of the liquid cryogen. In some examples, one of the heaters 102a to 102f is powered to heat the top portion of the liquid cryogen that is at or near the level L1.

[0057] For example, when starting a cryoablation treatment, heater 102a can be powered. Since heater 102a is at or near the level L1, only the targeted portion of the liquid cryogen is heated at or near the top surface of the liquid cryogen 110. The cryogen gas generated by such heating only needs to travel a short vertical distance before entering the top portion of the dewar 102 and causing an increase in the pressure P in the dewar. A controller, computing device, PLC, or other device can be used to monitor the position of the level L1. In some examples, one or more level sensors can be included in each of the heaters 102a to 102f. In other examples, the cryoablation device 100 can include a series of level sensors at other locations or include a continuous level sensor. For example, impedance can be collected to determine the position of the level L1 in the dewar 102. Then, the controller can power on the heaters 102a to 102f that are located at the position closest to the level L1 and below the top surface of the liquid cryogen 110.

[0058] As the level L1 in the dewar 102 drops, the controller can disconnect the power to one heater and power on a different heater that is at or below the level L1. In this way, as the level L1 in the dewar drops, the controller can continuously deactivate the heaters 102a to 102f vertically. As shown in Figure 1 Heater 102a is located at the position closest to the level L1 and below the surface of the liquid cryogen 110. This can be the first heater to be powered on during the operation of the cryoablation device 100. As shown in Figure 2 The level L2 in the dewar 102 has dropped. In this case, the controller can power on heater 120e because it is located at the position closest to the level L2 and below the top surface of the liquid cryogen 110.

[0059] A heating array or heating assembly that includes multiple heaters (such as heaters 102a to 102f) is an improvement over existing or known devices. As discussed above, by targeting portions at or near the liquid level of the liquid refrigerant, the refrigerant gas only needs to travel a short vertical distance before occupying the top portion of the dewar 102 that is above the liquid refrigerant 110. The refrigerant gas is less likely to be cooled enough to turn back into liquid refrigerant. Thus, the generation of the refrigerant gas is performed more efficiently, and less energy is required to pressurize the dewar 102. Additionally, the temperature of the liquid refrigerant does not increase unnecessarily. In devices that include heaters located at or near the base of the dewar 102 or at the distal end of the transfer conduit 104, the liquid refrigerant can be heated at a location well below the top surface of the liquid refrigerant. This may increase the overall temperature of the liquid refrigerant. By targeting the top portion of the liquid refrigerant, the overall temperature of the liquid refrigerant can be kept at a lower temperature, which can then be used to perform cryoablation therapy. Observations and tests indicate that the devices and methods of the present disclosure can allow the liquid refrigerant to be maintained and used at a temperature of about -196°C, while existing devices and methods may only be able to maintain and use the liquid refrigerant at a temperature of about -185°C.

[0060] Existing systems and methods also have long delays before the liquid refrigerant is ready to flow for cryoablation therapy. As discussed above, the cryoablation cycle may not be performed until the internal pressure in the dewar 102 increases to a predetermined threshold or a predetermined range. Existing systems that use other heating arrangements or systems (e.g., heaters located well below the liquid refrigerant level) to heat the liquid refrigerant require increased energy and a significant amount of time until the internal pressure of the dewar 102 reaches the predetermined pressure threshold or range. Existing systems may take more than 1 hour to achieve a suitable pressure and start the refrigerant flow. The cryoablation device 100 and other devices of the present disclosure can start moving the liquid refrigerant faster than existing systems. For example, in an embodiment with a resistive heater, the cryoablation device 100 can start moving the liquid refrigerant within a period of about 3 minutes to about 5 minutes, and the resistive heater can achieve a pressure of about 10 psi to about 15 psi at a power level in the range of about 200 watts to about 250 watts. In one example, compared to existing devices that include fully immersed heaters, in a dewar containing 20 liters (L) of liquid nitrogen, the time to achieve the predetermined pressure range is reduced by half. In other examples, for other types of heaters and other configurations of the dewar or other factors, the time required to reach a suitable pressure and / or start the refrigerant flow may require other time periods.

