Cryoablation iceball formation monitoring devices, systems and methods

Abstract

To provide devices, systems and methods for monitoring formation of an iceball at a cryoablation needle.SOLUTION: An example method includes receiving an impedance from at least one electrode in an electrode arrangement that is disposed at a cryoablation needle distal portion. The electrode arrangement is configured to engage the iceball as the iceball is formed over the cryoablation needle distal portion so as to cause a change in the impedance. The example method includes determining one or more physical attributes of the iceball based on a rate of the change in the impedance.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates generally to the field of cryosurgery, and more particularly to cryoablation needles for use on tumors or other tissue. [Background technology]

[0002] Cryosurgery systems include one or more cryoablation needles connected to one or more cryogenic sources. One common application of these systems is tumor or tissue ablation by subjecting the tumor or tissue to a freeze-thaw cycle. In such systems, a cryogen is delivered from the cryogenic source to the cryoablation needle, where expansion of the cryogen (e.g., a liquid cryogen such as liquid nitrogen and / or a gaseous cryogen such as nitrogen, nitrous oxide, oxygen, or argon) rapidly cools the needle tip, thereby freezing the tissue adjacent to the needle tip. In one type of cryoablation procedure, a physician percutaneously places a metal (e.g., stainless steel) probe into the patient's body under ultrasound guidance. A cryogenic agent is then circulated through the probe, creating a layer of ice (e.g., an "ice ball") that expands throughout the tumor and / or tissue. This process can be monitored by observing the progress of freezing within the tumor or tissue using conventional medical imaging (e.g., computed tomography (or "CT"), transcutaneous ultrasound (TUS), or MRI imaging, depending on the application). Cycles of freezing and thawing tissue result in coagulation necrosis of the tissue.

[0003] While useful to some extent, conventional monitoring methods have several drawbacks. During cryoablation of tumors and / or other tissues using such cryosurgery systems, clinicians closely monitor ice formation for several reasons. For example, such monitoring can be useful to verify that ice adequately covers the tissue and / or tumor with a margin. In another example, such monitoring can be useful to protect critical structures from cryoablation. CT, ultrasound, or MRI imaging methods do not lend themselves to real-time monitoring; they provide a snapshot in time. Furthermore, frequent CT images expose patients to excessive radiation. In some tissues (e.g., bone and lung), it is difficult to see the ice ball. MRI imaging can cause excessive heating on the needle shaft. Summary of the Invention

[0004] In Example 1, a method includes receiving an impedance from at least one electrode of an electrode arrangement disposed on a distal portion of a cryoablation needle. The electrode arrangement is configured to engage an ice ball as it forms on the distal portion of the cryoablation needle to cause a change in impedance. An exemplary method includes determining one or more physical attributes of the ice ball based on a rate of change in impedance.

[0005] According to another example ("Example 2") that further expands on Example 1, the one or more physical attributes include at least one of a size of the ice ball and a shape of the ice ball, and optionally, the rate of change of impedance is based on at least one reference position positioned on the cryoablation needle.

[0006] According to another example ("Example 3") that further adds to Example 2, the at least one reference position includes a first reference position positioned a distance from the tip section of the distal portion of the cryoablation needle to the at least one electrode.

[0007] According to another example ("Example 4") that further adds to Example 2, the electrode arrangement configuration includes a plurality of electrodes, at least one electrode being a first electrode, the plurality of electrodes including the first electrode and a second electrode, and at least one reference position defining a distance indicating a distance between the first electrode and the second electrode, and optionally, the second electrode being positioned in proximity to the first electrode.

[0008] According to another example ("Example 5") in addition to Examples 1-4, a cryoablation needle includes a needle body formed from a conductive material and a sheath configured to receive the needle body so as to form one or more exposed regions of the needle body and one or more unexposed regions of the needle body, and at least one electrode includes a first exposed region of the one or more exposed regions.

[0009] According to another example ("Example 6") in addition to Example 5, the at least one electrode includes a plurality of electrodes, the one or more exposed areas include a plurality of exposed areas, and each electrode of the plurality of electrodes corresponds to an exposed area in the plurality of exposed areas, or the needle body is movably received in the sheath.

[0010] According to another example ("Example 7") in addition to Examples 1-6, determining one or more physical attributes of the ice ball based on the rate of change of impedance includes using a transfer function correlating the one or more physical attributes to the rate of change of impedance, and optionally, determining the one or more physical attributes of the ice ball based on the rate of change of impedance is performed via a processor in communication with the electrode placement configuration.

[0011] In Example 8, a non-transitory computer-readable medium has processor-executable instructions for reading data from a processor in communication with at least one electrode of an electrode arrangement disposed on a cryoablation needle, the processor-executable instructions, when installed on a device, enabling the device to perform operations including receiving an impedance from at least one electrode of an electrode arrangement disposed on a distal portion of the cryoablation needle, the electrode arrangement configured to engage with an iceball when the iceball is formed on the distal portion of the cryoablation needle to cause a change in impedance; and determining one or more physical attributes of the iceball based on at least one of the impedance and a reference position disposed on the cryoablation needle.

[0012] According to another example ("Example 9") that further expands on Example 8, the one or more physical attributes include at least one of a size of the ice ball and a shape of the ice ball. According to another example ("Example 10") that adds to Examples 8-9, the operations further include generating, via a display device, an illustration of an ice ball having the determined one or more physical attributes, monitoring the formation of the ice ball, and updating the illustration of the ice ball when the one or more physical attributes of the ice ball change.

