# Patent

## Title
System and method for treating tissue using an expandable antenna

## Abstract

An ablation device includes an antenna assembly having a radiating portion configured to deliver energy from a power source to tissue of a patient. The radiating portion has an outer conductor and an inner conductor extending therethrough. The inner conductor is disposed within the outer conductor and defines a longitudinal axis. One of the inner conductor and the outer conductor is movable relative to the other to cause at least a portion of the outer conductor to expand radially relative to the longitudinal axis.

## Background
CROSS-REFERENCE TO RELATED APPLICATIONS
This application is a divisional application of U.S. application Ser. No. 13/344,790, now U.S. Pat. No. 9,119,648, filed on Jan. 6, 2012, the entire contents of which are incorporated by reference herein.


BACKGROUND
1. Technical Field
The present disclosure relates to electrosurgical ablation devices and methods. More particularly, the disclosure relates to treating tissue using a deployable antenna capable of being expanded.
2. Background of Related Art
In the treatment of diseases such as cancer, certain types of cancer cells have been found to denature at elevated temperatures that are slightly lower than temperatures normally injurious to healthy cells. These types of treatments, known generally as hyperthermia therapy, typically utilize electromagnetic radiation to heat diseased cells to temperatures above 41° C. while maintaining adjacent healthy cells at lower temperatures where irreversible cell destruction will not occur. Other procedures utilizing electromagnetic radiation to heat tissue also include ablation and coagulation of the tissue. Such microwave ablation procedures, e.g., such as those performed for menorrhagia, are typically done to ablate and coagulate the targeted tissue to denature or kill it. Many procedures and types of devices utilizing electromagnetic radiation therapy are known in the art. Such microwave therapy is typically used in the treatment of tissue and organs such as the prostate, heart, and liver.
One non-invasive procedure generally involves the treatment of tissue (e.g., a tumor) underlying the skin via the use of microwave energy. The microwave energy is able to non-invasively penetrate the skin to reach the underlying tissue. However, this non-invasive procedure may result in the unwanted heating of healthy tissue. Thus, the non-invasive use of microwave energy requires a great amount of control. This is partly why a more direct and precise method of applying microwave radiation has been sought.
Presently, there are several types of microwave probes in use, e.g., monopole, dipole, and helical. One type is a monopole antenna probe consisting of a single, elongated microwave conductor exposed at the end of the probe. The probe is sometimes surrounded by a dielectric sleeve. The second type of microwave probe commonly used is a dipole antenna consisting of a coaxial construction having an inner conductor and an outer conductor with a dielectric separating a portion of the inner conductor and a portion of the outer conductor. In the monopole and dipole antenna probe, microwave energy generally radiates perpendicularly from the axis of the conductor.
Because of the perpendicular pattern of microwave energy radiation, conventional antenna probes are typically designed to be inserted directly into the tissue, e.g., a tumor, to be radiated. However, such typical antenna probes commonly fail to provide uniform heating axially and/or radially about the effective length of the probe.
It is often difficult to assess the extent to which the microwave energy will radiate into the surrounding tissue, i.e., it is difficult to determine the area or volume of surrounding tissue that will be ablated. Furthermore, when conventional microwave antennas are inserted directly into the tissue, e.g., cancerous tissue, there is a potential of dragging or pulling cancerous cells along the antenna body into other parts of the body during insertion, placement, or removal of the antenna probe.
In certain circumstances, it is advantageous to create a relatively large ablation region, which often requires multiple ablation instruments inserted into a patient.
SUMMARY
As used herein the term “distal” refers to that portion of the microwave ablation device, or component thereof, farther from the user while the term “proximal” refers to that portion of the microwave ablation device or component thereof, closer to the user.
According to one aspect of the present disclosure, an ablation device is provided. The ablation device includes an antenna assembly having a radiating portion configured to deliver energy from a power source to tissue of a patient. The radiating portion has an outer conductor and an inner conductor extending therethrough. The inner conductor is disposed within the outer conductor and defines a longitudinal axis. One of the inner conductor and the outer conductor is movable relative to the other to cause at least a portion of the outer conductor to expand radially relative to the longitudinal axis.
Alternatively or in addition, the outer conductor may include a plurality of deployable conductors disposed at least partially along a length thereof configured to expand radially relative to the longitudinal axis.
Alternatively or in addition, the plurality of deployable conductors may be configured to mechanically cut through tissue.
Alternatively or in addition, the plurality of deployable conductors may be configured to cut through tissue with the aid of energy from the power source.
According to a further aspect of the present disclosure, at least a portion of the outer conductor may be flexible.
Alternatively or in addition, a distance between the outer conductors and the inner conductor may define an ablation region when the outer conductors are radially expanded relative to the longitudinal axis.
Alternatively or in addition, the outer conductor and the inner conductor may be configured to form an electromagnetic field within the ablation region upon actuation thereof.
Alternatively or in addition, distal movement of the outer conductor relative to the inner conductor may cause at least a portion of the outer conductor to expand radially relative to the longitudinal axis.
Alternatively or in addition, proximal movement of the inner conductor relative to the outer conductor may cause at least a portion of the outer conductor to expand radially relative to the longitudinal axis.
According to a further aspect of the present disclosure, a method of treating tissue is provided. The method includes the step of inserting at least a portion of a microwave ablation device into tissue. The microwave ablation device includes an inner conductor disposed within an outer conductor. The inner conductor defines a longitudinal axis. The method also includes the steps of expanding at least a portion of the outer conductor relative to the longitudinal axis to generate an ablation region between the outer conductor and the inner conductor and delivering energy to at least one of the inner conductor and the outer conductor to treat tissue disposed within the ablation region.
Alternatively or in addition, the expanding step of the method may further comprise the step of moving the inner conductor relative to the outer conductor.
Alternatively or in addition, the expanding step of the method may further comprise the step of moving the outer conductor relative to the inner conductor.
Alternatively or in addition, the method may also include the step of applying at least one of a distal force and a proximal force to the microwave ablation device subsequent to the expanding step to cut tissue.
Alternatively or in addition, the method may also include the step of providing energy to the outer conductor subsequent to the expanding step and prior to the applying step to cut tissue.
Alternatively or in addition, the method may also include the step of providing energy to the inner and outer conductors to generate a magnetic field within the ablation region configured to treat tissue.
Alternatively or in addition, the method may also include performing the expanding step to cut tissue.
According to a further aspect of the present disclosure, an electrosurgical system for treating tissue is provided. The system includes an electrosurgical generator and a microwave ablation device. The microwave ablation device includes a radiating portion configured to deliver energy from the electrosurgical generator to tissue of a patient. The radiating portion has an outer conductor and an inner conductor extending therethrough. The inner conductor is disposed within the outer conductor and defines a longitudinal axis. The microwave ablation device also includes a distal tip disposed in mechanical cooperation with at least one of the outer and inner conductors. One of the inner conductor and the outer conductor is movable along the longitudinal axis relative to the other such that the outer conductor expands radially relative to the longitudinal axis.
Alternatively or in addition, relative movement of the distal tip towards the distal end of the outer conductor may cause at least a portion of the outer conductor to expand radially relative to the longitudinal axis.
Alternatively or in addition, the outer conductor may be configured to separate into a plurality of conductors along at least a portion thereof. Alternatively or in addition, the conductors may be configured to expand relative to the longitudinal axis in response to relative proximal movement of the distal tip.
Alternatively or in addition, the inner conductor may be operably coupled to the distal tip such that movement of the inner conductor along the longitudinal axis translates relative movement of the distal tip.