[0061] Now refer to Figure 3, shows another example cryoablation device 300. In this embodiment, the cryoablation device 300 may be similar to the previously described cryoablation device 100. The cryoablation device 300 may include a dewar 302, a transfer catheter 104, a pump assembly 106, and a supply catheter 108. The cryoablation device 300 may further include an array of heaters 320a to 320f. In this example, the heaters 320a to 320f may be positioned within the dewar 302, but may be positioned and / or connected at or near the wall of the dewar 302. The cryoablation device 300 may be operated to heat a targeted portion at or near the liquid level L1 of the liquid cryogen 110. The cryoablation device 300 may operate similar to the cryoablation device 100 and may provide the same or similar improvements and advantages as the cryoablation device 100.

[0062] In other examples, the heater 320 may be integrated into the wall of the dewar. For example, a resistance wire may be implanted, attached, or otherwise integrated into the wall of the dewar 302. The wall of the dewar 302 may include a reflective surface or property to minimize or reduce radiant energy transfer to the dewar wall. The integrated heater 320 may be arranged at different vertical positions and operate as previously described. In the example shown, the cryoablation device 300 includes six heaters 320, but it may include other numbers of heaters 320, including more than six or less than six heaters 320. In other examples, the arrangement of the heaters 320 may be different from that shown and may be connected to the dewar at other locations, in a non-linear arrangement, or in other configurations.

[0063] Now referring to Figure 4 , shows another example cryoablation device 400. In this embodiment, the cryoablation device 400 may be similar to the previously described cryoablation devices 100, 300. The cryoablation device 400 may include a dewar 402, a transfer catheter 104, a pump assembly 106, and a supply catheter 108. The cryoablation device 400 may further include an array of heaters 420a to 420h. The cryoablation device 400 may further include a support rod 410. The support rod 410 may be a structure positioned within the dewar 402 that is configured to support the heaters 420 in a desired position within the dewar 402. The support rod 410 may be an independent support structure that provides support for the array of heaters 420. In other examples, in addition to supporting the array of heaters 420, the support rod 410 may provide other functions. For example, the support rod 410 may be a tube that can be used to refill the dewar 402. In other examples, the support rod 410 may provide other functions.

[0064] The cryoablation device 400 can be operated to heat a targeted portion at or near the liquid level L1 of the liquid cryogen 110. The cryoablation device 400 can operate similarly to the cryoablation device 100 or 300 and can provide the same or similar improvements and advantages as the cryoablation device 100. The cryoablation device 400 can include or be coupled to a controller (such as a PLC, computing device, etc.) that can energize and de-energize the heaters 420 in a desired sequence to heat the targeted portion of the liquid cryogen 110. In the example shown, the cryoablation device 400 includes eight heaters 420a through 420h, but it can include other numbers of heaters 420, including more than eight heaters 320 or less than eight heaters 320. In other examples, the heaters 420 can be arranged differently than shown and can be arranged in a non-linear arrangement or other configuration.

[0065] Now referring to Figure 5 , another example cryoablation device 500 is shown. In this embodiment, the cryoablation device 500 can be similar to the previously described cryoablation devices 100, 300. The cryoablation device 500 can include a dewar 502, a transfer catheter 104, a pump assembly 106, and a supply catheter 108. The cryoablation device 500 can also include an array of heaters 520a through 520f. The heaters 520a through 520f can be positioned on the transfer catheter 104 similar to the cryoablation device 100.

[0066] The cryoablation device 500 can also include a sleeve 504. The sleeve 504 can be positioned around the array of heaters 520. The sleeve 504 can have, for example, a cylindrical shape and be positioned radially outside the heaters 520. The sleeve 504 can have an outer thermal insulation layer to separate the heaters 520 from the bulk liquid cryogen in the dewar 502. For example, the sleeve 504 can include a vacuum chamber positioned between the inner and outer walls of the sleeve 504. The vacuum chamber can provide thermal insulation and can prevent or reduce the transfer of thermal energy from the liquid cryogen within the sleeve 504 to the bulk liquid cryogen surrounding the sleeve 504. When the heaters are energized during operation of the cryoablation device 500, the sleeve can further insulate the targeted liquid cryogen heated by the heaters 520a through 520f. The sleeve 504 can also prevent the heating of the bulk liquid cryogen and help maintain the overall temperature of the liquid cryogen lower than might otherwise be achieved.

