ELECTRODE ARRANGEMENT

Abstract

An electrode for an argon plasma surgical instrument. The electrode has a heat dissipation device in the form of a single- or multi-layer coating. The coating may have a greater electrical conductivity and also a greater thermal conductivity than that of the material of the electrode main body. The coating may also have a melting temperature less than that of the material of the electrode main body. The melting temperature of the coating may be below 1100° C. If the coating is multi-layered, the melting temperature of the outer surface layer may also be below 1100° C., and preferably below 1000° C.

Claims

1. An electrode for plasma coagulation electrosurgical instrument, the electrode comprising: a tip orientated in distal direction, wherein the electrode has a cross-section that increases in a proximal direction from the tip, the increase in cross-section being continuous or in at least one step, wherein the electrode comprises a material combination, the thermal conductivity of which is greater than 20 W/(m*K), and wherein the electrode further comprises an electrode base body having a thermally conductive overlay.

2. The electrode according to claim 1, wherein the electrode has a maximum transverse dimension and a radius of curvature at its tip that is less than one tenth of the maximum transverse dimension.

3. The electrode according to claim 1, wherein the electrode is configured in a wire-shaped manner or as platelet that comprises two flat sides that are connected with one another by means of narrow sides.

4. The electrode according to claim 3, wherein the electrode comprises at least one flat side and wherein the thermally conductive overlay comprises a layer configured to cover the entire flat side.

5. The electrode according to claim 1, wherein the overlay comprises a thermally conductive material, and wherein the overlay comprises a thermal and/or electrical conductivity that is respectively greater than the thermal and/or electrical conductivity of the base body.

6. The electrode according to claim 1, wherein the overlay extends up to a section configured for direct contact with a spark originating from the electrode.

7. The electrode according to claim 1, wherein the overlay consists of a metal or a metal alloy, the melting temperature of which is less than the melting temperature of the material of the base body.

8. The electrode according to claim 1, wherein the overlay comprises an intermediate layer that is in direct contact with the electrode base body and a surface layer, the surface layer being arranged on the intermediate layer.

9. The electrode according to claim 8, wherein the surface layer comprises a metal or a metal alloy having a melting temperature T.sub.O less than the melting temperature of the intermediate layer that in turn is less than the melting temperature of the material of the electrode base body.

10. The electrode according to claim 8, wherein the surface layer comprises a metal or a metal alloy having a thermal conductivity greater than the thermal conductivity of the intermediate layer that in turn is greater than the thermal conductivity of the material of the electrode base body.

11. The electrode according to claim 1, wherein the overlay comprises a cross-section area and the electrode base body comprises a cross-section area, and wherein the ratio between the cross-section area of the overlay to the cross-section area of the electrode base body is greater than 0.12.

12. The electrode according to claim 1, wherein the electrode further comprises a section extending at least 2.5 mm from the tip in proximal direction, the thermal capacity of the section being less than than 4.17 mJ/K.

13. The electrode according to claim 1, wherein the electrode comprises a volume and the overlay comprises a surface area, and wherein the ratio of the surface area of the overlay to the volume is greater than 2.24 mm.sup.−1.

14. An instrument having an electrode according to claim 1.

15. The instrument according to claim 14, further comprising a tube or hose surrounding a lumen that is open at a distal end of the tube or hose and configured to connect to an argon gas source, wherein the electrode is arranged in the lumen and configured to connect to a generator.

16. The electrode according to claim 5, wherein the thermally conductive material comprises a metal or a metal alloy.

Description

[0023] In the drawings embodiments of the invention are illustrated. The drawings show:

[0024] FIG. 1 an inventive instrument, the assigned supplying apparatus and a neutral electrode in very schematic partly perspective illustration,

[0025] FIG. 2 the distal end of the instrument according to FIG. 1 in perspective schematic longitudinal-section illustration,

[0026] FIG. 3 the electrode of the instrument according to FIG. 2 in side view,

[0027] FIGS. 4, 5 and 6 different cross-sections of the electrode according to FIG. 3,

[0028] FIG. 7 the instrument according to FIGS. 2-6 in a sectional perspective illustration during operation,

[0029] FIG. 8 a modified embodiment of an electrode for the instrument according to FIG. 2,

[0030] FIGS. 9 and 10 a further embodiment of an electrode for an instrument according to FIG. 2.

[0031] 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.

[0032] 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.

[0033] 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.

[0034] 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.

[0035] 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.

[0036] 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.

[0037] 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°.

[0038] 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.

[0039] In a preferred embodiment of the invention electrode 20 comprises a multiple layer configuration, as apparent from FIGS. 4, 5 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.

[0040] The instrument described so far operates as follows:

[0041] 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, for example, less than 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 can 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 in a substantially reduced material removal and in a highly reduced heat radiation therefrom. Preferably the thickness of the overlays—consisting e.g. of silver—has an amount of 20 μm, 30 μm or 50 μm. Preferably the overlay has a thermal conductivity of more than 400 W/(m*K). For example, the thickness of the electrode can be 0.1 mm. Also the thermal conductivity of the entire electrode preferably exceeds 400 W/(m*K). The electrode 20 consisting of the material combination stainless steel/silver thereby comprises a phenomenal lifetime.

[0042] 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.

