INSTRUMENT FOR PLASMA SURGERY AND METHOD FOR GENERATING PLASMA

Abstract

An electrosurgical instrument having an electrode arranged in a gas-carrying lumen and retained in a centred position. The electrode has an electrode body made of a thermally stable material, for example, hard metal, tungsten, steel, stainless steel or similar. The electrode has a coating made of a material with a low melting point, such as silver, silver alloys or another metal with a low melting point. A bonding layer, in particular a gold layer, can be provided between the coating and the electrode body.

Claims

1. An electrosurgical instrument for plasma coagulation, the electrosurgical instrument comprising: a fluid conductor that comprises at least one lumen; and an electrode having a coating and being arranged inside the fluid conductor at least in sections, the electrode comprising an electrode body extending from its distal end in a proximal direction into the fluid conductor.

2. The electrosurgical instrument according to claim 1, wherein the coating comprises a melting temperature and the electrode body comprises a melting temperature and the melting temperature of the coating is lower than the melting temperature of the electrode body.

3. The electrosurgical instrument according to claim 1, wherein the electrode body comprises a material having a melting temperature over 1000° C.

4. The electrosurgical instrument according to claim 1, wherein the coating comprises a material having a melting temperature below 1000° C.

5. The electrosurgical instrument according to claim 1, wherein the coating comprises an inert metal.

6. The electrosurgical instrument according to claim 1, wherein the coating has a cross-section with a coating area and the electrode has a cross-section with an electrode area, wherein the coating area is at least 12% of the electrode area and wherein the coating extends along a section of electrode of multiple millimeters.

7. The electrosurgical instrument according to claim 1, wherein electrode further comprises a section at its distal end of at least 2.5 mm length, the thermal capacity of which is lower than 4.5 mJ/K.

8. The electrosurgical instrument according to claim 1, wherein electrode further comprises a distal end held inside the lumen.

9. The electrosurgical instrument according to claim 1, further comprising a holder for arrangement of the electrode inside the lumen and on which the electrode is held, the holder arranged to center the electrode inside the lumen.

10. The electrosurgical instrument according to claim 9, wherein the holder comprises a poor thermally conductive material.

11. The electrosurgical instrument according to claim 9, wherein the holder comprises an electrically insulating material.

12. The electrosurgical instrument according to claim 1, wherein during operation the coating comprises a melted section in the proximity of the distal end.

13. The electrosurgical instrument according to claim 1, wherein during operation the electrode comprises a section at its distal end that is at least partly bare from material of the coating.

14. A method for generation of a plasma, the method comprising: providing an instrument according to, claim 1; generating a gas flow inside the lumen of the fluid conductor; applying an electrical voltage to the electrode for causing an electrical discharge at the distal end of the electrode to heat the distal end of the electrode at least up to locally reaching or exceeding the melting temperature of the coating; and further operating the instrument.

15. The method according to claim 14, further comprising: redistributing material of the coating away from the distal end of the electrode while at least partly clearing the electrode body.

16. The electrosurgical instrument according to claim 7, wherein the electrode further comprises a section at its distal end of at least 2.5 mm length, the thermal capacity of which is lower than 4.17 mJ/K.

Description

[0032] Further details of preferred embodiments of the invention are derived from the drawings and the following description. The drawings show:

[0033] FIG. 1 an instrument and the apparatus provided for supply in a schematic illustration,

[0034] FIG. 2 a distal end section of the inventive instrument in enlarged longitudinal section basic illustration,

[0035] FIG. 3 a distal end section of the instrument according to FIG. 2 during operation,

[0036] FIG. 4 a cross-section through the electrode according to FIG. 3 cut along the line IV-IV,

[0037] FIG. 5 an electrode in longitudinal section illustration of its distal end section prior to its first use,

[0038] FIG. 6 the electrode according to FIG. 5 in formed condition,

[0039] FIGS. 7 and 8 additional embodiments of an inventive electrode prior to the first use in longitudinal section.

[0040] FIG. 1 illustrates an instrument 10 that is configured as endoscope probe. It serves for plasma coagulation, particularly argon plasma coagulation, i.e. for treatment of human or animal tissue without direct physical contact between its electrode 11 and the respective biological tissue. The instrument 10 is configured as flexible probe. The principals explained in the following can, however, also be realized in a rigid instrument suitable for the laparoscopic use or in an instrument suitable for the open surgical use.

[0041] The instrument 10 comprises a fluid conductor 12, e.g. in form of a flexible hose 13, but extends from a distal end 14 up to its proximal end 15. A lumen 16 extends through the length of hose 13 that is particularly apparent from figure 2. During use a gas, typically an inert gas such as argon, flows through this lumen. For this, instrument 10 is connected to an apparatus 17 that comprises a gas source 18 or provides a connection to such a gas source. During use gas flows from proximal end 15 to the distal end 14 of hose 13 and thus of lumen 16 and therefrom out of the open end of hose 13.