[0067] The sleeve 504 can be included in other cryoablation devices of the present disclosure. The sleeve 504 can be positioned around other heaters or other arrays of heaters that can be included in various embodiments of the cryoablation devices described herein.

[0068] Now referring to Figure 6, another exemplary cryoablation device 600 is shown. In this embodiment, the cryoablation device 600 may be similar to the previously described cryoablation devices 100, 300. The cryoablation device 600 may include a dewar 602, a transfer catheter 104, a pump assembly 106, and a supply catheter 108. In this example, the cryoablation device 600 may include a heater 604 positioned at or near the top of the dewar 602. In this example, the heater 604 may be configured as a radiant heat element that can heat a targeted portion of the liquid cryogen 110 via radiation. The dewar 602 may include a radiation heat shield positioned on the inner wall of the dewar 602 and / or on the inner side of the lid or top of the dewar 602 to direct heat to the liquid cryogen and reduce or limit heating of the dewar 602.

[0069] Now referring to Figure 7 , a heating assembly 700 is shown. For example, the heating assembly 700 may be provided in the cryoablation device 100. The cryoablation device 100 may include the heating assembly 700 instead of an array of heaters 120. The heating assembly 700 may include an upper collar 704, a lower collar 706, a shaft 702, and a heater 710. The heater 710 may be positioned on the shaft 702 such that the heater 710 can slide or move along the axial length of the shaft 702. An opening 716 may be provided in the heater 710 to allow the heater 710 to slide along the shaft 702.

[0070] The heating assembly 700 may be positioned in the dewar 102. In some examples, in addition to supporting the heating assembly 700, the shaft 702 may also operate as the transfer catheter 104. In other examples, the shaft 702 may be independent of the transfer catheter 104 and may be positioned in the dewar similar to the support rod 410 shown in the cryoablation device 400. In other examples, the shaft 702 may be positioned at a different location and may be connected to the top or base of the dewar 102.

[0071] The heating assembly 700 may include a float 712 and a heating element 714. The float 712 may provide buoyancy to the heater 710 and cause the heater 710 to float at a desired position relative to the liquid level L1 of the liquid cryogen 110. The buoyancy of the float 712 may also position the heating element 714 at a desired position relative to the liquid level L1 of the liquid cryogen 110. The float 712 may position the heating element 714 below the top surface of the liquid cryogen. The heating element 714 may be positioned such that the heating element is submerged below the top surface of the liquid cryogen 110. Various suitable materials may be used for the float 712, such as suitable plastics, alloys, stainless steel, foam, or other materials. The heating element 714 may include a resistive heating element or other suitable heating device as previously described with respect to the heater 120.

[0072] It can be understood that during the operation of the cryoablation device, when the liquid level L1 of the liquid cryogen changes, the heater 710 can slide along the shaft 702. The float can hold the heating element in the desired position to heat the targeted portion of the liquid cryogen. In this way, the heating assembly 700 can provide the above improvements and advantages because the portion of the liquid cryogen at or near the top surface of the liquid cryogen is heated. In addition, the heater automatically adjusts or moves as the liquid level L1 in the dewar 102 changes. The top collar 704 can have an outer shape or dimension that limits the movement of the heater 710 along the shaft 702. The lower or bottom collar 706 can also have an outer shape or dimension that limits the movement of the heater 710 along the shaft 702. In addition, the lower collar 706 can prevent the heater from slipping off the shaft 702.

