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Electrosurgical probe and method of use Number:7,169,146 from the United States Patent and Trademark Office (PTO) owispatent

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Title: Electrosurgical probe and method of use

Abstract: An electrosurgical instrument that allows precise modulation of active Rf density in an engaged tissue volume. The working end of the instrument has a tissue-contacting surface of a conductive-resistive matrix that is variably resistive depending on its temperature. The matrix comprises a positive temperature coefficient (PTC) polymeric material hat exhibits very large increases in resistivity as any local portion increases beyond a selected temperature. In a method of use, the polymeric PTC material senses the temperature of engaged tissue in a manner akin to pixel-by-pixel sensing and thereby changes its resistance in a corresponding pixel-by-pixel manner. The instrument further carries cooling means to cause accelerated thermal relaxation of the PTC matrix during use to make the engagement surface highly responsive to temperature changes that in turn alter the matrix between being electrically conductive and electrically resistive.

Patent Number: 7,169,146 Issued on 01/30/2007 to Truckai,   et al.


Inventors: Truckai; Csaba (Saratoga, CA), Shadduck; John H. (Tiburon, CA)
Assignee: SurgRx, Inc. (Redwood City, CA)
Appl. No.: 10/781,925
Filed: February 17, 2004


Current U.S. Class: 606/41 ; 606/49; 606/50; 606/51; 606/52
Current International Class: A61B 18/18 (20060101)
Field of Search: 606/41,49-52


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Primary Examiner: Peffley; Michael
Assistant Examiner: Toy; Alex
Attorney, Agent or Firm: Townsend and Townsend and Crew LLP

Claims



What is claimed is:

1. An electrosurgical instrument for delivering energy to tissue, comprising: a working end for engaging the tissue; a surface layer at an exterior portion of the working end, the surface layer comprising a matrix of polymeric PTC composition adapted to deliver electrical current to the tissue; and a cooling structure at an interior portion of the working end; wherein the cooling structure cools the PTC matrix to lower the temperature of one or more portions of the PTC matrix.

2. The electrosurgical instrument of claim 1, wherein the PTC matrix defines a switching range at which the electrical resistance substantially increases in a selected temperature range.

3. The electrosurgical instrument of claim 2, wherein the surface layer has a thickness of less than about 500 microns.

4. The electrosurgical instrument of claim 3, wherein the surface layer has a thickness ranging between about 0.1 microns and 200 microns.

5. The electrosurgical instrument of claim 4, wherein the surface layer has a thickness ranging between about 0.5 microns and 100 microns.

6. The electrosurgical instrument of claim 1, wherein the cooling structure passively cools the PTC matrix.

7. The electrosurgical instrument of claim 6, wherein the cooling structure comprises a thermally conductive material forming an electrode which conducts electrical current from a power source to the PTC matrix.

8. The electrosurgical instrument of claim 7, wherein the cross-section of the conductive portion is significantly larger than the PTC surface layer.

9. The electrosurgical instrument of claim 7, wherein the cooling structure comprises a material selected from a group consisting of copper-beryllium alloy, copper, aluminum, silver, or gold.

10. The electrosurgical instrument of claim 7, further comprising a ground electrode, and wherein the power is supplied to the thermally conductive electrode in a mono-polar configuration.

11. The electrosurgical instrument of claim 1, wherein the cooling structure actively cools the PTC matrix.

12. The electrosurgical instrument of claim 11, wherein the cooling structure communicates with a fluid-cooling circulation system.

13. The electrosurgical instrument of claim 12, further comprising a fluid source, wherein the cooling structure has a flow channel to form a flow loop through which the fluid source circulates a fluid.

14. The electrosurgical instrument of claim 13, further comprising a heat exchanger, wherein the fluid pump circulates the fluid through the heat exchanger.