[0042] The electrode 11 is arranged in the lumen 16, the distal end 19 of which preferably does not project from the fluid conductor 12, but is rather still positioned inside lumen 16. However, it can also extend with a section out of the fluid conductor 12 and/or lumen 16 in some embodiments. Electrode 11 is preferably a pin or needle electrode that can be configured, for example, by a round or profile wire or also by a small tube or cannula. The electrode 11 can also be the distal end of the wire extending through the lumen 16. The electrode 11 can comprise a substantially constant cross-section. It can be held inside lumen 16 preferably in a centered manner and immovably or axially movable independent from its specific shape. The holder 20 provided for this purpose supports electrode 11 and is supported on the inside of fluid conductor 12 or hose 13.

[0043] The electrode 11 is electrically connected with a generator 21, e.g. an RF generator, that supplies a radio frequency electrical voltage to the electrode 11. A respective connection conductor can extend from electrode 11 through the entire lumen 16 up to the proximal end 15 at which an electrical connector provides the contact with generator 21.

[0044] Generator 21 is preferably configured to supply a voltage that is sufficiently high in order to create an electrical discharge at the tip of electrode 11 and in doing so, to ionize the gas stream flowing along electrode 11 at least partly. A plasma jet for treatment of biological tissue is created.

[0045] A decisive particularity of the present instrument 10 is the characteristic of electrode 11. It is, for example, configured as slim cylinder having a flat, round, cone-shaped or tapered tip or entirely as slim cone. It comprises preferably a diameter of less than 0.5 mm, preferably at most 0.3 mm at least in the proximity of its distal end 19. Thus, its radius R, apparent from FIG. 4, is smaller than 0.25 mm, preferably smaller than 0.15 mm. Radii smaller than 0.1 mm are possible. Electrode 11 can, however, also comprise a prismatic shape, e.g. in that it is configured as profile wire. In addition, it can be configured as flat platelet having a tip orientated in distal direction.

[0046] FIG. 4 illustrates a cross-section of electrode 11 in an axial distance of some millimeters toward the distal end 19 of the electrode 11. The distance is so long that the structure of electrode 11 remains unchanged during use. As apparent, electrode 11 comprises an electrode body 22 that is provided with a coating 23. The electrode body 22 and the coating 23 consist of different materials. Preferably the melting temperature TK of the electrode body 22 is above 1000° C. Also the electrode body 22 can consist of another thermal-resistant electrically conductive or also—at least in cold condition—of an electrically non-conductive material, such as ceramic, for example.

[0047] Electrode body 22 can consist of a high-melting metal such as, for example, steel, stainless steel, hard metal, molybdenum, tungsten or the like. Particularly alloys are suitable as material for the electrode body 22 that contain ion and/or chromium and/or nickel. Moreover, carbon and/or manganese and/or phosphor and/or sulphur and/or silicon and/or nickel and/or nitrogen and/or molybdenum can be present as additional alloy components. A stainless steel preferred as base material has the following composition:

TABLE-US-00001 Fe C Cr Mn P S Si Ni N Mo min 0.05 16.0 6.0 max 47.605 0.15 19.0 2.0 0.045 0.15 2.0 9.5 0.11 0.8

[0048] On the contrary, coating 23 preferably consists at least partly of an electrically well conductible low-melting material having a melting point preferably lower than 1000° C., the coating 23 can consist of silver or silver alloys, for example. The thickness D of coating 23 is preferably at least so thick that the portion of the area of the cross-hatched cross-section area of coating 23 in FIG. 4 of the total cross-section area of electrode 11 is higher than 10%, preferably higher than 12%. The total cross-section area is the cross-section area having the area of a circle with radius R. This corresponds to the sum of the area of the cross-section of the electrode body 22 (obliquely hatched in the figure) and the area of the cross-section of the coating 23 (cross-hatched in FIG. 4) in FIG. 4. The explained correlation between the cross-section area of the coating 23 and the total cross-section area of electrode 11 applies independent from its specific cross-section shape. Thus, electrode 11 can comprise a hollow cylindrical or a polygonally limited cross-section.

[0049] An intermediate layer 24 can be provided between the coating 23 and the electrode body 22. It can consist of a metal, preferably a noble metal, a noble metal alloy or an inert metal, e.g. nickel, a nickel alloy, gold or a gold alloy. The melting temperature T.sub.z of the material of intermediate layer 24 is preferably between the melting temperatures T.sub.K and T.sub.B of the materials of the electrode body 22 and the coating 23 (T.sub.K>T.sub.Z>T.sub.B). The intermediate layer 24 can act as adhesive and concurrently support the retraction of the melting coating 23 from electrode body 22 at the distal end 19.

[0050] Advantageous thermal conditions result when complying with the indicated parameters, i.e. diameter of the electrode 11 smaller than 0.3 mm and portion of the cross-section area of the coating 23 larger than 10%, preferably larger than 12% of a total cross-section area of electrode 11. Instruments 11 having filigree outer dimensions can be configured in this manner. The outer diameter of the fluid conductor 12 can be 1 mm or less if required.