[0073] Now referring to Figure 8 , another example heater 800 is shown. The heater 800 has a similar function and operation as the previously described heater 710. Although not shown, the heater 800 can be positioned in the dewar 102 and can be configured to slide along a shaft (not shown). In this example, the heater 800 includes a heating element 804, a float 802, and a platform 806. The heating element 804 can be a resistive heater, such as a coil of resistive wire through which current passes to generate heat. The resistive heater can have a circular or other suitable shape. The platform 806 can be shaped similarly to the resistive heater and is configured to support the resistive heater. In this example, the platform 806 includes several openings through which all of the liquid cryogen passes as the heater 800 moves along the cooperating shaft in the dewar.

[0074] In this example, the float 802 is positioned below the resistive heater. The combined buoyancy of the float 802, the platform 806, and the heating element 804 can be configured such that the heating element 804 is positioned below the top surface of the liquid cryogen in the dewar. The heater 800 can include an opening 808 sized and shaped to receive the shaft and allow the heater 800 to slide along its axial length. In this example, the opening 808 has a non-circular shape. This configuration prevents the heater 800 from rotating about the shaft. Such an anti-rotation feature may be desirable to prevent wires or other connecting elements from winding around the shaft during operation, which could limit the movement of the heater 800. In other examples, the opening 808 can have other shapes, or the heater 800 can include other anti-rotation features, such as grooves and teeth, other non-circular shapes, etc.

[0075] Heater 800 is only one example of a possible heater that can be used. In other embodiments, the float 802 can have a different shape, and the heating element 804 and / or the platform 806 can have different shapes and relative dimensions. In other examples, the heater 800 can include more than one heating element 804, and the float 802 can be positioned above the heating element 804.

[0076] Now referring to Figure 9 , another example cryoablation device 900 is shown. In this example, the cryoablation device 900 operates to increase the internal pressure in the dewar 902 when desired. In this example, the cryoablation device 900 includes a dispenser 904. The dispenser 904 can include one or more pressure-inducing tablets 906. When it is desired to increase the pressure inside the dewar 902, the operator or controller can cause the dispenser 904 to dispense one or more pressure-inducing tablets 906. The pressure-inducing tablets 906 can react with the liquid cryogen 110 so that a gas is generated, which increases the internal pressure in the dewar. The pressure-inducing tablets 906 can operate or react so as not to raise the overall temperature of a large amount of liquid cryogen. Thus, the cryoablation device 900 can provide improvements and advantages compared to the previously described existing systems. In some examples, the pressure-inducing tablets can be effervescent tablets. In other examples, different tablets or different forms of chemicals can be used to increase the pressure in the dewar 902. The vaporization / heating / expansion effects for nitrogen-pressurized chemical tablets or similar materials can be achieved with different chemicals, including but not limited to tablets, gases, size / volume expansion characteristics, etc. Various chemicals and materials can be used for such pressurization purposes to increase the dewar pressure efficiency that can be applied without adding any contamination or noise to the system and equipment.

[0077] In the example shown, the dispenser 904 is located at the top of the dewar 902. In other examples, the dispenser 904 can be positioned in the wall of the dewar or at other suitable locations. The dispenser 904 can be a housing having an actuator that causes the tablets or other chemicals to be introduced into the dewar 902. In other examples, other dispensers, nozzles, valves, or other devices can be used to introduce the chemicals or materials into the dewar 902.

[0078] Now referring to Figure 10 , an example method 1000 is shown. The method 1000 can provide a method for heating a targeted portion of a liquid cryogen. The method 1000 can be performed using one or more of the previously described cryoablation devices 100, 300, 400, 500, and / or 600. The method 1000 is described below with reference to the cryoablation device 100 only for illustrative purposes. It should be understood that the method 1000 can be performed by other cryoablation devices of the present disclosure or variations thereof.

[0079] Method 1000 may begin at step 1002. At step 1002, the cryoablation device 100 may obtain cryogen level information. It should be understood that although not shown in Figure 1 , the cryoablation device 100 of the present disclosure or other cryoablation devices may include a cryoablation controller, a computing device, a dedicated circuit, a PLC, or other controllers that may be combined with the Figure 1 elements shown to perform one or more functions. For the sake of brevity, the term controller is used when describing the functions of method 1000, but it should be understood that using the term controller does not limit these functions to be performed by other or multiple control devices (such as those listed above).

