ELECTRODE ARRANGEMENT

Abstract

An electrode for an electrosurgical instrument for plasma coagulation. The electrode has a heat dissipation element arranged such that the thermal resistance of the electrode, measured in the longitudinal direction (in distal or proximal direction), is 2: 300 WI (m*K). The heat dissipation element may be formed by a coating having a higher electrical conductivity and a higher thermal conductivity than the material of the electrode main part.

Claims

1. An electrode arrangement for an electrosurgical instrument for plasma coagulation, the electrode arrangement comprising: an electrode that comprises a tip orientated in distal direction, the electrode having a cross-section that increases in proximal direction from the tip, wherein the electrode comprises a material or a material combination having a thermal conductivity that is larger than 20 W/(m*K).

2. The electrode arrangement according to claim 1, wherein the electrode has a maximum transverse dimension and a radius of curvature at its tip that is smaller than 1/10 of the maximum transverse dimension.

3. The electrode arrangement according to claim 1, wherein the transverse dimension is configured to continuously increase in proximal direction starting from the tip.

4. The electrode arrangement according to claim 1, wherein the electrode comprises steplessly configured edges originating at the tip.

5. The electrode arrangement according to claim 1, wherein the electrode is configured as a platelet that comprises two flat sides that are connected with each other by means of narrow sides.

6. The electrode arrangement according to claim 1, wherein edges are formed between the narrow sides and the flat sides.

7. The electrode arrangement according to claim 1, wherein the electrode comprises a base body that comprises at least one surface on which a heat dissipation device is attached.

8. The electrode arrangement according to claim 7, wherein the heat dissipation device is a layer arranged on the base body.

9. The electrode arrangement according to claim 8, wherein the electrode comprises at least one flat side, and the layer is configured to cover the entire flat side.

10. The electrode arrangement according to claim 1, wherein the heat dissipation device comprises a thermally conductive material.

11. The electrode arrangement according to claim 7, wherein the heat dissipation device comprises a metallic material.

12. The electrode arrangement according to claim 7, wherein the heat dissipation device comprises a non-metallic material.

13. The electrode arrangement according to claim 7, wherein the heat dissipation device is configured and arranged to extend up to an area that is provided for direct contact with a spark originating from the electrode.

14. The electrode arrangement according to claim 7, wherein the heat dissipation device comprises an electrical conductivity that is larger than the electrical conductivity of the base body.

15. The electrode arrangement according to claim 7, wherein the heat dissipation device has a thermal conductivity that is larger than the thermal conductivity of the base body.

Description

[0018] In the drawings embodiments of the invention are illustrated. The drawings show:

[0019] FIG. 1 an inventive instrument, the assigned supplying apparatus and a neutral electrode in very schematic partly perspective illustration,

[0020] FIG. 2 the distal end of the instrument according to FIG. 1 in perspective schematic longitudinal-section illustration,

[0021] FIG. 3 the electrode of the instrument according to FIG. 2 in side view,

[0022] FIGS. 4, 5 and 6 different cross-sections of the electrode according to FIG. 3,

[0023] FIG. 7 the instrument according to FIGS. 2-6 in a sectional perspective illustration during operation,

[0024] FIG. 8 a modified embodiment of an electrode for the instrument according to FIG. 2.

[0025] In FIG. 1 an instrument 10 is illustrated that serves for plasma-based tissue treatment. The tissue treatment can comprise ablation, coagulation, cutting or other types of treatment.

[0026] The instrument is connected to an apparatus 11 that contains a gas source 12, e.g. an argon source, as well as a generator 13 for electrical supply of the instrument 10. It is connected via respective connection means with a line 14 that leads to the instrument 10 and that is introduced in a line 15 via which instrument 10 is supplied with gas. The generator 13 is in addition connected via respective connection means with a neutral electrode 16 that is to be attached to a patient prior to the use of instrument 10. The following description, however, also applies for instruments with other neutral electrode configuration.

[0027] The instrument 10 comprises a distal end 17 that is separately illustrated in FIG. 2. As apparent, a tube or hose 18 is part of instrument 10 that surrounds a lumen 19 that is open at the distal end 17 of hose 18. In the area of the distal end 17 hose 18 can be provided with an inner or outer reinforcement, e.g. in form of a ceramic sleeve, which is not further illustrated in FIG. 2. The hose 18 can thus be configured with one or multiple layers. Examples for instruments with a ceramic sleeve inserted in the open end of hose 18 can be taken from WO 2005/046495 A1.