[0013] According to another example ("Example 11") that adds to Examples 8-10, determining a physical attribute of the ice ball based on at least one of impedance and a reference location placed on the cryoablation needle includes using a transfer function that correlates the physical attribute to a rate of change of impedance.

[0014] According to another example ("Example 12") that adds to Examples 8-11, the operations further include determining whether the one or more ice balls have coalesced. In Example 13, a cryoablation needle comprises: a needle body having a proximal portion and a distal portion opposite the proximal portion; an electrode arrangement including at least one electrode, the electrode arrangement being disposed on the distal portion of the cryoablation needle, the at least one electrode being configured to generate an impedance; and a conductor wire assembly including at least one conductor wire, the conductor wire assembly in communication with the electrode arrangement such that a measure indicative of ice ball size or ice ball shape can be determined based on a rate of change of the impedance.

[0015] According to another example ("Example 14") in addition to Example 13, a cryoablation needle comprises: a needle body formed from a conductive material; and a sheath configured to receive the needle body to form one or more exposed regions of the needle body and one or more unexposed regions of the needle body; at least one electrode comprises a first exposed region of the one or more exposed regions; the at least one electrode comprises a plurality of electrodes; the one or more exposed regions comprise a plurality of exposed regions; each electrode of the plurality of electrodes corresponds to an exposed region in the plurality of exposed regions; and optionally, the needle body is movably received in the sheath.

[0016] According to another example ("Example 15") in addition to Examples 13-14, the electrode arrangement configuration includes a plurality of electrodes, at least one electrode being a first electrode, and the plurality of electrodes including the first electrode and a second electrode, and the rate of change of impedance is based on at least one reference position indicating a distance corresponding to a distance from a tip section of a distal portion of the cryoablation needle to either the first electrode or the second electrode, or a distance between the first electrode and the second electrode.

[0017] While multiple embodiments are disclosed, still other embodiments of the present invention will become apparent to those skilled in the art from the following detailed description, which shows and describes illustrative embodiments of the invention. Accordingly, the drawings and detailed description are to be regarded as illustrative in nature and not restrictive. [Brief explanation of the drawings]

[0018] [Figure 1] FIG. 1 is a schematic diagram of a cryosurgery environment. [Figure 2A] FIG. 2A is an illustration of a cryoablation needle in accordance with the principles of the present disclosure. [Figure 2B] FIG. 2B illustrates the rate of change of impedance over time for the cryoablation needle shown in FIG. 2A. [Figure 3] FIG. 3 is a flowchart of a method according to the principles of the present disclosure. [Figure 4] FIG. 4 is a diagram illustrating the rate of change of impedance according to the principles of the present disclosure. [Figure 5] FIG. 5 is a diagram of a data processing system in accordance with the principles of the present disclosure. [Figure 6A] FIG. 6A is an illustration of a cryoablation needle with multiple separate electrodes in accordance with the principles of the present disclosure. [Figure 6B] FIG. 6B is a plot of the rate of change of impedance of the cryoablation needle shown in FIG. 6A. [Figure 7A] FIG. 7A is an illustration of a sheathed cryoablation needle in accordance with the principles of the present disclosure. [Figure 7B] FIG. 7B is a plot of the rate of change of impedance of the cryoablation needle shown in FIG. 7A. [Figure 8A] FIG. 8A is an illustration of a sheathed cryoablation needle with multiple sensing locations in accordance with the principles of the present disclosure. [Figure 8B] FIG. 8B is a plot of the rate of change of impedance of the cryoablation needle shown in FIG. 8A. DETAILED DESCRIPTION OF THE INVENTION

[0019] While the invention is amenable to various modifications and alternative forms, specific embodiments have been shown by way of example in the drawings and are described in detail below. The intention, however, is not to limit the invention to the particular embodiments described. On the contrary, the invention is intended to cover all modifications, equivalents, and alternatives falling within the scope of the invention as defined by the appended claims.

[0020] For purposes of promoting an understanding of the principles of the present disclosure, reference will be made to the examples illustrated in the drawings described below. The illustrative examples disclosed herein are not intended to be exhaustive or to limit the disclosure to the precise form disclosed in the following detailed description. Rather, these illustrative examples have been chosen and described so that others skilled in the art may utilize their teachings. It would not be beyond the scope of the present disclosure to require that multiple (e.g., all) features in a given example be used across all examples.

[0021] Disclosed herein are principles that may be employed in a cryosurgery system to inform a physician of information related to iceball formation. Figure 1 shows a schematic diagram of a cryosurgery environment. In particular, Figure 1 is a schematic diagram of a magnetic resonance imaging (hereinafter "MRI")-guided cryosurgery system 10, according to a non-limiting example of the present disclosure.

[0022] Cryosurgery systems can be used to cryoablate target tissue (e.g., tissue and / or tumors). Typically, such systems include one or more cryoablation needles, one or more cryosources 60, and a controller. The cryosources 60 can supply gases (e.g., cryogas) such as argon, nitrogen, air, krypton, CO2, CF4, xenon, and various other gases. As used herein, "cryogen" can refer to any fluid or gas that reaches low temperatures (e.g., less than 170 Kelvin). In some non-limiting examples, the fluid can be pressurized to a pressure greater than about 1000 psi (about 6.89476 MPa) (e.g., typically about 3500 psi (about 24.13166 MPa)) and reach low temperatures (e.g., less than 170 Kelvin) when subjected to expansion (e.g., Joule-Thomson expansion as further described below). Cryosurgical system 10 may also include a controller having one or more sensors, flow meters, timers, analog-to-digital converters, wired or wireless communication modules, etc. Additionally, the controller may regulate one or more of the flow rate, temperature, and pressure of the cryogen supplied to cryoablation needle 100.