[0080] The cryoablation device 100 may obtain cryogen level information from one or more sensors (such as impedance sensors) that may be located in the dewar 102. The cryogen level information may characterize the position of the liquid level L1 in the dewar 102.

[0081] At step 1004, the cryoablation device 100 may obtain internal pressure information. The pressure information may be obtained from one or more pressure sensors located in the dewar or at different positions in the cryogen flow path in the dewar or outside the dewar. The pressure information may characterize the pressure in the cryogen flow path and / or the dewar 102.

[0082] At step 1006, the cryoablation device 100 may determine whether the pressure information indicates whether the pressure in the dewar 102 is within the desired range. To initiate cryoablation therapy, the internal pressure in the dewar 102 may need to be within the desired range in order to fill the cryogen pump and / or cause the liquid cryogen to begin flowing from the dewar 102 to the cryoablation probe. The desired range may be a predetermined pressure range that allows such an action to occur. In some examples, the predetermined or desired pressure range may be in the range of about 10 psi to about 15 psi. In other examples, other pressure ranges may be used. If the pressure information indicates that the pressure is within the desired range, no further action may be required and method 1000 may proceed to step 1010. If the pressure information indicates that the pressure in the dewar 102 is not within the desired range, method 1000 may proceed to step 1008.

[0083] In step 1008, the controller may adjust the heater. The heater may be any one or more of the various heaters and heating components described above. In one example, the controller may adjust the heater based on the refrigerant level information obtained in step 1002. The controller may determine which heater in the heater array is located at or near the targeted portion of the liquid refrigerant. The targeted portion may be at or near the surface or level L1 of the liquid refrigerant. The controller may then energize the heater located at and / or below the liquid refrigerant level L1. The controller may cause a power signal having desired characteristics (such as voltage, current, pulse width, duty cycle, etc.) to be delivered to the identified heater. The heater may then heat the targeted refrigerant to convert the liquid refrigerant into refrigerant gas, which may cause an increase in pressure in the dewar 102. Method 1000 may then return to step 1002, where the level information and pressure information are obtained again to determine if an adjustment is needed.

[0084] In step 1010, the controller may determine whether the energized heater is located at the targeted refrigerant. In this step 1010, the controller may consider the level information to determine if the correct heater is energized. During cryoablation therapy, a liquid refrigerant may be used such that the level drops below the energized heater. The controller may determine this and then de-energize one heater and energize the next heater in the heater array. The controller may take such action to energize the heater located at the position closest to and below the liquid level. Thus, as the liquid refrigerant depletes and the level moves down in the dewar 102, effective heating of the liquid refrigerant is performed. If the controller determines that the energized heater is located at the targeted refrigerant, the method proceeds to step 1012. If the controller determines that the energized heater is not at the targeted refrigerant (or above the liquid level), the method moves to step 1008. In step 1008, the controller may take the actions as described above to de-energize one heater and energize the succeeding heater located below the previously energized heater.

[0085] At step 1012, the controller can determine whether the cycle time has been reached. A cryoablation cycle typically has predetermined parameters, such as the time required to reach a certain ice ball size. The cycle time can also be determined by measuring the temperature at or near the cryoablation probe and / or monitoring the growth or size of the ice ball. When the cycle time of the cryoablation cycle is reached, the method can end. If the cycle time is not reached, the method can return to step 1008, where the heater is adjusted (if necessary). Method 1000 can then return to step 1002, where these steps are re-executed to monitor the cryogen level, internal pressure, and cycle time, and to take action if necessary to adjust which heater is powered off or on, and / or to adjust the power signal provided to the powered heater. In this way, a closed-loop feedback loop is created to ensure that during operation of the cryoablation device, liquid cryogen flows to the cryogen probe in an efficient manner.

