Abstract:
A method and apparatus for thermal treatment of tissue employing microwave energy is disclosed. Preferably, the apparatus includes an elongated member having a tissue capturing portion. A microwave conductor operatively mounts with the elongated member and has a forward conductor end. The microwave conductor is adapted for movement between an unadvanced position where the forward conductor end is displaced from the tissue capturing portion and an advanced position where the forward conductor end is adjacent to the tissue capturing portion to direct microwave energy toward the body tissue portion supported therein. A source of microwave energy in electrical communication with the microwave conductor supplies microwave energy having a frequency ranging from about 400 MHz to about 2500 MHz. Preferably, the microwave conductor includes an active conductor and a return conductor in a coaxial arrangement. The forward conductor end may be uninsulated or insulated. Most preferably, a handle is connected to the elongated member.

Description:
1. TECHNICAL FIELD 
     The present disclosure relates generally to apparatus and methods for thermally treating tissue and more particularly, to an apparatus for applying microwave frequency energy to seal a body vessel or tissue. 
     2. BACKGROUND OF THE DISCLOSURE 
     In many surgical procedures, body vessels, e.g., blood vessels, ducts, adhesions, fallopian tubes, etc. . . . are sealed to defunctionalize or close the vessel. Traditionally, staples, clips or sutures have been used to close a body vessel. However, these traditional procedures often leave foreign body material inside a patient. In an effort to reduce foreign body material left within the patient and to more effectively seal the body vessel, energy techniques that seal by heat processes have been employed. The present disclosure include apparatus and methods that combine applying a force to greatly compress the target tissue as well as applying energy such that collagen will melt and reform in a permanently compressed state. 
     Current vessel sealing procedures utilize heat treatment in the form of radio frequency (RF) energy in the frequency range of 200 to 1000 kHz to heat and desiccate tissue causing closure and sealing of the body vessel. For example, U.S. Pat. No. 5,258,006 discloses electrosurgical bipolar RF forceps which cauterize blood vessels during a percutaneous laparoscopic cholecystectomy procedure. 
     Accordingly, there is a need for an apparatus which provides a uniform, controllable seal and that is capable of providing such a seal with minimum collateral damage to body tissue. 
     SUMMARY 
     Accordingly, the present disclosure is directed to apparatus for thermal treatment of tissue. The apparatus has particular application in sealing of body tissue, including vessels such as blood vessels, fallopian tubes, bundled tissue incl. vein, artery and/or nerves, ducts, adhesions, etc. The apparatus advantageously compresses the tissue and provides a non-stick application of microwave frequency electrosurgical energy thereby avoiding sticking of tissue to the apparatus and providing a more controllable seal. The apparatus can also seal body tissue without undesired collateral damage. It is contemplated that at least a portion of the apparatus may be constructed from flexible material. It is further contemplated that at least a portion of the apparatus may be constructed from a deformable material. 
     The apparatus includes an elongated member having proximal and distal ends and having a tissue capturing portion for capturing tissue. The apparatus further includes a microwave conductor operatively mounted with the elongated member and having a forward conductor end. The microwave conductor is adapted for reciprocal axial movement relative to the elongated member between an unadvanced position where the forward conductor end is displaced from the tissue capturing portion and an advanced position where the forward conductor end is adjacent to the tissue capturing portion to direct microwave energy toward the body tissue portion supported therein. A source of microwave energy in electrical communication with the microwave conductor supplies microwave energy having a frequency ranging from about 400 MHz to about 2500 MHz. 
     In a preferred embodiment, the microwave conductor includes an active or inner conductor and a return or outer conductor mounted in coaxial arrangement. The forward conductor end of the microwave conductor is uninsulated to expose the active conductor and the return conductor to permit direct contact with the body tissue portion. Preferably, the tissue capturing portion defines a tissue capturing surface whereby the tissue capturing surface comprises a dielectric material. It is also envisioned that an insulator can be mounted to the forward conductor end to prevent direct contact between the body tissue and the forward conductor end to limit collateral tissue damage and inhibit eschar buildup and sticking to the apparatus. 
     In one preferred embodiment, the active conductor of the microwave conductor is dimensioned to extend distally beyond the return conductor. Desirably, an insulating material is disposed about a portion of the active conductor extending distally beyond the return conductor. 
     In another preferred embodiment, the microwave conductor includes at least one ground plane in electrical contact with the outer conductor. Preferably, an insulating material is disposed on a tissue contacting surface of the one ground plane. 
     In yet another preferred embodiment, the return conductor of the microwave conductor is dimensioned to extend distally beyond the active conductor. 
     In a most preferred embodiment, the apparatus includes a handle connected to the elongated member. The handle includes a manual actuator operatively connected to the microwave conductor. The actuator is movable to cause corresponding movement of the microwave conductor between the unadvanced and the advanced positions. 