[0051] The obtained miniaturization possibility is based on the low thermal development and thermal radiation at and from electrode 11. This is achieved by the combination of at least some of the measures described above. In doing so, it is particularly achieved that the electrical discharge during operation is concentrated on the distal end 19 of electrode 11. It comprises a section 25 adjoining the distal end 19 that has a length of preferably several millimeters. Inside it the conditions with regard to the cross-section areas of the electrode body 22 and the coating 23 described in connection with FIG. 4 apply. Preferably section 25 ends proximally ahead of or at holder 20. The coating can, however, extend and can be continued beyond holder 20 in proximal direction. In distal direction section 25 ends at the distal end 19 of electrode 11. The distal end 19 starts at an area 26 apparent from FIG. 3 that is located so close to the forming discharge root points 27 that material of the coating 23 in this area 26 is present or can be present in liquid condition during operation.

[0052] At the distal end 19 at least parts of electrode body 22 are bare during operation. The bare area forms the distal end 19. Starting from the face side end of electrode 11 up to approximately 2 mm to 2.5 mm in proximal direction, a section 19a is formed, the thermal capacity of which is preferably less than 4.5 mJ/K and further preferably less than 4.17 mJ/K. The section 19a can be formed by the distal end 19. The low thermal capacity of section 19a allows local melting of coating 23. Also the continuous electron emission of end 19 is guaranteed immediately after ignition of a plasma also with low RF power. This supports the concentration of the plasma discharge on the distal end of the electrode and thus mitigates thermal introduction therein.

[0053] The instrument 10 described so far is used as follows and its electrode 11 is operated as follows:

[0054] In operation first lumen 16 is supplied with gas, such that a gas flow results in distal direction. For example argon can serve as gas that longitudinally flows along electrode 11. Electrode 11 is electrically connected with generator 21. The voltage applied to the distal end 19 results in a spark ignition to a counter electrode located in the proximity that can be biological tissue, for example.

[0055] Directly before or after start of this process, electrode 11 has the initial shape illustrated in FIG. 5 that is geometrically defined. For example, electrode body 22 is cylindrical, while coating 23 essentially has a constant thickness everywhere. Coating 23 extends starting from the distal end 19 some millimeters or centimeters in proximal direction and can end then or can be extended. Coating 23 can extend over the face of electrode body 22 or can leave it bare, as apparent from FIG. 8, for example. Coating 23 can also already be removed from an end section, e.g. from the distal end 19, during production of electrode as shown in FIG. 7. For this, distal end 19 of electrode 11 can be conically pointed, configured as truncated cone or also as wedge. For example, electrode 11 can be manufactured by cutting a sufficiently long part from an endlessly supplied coated wire. As necessary, distal end 19 can be processed subsequently in a material removal manner in order to remove coating 23 at the end 19 completely or partly.

[0056] With the first initial use, first distal end 19 of electrode 11 is heated such that it is reshaped for the further operation. An area 26 is formed on electrode 11 in which material of coating 23 is at least partly melted, as illustrated in FIG. 6. In this area 26 coating can be thicker than in the remaining region of electrode 11. On the contrary, coating can have a lesser thickness, can be interrupted or can be completely missing at the outermost end 19.

[0057] The procedures described above in connection with the first initial use can also be carried out in the context of the manufacturing of instrument 10. For this, the manufacturer can operate instrument 10 under controlled conditions for a short period. The manufacturer can thereby define the gas type and gas flow as well as voltage and current, just as for the operation on the patient. It can, however, also select different gas types, gas flows or operating voltages or currents.

[0058] During operation distal end 19 of electrode 11 is heated and able to emit electrons, while electrode 11 reaches remarkably lower temperatures in the area 26 and particularly farther proximally in section 25 and remains relatively cool there. At the distal end 19 discharge root points 27 are fixed (FIG. 3) without travelling in proximal direction. Electrode 11 thus radiates only low heat and does not substantially contribute to heating the fluid conductor 12.

[0059] The instrument 10 according to the invention comprises an electrode 11, which is arranged in a gas-conducting lumen 16 and held in a centered position. Electrode 11 comprises an electrode body 22 made of a thermally stable material, e.g. hard metal, tungsten, steel, stainless steel or similar. The electrode 11 is provided with a coating 23 made of a material with a low melting point, such as silver, silver alloys or another metal having a low melting point. An adhesive layer 24, particularly a gold layer, can be provided between the coating 23 and the electrode body 22. It can facilitate the retraction of coating 23 during initial use and thus the formation of electrode 11 desired for operation (e.g. according to FIG. 6).

Reference Signs

[0060] 10 instrument

[0061] 11 electrode

[0062] 12 fluid conductor

[0063] 13 hose

[0064] 14 distal end of fluid conductor 12/hose 13

[0065] 15 proximal end of fluid conductor 12/hose 13

[0066] 16 lumen

[0067] 17 apparatus

[0068] 18 gas source

[0069] 19 distal end of electrode 11

[0070] 19a section of electrode 11 (2 to 2.5 mm length)

[0071] 20 holder

[0072] 21 generator

[0073] 22 electrode body

[0074] 23 coating

[0075] 24 intermediate layer

[0076] 25 section

[0077] 26 area in which the coating material can be liquid

[0078] 27 discharge root points