BRIEF DESCRIPTION OF THE DRAWINGS
Various embodiments of the present disclosure are described herein with reference to the drawings wherein:
FIG. 1 shows a diagram of a microwave antenna assembly in accordance with an embodiment of the present disclosure;
FIG. 2 is a schematic view of the microwave antenna assembly of FIG. 1 connected to a generator;
FIG. 3 is a cross-sectional view taken along section line 3-3 of FIG. 2;
FIG. 4 is a side view of a distal portion of the microwave antenna assembly of FIGS. 1-3;
FIG. 5 is a perspective view of the distal portion of the microwave ablation device of FIGS. 1-4;
FIG. 6A is a side view of the distal portion of the microwave ablation device of FIGS. 1-5 unexpanded and disposed within a vessel; and
FIG. 6B is a side view of the distal portion of the microwave ablation device of FIGS. 1-6 expanded and disposed within the vessel.



DETAILED DESCRIPTION
Embodiments of the presently disclosed microwave ablation devices are described in detail with reference to the drawings, in which like reference numerals designate identical or corresponding elements in each of the several views.
An ablation device (e.g., a microwave ablation device) in accordance with the present disclosure is referred to in the figures as reference numeral 10. Referring initially to FIG. 1, microwave ablation device 10 includes a handle portion 13 and a microwave antenna 12 having a shaft or feedline 14. Feedline 14 includes an outer conductor 20 and an inner conductor 18, that defines a longitudinal axis X-X. A power transmission cord 21 is shown to connect microwave ablation device 10 to a suitable electrosurgical generator 22 (see FIG. 2). Additionally, an actuation element 7 is illustrated in FIG. 1 in accordance with various embodiments of the present disclosure.
As seen in FIG. 2, a distal tip 30 is disposed adjacent to or coupled to a distal end of inner conductor 18 and/or outer conductor 20. In the illustrated embodiment, the proximal end of feedline 14 includes a coupler 19 that electrically couples antenna 12 to generator 22 via power transmission cord 21. As will be discussed in further detail below, outer conductor 20 includes a distal portion 23 configured to expand radially relative to longitudinal axis X-X such that distal portion 23 separates into a plurality of radially deployable conductors (e.g., conductors 20a, 20b, 20c, 20d, and 20e) upon actuation of actuation element 7.
Microwave ablation device 10 may be introduced to a treatment site via a straight, arcuate, non-deployable and/or deployable applicator or introducer. In embodiments, tip 30 is configured to pierce tissue to facilitate introduction of microwave ablation device 10 to the treatment site. Tip 30 may be insulative and/or formed of a dielectric material.
As described above and as shown in FIGS. 2 and 3, feedline 14 may be in the form of a coaxial cable. Portions of feedline 14 may be flexible and formed of outer conductor 20 surrounding inner conductor 18. Inner conductor 18 and/or outer conductor 20 may be made of a suitable conductive metal that may be semi-rigid or flexible, such as, for example, copper, gold, or other conductive metals with similar conductivity values. Alternatively, portions of inner conductor 18 and outer conductor 20 may also be made from stainless steel that may additionally be plated with other materials, e.g., other conductive materials, to improve their properties, e.g., to improve conductivity or decrease energy loss, etc.
With continued reference to FIG. 3, feedline 14 of antenna 12 is shown including a dielectric material 28 surrounding at least a portion of a length of inner conductor 18 and outer conductor 20 and/or conductors 20a-20e surrounding at least a portion of a length of dielectric material 28 and/or inner conductor 18. That is, a dielectric material 28 is interposed between inner conductor 18 and outer conductor 20, to provide insulation therebetween and may be comprised of any suitable dielectric material.