15. The electrosurgical instrument of claim 13, wherein the fluid comprises water.

16. The electrosurgical instrument of claim 13, wherein the fluid comprises a cooling gas.

17. The electrosurgical instrument of claim 16, wherein the cooling gas comprises a cryogen selected from the group consisting of freon or CO.sub.2.

18. The electrosurgical instrument of claim 17, further comprising an expansion chamber, wherein the cooling gas absorbs heat as it changes its phase state while in the expansion chamber.

19. The electrosurgical instrument of claim 18, further comprising an inflow channel and outflow channel for circulating the gas between the fluid pump and the expansion chamber.

20. The electrosurgical instrument of claim 1, wherein the cooling structure comprises a Peltier element.

21. The electrosurgical instrument of any of claims 6 or 11, wherein the surface layer defines an engagement surface for engaging tissue.

22. The electrosurgical instrument of claim 21, wherein the engagement surface is carried on the working end of a probe.

23. The electrosurgical instrument of claim 21, wherein the engagement surface is carried on the working end of a jaw structure, the jaw structure comprising paired first and second jaws moveable between an open position and a closed position.

24. The electrosurgical instrument of claim 23, wherein at least one jaw defines an engagement plane, the engagement plane carrying at least a portion of the engagement surface.

25. The electrosurgical instrument of claim 24, wherein the wherein the cooling structure comprises a thermally conductive material forming an electrode which conducts electrical current from a power source to the PTC matrix.

26. The electrosurgical instrument of claim 25, wherein a plurality of electrodes are formed on the jaw structure, and wherein power is delivered to the electrodes in a bipolar configuration.

27. A method of controlled delivery of energy to tissue, comprising the steps of: engaging tissue with an engagement surface at least a portion of which comprises a body of temperature-responsive variable impedance material that is intermediate opposing polarity conductor regions operatively coupled to an RF power source; delivering current flow within the engaged tissue and the engagement surface to cause ohmic heating of the tissue, wherein the ohmically heated tissue conductively heats adjacent regions of the engagement surface, and wherein the engagement surface varies its impedance to modulate current flow between the engagement surface and the tissue; and contemporaneously cooling the variable impedence body to thereby accelerate modulation of current flow between the engagement surface and the engaged tissue.

28. The method of claim 27, wherein cooling the variable impedance body comprises passively cooling the engagement surface.

29. The method of claim 28, wherein passively cooling the variable impedance body comprises providing a cooling structure at an interior of the working end, wherein the cooling structure comprises a thermally conductive material.

30. The method of claim 28, wherein the cooling structure comprises an electrically conductive material forming an electrode, and wherein delivering current flow comprises delivering RF energy to the engagement surface via the electrically conductive material.

31. The method of claim 27, wherein cooling the variable impedance body comprises actively cooling the engagement surface.

32. The method of claim 31, wherein actively cooling the variable impedance body comprises cooling the engagement surface via a fluid-cooling circulation system.

33. The method of claim 32, wherein cooling the variable impedance body comprises circulating a fluid through a flow channel proximal to the engagement surface.

34. The method of claim 33, wherein cooling the variable impedance body further comprises circulating the fluid through a heat exchanger.

35. The method of claim 33, wherein the fluid comprises water.

36. The method of claim 33, wherein the fluid comprises a cooling gas.

37. The method of claim 36, wherein the cooling gas comprises a cryogen selected from the group consisting of freon or CO.sub.2.

38. An electrosurgical instrument for delivering energy to tissue, comprising: an introducer member having at least one working surface for engaging tissue, wherein at least a portion of the at least one working surface comprises a polymeric PTC composition; and a conductor at an interior of the PTC composition, the conductor having at least one open region at an interior of the conductor for cooling the assembly of the conductor and PTC composition.

39. The electrosurgical instrument of claim 38, wherein the conductor comprises an electrically conductive material forming an electrode, the electrode connected to a radiofrequency power source to ohmically heat the tissue.

40. The electrosurgical instrument of claim 39, wherein the conductive material is also thermally conductive to act as a heat sink.