[0028] An electrode 20 is arranged in lumen 19 that is electrically connected with a wire 21 extending through lumen 19 and being part of line 14. The wire 21 can be welded to electrode 20 or can also be connected mechanically, e.g. by crimping.

[0029] Electrode 20 preferably comprises the basic shape illustrated in FIG. 3. At its distal end a sharp or at most slightly rounded tip 22 is configured on the electrode 20, the radius of curvature R of which (FIG. 2) is as small as possible and preferably smaller than one tenth of the transverse dimension q that is to be measured transverse to the axial direction and largely corresponds to the inner diameter of lumen 19. Electrode 20 is preferably configured in a plate-shaped manner, i.e. its thickness is remarkably smaller than its transverse dimension q. This is, for example, apparent from FIG. 4 that shows a cross-section of electrode 20 at the chain-dotted cutting line IV-IV in FIG. 3. The thickness d is smaller than ⅕, preferably smaller than 1/10 of the transverse dimension q.

[0030] As further apparent from FIG. 4, electrode 20 comprises two flat sides 23, 24 that are connected by means of narrow sides 25, 26. Thus, in total a quadrangular, preferably rectangular cross-section Q is obtained that is bordered by the flat sides 23, 24 and narrow sides 25, 26. The quadrangular cross-section can also be bent one time or multiple times, e.g. S-shaped.

[0031] Electrode 20 comprises a tapering section at its distal end in which the narrow sides 25, 26—extending parallel to one another apart therefrom—are convergingly arranged toward the tip 22. The convergingly toward one another extending sections of the narrow sides 25, 26 can be configured in a straight manner, as shown in FIG. 3, or also in a convex or concave manner. They define an angle α between each other that is preferably in the range of 20° to 100°.

[0032] As the cross-sections V-V and VI-VI show, that are separately illustrated in FIGS. 5 and 6, the cross-section of electrode 20 decreases toward tip 22 in distal direction D or in other words increases in proximal direction P. Thereby the thickness d of electrode 20 can be constant in the tapering section toward tip 22, as shown in FIGS. 5 and 6. The thickness d can, however, also decrease toward tip 22. However, in any case the transverse dimension q decreases in the tapering section toward tip 22.

[0033] In a first embodiment electrode 20 consists entirely of a material being well thermally conductive, as e.g. tungsten, a hard metal, copper, aluminum, or a combination of these materials. Thereby metals and also non-metallic electrically conductive materials can be used, such as DLC or a combination of metal and such materials. However, in any case the used material then has a thermal conductivity λ that is larger, preferably remarkably larger than the thermal conductivity of stainless steel. Particularly is λ≥50 W/(m*K), ≥100 W/(m*K), ≥200 W/(m*K), ≥300 W/(m*K), ≥400 W/(m*K).

[0034] In a preferred embodiment electrode 20 comprises a multiple layer configuration, as apparent from FIGS. 4 and 6. For this electrode 20 comprises an electrode base body 27 that is connected with a heat dissipation device 28 at least on its flat sides 23, 24, however as an option also on its narrow sides 25, 26. The heat dissipation device 28 consists in the present embodiment of a two-dimensional coating of the flat sides of the electrode base body 27 with thermally conductive overlays 29, 30. In the embodiment the base body 27 can consist of stainless steel, whereas the overlays 29, 30 consist of another material having a better thermal conductivity and/or a better electrical conductivity. Silver has shown to be particularly suitable for this purpose. Possible other overlays consist of aluminum and/or copper and/or hard metal and/or DLC and/or tungsten and/or a layer, e.g. metal layer with CBN (cubic boron nitride), diamond powder or similarly well thermally conductive material embedded therein.

[0035] The instrument described so far operates as follows:

[0036] As illustrated in FIG. 7, a gas stream 31 originating from the gas source 12 flows through lumen 19 of instrument 10 during operation. This gas stream (preferably argon stream) flows along both flat sides 23, 24 of electrode 20. Concurrently electrode 20 is supplied with radio frequency electrical current via wire 21. The working frequency of generator 13 and thus the frequency of the current is thereby preferably above 100 kHz, preferably above 300 kHz, further preferably above 500 kHz. At the tip 22 and an adjoining area thereof the current exits electrode 20 and forms a spark igniting toward the not further illustrated biological tissue of the patient or a plasma 32 flowing thereto. The root point 33 of the spark or plasma thereby touches the narrow sides 25, 26, however, particularly the flat sides 23, 24 of electrode 20, whereby this root point area 33 occupies at least 1/10 of the axial length (to be measured in proximal direction) of the area of electrode 20 in which the narrow sides 25, 26 diverge away from tip 22. The overlays 29, 30 extend into this area and preferably up to the tip 22. Thus, the spark or plasma stream is electrically directly supplied by overlay 29, 30. The thickness of overlays 29, 30 can be relatively small. It has shown that already coatings being 10 to 20 μm thick result in a substantial extension of the lifetime of electrode 20 and to a substantially reduced material removal therefrom. Preferably the thickness of the overlays—consisting e.g. of silver—has an amount of 20 μm, 30 μm or 50 μm, whereby in case of a thickness of the electrode of, e.g. 0.1 mm, a thermal resistance of more than 400 W/(m*K) is obtained. The electrode 20 consisting of the material combination stainless steel/silver thereby comprises a phenomenal lifetime.

[0037] In a modified embodiment it is also possible to let the electrode cross-section increase in proximal direction not continuously, different to the embodiments described above, but in a step-like manner, i.e. in one or multiple steps. Such an embodiment is illustrated in FIG. 8. However, this embodiment also realizes the inventive concept, which is why for the description of this electrode 20′ it is referred to the embodiment according to FIGS. 1-7. The already introduced reference numerals are used in the following, whereby they are provided with an apostrophe for the purpose of distinction. The description above accordingly applies apart from the following particularities for the embodiment according to FIG. 8.

[0038] The electrode 20′ comprises a tip 22′ that can be formed here by the pointed or blunt end of a wire-shaped electrode section. This wire-shaped electrode section 34 comprises a core 35 that forms the base body 27′ and for its part can be configured as thin cylinder pin. The core 35 is provided with an overlay 29′ that here—as appropriate in connection with an electrode holding platelet 36—forms the heat dissipation device 28′. The electrode section 34 can be welded, crimped or otherwise connected with the electrode holding platelet 36. A substance bond connection is preferred, because of the better heat transfer. The electrode holding section 36 can consist of stainless steel or another material that is provided with a thermally conductive coating, such as tungsten, copper, aluminum, DLC or the like or that is configured of thermally conductive material, such as tungsten, copper, aluminum, DLC or the like.

[0039] In operation of instrument 10 with an electrode 20′ according to FIG. 8, an electrical discharge and thus the forming spark or plasma stream origins first from tip 22 and then from at least a part of the wire-shaped electrode section 34. The electrically and thermally conductive coating 29′, that is preferably a silver coating, remarkably reduces the electrical resistance of electrode 20 or 20′. The radio frequency alternating current of generator 13 concentrates in the outer layers of electrode 20, 20′ and in this manner flows substantially through coatings 29, 30, 29′. Thereby ohmic losses at the electrode 20, 20′ are minimized and in addition the reduced amount of heat is dissipated substantially better away from the discharge root by the coating and is distributed such that it can be transferred to the gas stream extensively.

[0040] In the improved instrument 10 electrode 20, 20′ is provided with a heat dissipation device 28, 28′, such that the thermal resistance of electrode 20, 20′ measured in longitudinal direction (in distal or proximal direction) is preferably ≥300 W/(m*K). In a preferred embodiment the heat dissipation device 28, 28′ is formed by an overlay 29, 30, 29′ that comprises a higher electrical conductivity and also a higher thermal conductivity compared with the material of the electrode base body 27, 27′.

REFERENCE SIGNS

[0041] 10 instrument [0042] 11 apparatus [0043] 12 gas source [0044] 13 generator [0045] 14 line (for current) [0046] 15 line (for gas) [0047] 16 neutral electrode [0048] 17 distal end of instruments 10 [0049] 18 hose [0050] 19 lumen [0051] 20 electrode [0052] 21 wire [0053] 22 tip [0054] q transverse dimension of electrode 20 [0055] d thickness of electrode 20 [0056] 23, 24 flat sides of electrode 20 [0057] 25, 26 narrow sides of electrode 20 [0058] Q cross-section of electrode 20 [0059] α angle between sections of narrow sides 25, 26 [0060] D distal direction [0061] P proximal direction [0062] λ thermal conductivity [0063] 27 electrode base body [0064] 28 heat dissipation device [0065] 29, 30 coatings [0066] 31 das stream [0067] 32 plasma [0068] 33 root point [0069] 34 wire-shaped electrode section [0070] 35 core [0071] 36 electrode holding section