[0086] The description of the above embodiments is provided for purposes of illustration and description. The description is not intended to be exhaustive or to limit the disclosure. The various elements or features of a particular embodiment are generally not limited to that particular embodiment, but are interchangeable where applicable and can be used in a selected embodiment even if not specifically shown or described. The same can also vary in many respects. Such variations should not be regarded as a departure from the disclosure, and all such modifications are intended to be included within the scope of the disclosure.

[0087] The following is a list of non-limiting illustrative embodiments disclosed herein:

[0088] Illustrative Embodiment 1: A cryoablation device, comprising: a dewar configured to hold a volume of cryogen; and a heater assembly positioned within the dewar, the heater assembly including at least one heater configured to heat a targeted portion of the cryogen when the volume of the cryogen within the dewar changes.

[0089] Illustrative Embodiment 2: The cryoablation device according to Illustrative Embodiment 1, wherein the targeted portion of the cryogen includes a portion of the cryogen at or near the level of the cryogen.

[0090] Illustrative Embodiment 3: The cryoablation device according to Illustrative Embodiment 1, wherein the targeted portion of the cryogen includes a portion within a predetermined distance from the level of the cryogen.

[0091] Illustrative Embodiment 4: The cryoablation device according to any of the preceding illustrative embodiments, wherein the heater is configured to convert liquid cryogen into cryogen vapor.

[0092] Illustrative Embodiment 5: The cryoablation device according to any one of the foregoing illustrative embodiments, wherein the heater assembly is coupled to a transfer catheter inside the dewar.

[0093] Illustrative Embodiment 6: The cryoablation device according to any one of Illustrative Embodiments 1 to 4, wherein the heater assembly is coupled to the wall of the dewar.

[0094] Illustrative Embodiment 7: The cryoablation device according to any one of Illustrative Embodiments 1 to 4, wherein the heater assembly is coupled to a support rod in the dewar.

[0095] Illustrative Embodiment 8: The cryoablation device according to any one of the foregoing illustrative embodiments, wherein the heater assembly includes a plurality of heaters, and the plurality of heaters are each positioned at different heights relative to the base of the dewar.

[0096] Illustrative Embodiment 9: The cryoablation device according to Illustrative Embodiment 8, wherein the plurality of heaters are positioned inside a heat-insulating enclosure in the dewar.

[0097] Illustrative Embodiment 10: The cryoablation device according to any one of Illustrative Embodiments 1 to 4, wherein the at least one heater is positioned at the top of the dewar.

[0098] Illustrative Embodiment 11: The cryoablation device according to any one of Illustrative Embodiments 1 to 4, wherein the at least one heater is configured to move in the dewar.

[0099] Illustrative Embodiment 12: The cryoablation device according to Illustrative Embodiments 1 to 4, wherein the at least one heater is slidably positioned on a shaft in the dewar, and the at least one heater is configured to slide along the shaft when the level of the cryogen in the dewar changes.

[0100] Illustrative Embodiment 13: The cryoablation device according to Illustrative Embodiment 12, wherein the at least one heater includes a float having a predetermined buoyancy, and the float is configured to hold the at least one heater at a predetermined position relative to the level of the cryogen in the dewar.

[0101] Illustrative Embodiment 14: The cryoablation device according to any one of the illustrative embodiments herein, wherein the cryogen is nitrogen.

[0102] Exemplary Embodiment 15: A method of heating a targeted portion of a cryogen, comprising: obtaining cryogen level information characterizing a position of a level of the cryogen in a Dewar flask, obtaining pressure information characterizing an internal pressure of the Dewar flask, and energizing a heater in the Dewar flask to heat the targeted portion of the cryogen in the Dewar flask when the pressure information indicates that the internal pressure of the Dewar flask is less than a predetermined pressure value.

[0103] Exemplary Embodiment 16: The method according to Exemplary Embodiment 15, wherein the targeted portion of the cryogen comprises a portion of the cryogen at or near the level of the cryogen.