41. The electrosurgical instrument of claim 38, wherein the open region communicates with a fluid-cooling circulation device.

42. The electrosurgical instrument of claim 41, wherein the fluid cooling circulation device comprises a fluid source for providing fluid flow through the at least one open region.

43. The electrosurgical instrument of claim 42, wherein the fluid source communicates with a heat exchange structure.

44. The electrosurgical instrument of claim 43, wherein the fluid comprises water.

45. The electrosurgical instrument of claim 41, wherein the fluid comprises a cooling gas.

46. The electrosurgical instrument of claim 45, wherein the cooling gas comprises a cryogen selected from the group consisting of freon or CO.sub.2.

47. The electrosurgical instrument of claim 40, wherein the working surface defines an engagement surface for engaging tissue.

48. The electrosurgical instrument of claim 47, wherein the engagement surface is carried on the working end of a probe.

49. The electrosurgical instrument of claim 47, wherein the engagement surface is carried on the working end of a jaw structure, the jaw structure comprising paired first and second jaws moveable between an open position and a closed position.

50. The electrosurgical instrument of claim 49, wherein at least one jaw defines an engagement plane, the engagement plane carrying at least a portion of the engagement surface.
Description



CROSS-REFERENCES TO RELATED APPLICATIONS

This application claims benefit of Provisional U.S. Patent Application Ser. No. 60/447,535 filed Feb. 14, 2003 entitled "Electrosurgical Probe and Method."

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to medical devices and methods and more particularly relates to electrosurgical jaw, probe and needle structures with at least one polymer positive temperature coefficient of resistance (PTC) body portion for sensing tissue temperature and modulating ohmic tissue heating together with multiple circuitry components for intraoperative control of voltage applied to the engaged tissue.

2. Description of the Related Art

In the prior art, various energy sources such as radiofrequency (RF) sources, ultrasound sources and lasers have been developed to coagulate, seal or join together tissues volumes in open and laparoscopic surgeries. The most important surgical application relates to sealing blood vessels which contain considerable fluid pressure therein. In general, no instrument working ends using any energy source have proven reliable in creating a "tissue weld" or "tissue fusion" that has very high strength immediately post-treatment. For this reason, the commercially available instruments, typically powered by RF or ultrasound, are mostly limited to use in sealing small blood vessels and tissues masses with microvasculature therein. The prior art RF devices also fail to provide seals with substantial strength in anatomic structures having walls with irregular or thick fibrous content, in bundles of disparate anatomic structures, in substantially thick anatomic structures, or in tissues with thick fascia layers (e.g., large diameter blood vessels).

In a basic bi-polar RF jaw arrangement, each face of opposing first and second jaws comprises an electrode and RF current flows across the captured tissue between the opposing polarity electrodes. Such prior art RF jaws that engage opposing sides of tissue typically cannot cause uniform thermal effects in the tissue--whether the captured tissue is thin or substantially thick. As RF energy density in tissue increases, the tissue surface becomes desiccated and resistant to additional ohmic heating. Localized tissue desiccation and charring can occur almost instantly as tissue impedance rises, which then can result in a non-uniform seal in the tissue. The typical prior art RF jaws can cause further undesirable effects by propagating RF density laterally from the engaged tissue thus causing unwanted collateral thermal damage.

The commercially available RF sealing instruments typically adopt a "power adjustment" approach to attempt to control RF flux in tissue wherein a system controller rapidly adjusts the level of total power delivered to the jaws' electrodes in response to feedback circuitry coupled to the electrodes that measures tissue impedance or electrode temperature. Another approach used in the prior art consists of jaws designs that provide spaced apart of offset electrodes wherein the opposing polarity electrode portion s are spaced apart by an insulator material--which may cause current to flow within an extended path through captured tissue rather that simply between opposing electrode surfaces of the first and second jaws. Electrosurgical grasping instruments having jaws with electrically-isolated electrode arrangements in cooperating jaws faces were proposed by Yates et al. in U.S. Pat. Nos. 5,403,312; 5,735,848; and 5,833,690. In general, the prior art instruments cannot reliably create high strength seals in larger arteries and veins.