[0023] For example, during cryosurgery, a surgeon may deploy one or more cryoablation needles within a patient 20. These cryoablation needles may cryoablate a target region of a patient's anatomy by positioning the cryoablation needle 100 at or near the target region of the patient's anatomy. In one example, the cryoablation needle 100 uses the Joule-Thomson effect to achieve cooling or heating. In such cases, a cryogen expands within the cryoablation needle 100 from a higher pressure to a lower pressure. The expansion of the cryogen brings the tissue near the tip of the cryoablation needle 100 to a temperature at or below the temperature required to cryoablate the tissue. Heat transfer between the expanding cryogen and the outer wall of the cryoablation needle 100 forms an ice ball that can then be used to cryoablate tissue.

[0024] The system 10 of FIG. 1 may include a magnet room 12 with an MRI scanner 14 that includes an MRI magnet 16 for housing a patient 20. The MRI magnet 16 may be open or closed and may include an access port that allows a surgeon to access the patient 20. The MRI magnet 16 may also have electrical connection lines (indicated by solid lines) and / or mechanical connection lines (indicated by dashed lines) in FIG. 1 for connection to various electrical systems, control systems, and / or cryoablation systems, as described further below. The system 10 may include a control room 22 that is electrically (and / or magnetically) isolated from the magnet room 12 (by electrical and / or magnetic isolation 23) and an equipment room 24. The MRI system 10 may be used to image the patient 20 prior to insertion of a surgical instrument 32 to visualize a region of interest in the patient 20, such as a tumor or a cavity in the patient 20. Furthermore, imaging may be performed during insertion to guide the surgical instrument to its intended location within the patient 20. Additionally, imaging may be performed after insertion and during surgery, as well as post-surgery.

[0025] Continuing to refer to FIG. 1 , in a non-limiting example, the connection lines can terminate in one or more surgical instruments 32, such as cryoablation needles, insertable into the patient 20. Accordingly, in some such examples, the system 10 can include a connector interface 30 disposed inside the magnet room 12 to enable connection of one or more surgical instruments 32, 34, 36 to other components of the cryoablation system, which can be located outside the magnet room 12 (e.g., in the control room 22 or the equipment room 24). For example, the system 10 can include electrical and fluid connection lines extending from the control room 22 to the magnet room 12 to operably connect the control system 40 to the surgical instruments 32. The connector interface 30 can, in some examples, be provided on a cart 50 (which can be stationary or mobile) disposed in proximity to the magnet to enable multiple surgical instruments 32 to be directly or indirectly (e.g., electrically and / or fluidly) connected to the control system 40 located outside the magnet room 12 (e.g., in the control room 22). In the illustrated embodiment, the cart 50 is a mobile cart 50 .

[0026] Electrical and fluid connections between the control system 40 and the surgical instrument 32 will now be described according to an example. The control system 40 may be electrically connected to a connection box 52 located outside the magnet room 12 via a first set of electrical connection lines 54. Additionally, the connection box 52 may include a second set of electrical connection lines 56 for connecting to electrical and / or imaging equipment 57 (such as an imaging router and electrical filters) located outside the magnet room 12 (e.g., in the equipment room 24). A third set of electrical connection lines 58 may connect the electrical and / or imaging equipment 57 to the connector interface 30 and / or mobile cart 50 located inside the magnet room 12. The connection box 52 may enable removable electrical connections between components within the magnet room 12 and components within the electrical and / or control room.

[0027] 1 , in some examples, the system 10 may be used to perform a cryosurgery procedure (e.g., cryoablation). Accordingly, in some examples, the system 10 may include one or more cryosources 60. The cryosources may be liquid or gas containers capable of providing fluid at cryogenic temperatures and pressures to the surgical instrument 32 (e.g., a cryoablation needle). The cryosources may be cryogenic gases such as argon, nitrogen, air, krypton, CF4 xenon, or NO.

[0028] As can be seen in FIG. 1 , the cryosource is disposed outside the magnet room 12 and is fluidly connectable to the control system 40 via a first set of fluid connection lines 62. The control system 40 may then be fluidly connected to the connector interface 30 and / or the mobile cart 50 via a second set of fluid connection lines 64 and a third set of fluid connection lines 66. A fourth set of fluid connection lines 68 may fluidly connect the surgical instrument 32 (e.g., a cryoablation needle) to the connector interface 30 and / or the mobile cart 50. The fluid lines may be flexible and / or detachable and may include other fluid components for regulating the pressure of the fluid passing therethrough. Thus, fluid from the cryosource may be transported to the surgical instrument 32 via the set of fluid connection lines 62, 64, 66, and 68. Optionally, the system 10 may include a fluid connection panel 70 electrically isolated from the magnet room 12 to enable fluid connection between components residing within the magnet room 12 and components within the control room 22. Similarly, the electrical connection panel 72 may facilitate electrical connections between components present within the magnet room 12 and components within the control room 22 and / or electrical room.

