Apparatus for treating body tissue

Abstract: An apparatus, system, and method for treating body tissue includes an electrode assembly having a first electrode and a second electrode, with at least the first electrode formed of porous conductive material, such as porous metal. Conductive fluid is delivered to the operating site through the porous metal of the first electrode via a fluid supply conduit. The apparatus may also include a fluid withdrawal conduit. The second electrode may also be formed of porous metal, and may serve as the intake opening for the fluid withdrawal conduit. The electrode assembly may be positioned on a catheter shaft having a distal end, with the first electrode positioned on the catheter shaft distal end. In treating desired tissue at a selected operational site, the electrode assembly is introduced to the site with the first electrode positioned adjacent to the desired tissue. Conductive fluid, such as a saline solution, is delivered to the operational site via the supply conduit. Electrical power is provided across the first electrode and second electrode via a power supply, which may be an RF power supply.

Description: BACKGROUND OF THE INVENTION Field of the Invention The invention relates to a device for treatment of body tissues. More particularly, the present invention relates to an apparatus for treatment, including vaporization and coagulation, of body tissues using electrodes comprising a porous metal in conjunction with a conductive fluid such as saline. Description of Related Art Electrosurgery has been used for treating body tissue, including coagulation, desiccation, and vaporization of tissue. A common method of performing electrosurgery involves injecting conductive fluid, such as saline solution, into the operational site. The conductive fluid serves to create an electrical path between the electrodes and the body tissue. Continuous replenishment of the conductive fluid can be important during various procedures. The fluid can be absorbed by the patient's body. Furthermore, fluid may become contaminated, thus compromising its conductivity and/or other desirable characteristics, such as clarity. When sufficient power is applied across the electrodes, the electrodes can become heated and may vaporize all fluid in immediate contact with the electrodes. The electrodes may then heat up to a point where they are damaged. To maintain a constant supply of conductive fluid at the operational site, fluid can be continuously introduced to the operational site. However, delivering the fluid to the area immediately adjacent the electrode, without adversely interfering with the electrode function, can be critical to system performance. US-A-5643197 describes an ablation catheter having a tip structure formed with path means, e.g. by making the tip structure from a sintered metal which contains a plurality of randomly formed through-passages, for directing a fluid from a central lumen within the tip structure to portions of the tip structure exterior surface so as to provide a fluid protective layer around the tip structure. WO-A-9715238 describes a radiofrequency ablation apparatus in the form of a pair of electrodes having a central lumen through which an electrolytic solution or gel may be delivered to the selected ablation tissue site through fluid distribution ports formed in the electrode. A pump is used to transfer fluid through the central lumen to both electrodes. Returning electrolytic solution or gel is passed to a waste container. WO-A-9607360 describes a radiofrequency ablation apparatus in the form of a porous electrode, which provides a high resistance to fluid flow, for supplying a heated conductive fluid to an ablation site from a pressurised source of the fluid. Two additional conduits are provided within the apparatus for supplying and removing a cooling or heating fluid for maintaining the conductive fluid at a desired temperature. Consequently, there is a need to efficiently introduce fluid to an operational site, and specifically over the electrosurgical electrodes, without adversely impacting the function of the electrodes. The present invention satisfies these needs. SUMMARY OF THE INVENTION Briefly and in general terms, the present invention provides an electrosurgical instrument as defined in claim 1 and a system as defined in claim 4. The instrument may be part of an electrosurgical system including a power supply for generating a voltage between the first electrode and the second electrode. The system may further include a fluid source providing fluid to the operational site via the fluid supply conduit. A controller may be used to monitor and control the power supply, fluid source, and fluid withdrawal. During a surgical procedure, the first electrode is positioned adjacent the tissue to be treated. Conductive fluid is introduced to the operational site by injecting fluid from a supply conduit through the porous metal of the first electrode. Electrical power is provided to the first electrode to effect the desired treatment. Other features and advantages of the present invention will become more apparent from the following detailed description of the invention when taken in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS FIGURE 1 is a side view, in partial cross section, of a system which does not constitute an embodiment of the present invention. FIG. 1a is a side view, in cross section, of an electrosurgical instrument according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT The present invention is described with reference to FIGS. 1 and 1a for use in treating body tissues, including use in treating a human uterus. However, the present invention is not limited to use in the female reproductive system, and may be applied to various electrosurgical procedures. Referring now to FIG. 1, an arrangement which does not constitute an embodiment of the invention comprises an electrosurgical instrument 12 including a generally elongated shaft 14 having an electrode assembly 16 at the shaft distal end 18. The electrode assembly is shown positioned at a desired operational site 20. The electrode assembly 16 includes a first electrode 22 formed of sintered metal. A sintered metal structure is typically made by placing a metal powder or a collection of very small metal spheres (such as BB pellets) in an oven. By increasing the temperature in the oven to the point where the surface of the pellets reach the softening point, but not quite the melting point, adjacent spheres will fuse together at their points of contact, thereby becoming sintered. The voids between the spheres preferably remain open, thereby forming a generally-open cell foam-like structure. Because the spheres did not entirely melt, they did not coalesce into a single and generally solid mass. The resulting structure is a porous metal structure with a plurality of small passageways. An alternative to sintered metal is to form multiple holes, such as by drilling, in a metal structure, thereby forming a porous metal structure. For example, multiple holes could be drilled into a section of tubing, thereby creating multiple passageways for fluid to flow out of and/or into the tubing. The electrode assembly 16 may include a second electrode 24 positioned on the shaft 14. The second electrode 24 and the first electrode 22 are preferably insulated from each other. For example, in the arrangement of FIG. 1, the catheter shaft 14 is formed of a generally non-conductive material. The catheter shaft portion 26 between the first electrode 22 and the second electrode 24 thus serves as an insulator. The first electrode 22 and second electrode 24 are electrically connected, via a first electrical lead 28 and a second electrical lead 30, respectively, to a power supply 32 that generates a voltage between the first electrode 22 and second electrode 24. In the arrangement shown, a controller 34 monitors and controls the output power according to preprogrammed instructions and/or input from the surgeon or other user. In the arrangement of FIG. 1, the first electrode 22 is positioned at the distal end 18 of the catheter shaft 14. A fluid supply conduit 36 within the catheter shaft leads to the first electrode 22, so that fluid introduced to the fluid supply conduit 36 from a fluid supply 38 will flow out of the porous metal of the first electrode 22, thereby introducing the fluid to the operational site 20. The fluid is preferably a conductive fluid. A fluid withdrawal conduit 40 may be provided through which fluid may be withdrawn from the operational site 20 by a fluid withdrawal device, such as the fluid withdrawal pump 42 shown in FIG. 1. The fluid withdrawal conduit 40 is shown with an intake opening 44 positioned on the catheter shaft 14 proximally of the first electrode 22. In the embodiment of the invention shown in FIG. 1a, the second electrode 24a is formed of porous metal. The second electrode 24a is positioned over the intake opening 44, so that fluid is withdrawn through the porous metal of the second electrode 24a. Referring again to FIG. 1, the controller 34 may monitor and control the fluid supply 38 and, in the event of a malfunction of either the fluid supply 38 or the power supply 32, operate to shut down operation. For example, the controller 34 may automatically shut off the power supply 32 if the fluid supply 38 is no longer providing fluid to the operational site 20. In the arrangement shown in FIG. 1, the electrode assembly 16 is a bipolar electrode assembly, including a first electrode 22 and a second electrode 24. Although a preferred embodiment of the invention has been described and illustrated, the invention is susceptible to modifications and adaptations within the ability of those skilled in the art and without the exercise of inventive faculty. Thus, it should be understood that various changes in form, detail, and usage of the present invention may be made without departing from the scope of the invention. Accordingly, it is not intended that the invention be limited, except as by the appended claims.