Referring now to FIGS. 4 and 5, the distal portion 23 of outer conductor 20 is separated into a plurality of radially deployable outer conductors 20a, 20b, 20c, 20d, and 20e. Conductors 20a-20e are illustrative only in that the distal portion 23 of outer conductor 20 may be separated into any two or more radially deployable conductors. Outer conductor 20 may be at least partially formed of a flexible material wherein separation of the distal portion 23 of outer conductor 20 into conductors 20a-20e may be achieved during the manufacturing process by cutting or slicing through the flexible material along at least a portion of the distal portion 23 of outer conductor 20 in multiple locations around the circumference of distal portion 23. Distal tip 30 is in mechanical cooperation with each conductor 20a-20e or inner conductor 18. In one embodiment, inner conductor 18 is movable relative to outer conductor 20 via translation of actuation element 7 (See FIG. 1), as discussed in detail below. In another embodiment, outer conductor 20 is movable relative to inner conductor 18 and distal tip 30, as discussed in detail below. In some embodiments, distal tip 30 is also in electrical communication with either outer conductors 20a-20e or inner conductor 18.
Translation of actuation element 7 (see FIG. 1) causes movement of inner conductor 18 (substantially along longitudinal axis X-X) with respect to outer conductor 20 or vice-versa. More specifically, distal translation of actuation element 7 causes inner conductor 18 to move distally in the direction of arrow “A” and proximal translation of actuation element 7 causes inner conductor 18 to move proximally in the direction of arrow “B.” In response to proximal movement of inner conductor 18, the distal portion 23 of outer conductor 20 is forced or expanded radially relative to longitudinal axis X-X in the direction of arrow “C” (see FIGS. 4 and 5) such that outer conductor 20 separates into conductors 20a-20e. Thus, an ablation region 40, as defined by the boundaries of conductors 20a-20e (including the area between conductors 20a-20e and inner conductor 18), is expanded (e.g., widened) as a distance between conductors 20a-20e and inner conductor 18 becomes larger. In response to distal movement of inner conductor 18, conductors 20a-20e retract toward longitudinal axis X-X in the direction opposite to arrows “C”.
In embodiments, at least a portion of each conductor 20a-20e is flexible to facilitate the radial expansion of conductors 20a-20e relative to longitudinal axis X-X. The ablation region 40 may be an electromagnetic field generated by opposing polarities of inner conductor 18 (e.g., positive) relative to conductors 20a-20e (e.g., negative) for ablating tissue disposed within the ablation region 40.
In one embodiment, translation of actuation element 7 (see FIG. 1) causes movement of outer conductor 20 (substantially along longitudinal axis X-X) with respect to inner conductor 18 and distal tip 30. In this embodiment, inner conductor 18 and distal tip 30 are stationary along the longitudinal axis X-X. More specifically, distal translation of actuation element 7 causes outer conductor 20 to move distally in the direction of arrow “A” and proximal translation of actuation element 7 causes outer conductor 20 to move proximally in the direction of arrow “B.” In response to distal movement of outer conductor 20, the distal portion 23 of outer conductor 20 is forced or expanded radially relative to longitudinal axis X-X, in the direction of arrow “C” (see FIGS. 4 and 5) such that outer conductor 20 separates into conductors 20a-20e. In response to proximal movement of outer conductor 20, conductors 20a-20e retract toward longitudinal axis X-X in the direction opposite to arrow “C”.
Each conductor 20a-20e may be configured to pierce or slice through tissue, either mechanically and/or with the aid of energy, e.g., radiofrequency energy, heat energy, resistive energy, etc. In the embodiment where conductors 20a-20e can mechanically pierce or slice through tissue, conductors 20a-20e may be thin enough to pierce or slice through tissue upon the exertion of a predetermined amount of force (e.g., the amount of force generated upon retraction of inner conductor 18 and/or radial expansion of conductors 20a-20e). In other words, antenna 12 is positioned within tissue when conductors 20a-20e are disposed in a non-expanded, parallel configuration relative to the longitudinal axis X-X and then the conductors 20a-20e are expanded to pierce into and through tissue. As a result thereof, tissue is embedded within the ablation zone 40 for treatment. Additionally or alternatively, conductors 20a-20e may be configured to conduct energy, e.g., from generator 22, to slice or pierce through tissue. Deployment of conductors 20a-20e also helps secure the antenna 12 relative to a tumor and maintain the antenna 12 in place during treatment.
Referring specifically to FIG. 4, conductors 20a-20e are shown radially expanded relative to the longitudinal axis X-X prior to insertion of antenna 12 into tissue “T”. In this scenario, a distal force applied to antenna 12 in the direction of arrow “A” causes conductors 20a-20e to slice through the tissue “T” such that at least a portion of tissue “T” is disposed within ablation region 40.