     A method is disclosed for sealing body tissue and including the steps of: positioning a surgical instrument adjacent body tissue; and supplying microwave energy having a frequency ranging from about 400 MHz to about 2500 MHz to the surgical instrument to cause desiccation of the body tissue portion to thereby substantially seal a portion of the body tissue. 
     In a preferred embodiment, the surgical instrument includes a microwave conductor, and the step of positioning includes placing the microwave conductor in direct contact with the body tissue. Preferably, the surgical instrument includes an elongated member having a tissue capturing portion at a distal end, and the step of positioning includes arranging the surgical instrument such that the body vessel portion is disposed between the microwave conductor and the tissue capturing portion. Most preferably, the step of positioning includes clamping the body vessel portion between the microwave conductor and the tissue capturing portion. Desirably, the microwave conductor includes an active conductor and a return conductor mounted in coaxial arrangement, the forward conductor end of the microwave conductor being uninsulated to expose the active conductor and the return conductor, and wherein the step of positioning includes directly contacting the vessel portion with the forward conductor end. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Preferred embodiments of the disclosure are described herein with reference to the drawings wherein: 
     FIG. 1 is a side view of a microwave system in accordance with the principles of the present disclosure including a microwave instrument and a microwave generator; 
     FIG. 2 is a side view in partial cross-section, of the microwave instrument of FIG. 1 illustrating the elongated portion connected to the handle and the microwave conductor mounted within the elongated portion; 
     FIG. 3 is a transverse cross-sectional view of the microwave instrument taken along lines  3 — 3  of FIG. 1; 
     FIG. 4 is an enlarged side view of the distal end of the microwave instrument of FIG. 1 illustrating the microwave conductor in an initial unadvanced position; 
     FIG. 5 is a view similar to the view of FIG. 4 illustrating the microwave conductor in an advanced position to treat a vessel portion; 
     FIG. 6 is an enlarged perspective view of a vessel treated within the microwave system; 
     FIG. 6A is a side view of an alternate embodiment of the microwave conductor showing an insulating dielectric material on the distal end; 
     FIG. 7 is a cross-sectional view, in part elevation, of an alternate embodiment of the microwave instrument; 
     FIG. 8 is a cross-sectional view, in part elevation, of another alternate embodiment of the microwave instrument; 
     FIG. 9 is a cross-sectional view, in part elevation, of another alternate embodiment of the microwave instrument; and 
     FIG. 10 is an enlarged perspective view of a vessel treated within an alternate embodiment of the microwave system. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The preferred embodiment(s) of the methods and apparatus disclosed herein are discussed in terms of tissue sealing procedures and instrumentation. It is contemplated that the present methods and apparatus find application in both open and minimally invasive procedures including endoscopic and laparoscopic procedures wherein access to the surgical site is achieved through a cannula, small incision, or naturally occurring orifice. 
     In the discussion which follows, the term “proximal”, as is traditional, will refer to the portion of the structure which is closer to the operator, while the term “distal” will refer to the portion which is further from the operator. 
     In accordance with the present disclosure, referring now in detail to the drawings wherein like reference numerals identify similar or like components throughout the several views, FIG. 1 illustrates a side view of a microwave system  10  in accordance with the principals of the present disclosure. System  10  includes a microwave instrument  12  and a microwave generator  14  electrically connected to instrument  12  by coaxial cable  15 . Generator  14  provides microwave frequency energy for application to tissue. Generator  14  may be any commercially available generator suitable for delivering microwave energy and includes an amplifier, such as model 100 S1G4 manufactured by Amplifier Research, Souderton, Pa., USA. The driving signal is provided by a synthesizer such as HP 83731 B manufactured by Hewlett-Packard, Palo Alto, Calif., USA. Generator  14  preferably supplies microwave energy having a frequency ranging from about 400 MHz to about 2500 MHz. 
     Instrument  12  includes a handle  16  and an elongated member or chassis  18  extending distally from handle  16 . Handle  16  includes first and second handle grips  20 ,  22  pivotally connected to each other about pivot pin  24 . Each handle grip  20 ,  22  defines a finger loop. First handle grip  20  is fixedly connected to elongated member  18  by suitable means including screws, adhesives or the like. Second handle grip  22  pivots about pivot pin  24  movable relative to first handle grip  20  to retract and advance distally mounted end effectors (described in greater detail below) for microwave communication and achieving an adequate compression force for sealing tissue. As shown in FIG. 2, handle  16  also includes a coaxial connector  25  having a microwave inner conductor terminal  26  and a microwave outer conductor terminal  28  for connecting instrument  12  to a source of microwave frequency energy, namely, microwave generator  14  (FIG.  1 ). 