[0029] Turning to a discussion of specific exemplary features of the present disclosure, first, several advantages are provided by employing the principles disclosed herein. For example, in one example among many disclosed herein, the principles of the present disclosure involve measuring AC electrical impedance (e.g., in the range of 1 kHz to 1 MHz) to identify iceball formation on a cryoablation needle. This formation includes physical attributes of the iceball relative to the cryoablation needle, such as iceball diameter, iceball length along the cryoablation needle, and iceball coalescence between two or more needles. Such principles may be advantageous over existing monitoring methods and imaging modalities (e.g., MRI, ultrasound, or CT). Among these advantages are the ability to provide continuous monitoring without the need for physician involvement, reduced patient radiation exposure (e.g., from CT), and the ability to monitor iceball formation in locations where current imaging modalities do not work well, such as within bones and spinal cord. These principles and advantages of the present disclosure will be discussed in more detail below with reference to the drawings and / or will become apparent to those skilled in the art once armed with this disclosure.

[0030] Descriptions of various examples according to the principles of the present disclosure are discussed in further detail below. For example, the discussion begins with an example of a single-electrode cryoablation needle, followed by a discussion of examples of a multi-electrode cryoablation needle and a sheathed cryoablation needle. These are merely a few examples of the many contemplated by the present disclosure. Therefore, as noted throughout the following discussion, the discussion of these examples should not limit the present disclosure. Similarly, it is contemplated that any features throughout these examples may be combined in whole or in part without departing from the scope of the present disclosure. Furthermore, those skilled in the art will recognize that other variations logically extend from those described herein. These should not be considered outside the scope of the present disclosure.

[0031] 2A and 2B illustrate various features of an exemplary cryoablation needle 100 in accordance with the principles of the present disclosure. Fig. 2A illustrates the cryoablation needle 100. Fig. 2B illustrates the rate of change of impedance over time for the cryoablation needle 100 shown in Fig. 2A.

[0032] As shown in FIG. 2A , the cryoablation needle 100 can have an ice ball 201 formed thereon. The cryoablation needle 100 can include a needle body 202 having a cryoablation needle proximal portion 204 and a cryoablation needle distal portion 206 opposite the cryoablation needle proximal portion 204. The cryoablation needle 100 can include an electrode arrangement 210 that can include at least one electrode 212. The electrode arrangement 210 can be disposed on the distal portion of the cryoablation needle 100. The at least one electrode 212 can be configured to generate an impedance (e.g., the at least one electrode can be a sensing electrode). The cryoablation needle 100 can include a conductor wire assembly 220 having at least one conductor wire 222. The conductor wire assembly 212 can be in communication with the electrode arrangement 210, for example, with the at least one electrode 212. In certain instances, such as when the cryoablation needle 100 includes a separate electrode 212, a sleeve (e.g., shrink wrap) can be attached over the cryoablation needle 100 to secure the electrode 212 and conductor wire in place for operation. Usefully, in these instances, a measure indicative of the size or shape of the iceball 201 can be determined based on the rate of change of impedance (e.g., as shown in FIG. 2B ). Some additional features and / or examples of cryoablation needles will be discussed further below after a description of a method for using the cryoablation needle 100 in accordance with the principles of the present disclosure.

[0033] For clarity, it should be understood that the illustrated example is only one of many examples disclosed herein. Accordingly, those skilled in the art will appreciate that many variations of the cryoablation needle 100 can be made without departing from the scope of the present invention. For example, the cryoablation needle 100 is shown with a single electrode 212 and a single conductor wire 222. In certain examples, other sensing elements and conductor wires 222 may be present, and / or there may be more than one wire connected to each electrode. In certain examples, the electrodes may be sensing electrodes, sensors, or any other suitable electromechanical devices or sensing media, none of which are outside the scope of the present disclosure.

[0034] Disclosed herein is a method for monitoring iceball formation in a cryoablation needle. Figure 3 is a flowchart of a method 300 according to the principles of the present disclosure. As discussed herein, methods including method 300 may employ any and all features of cryosurgery system 10 and / or cryoablation needle 100 discussed above and / or below.

[0035] In the illustrated example, the method 300 may include, at step 302, receiving an impedance from at least one electrode of an electrode arrangement disposed on a distal portion of a cryoablation needle. The electrode arrangement may be configured to engage with an ice ball as it forms on the distal portion of the cryoablation needle, causing a change in impedance. In a particular example in which multiple ice balls are formed on separate cryoablation needles, the electrode arrangement may be configured to engage with the multiple ice balls. At step 304, the method 300 may include determining one or more physical attributes of the ice ball based on the rate of change of impedance. In some examples, the one or more physical attributes may include at least one of ice ball size and ice ball shape. Further details of the principles for determining the one or more physical attributes are described further below.

[0036] Principles of the present disclosure can provide a visual display of the formation of the ice ball. In some examples, at step 306, method 300 can include generating, via a display device, an illustration of the ice ball having the determined one or more physical attributes. For example, the display device can generate the illustration on a graphic user interface for interpretation by the practitioner. In this regard, in some examples, at step 308, method 300 can include monitoring the formation of the ice ball, for example, as the ice ball changes form over time. In some examples, at step 310, method 300 can include updating the illustration of the ice ball when one or more physical attributes of the ice ball change.

[0037] The physical attributes of the ice ball can be determined by using a varying number of reference points disposed on the cryoablation needle. For example, as described above, the cryoablation needle can include at least one reference position. In some examples, the rate of change of impedance can be based on at least one reference position defining various distances. In some examples, the rate of change of impedance can be based on at least one reference position disposed along the length of the cryoablation needle. For example, the at least one reference position can indicate a distance corresponding to a distance from the tip section of the distal portion of the cryoablation needle to either the first electrode or the second electrode, or a distance between the first electrode and the second electrode. In certain examples, the at least one reference position can include a first reference position. The first reference position can be disposed at a distance from the tip section of the distal portion of the cryoablation needle to at least one electrode. As further described below, examples disclosed herein can include two or more reference positions (e.g., a first reference position, a second reference position, and a third reference position, etc.).

