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.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a continuation application of U.S. application Ser. No. 14/806,080, filed on Jul. 22, 2015, which is a divisional application of U.S. application Ser. No. 13/344,790, filed on Jan. 6, 2012, now U.S. Pat. No. 9,119,648, the entire contents of each of which are incorporated by reference herein. 
     
    
     BACKGROUND 
     1. Technical Field 
       [0002]    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 
       [0003]    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. 
         [0004]    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. 
         [0005]    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. 
         [0006]    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. 
         [0007]    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. 
         [0008]    In certain circumstances, it is advantageous to create a relatively large ablation region, which often requires multiple ablation instruments inserted into a patient. 
       SUMMARY 
       [0009]    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. 
         [0010]    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. 
         [0011]    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. 
         [0012]    Alternatively or in addition, the plurality of deployable conductors may be configured to mechanically cut through tissue. 
         [0013]    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. 
         [0014]    According to a further aspect of the present disclosure, at least a portion of the outer conductor may be flexible. 
         [0015]    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. 
         [0016]    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. 
         [0017]    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. 
         [0018]    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. 
         [0019]    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. 
         [0020]    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. 
         [0021]    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. 
         [0022]    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. 
         [0023]    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. 
         [0024]    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. 
         [0025]    Alternatively or in addition, the method may also include performing the expanding step to cut tissue. 
         [0026]    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. 
         [0027]    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. 
         [0028]    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. 
         [0029]    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 
         [0030]    Various embodiments of the present disclosure are described herein with reference to the drawings wherein: 
           [0031]      FIG. 1  shows a diagram of a microwave antenna assembly in accordance with an embodiment of the present disclosure; 
           [0032]      FIG. 2  is a schematic view of the microwave antenna assembly of  FIG. 1  connected to a generator; 
           [0033]      FIG. 3  is a cross-sectional view taken along section line  3 - 3  of  FIG. 2 ; 
           [0034]      FIG. 4  is a side view of a distal portion of the microwave antenna assembly of  FIGS. 1-3 ; 
           [0035]      FIG. 5  is a perspective view of the distal portion of the microwave ablation device of  FIGS. 1-4 ; 
           [0036]      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 
           [0037]      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 
       [0038]    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. 
         [0039]    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. 
         [0040]    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  20   a,    20   b,    20   c,    20   d,  and  20   e ) upon actuation of actuation element  7 . 
         [0041]    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. 
         [0042]    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. 
         [0043]    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  20   a - 20   e  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. 
         [0044]    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  20   a,    20   b,    20   c,    20   d,  and  20   e.  Conductors  20   a - 20   e  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  20   a - 20   e  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  20   a - 20   e  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  20   a - 20   e  or inner conductor  18 . 
         [0045]    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  20   a - 20   e.  Thus, an ablation region  40 , as defined by the boundaries of conductors  20   a - 20   e  (including the area between conductors  20   a - 20   e  and inner conductor  18 ), is expanded (e.g., widened) as a distance between conductors  20   a - 20   e  and inner conductor  18  becomes larger. In response to distal movement of inner conductor  18 , conductors  20   a - 20   e  retract toward longitudinal axis X-X in the direction opposite to arrows “C”. 
         [0046]    In embodiments, at least a portion of each conductor  20   a - 20   e  is flexible to facilitate the radial expansion of conductors  20   a - 20   e  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  20   a - 20   e  (e.g., negative) for ablating tissue disposed within the ablation region  40 . 
         [0047]    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  20   a - 20   e.  In response to proximal movement of outer conductor  20 , conductors  20   a - 20   e  retract toward longitudinal axis X-X in the direction opposite to arrow “C”. 
         [0048]    Each conductor  20   a - 20   e  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  20   a - 20   e  can mechanically pierce or slice through tissue, conductors  20   a - 20   e  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  20   a - 20   e  ). In other words, antenna  12  is positioned within tissue when conductors  20   a - 20   e  are disposed in a non-expanded, parallel configuration relative to the longitudinal axis X-X and then the conductors  20   a - 20   e  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  20   a - 20   e  may be configured to conduct energy, e.g., from generator  22 , to slice or pierce through tissue. Deployment of conductors  20   a - 20   e  also helps secure the antenna  12  relative to a tumor and maintain the antenna  12  in place during treatment. 
         [0049]    Referring specifically to  FIG. 4 , conductors  20   a - 20   e  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  20   a - 20   e  to slice through the tissue “T” such that at least a portion of tissue “T” is disposed within ablation region  40 . 
         [0050]    Referring specifically to  FIG. 5 , antenna  12  is shown inserted into or through tissue “T” prior to radial expansion of conductors  20   a - 20   e  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  20   a - 20   e  to slice through tissue “T” such that at least a portion of tissue “T” is disposed within ablation region  40 . 
         [0051]    As discussed above, conductors  20   a - 20   e  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  20   a - 20   e  utilizing the aid of energy from generator  22  to pierce or slice through tissue, conductors  20   a - 20   e  may be energized prior to engagement with tissue “T” or, alternatively, substantially simultaneously therewith. 
         [0052]    By retracting and expanding the conductors  20   a - 20   e  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. 
         [0053]    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  20   a - 20   e  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  20   a - 20   e  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  20   a - 20   e  to expand radially relative to the longitudinal axis X-X. 
         [0054]    In either scenario, radial expansion of conductors  20   a - 20   e  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  20   a - 20   e  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  20   a - 20   e  and/or inner conductor  18 . Examples of such vessel repairing sealants include, without limitation, Evicel® liquid fibrin sealant and the CryoSeal® FS system. 
         [0055]    Once a desired portion of sealant  50  is applied to the inner wall of vessel “V”, conductors  20   a - 20   e  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  20   a - 20   e  and/or inner conductor  18 . 
         [0056]    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.