     Elongated member or chassis  18  of instrument  12  includes outer tube  30  and a chassis extension  32  extending from the distal end of outer tube  30 . Outer tube  30  defines a longitudinal opening therethrough, preferably, having a diameter ranging from 5-10 millimeters for insertion through a trocar  120  (FIG.  6 ). It is contemplated that outer tube  30  may be constructed of various sizes according to the particular surgical application. 
     Chassis extension  32  is, preferably, monolithically formed with outer tube  30 . Alternatively, outer tube  30  may be brazed, welded or soldered to the chassis extension  32 . Chassis extension  32  defines a longitudinal portion  34  and a tissue capturing portion  36  disposed adjacent the distal end of longitudinal portion  34 . Tissue capturing portion  36  extends in general transverse relation to longitudinal portion  34  and axis C—C, and defines a capturing surface  38  dimensioned to capture tissue positioned thereagainst during operation of instrument  12 . Tissue capturing portion  36 , preferably, has a layer of dielectric material  40  disposed on capturing surface  38  to electrically insulate chassis extension  32  and outer tube  30  from the microwave circuit. 
     With reference to FIGS. 1-3, instrument  12  further includes a microwave conductor  42  extending through outer tube  30  and is axially movable therewithin. As best shown in FIGS. 2 and 3, microwave conductor  42  includes a conventional coaxial microwave transmission cable having an inner active conductor  44  and an outer return conductor  46  separated by a layer of insulation  48  and surrounded by an outer insulating sheath  54 . Conductor  42  is mechanically connected to second handle grip  22  whereby pivotal movement of handle grip  22  (shown by arrows A and B in FIGS. 1 and 2) causes corresponding reciprocal axial movement of conductor  42  (along axis C—C) between an unadvanced position (FIG. 4) and an advanced position (FIG.  5 ). More particularly, pivotal movement of second handle grip  22  towards first handle grip  20  (in the direction of arrow A in FIG. 1) effects distal axial movement of conductor  42  while pivotal movement of second handle grip  22  away from handle grip  20  (in the direction of arrow B) effects proximal movement of conductor  42 . Further, conductor  42  is manipulated axially, in the embodiment shown in FIGS. 1-6, to achieve a sufficient compressive force for sealing tissue. 
     In one preferred embodiment, distal end  52  of conductor  42  is uninsulated or exposed to directly contact tissue supported by tissue capturing portion  36  of chassis extension  32 . Such exposure may alter the transmission energy field at least adjacent distal end  52  of conductor  42 , the benefits of such configuration being discussed hereinbelow. 
     The use of system  10  in conjunction with sealing a body vessel, e.g., a blood vessel  100 , will now be described. Initially, the surgical site is accessed through conventional techniques. With reference to FIG. 6, during laparoscopic procedures, a body cavity  110  may be insufflated with insufflation gases to raise a body cavity wall  11   2  from the internal organs (not shown). A trocar  120  may be utilized to enter a body cavity wall  112  to provide access to the operative site. Instrument  12  is manipulated to the operative site such that a targeted vessel portion  102  is positioned within the recess or gap  60  defined between distal end  52  of conductor  42  and tissue capturing portion  36  of chassis extension  32 . It is envisioned that instrument  12  may be constructed from flexible materials such as suitable alloys and rubbers and resins including plasticizers, for providing additional degrees of freedom and positioning capabilities. It is further envisioned that instrument  12  may be constructed from a deformable material such as suitable alloys and polymers, providing additional orientations and predetermined configurations for positioning instrument  12 . 
     With vessel  100  appropriately positioned, second handle grip  22  (FIG. 1) is pivoted in the direction of arrow A to cause advancement of conductor  42  to compress vessel portion  102  between conductor  42  and tissue capturing portion  36 , as best shown in FIG.  5 . 
     Referring back now to FIG. 6, microwave generator  14  (FIG. 1) is actuated to provide microwave energy to instrument  12 . Due to the exposure of distal end  52  of conductor  42 , microwave frequency current flows from inner active conductor  44 , through vessel  100 , and subsequently through outer return conductor  46 . More particularly, the low resistive characteristics of the tissue in direct contact with distal end  52  of conductor  42  provides a lower impedance path for the microwave energy thereby inducing the current path or flow through vessel portion  102  to cause a circular zone of desiccation within vessel portion  102 . As discussed above, the tissue targeted for treatment, as here, vessel portion  102 , is compressed for sealing in addition to the application of microwave energy to the tissue. Handle grips  20  and  22  are manipulated to produce a compressive force in an amount sufficient to adequately compress the captured tissue. Preferably, such force is in a range of about 500-400 gms. Accordingly, vessel portion  102  becomes sealed as desired. 