Claims: An electrosurgical instrument (12) for treating tissue at a selected operation site (20), the instrument (12) comprising: first (22) and second (24a) electrodes comprising porous metal and being in electrical connection with first (28) and second (30) electrical leads respectively ; a fluid supply conduit (36) in fluid communication with the porous metal of the first electrode (22), wherein fluid may be supplied to the operation site (20) via the fluid supply conduit (36) and the porous metal of the first electrode (22); characterised in that said instrument further comprises: a fluid withdrawal conduit (40) in fluid communication with the porous metal of the second electrode (24a), whereby fluid may be withdrawn from the operation site (20) via the porous metal of the second electrode (24a) and the fluid withdrawal conduit (40). An instrument as claimed in claim 1, wherein the porous metal comprises sintered metal. An instrument as claimed in claim 1 or claim 2, further comprising a catheter shaft (14) having a distal end (18) and a proximal end, and wherein the first electrode (22) is positioned on the shaft distal end (18), and the second electrode (24a) is positioned on the shaft (14) proximal of the first electrode (22). A system (10) for treating tissue at a selected operation site (20), the system (10) comprising: an electrosurgical instrument (12) as claimed in any preceding claim; a power supply (32) for generating a voltage between the first electrode (22) and the second electrode (24a); means (38) for supplying fluid to the fluid supply conduit; and means (42) for withdrawing fluid from the fluid withdrawal conduit.

Inventors: SAADAT VAHID, SAADAT, VAHID
Applicants: ETHICON INC, ETHICON, INC.
Application year: 1998
Main classification: A61B18
IPC codes: A61B18