[0038] Models, such as analytical models, can be useful in determining the physical attributes of an ice ball. FIG. 4 illustrates the rate of change of impedance. In particular, the impedance shown here is normalized impedance and is shown for different electrode lengths (e.g., 1 mm, 2 mm, 3 mm, and 4 mm). The nonlinearity of the lines in the diagram indicates a nonlinear output for a given input. In some examples, determining one or more physical attributes of an ice ball based on the rate of change of impedance can be performed using a model. For example, the model can include a transfer function, which is generally a representation of a time-dependent correlation between an input and an output using a Laplace transform. In this regard, the transfer function used in the present disclosure can adapt to the nonlinearity of the line to correlate one or more physical attributes to the rate of change of impedance. For example, the transfer function can be a nonlinear transfer function between ice thickness (e.g., on the electrode) and impedance change.

[0039] 5 illustrates various features of a data processing system 500. The data processing system 500 can include any and all features of the cryoablation needles and related systems and methods described elsewhere herein, including the cryoablation needle 100, the system 10, and the method 300.

[0040] As shown here, the data processing system 500 is configured for visualization and planning using various reference locations. The reference locations may be on the patient (e.g., via reference pads 501), on the sheath, on electrodes disposed on one or more cryoablation needles 100a, 100b, and / or on the one or more cryoablation needles 100a, 100b themselves. In these situations, imaging methods such as MRI, CT, or ultrasound can be used to display images of one or more cryoablation needles 100a, 100b within the patient's body during surgery. As shown, multiple cryoablation needles 100a, 100b can be used with the control system 40 and connected to a processor 502 (e.g., an impedance sensing unit). The processor 502 can use time switching or multiple frequencies for simultaneous impedance sensing, as discussed elsewhere herein. Optionally, as shown here, an impedance needle 506 with cryocapability may be placed between or around one or more cryoablation needles 100a, 100b to sense ice ball growth. In some examples, impedance can be measured between a needle and a reference pad 501, between needles, or between electrodes on the same needle (e.g., in the form of a segment of the needle shaft or separate electrodes). As used herein, needle can refer to one or more cryoablation needles 100a, 100b and / or the impedance needle 506. The display device 504 can display, among other things, a representation of the ice ball's physical attributes (e.g., size, shape, etc.) in real time. In some examples, the display device 504 can also display any information that contributes to determining the ice ball's physical attributes.

[0041] Computer-implemented methods and systems employing such methods are also disclosed herein. For example, a data processing system 500 may include a memory 510 for storing one or more models 518, such as the model described in connection with FIG. 4, and any auxiliary modules. Additionally or alternatively, the data processing system 500 may include either a processor 502 or a computer 502, each of which may be configured to access the memory 510. In this regard, exemplary procedures according to the disclosure described herein may be performed by a processing arrangement (e.g., one or more processors 502), a computing arrangement (e.g., one or more computers 502), or both. Such arrangements may, for example, be or include all or part of a computer 502, a processor 502, or both, but are not limited thereto, each of which may include, for example, one or more processors 502 (e.g., CPUs or microprocessors) and may use a non-transitory computer-readable medium (“CRM”) 530 (e.g., RAM, ROM, hard drive, or other storage device) having instructions 532 stored thereon. Although shown in a particular configuration here, data processing system 500 may perform essentially the same functions in other configurations (e.g., where CRM 530, display device 504, and memory 510 are provided by a single component such as a mobile device or computer), as will be understood by those skilled in the art.

[0042] In an example computer-implemented method, an illustration of the physical attributes of one or more ice balls can be generated for use on a display device 504. As shown here, in some examples, multiple cryoablation needles 100a, 100b can be connected to a processor 502. In this regard, determining one or more physical attributes of one or more ice balls based on the rate of change of impedance is performed via the processor 502 in communication with an electrode arrangement on each of the multiple cryoablation needles 100a. Under these circumstances, time switching, multiple frequencies, etc. can be used for one or more electrodes on a given cryoablation needle and for simultaneous impedance sensing across multiple cryoablation needles 100a. The processor 502 can be in communication with a display device 504, which, according to some examples of the present disclosure, can be a touchscreen configured to input information to the processor 502 in addition to outputting information from the processor 502. Additionally, the display device 504, the memory 518, or both, may be used to display, store, or both display and store certain data (e.g., time, impedance, physical attributes of the ice ball, etc.) in a format that is user readable, user accessible, or both.

[0043] Continuing with these examples, as previously described, ice ball formation may be monitored and the illustration of the ice ball may be updated subsequently. In this regard, the processor 502 may be included in the impedance sensing unit. Impedance measurements (e.g., performed by the impedance sensing unit) may be monopolar (electrode-independent), bipolar (between two electrodes on the same cryoablation needle, between an electrode on a cryoablation needle (e.g., 100a) and a separate cryoablation needle (e.g., 100b)), or tetrapolar impedance may monitor tissue impedance changes without regard to the electrode. As the impedance increases, an adaptive current output may be used (e.g., so that higher resolution occurs at lower impedance values and lower resolution but a higher dynamic range occurs at higher impedance values).