[0043] The electrode 20′ comprises a tip 22′ that can be formed here by the pointed or blunt end of a wire-shaped straight or corrugated 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 diameter of the wire-shaped electrode section is preferably smaller than 0.5 mm and has an amount of, e.g. 0.3 mm. 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. At the transition location from the wire-shaped electrode section to the electrode holding platelet 36, the cross-section of the electrode increases in a stepwise manner.

[0044] The electrode 20 can also be configured according to FIGS. 9 and 10 and can comprise in the cross-section circular-shaped sections with axial distance having different diameters.

[0045] In all electrodes 20, 20′ it applies independent from the geometric shape and independent therefrom whether the electrode cross-section increases in proximal direction continuously or in steps or whether it remains constant or decreases locally that the overlay 29, 29′, 30 remarkably increases the lifetime of electrode 20, 20′ and instrument 10. Thereby it is particularly advantageous, if the overlay 29, 29′, 30 extends starting from tip 22 at least approximately 5 mm to 10 mm or also approximately 10 to 20 mm in proximal direction. Preferably the overlay 29, 29′, 30 consists of a metal, e.g. silver, the melting temperature T.sub.U is lower than the melting temperature T.sub.G of the base material, e.g. stainless steel. Also the overlay 29, 29′, 30 preferably comprises a thermal conductivity λ.sub.u that is higher than the thermal conductivity λ.sub.G of the base material.

[0046] Moreover, the overlay 29, 29′, 30 can consist of an adhesion influencing intermediate layer 37 arranged in direct contact to the base body 27 and a surface layer 38 arranged on the intermediate layer 37. The surface layer 38 consists preferably of a metal, the melting temperature T.sub.O is lower than or is approximately as high as the melting temperature T.sub.Z of the intermediate layer that in turn is, however, lower than the melting temperature T.sub.G of the material of the electrode base body 27. In addition the surface layer 38 consists preferably of a material, the thermal conductivity λ.sub.O is minimum as high as the thermal conductivity λ.sub.Z of the intermediate layer 37. The thermal conductivity λ.sub.Z of the intermediate layer 37 is preferably higher than the thermal conductivity λ.sub.G of the material of the electrode base body 27.

[0047] In all of the electrodes 20, 20′ described previously it also applies that the cross-section surface Au of the overlay 29, 29′, 30 comprises at least at the tip 22 (up to approximately 2.5 mm in proximal direction) at least 10-12% of the cross-section area A.sub.G of the electrode base body. In addition the electrode 20, 20′ comprises a section originating from its tip 22 extending in proximal direction along at least 2.5 mm, the thermal capacity of which is lower than 4.17 mJ/K. The electrode 20, 20′ comprises a volume V.sub.E that is preferably in a defined ratio to the area of the surface A.sub.UO of the overlay 29, 29′, 30. Preferably the ratio of the surface area A.sub.UO to the volume V.sub.E is larger than 2.24 mm.sup.−1.

[0048] In operation of instrument 10 with an electrode 20′ according to FIG. 8, 9 or 10 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. The surface layer 38 and potentially also the intermediate layer 37 can melt and can retract slightly from the tip 22 in proximal direction. The discharge root point 33 remains stationary at the tip 22 (and the section directly adjoining thereto, approximately 2.5 mm). This mitigates the thermal stress of electrode 20, 20′ as well as instrument 10.

[0049] In an improved instrument 10 the electrode 20, 20′ is provided with a heat dissipation device 28, 28′ in the form of a single layer or multiple layer overlay 29, 29′, 30. It comprises preferably a higher electrical conductivity, as well as a higher thermal conductivity compared with the material of the electrode base body 27, 27′. In addition, it preferably comprises a lower melting temperature than the material of the electrode base body 27. The melting temperature T.sub.U of the overlay is preferably below 1100° C. If the overlay 29, 29′, 30 is multi-layered, the melting temperature T.sub.O of the outer surface layer 38 is preferably also below 1100° C., further preferably below 1000° C.

REFERENCE SIGNS

[0050] 10 instrument [0051] 11 apparatus [0052] 12 gas source [0053] 13 generator [0054] 14 line (for current) [0055] 15 line (for gas) [0056] 16 neutral electrode [0057] 17 distal end of instrument 10 [0058] 18 hose [0059] 19 lumen [0060] 20 electrode [0061] 21 wire [0062] 22 tip [0063] q transverse dimension of electrode 20 [0064] d thickness of electrode 20 [0065] 23, 24 flat sides of electrode 20 [0066] 25, 26 narrow sides of electrode 20 [0067] Q cross-section of electrode 20 [0068] a angle between parts of narrow sides 25, 26 [0069] D distal direction [0070] P proximal direction [0071] λ thermal conductivity [0072] λ.sub.U thermal conductivity of overlay 29, 29′, 30 [0073] λ.sub.Z thermal conductivity of intermediate layer 37 [0074] λ.sub.G thermal conductivity of base body 27 [0075] λ.sub.O thermal conductivity of surface layer 38 [0076] 27 electrode base body [0077] 28 heat dissipation device [0078] 29, 29′, 30 overlays [0079] 31 gas stream [0080] 32 plasma [0081] 33 root point [0082] 34 wire-shaped electrode section [0083] 35 core [0084] 36 electrode holding section [0085] 37 intermediate layer [0086] 38 surface layer [0087] T.sub.U melting temperature of overlay 29, 29′, 30 [0088] T.sub.G melting temperature of electrode base body 27 [0089] T.sub.O melting temperature of surface layer 38 [0090] T.sub.Z melting temperature of intermediate layer 37