ELECTRODE ARRANGEMENT

Description

[0001] The invention relates to an electrode arrangement for an electrosurgical instrument, in particular for an instrument for plasma coagulation of biological tissue.

[0002] Instruments for tissue coagulation are known from various publications and from practical experience. Reference is made to DE 10 2011 116 678 A1 and DE 699 28 370 T2. Both publications disclose instruments with electrodes that are, for example, ring-shaped and made of a suitable material, such as tungsten, which is characterized by its heat resistance.

[0003] Furthermore, DE 100 30 111 A1 discloses a plasma coagulation instrument with a tube-like instrument body in whose lumen a hexagonal electrode made of metal is arranged. This electrode is connected to an electrical lead to supply the electrode located at the distal end of the tube with RF voltage. An electrical discharge emanates from the tip formed at the distal end of the plate-shaped electrode, thereby generating a plasma current, in particular a noble gas plasma current. The gas flow surrounding the electrode simultaneously serves to dissipate heat from the electrode, thus preventing excessive heating. This heat dissipation is also intended to minimize wear at the discharge section of the electrode and thereby increase the instrument's service life.A similar instrument is described in DE 10 2017 127 976 A1, which features a hollow cylindrical electrode holder with a wall diametrically traversing the central passage. A tungsten electrode is mounted centrally in the wall. To reduce heat transfer to the wall, a notch is provided in the electrode between the wall and the tip, thus reducing the cross-section available for heat transfer.

[0004] However, efficient cooling of the electrode plate by the gas flow requires a high gas flow, which is not always desirable.

[0005] Furthermore, WO 2005 / 046495 A1 discloses the use of an ignition electrode made of a tungsten wire, the end of which is positioned at the distal end of an otherwise tubular or tube-shaped instrument body. The tungsten wire, located within the lumen of this body, is held at a certain distance from its distal end by a plate to which it is attached and which serves to cool it. However, heat dissipation from the tungsten wire is hindered by the interface between the plate and the tungsten wire.

[0006] Electrode erosion can cause particles, particularly metal particles, to enter the spark and / or plasma stream, and thus ultimately living tissue, which is increasingly undesirable. Therefore, the object of the invention is to provide a concept for reducing material loss from the electrode used in an electrosurgical instrument during operation.

[0007] This problem is solved with the electrode arrangement according to claim 1:

[0008] The electrode arrangement according to the invention comprises an electrode with a distally oriented tip. The electrode cross-section increases in the proximal direction away from the tip. In conjunction with the further feature that the electrode consists of a material or material combination with a thermal conductivity greater than 20 W / (m*K), a significantly reduced electrode erosion can be achieved.

[0009] The electrode cross-section can increase in steps or continuously from the distal tip until the electrode touches the wall of the lumen in which it is located. If the cross-sectional increase from the tip to a proximal part of the electrode occurs in steps, one or more steps may be provided. The tip of the electrode (and the flank region of the electrode adjacent to the tip) is the point from which a spark or plasma current typically originates. The tip and the immediately adjacent part of the electrode thus form the area where the discharge point of the electrical discharge is located. At this discharge point, a current concentration occurs, which simultaneously constitutes a heat source.Both measures—namely, increasing the cross-sectional area of ​​the electrode in the proximal direction and using a material or material combination for the electrode with a thermal conductivity greater than 20 W / (m*K)—dissipate heat generated at the electrode base far more effectively than was previously the case when using stainless steel electrodes of the same design. The electrode according to the invention is thus characterized in particular by the fact that its thermal conductivity from the tip, measured in the proximal direction and / or measured perpendicular to the proximal direction, is greater than the thermal conductivity of stainless steel. Preferably, the thermal conductivity λ of the electrode is greater than 27 W / (m*K), more preferably greater than 50 W / (m*K), greater than 100 W / (m*K), greater than 200 W / (m*K), greater than 300 W / (m*K), and particularly greater than 400 W / (m*K).