[0044] Such a computer-implemented method may include a non-transitory computer-readable medium 530 with processor-executable instructions 532 for reading data from a processor. The processor may communicate with at least one electrode of an electrode arrangement disposed on the cryoablation needle. When installed on a device such as a computer, the processor-executable instructions 532 may enable the device to perform operations. These operations may be similar to, and therefore include all of the features of, the operations of the methods disclosed elsewhere herein. For example, the operations may include receiving an impedance from at least one electrode of an electrode arrangement disposed on the distal portion of the cryoablation needle. The electrode arrangement may be configured to engage with the iceball as it forms on the distal portion of the cryoablation needle, causing a change in impedance. The operations may include determining one or more physical attributes of the iceball based on at least one of the impedance and a reference location disposed on the cryoablation needle. In some examples, the one or more physical attributes include at least one of the size of the iceball and the shape of the iceball, as discussed elsewhere herein.

[0045] In some examples, the operations may include generating, via the display device 504, an illustration of the ice ball having the determined one or more physical attributes. For example, the display device 504 may generate the illustration on a graphic user interface for interpretation by the practitioner. In this regard, in some examples, the operations may include monitoring the formation of the ice ball, for example, as the ice ball changes morphology over time. In some examples, the operations may include updating the illustration of the ice ball when one or more physical attributes of the ice ball change. As described elsewhere herein in connection with the methods, in some examples, determining the physical attributes of the ice ball based on at least one of the impedance and the reference location placed on the cryoablation needle may include using a transfer function that correlates the physical attributes to a rate of change of impedance.

[0046] Various configurations of cryoablation needle 100 are shown in Figures 6A, 6B, 7A, 7B, 8A, and 8B. In particular, Figures 6A and 6B relate to a cryoablation needle 100 similar to that described in connection with Figures 2A and 2B, but with multiple separate electrodes 212. In particular, Figure 6A illustrates a cryoablation needle 100 with multiple separate electrodes 212, and Figure 6B illustrates an impedance rate of change diagram for the cryoablation needle 100 shown in Figure 6A. Figures 7A and 7B relate to a sheathed cryoablation needle 100, in which the body 202 of the cryoablation needle functions as the electrode 212, such that a single adjustable electrode is present. In particular, Figure 7A illustrates a sheathed cryoablation needle 100, and Figure 7B illustrates an impedance rate of change diagram for the cryoablation needle 100 shown in Figure 7A. 8A and 8B relate to a sheathed cryoablation needle 100, in which the body 202 of the cryoablation needle functions as an electrode with multiple distinct sensing locations 212. In particular, FIG. 8A illustrates a sheathed cryoablation needle 100 with multiple sensing locations, and FIG. 8B illustrates a plot of the rate of change of impedance for the cryoablation needle 100 shown in FIG. 8A. Note that the cryoablation needle in these figures is similar to, and therefore can include, any of the features of the cryoablation needles discussed elsewhere herein. Likewise, the cryoablation needle 100 can be similarly employed in the devices, systems, and methods discussed elsewhere herein.

[0047] 6A , the electrode arrangement configuration 210 can include a plurality of electrodes 212. In this regard, the plurality of electrodes 212 can include any number of electrodes 212 (e.g., 1, 2, 5, 9, 12, etc., all even and / or odd). For purposes of illustration, the example shown here includes two electrodes: a first electrode 212 and a second electrode 402. In this regard, the at least one electrode 212 described with reference to FIG. 2A can be the first electrode 212, and the plurality of electrodes 212 can include the first electrode 212 and the second electrode 402. The at least one reference position can define a distance corresponding to the distance between the first electrode 212 and the second electrode 402. In some examples, the second electrode 402 can be positioned proximate to the first electrode 212. For example, the first electrode and the second electrode 212 may be longitudinally arranged (e.g., evenly or randomly spaced, or arranged in any combination or configuration). In all other respects, the second electrode 402 may be configured similarly to the first electrode 212, e.g., the processor may communicate with and sense impedance from the second electrode 402. Such a configuration may achieve, in a non-limiting example, an expansion of the cryoablation needle 100's ability to determine iceball size and shape. Additionally or alternatively, continuing with the size and shape example, at least the second electrode 402 may provide another reference location and impedance measurement for the model, thereby improving the accuracy of the determination. Adding additional electrodes 212 may further improve these capabilities.

[0048] A sheathed cryoablation needle 100 is shown in Figures 7A, 7B, 8A, and 8B. In some examples, the needle body 202 can be received by the sheath 700. In particular examples, the sheathed cryoablation needle 100 can be snugly received by the sheath 700 so as to be fixed relative to the needle body 202. In other examples, the sheathed cryoablation needle 100 can be movably received by the sheath 700. In this regard, the sheath 700 can be slidable relative to the needle body 202 in both a proximal and distal direction (as indicated by the dashed double arrow).

[0049] In some examples, the cryoablation needle 100 can include a needle body 202 formed from a conductive material and a sheath 700 formed from a non-conductive material. For example, the needle body 202 can comprise a conductive metal, such as stainless steel. In certain examples, the needle body 202 can comprise multiple conductive materials, such as having a gold-plated and / or copper tip. The sheath 700 can be an insulating coating, such as a PTFE heat shrink or a fluoropolymer coating. In certain examples, the insulating coating can comprise multiple materials, such as PTFE, FEP, PFA, PET, PEEK, or polyimide, in a proximal portion of the sheath 700, and a fluoropolymer in a distal portion of the sheath 700.