     In another preferred embodiment, as best shown in FIG. 6A, a dielectric portion  53  is fixedly mounted to distal end  52  of microwave conductor  42 . In this embodiment, direct contact between microwave conductor  42  and tissue targeted for treatment is not required enabling a surgeon to treat tissue in particular surgical applications where contacting tissue is not desirable, providing instrument  12  a broader range of utility for the surgeon. It is envisioned that dielectric portion  53  may be removably mounted to distal end  52  of microwave conductor  42  and may be constructed from any suitable dielectric material. Dielectric portion  53  may also prevent buildup of residue, eschar and the like on microwave conductor  42 , facilitating prolonged use of instrument  12  before cleaning is required. In use, conductor  42  irradiates microwave frequency energy through insulator  53  to treat body tissue. Distal end  52  of conductor  42  does not directly contact the tissue targeted for treatment. However, manipulation of handle grips  20 ,  22  forces insulator  53  to compress tissue, as discussed, to sufficiently seal the tissue portion when microwave energy is applied. 
     The application of microwave frequency energy inhibits sticking of instrument  12  to vessel  100 . In addition, the microwave energy provides a more controllable seal in that as the tissue desiccates, the electrical properties change so as to absorb less of the applied energy. It is envisioned that instrument  12  may also be utilized in surgical applications, whereby a body vessel requires sealing but collateral damage to the vessel is to be avoided, such as treating fibrous connective tissue. For example, in the treatment of tendons and the like, instrument  12  irradiates the tissue to temperatures in the range of 65° C.-80° C. to shrink collagen in the tendon reducing its thickness 25%-50%. Higher irradiating temperatures are also contemplated. 
     Referring now to FIG. 7, there is illustrated one particular embodiment of inner active conductor  44  and outer return conductor  46  of instrument  12  (shown in FIGS.  1 - 6 ). In this embodiment, inner active conductor  44  of conductor  42  has a forward portion  64  which extends to protrude beyond outer return conductor  46 . A dielectric material  65 , e.g., PTFE, surrounds the distal end of inner active conductor  44 . This configuration provides a microwave energy path that travels from inner active conductor  44  through a compressed vessel  102  to reach outer return conductor  46 . Thus, the desiccation zone is broadened, in effect, the electromagnetic wave launched from inner active conductor  44  will travel a broader path to outer return conductor  46 . 
     FIG. 8 illustrates an alternate embodiment where outer return conductor  46  extends beyond active inner conductor  44 . This configuration defines a recess  70  in the shape of a truncated cone. Dielectric portion  72  is disposed within recess  70 . This configuration spreads the desiccation zone of vessel  102  by broadening the current distribution as the current travels from inner active conductor  44  to outer return conductor  46 . The electromagnetic wave launched from inner active conductor  44  will broaden through dielectric portion  72  before contacting vessel  102 . 
     FIG. 9 illustrates another embodiment where outer return conductor  46  includes ground planes  80 . Inner active conductor  44  protrudes beyond ground planes  80  contacting vessel portion  102 . Dielectric portion  82  is disposed on ground planes  80 . Distal end  84  of inner active conductor  44  may be positioned in flush cooperation with dielectric portion  82  or extend beyond the contact region of vessel portion  102 . This alternate configuration will broaden the cross-sectional area of vessel  102  that is affected by the electromagnetic wave launched from inner active conductor  44 . Current will travel through vessel portion  102  from inner active conductor  44 , to ground planes  80  through the thin dielectric portions  82  covering ground planes  80 . 
     In an alternate preferred embodiment, as illustrated in FIG. 10, instrument  12  is configured for surgical treatment of tissue relating to bodily joints and the like, such as arthroscopic applications. Chassis  18  includes outer tube  30  having microwave conductor  42  extending therethrough and axially movable therewithin, as described in greater detail hereinabove. In operation, as shown in FIG. 10, microwave conductor  42  is manipulated to advance distal end  52  in contact with tissue portion  104 . Microwave energy is provided to instrument  12 , as discussed previously. Due to the contact of distal end  52  of microwave conductor  42 , microwave current flows from inner active conductor  44 , through vessel portion  104 , and through outer return conductor  46 . Accordingly, tissue portion  104  becomes treated as desired. 
     It will be understood that various modifications may be made to the embodiments disclosed herein. For example, while specific preferred embodiments of the microwave system have been described in detail, structures that perform substantially the same function in substantially the same way to achieve the same result may also be used. In addition, the inner active and outer return conductors may include electrodes in a parallel configuration for treating tissue. Further, although an instrument having a chassis extension extending from the chassis is disclosed, it is contemplated that the chassis extension may extend from the microwave conductor. Moreover, the inner active and outer return conductors may include multiple electrode configurations. Therefore, the above description should not be construed as limiting, but merely as exemplifications of preferred embodiments. Those skilled in the art will envision other modifications within the scope and spirit of the claims appended hereto.