Referring specifically to FIG. 5, antenna 12 is shown inserted into or through tissue “T” prior to radial expansion of conductors 20a-20e relative to the longitudinal axis X-X. In this scenario, a proximal force applied to antenna 12 in the direction of arrow “B” causes conductors 20a-20e to slice through tissue “T” such that at least a portion of tissue “T” is disposed within ablation region 40.
As discussed above, conductors 20a-20e may be configured to pierce or slice through tissue mechanically and/or with the aid of energy from generator 22. In the case of conductors 20a-20e utilizing the aid of energy from generator 22 to pierce or slice through tissue, conductors 20a-20e may be energized prior to engagement with tissue “T” or, alternatively, substantially simultaneously therewith.
By retracting and expanding the conductors 20a-20e during a procedure, the effective length and impedance of the antenna 12 is changed, thereby changing the performance of the antenna 12. In this manner, the antenna 12 may be actively tuned during a procedure.
Referring now to FIGS. 6A and 6B, feedline 14 is shown disposed within a vessel “V”. A vessel repairing sealant 50 (e.g., fibrin or elastic/collagen matrix) is disposed between an inner wall of vessel “V” and outer conductor 20 and is configured to repair the inner walls of vessel “V” once properly deployed. Sealant 50 may be, for example, a sleeve and/or a mesh matrix configured to be slid over at least a portion of feedline 14 such that upon deployment of feedline 14 within vessel “V”, sealant 50 is disposed between the inner surface of vessel “V” and at least a portion of feedline 14. As illustrated in FIG. 6A, feedline 14 is inserted within vessel “V” while conductors 20a-20e are disposed in a non-expanded or retracted state relative to longitudinal axis X-X. Once feedline 14 is positioned relative to sealant 50 within vessel “V”, actuation element 7 is translated proximally in the direction of arrow “F” to retract inner conductor 18, thereby pulling distal tip 30 proximally to force conductors 20a-20e to expand radially relative to longitudinal axis X-X. As discussed above, actuation element 7 may, in certain embodiments, be translated distally in the direction of arrow “E” to move outer conductor 20 distally to engage distal tip 30, thereby forcing conductors 20a-20e to expand radially relative to the longitudinal axis X-X.
In either scenario, radial expansion of conductors 20a-20e forces sealant 50 to engage the inner wall of vessel “V” to repair cracks or damaged areas in the vessel “V”, as shown in FIG. 6B. In embodiments, once sealant 50 engages the inner wall of vessel “V”, generator 22 is configured to selectively supply energy (e.g., RF or microwave energy) to conductors 20a-20e to activate or cure sealant 50 via the generation of heat. That is, sealant 50 may be a mesh matrix having vessel repairing gel or collagen disposed thereon that is configured to leach to the inner wall of vessel “V” upon the application of heat caused by the supply of energy through conductors 20a-20e and/or inner conductor 18. Examples of such vessel repairing sealants include, without limitation, Evicel® liquid fibrin sealant and the CryoSeal® FS system.
Once a desired portion of sealant 50 is applied to the inner wall of vessel “V”, conductors 20a-20e may be radially retracted toward longitudinal axis X-X via actuation of actuation element 7 such that antenna 12 is movable proximally (arrow “F”) or distally (arrow “E”) within vessel “V” for purposes of removal therefrom or for purposes of movement relative to sealant 50, as shown in FIG. 6A. In this manner, distal portion 23 of outer conductor 20 may be positioned or re-positioned to substantially align with a portion of sealant 50 that has not yet been forced to engage the inner wall of vessel “V” and/or been activated or cured by the application of heat generated by the supply of energy through conductors 20a-20e and/or inner conductor 18.
The described embodiments of the present disclosure are intended to be illustrative rather than restrictive, and are not intended to represent every embodiment of the present disclosure. Various modifications and variations can be made without departing from the spirit or scope of the disclosure as set forth in the following claims both literally and in equivalents recognized in law.