[0050] Certain sections of the sheath 700 can cover the needle body 202 with certain sections (e.g., windows 710) removed to facilitate the needle body 202 as an impedance sensing electrode. In other words, each window can form a sensing location such that the underlying needle body 202 functions as an electrode 212 at each window 710. As previously described, the cryoablation needle 100 can include a needle body 202 formed from a conductive material and a sheath 700 formed from a non-conductive material. The sheath 700 can have one or more windows 710 formed therein or can comprise multiple individual sleeve segments. In this regard, the sheath 700 can form one or more exposed regions of the needle body 202 and one or more unexposed regions of the needle body 202.

[0051] Continuing with reference to the sheath-catheter configuration, as shown in FIG. 7A , at least one electrode 212 can include a first exposed region of one or more exposed regions. In this example, the first exposed region extends from the distal end 702 of the sheath to the tip of the needle body 202. As the ice ball grows over time, a window 710 (e.g., in this case, the first exposed region) can be successively covered (e.g., in a distal-to-proximal direction) by the growing ice ball. As seen in FIG. 7B , impedance can correspondingly rise in multiple discrete steps as the ice ball covers the sheath 700 and as the ice ball grows to cover the corresponding window 710 along the length of the needle body 202. An ice ball engaging the sheath 700 can cause a more rapid rise in impedance than when the ice ball engages the needle body 202 through the window 710. This relationship can be used to monitor ice ball formation.

[0052] 8A , the electrode arrangement 210 can include multiple windows 710, thereby allowing the needle body 202 to function as an electrode 212 at a sensing location formed in an exposed area by each window 710. In other words, at least one electrode 212 can include an electrode arrangement 210 that functions as multiple electrodes 212 at a sensing location formed between the window 710 of the sheath 700 and the needle body 202. For example, the one or more exposed areas can include multiple exposed areas. In this regard, each electrode 212 of the multiple electrodes 212 corresponds to one exposed area in the multiple exposed areas. At least one electrode 212 can include a first exposed area of the one or more exposed areas. At least one electrode 212 can include a second exposed area of the one or more exposed areas. Continuing in this manner, an increasing number of electrodes 212 (e.g., 3, 5, 8, 11, etc.) can correspond to an increasing number of exposed areas. In some examples, the at least one electrode 212 comprises a plurality of electrodes 212, and the one or more exposed regions include a plurality of exposed regions, each electrode 212 of the plurality of electrodes 212 corresponding to one exposed region in the plurality of exposed regions. Staggered exposed regions (e.g., when the sheath 700 includes an intermediate window 710 or separate, spaced-apart segments) can monitor ice ball formation as the ice ball grows / expands and / or coalesces with other ice balls. Similar to FIG. 7B and as seen in FIG. 8B , impedance can correspondingly rise in multiple discrete steps as the ice ball covers the sheath 700 and grows to cover an increasing number of corresponding windows 710 along the length of the needle body 202. An ice ball engaging the sheath 700 can cause a more rapid rise in impedance than when the ice ball engages the needle body 202 through the window 710. Such a relationship can be used to monitor ice ball formation.

[0053] 7A and 8A , the sheath 700 is movable relative to the needle body 202 and can therefore move along the length of the needle body 202. In this manner, movement of the sheath 700 can affect, for example, iceball formation and / or impedance measurements. In the illustrated example, the distal end 702 of the sheath is shown proximal to the tip region of the cryoablation needle 100. In one example, the distal end 702 of the sheath can be moved distally from the illustrated position toward the tip region to further cover the tip region. In one example, the distal end 702 of the sheath can be moved proximally from the illustrated position away from the tip region to expose more of the needle body 202. As previously mentioned, if the needle body 202 comprises a conductive material, the exposed region (e.g., the region not covered by the sheath 700) can be an electrode for use in the methods described above. Under certain circumstances, for example, if the sheath 700 can be moved both proximally and distally, the electrode can be said to be an adjustable-length electrode. In this regard, the length of the electrode can affect the physical attributes of the ice ball (e.g., size, shape, etc.). For example, in some circumstances, exposed areas can facilitate the formation of ice balls thereon, while unexposed areas (e.g., areas covered by sheath 700) can inhibit the formation of ice balls thereon.

[0054] The sheath 700 can be integrally formed or separately formed. In some embodiments, the sheath 700 comprises separate sheath 700 segments such that the exposed area within the windows 710 between any two given sheath 700 segments is adjustable. In some embodiments, the windows 710 are a fixed distance apart as the sheath 700 moves along the length of the needle body 202. Other embodiments can have some combination of adjustable and fixed windows 710.

[0055] The measured impedance may be useful in other methods well within the scope of the present disclosure. In some examples, operations may include determining whether one or more ice balls have coalesced (e.g., two ice balls have coalesced into one ice ball) because there is a corresponding change in impedance. The measured impedance may facilitate monitoring when the cryoablation needle 100 is in tissue relative to air or in a different type of tissue. The measured impedance may facilitate monitoring changes around the electrode 212 before and after cryoablation. The determined physical attributes of the ice ball may be used as feedback to the processor as it controls the cryogas flow to optimize cryogas consumption. For example, after the ice ball reaches a certain size, less cryogas (e.g., argon) is needed to maintain it. In this regard, the processor may decrease the cryogas flow. Of course, as will be appreciated by those skilled in the art, there may also be cases where the processor can increase the cryogas flow.