BRIEF SUMMARY OF THE INVENTION

The electrosurgical instrument corresponding to the invention provides novel means for modulating RF energy application to biological tissue to create high strength thermally welds or seals in targeted tissues. The system allows for a "one-step" welding-transecting procedure wherein the surgeon can contemporaneously (i) engage tissue within a jaw structure (ii) apply RF energy to the tissue, and (iii) transect the tissue. Such one-step welding and transecting has never been considered in the prior art.

Another particular objective is to provide a jaw structure that can engage and weld tissue bundles, defined herein as bundles of disparate tissue types (e.g., fat, blood vessels, fascia, etc.). For the welding of tissue bundles, the jaw surfaces must apply differential energy levels to each different tissue type simultaneously that has not been accomplished in the prior art. The invention provides an electrosurgical system that applies differential energy levels across the jaws engagement surfaces with "smart" materials without the need for complex feedback circuitry coupled to thermocouples or other sensors in the jaw structure.

In order to create the most effective "weld" in tissue, the targeted volume of tissue must be uniformly elevated to the temperature needed to denature proteins therein. To create a "weld" in tissue, collagen, elastin and other protein molecules within an engaged tissue volume must be denatured by breaking the inter- and intra-molecular hydrogen bonds--followed by re-crosslinking on thermal relaxation to create a fused-together tissue mass. It can be easily understood that ohmic heating in tissue--if not uniform--an at best create localized spots of truly "welded" tissue. Such a non-uniformly denatured tissue volume still is "coagulated" and will prevent blood flow in small vasculature that contains little pressure. However, such non-uniformly denatured tissue will not create a seal with significant strength, for example in 2 mm. to 10 mm. arteries that contain high pressures.

The systems and methods corresponding to invention relate to creating thermal "welds" or "fusion" within native tissue volumes. The alternative terms of tissue "welding" and tissue "fusion" are used interchangeably herein to describe thermal treatments of a targeted tissue volume that result in a substantially uniform fused-together tissue mass, for example in welding blood vessels that exhibit substantial burst strength immediately post-treatment. The strength of such welds is particularly important (i) for permanently sealing blood vessels in vessel transection procedures, (ii) for welding organ margins in resection procedures, (iii) for welding other anatomic ducts wherein permanent closure is required, and also (iv) for vessel anastamosis, vessel closure or other procedures that join together anatomic structures or portions thereof. The welding or fusion of tissue as disclosed herein is to be distinguished from "coagulation", "sealing", "hemostasis" and other similar descriptive terms that generally relate to the collapse and occlusion of blood flow within small blood vessels or vascularized tissue. For example, any surface application of thermal energy can cause coagulation or hemostasis--but does not fall into the category of "welding" as the term is used herein. Such surface coagulation does not create a weld that provides any substantial strength in the affected tissue.

At the molecular level, the phenomena of truly "welding" tissue as disclosed herein may not be fully understood. However, the authors have identified the parameters at which tissue welding can be accomplished. An effective "weld" as disclosed herein results from the thermally-induced denaturation of collagen, elastin and other protein molecules in a targeted tissue volume to create a transient liquid or gel-like proteinaceous amalgam. A selected energy density is provided in the targeted tissue to cause hydrothermal breakdown of intra- and intermolecular hydrogen crosslinks in collagen and other proteins. The denatured amalgam is maintained at a selected level of hydration--without desiccation--for a selected time interval which can be very brief. The targeted tissue volume is maintained under a selected very high level of mechanical compression to insure that the unwound strands of the denatured proteins are in close proximity to allow their intertwining and entanglement. Upon thermal relaxation, the intermixed amalgam results in "p


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