## Claims

1. A method of treating tissue, comprising:
inserting at least a portion of a microwave ablation device into tissue, the microwave ablation device defining a longitudinal axis and including an inner conductor disposed within an outer conductor, the inner and outer conductors separated by a dielectric material, the dielectric material disposed on the inner conductor;
expanding at least a portion of the outer conductor relative to the longitudinal axis to generate an ablation region between the outer conductor and the inner conductor; and
delivering energy to at least one of the inner conductor or the outer conductor to treat tissue disposed within the ablation region.

2. A method according to claim 1, wherein expanding at least a portion of the outer conductor relative to the longitudinal axis includes moving the inner conductor relative to the outer conductor.

3. A method according to claim 1, wherein expanding at least a portion of the outer conductor relative to the longitudinal axis includes moving the outer conductor relative to the inner conductor.

4. A method according to claim 1, further comprising applying at least one of a distal force or a proximal force to the microwave ablation device to cut tissue subsequent to expanding at least a portion of the outer conductor relative to the longitudinal axis.

5. A method according to claim 4, further comprising providing energy to the outer conductor to cut tissue subsequent to expanding at least a portion of the outer conductor relative to the longitudinal axis and prior to applying at least one of a distal force or a proximal force to the microwave ablation device.

6. A method according to claim 5, further comprising providing energy to the inner and outer conductors to generate a magnetic field within the ablation region.

7. A method according to claim 4, further comprising cutting tissue by expanding at least a portion of the outer conductor relative to the longitudinal axis.

8. A method according to claim 1, wherein expanding at least a portion of the outer conductor relative to the longitudinal axis includes moving the inner conductor relative to the dielectric material.

9. A method according to claim 1, wherein expanding at least a portion of the outer conductor relative to the longitudinal axis includes moving the outer conductor relative to the dielectric material.

10. A method according to claim 1, further comprising radially expanding a plurality of outer conductors disposed at least partially along a length of the outer conductor.

11. A method according to claim 1, further comprising cutting through tissue by radially expanding a plurality of outer conductors disposed at least partially along a length of the outer conductor and delivering energy to the plurality of outer conductors.

12. A method according to claim 1, wherein expanding at least a portion of the outer conductor relative to the longitudinal axis includes distally moving the outer conductor relative to the inner conductor.

13. A method according to claim 1, wherein expanding at least a portion of the outer conductor relative to the longitudinal axis includes proximally moving the inner conductor relative to the outer conductor.