[0056] It is fully understood that unless there is an express or implied statement to the contrary in the specification or claims themselves, of methods including one or more steps, the recited order does not limit the scope of the claims. It is also fully understood that the illustrated methods are only a few examples of many disclosed, and that certain steps can be added or omitted without departing from the scope of the present disclosure. Such steps may include incorporating devices, systems, or methods, or components thereof, as well as those that are well understood, routine, and conventional in the art.

[0057] The connecting lines shown in the various figures contained herein are intended to represent example functional relationships and / or physical couplings between the various elements. It should be noted that many alternative or additional functional relationships or physical connections may exist in an actual system. However, benefits, advantages, solutions to problems, and any elements that may give rise to or make more noticeable any benefit, advantage, or solution should not be construed as critical, required, or essential features or elements. Accordingly, the scope should not be limited by anything other than the appended claims, and references to elements in the singular are not intended to mean "only one" unless expressly so stated, but rather "one or more." Furthermore, when a phrase similar to "at least one of A, B, or C" is used in the claims, the phrase is intended to be interpreted to mean that in an embodiment, only A may be present, in an embodiment, only B may be present, in an embodiment, only C may be present, or any combination of elements A, B, or C, e.g., A and B, A and C, B and C, or A, B, and C, may be present in a single embodiment.

[0058] In the detailed description herein, references to "one embodiment," "an embodiment," "an exemplary embodiment," etc. indicate that the described embodiment may include a particular feature, structure, or characteristic, but not all embodiments necessarily include the particular feature, structure, or characteristic. Moreover, such phrases do not necessarily refer to the same embodiment. Furthermore, when a particular feature, structure, or characteristic is described in connection with an embodiment, it is within the knowledge of one of ordinary skill in the art having the benefit of this disclosure to affect such feature, structure, or characteristic in connection with other embodiments, whether or not explicitly described. After reading the description, it will be apparent to one of ordinary skill in the art how to implement the present disclosure in alternative embodiments.

[0059] Furthermore, no element, component, or method step of this disclosure is intended to be dedicated to the public, regardless of whether that element, component, or method step is expressly recited in a claim. No claim element herein is to be construed under the provisions of 35 U.S.C. 112(f) unless that element is expressly recited using the phrase "means for." As used herein, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus comprising a list of elements may include not only those elements, but also other elements not expressly listed or elements inherent to such process, method, article, or apparatus.

[0060] Various modifications and additions can be made to the described exemplary embodiments without departing from the scope of the present invention. For example, while the above embodiments refer to particular features, the scope of the present invention also includes embodiments having different combinations of features and embodiments that do not include all of the described features. Accordingly, the scope of the present invention is intended to embrace all such alternatives, modifications, and variations that fall within the scope of the claims, together with all equivalents thereof.

Claims

1. 1. A non-transitory computer readable medium having processor-executable instructions for reading data from a processor in communication with a first electrode and a second electrode of an electrode arrangement disposed on a cryoablation needle, the processor-executable instructions, when installed on a device, enable the device to perform operations, the operations including: receiving an impedance from a first electrode of the electrode arrangement disposed on a distal portion of a cryoablation needle, the first electrode being configured to engage an iceball when the iceball forms on the distal portion of the cryoablation needle to cause a first change in the impedance; receiving, after receiving the impedance from the first electrode, an impedance from a second electrode of the electrode arrangement arrangement disposed at a position proximate to the first electrode, the second electrode being configured to engage the ice ball when the ice ball forms over the position of the second electrode to cause a second change in the impedance; determining one or more physical attributes of the ice-ball based on the impedance and at least one reference location disposed on the cryoablation needle; wherein the at least one reference position defines a distance corresponding to a distance between the first electrode and the second electrode.

2. The non-transitory computer-readable medium of claim 1 , wherein the one or more physical attributes include at least one of a size of the ice ball and a shape of the ice ball.

3. The operation is generating, via a display device, an illustration of the ice ball having the determined one or more physical attributes; monitoring the formation of said ice ball; updating the illustration of the ice ball when the one or more physical attributes of the ice ball change; 3. The non-transitory computer-readable medium of claim 1 or 2, further comprising:

4. 3. The non-transitory computer-readable medium of claim 1, wherein determining one or more physical attributes of the ice-ball based on the impedance and the at least one reference position disposed on the cryoablation needle comprises using a transfer function that correlates the physical attribute to a rate of change of the impedance.

5. The non-transitory computer-readable medium of claim 1 or 2, wherein the operations further include determining whether multiple ice balls have merged.

6. 1. A cryoablation needle, comprising: a needle body having a proximal portion and a distal portion opposite the proximal portion; an electrode arrangement including a first electrode and a second electrode, the first electrode disposed at the distal portion of the cryoablation needle and the second electrode disposed proximate to the first electrode, each of the first electrode and the second electrode configured to generate an impedance; a conductor wire assembly including at least one conductor wire; the conductor wire assembly is in communication with the electrode arrangement such that a measure indicative of ice-ball size and / or ice-ball shape can be determined based on the rate of change of the impedance and at least one reference position disposed on the cryoablation needle, the at least one reference position defining a distance corresponding to a distance between the first electrode and the second electrode.

7. 7. The cryoablation needle of claim 6, wherein the cryoablation needle comprises: a needle body formed from a conductive material; and a sheath configured to receive the needle body to form one or more exposed regions of the needle body and one or more unexposed regions of the needle body, the first electrode comprising a first exposed region of the one or more exposed regions and the second electrode comprising a second exposed region of the one or more exposed regions, and optionally the needle body being movably received in the sheath.

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