[0104] Exemplary Embodiment 17: The method according to Exemplary Embodiment 15, wherein the targeted portion of the cryogen comprises a portion within a predetermined distance from the level of the cryogen.

[0105] Exemplary Embodiment 18: The method according to Exemplary Embodiment 15, wherein the heater is a first heater, and the method further comprises de-energizing the first heater when the level moves below the first heater, and energizing a second heater, wherein the second heater is located a predetermined distance below the first heater.

[0106] Exemplary Embodiment 19: The method according to Exemplary Embodiment 15, further comprising de-energizing the heater when the pressure information indicates that the internal pressure of the Dewar flask is greater than a predetermined threshold.

[0107] Exemplary Embodiment 20: The method according to Exemplary Embodiment 15, wherein the heater is slidably positioned on a shaft in the Dewar flask, and the heater is configured to slide along the shaft when the level of the cryogen in the Dewar flask changes.

Claims

1. A cryoablation device, comprising: A Dewar flask, configured to hold a volume of cryogen; as well as A heater assembly is positioned in the dewar, the heater assembly comprising at least one heater configured to heat a targeted portion of the cryogen when the volume of cryogen in the dewar changes.

2. The cryoablation device of claim 1, wherein the targeted portion of the cryogen comprises a portion of the cryogen that is at or near a liquid level of the cryogen.

3. The cryoablation device of claim 1, wherein the targeted portion of the cryogen comprises a portion within a predetermined distance from a liquid level of the cryogen.

4. The cryoablation device of claim 1, wherein the heater is configured to convert liquid cryogen into cryogen vapor.

5. The cryoablation device of claim 1, wherein the heater assembly is coupled to a transfer catheter inside the dewar.

6. The cryoablation device of claim 1, wherein the heater assembly is coupled to a wall of the Dewar.

7. The cryoablation device of claim 1, wherein the heater assembly is coupled to a support rod in the Dewar.

8. The cryoablation device of claim 1, wherein the heater assembly comprises a plurality of heaters, each of the plurality of heaters being positioned at a different height relative to a base of the Dewar.

9. The cryoablation device of claim 8, wherein the plurality of heaters are positioned inside an insulating enclosure in the Dewar.

10. The cryoablation device of claim 1, wherein the at least one heater is positioned at a top portion of the Dewar.

11. The cryoablation device of claim 1, wherein the at least one heater is configured to move within the Dewar.

12. The cryoablation device of claim 1, wherein the at least one heater is slidably positioned on an axis in the Dewar, the at least one heater being configured to slide along the axis when a liquid level of the cryogen in the Dewar changes.

13. The cryoablation device of claim 12, wherein the at least one heater comprises a float having a predetermined buoyancy, the float being configured to maintain the at least one heater at a predetermined position relative to the liquid level of the cryogen in the Dewar vessel.

14. The cryoablation device of claim 1, wherein the cryogen is nitrogen.

15. A method of heating a targeting portion of a cryogen, comprising: obtaining cryogen level information indicative of a position of a cryogen level in the Dewar vessel; obtaining pressure information representative of the internal pressure of the Dewar flask; as well as When the pressure information indicates that the internal pressure of the dewar is less than a predetermined pressure value, a heater in the dewar is energized to heat a targeted portion of the cryogen in the dewar.

16. The method of claim 15, wherein the targeted portion of the cryogen comprises a portion of the cryogen that is at or near the liquid level of the cryogen.

17. The method of claim 15, wherein the targeted portion of the cryogen comprises a portion within a predetermined distance from a liquid level of the cryogen.

18. The method of claim 15, wherein the heater is a first heater, and the method further comprises: de-energizing the first heater when the liquid level moves below the first heater; as well as A second heater is energized, wherein the second heater is located a predetermined distance below the first heater.

19. The method according to claim 15, further comprising: When the pressure information indicates that the internal pressure of the Dewar vessel is greater than a predetermined threshold, the heater is de-energized.

20. The method of claim 15, wherein the heater is slidably positioned on a shaft in the dewar, the heater being configured to slide along the shaft as the level of the cryogen in the dewar changes.

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