[0010] The combination of an electrode geometry in which the electrode cross-section increases from the tip in a proximal direction, and where the electrode is made of a highly thermally conductive material or a combination of such materials, enables the use of a tip with a particularly small radius of curvature, which can be less than 1 / 10 of the maximum transverse dimension of the electrode. This results in a high field strength at the electrode tip, which can lead to the formation of a spark and a plasma even at low RF voltages and currents. The electrode is then particularly prone to ignition.

[0011] The electrode is plate-shaped, with the increased cross-sectional area achieved by a lateral dimension that increases along the axial direction in a proximal direction away from the tip. This lateral dimension can increase continuously, resulting in particularly good heat dissipation. The continuous increase in cross-sectional area and lateral dimension is achieved by seamlessly integrated edges extending from the electrode tip.

[0012] The electrode is designed as a plate with two flat sides connected by narrow sides. Edges may be formed between the narrow sides and the flat sides. Such an electrode can, for example, be supplied as a sheet metal blank.

[0013] Suitable electrode materials include metals with high thermal conductivity, such as silver, copper, tungsten, hard metal (e.g., tungsten carbide sinter), or similar materials. The high thermal conductivity prevents heat buildup at the electrode tip and facilitates heat dissipation throughout the entire electrode body, thus also facilitating heat transfer to the gas flow. This means that a relatively small gas flow is sufficient to cool the electrode.

[0014] According to the invention, the electrode consists of a material combination formed by a base body having at least one surface to which a heat dissipation device is attached. The heat dissipation device extends distally, preferably to the tip of the electrode, at least to an area occupied by the discharge point during operation. The heat generated there can thus be transferred directly to the heat dissipation device without the need for heat transfer from the electrode to the heat dissipation device. In other words, the heat dissipation device is in direct contact with the heat source, here in the form of the discharge point. In the proximal direction, the heat dissipation device preferably extends at least to an area of ​​the electrode where it has its maximum transverse dimension.

[0015] In the simplest case, the electrode consists of a base material onto which a thermally conductive coating is applied as a heat dissipation device. This layer preferably extends to the tip of the electrode and over large portions of the flat sides or over the entire flat sides of the electrode. The coating can also extend over the narrow sides of the electrode. If the electrode is made of, for example, stainless steel or another material with lower thermal conductivity, the heat dissipation device is made of a particularly highly thermally conductive material, such as silver, carbon-like diamond (CLD), or the like.Preferably, the heat dissipation device is made of a metallic material that is also electrically conductive, so that the heat dissipation device, for example in the form of a heat-dissipating layer, contributes to electrical conductivity and can come into direct contact with the discharge point. Preferably, the heat dissipation device, which is designed, for example, as a thermally conductive coating, is also particularly good at conducting electricity. It is especially advantageous if the electrical conductivity of the coating is greater than the electrical conductivity of the base material.

[0016] In a particularly preferred embodiment, the heat dissipation device thus has an electrical conductivity and, in particular, also a thermal conductivity that is greater than the electrical and thermal conductivity of the base body.

[0017] When the electrode is subjected to high-frequency alternating voltage, the current flow can concentrate on the highly conductive coating, with low ohmic losses due to the high surface conductivity. This reduces heat generation at the electrode caused by ohmic losses. The reduction in heat generation significantly contributes to extending the electrode's service life and minimizing material loss.

[0018] The drawing illustrates exemplary embodiments of the invention. It shows: Figure 1 an instrument according to the invention, the associated power supply device and a neutral electrode, in a highly schematic, partly perspective representation, Figure 2 the distal end of the instrument according to Figure 1, in a perspective schematic longitudinal section view, Figure 3 the electrode of the instrument after Figure 2 , in side view, Figures 4, 5 and 6different cross-sections of the electrode according to Figure 3 , Figure 7 the instrument after the Figures 2 to 6 , in a cropped perspective view during operation, Figure 8 a modified embodiment of an electrode for an instrument according to Figure 2 .

[0019] In Figure 1 Figure 10 illustrates an instrument used for plasma-assisted tissue treatment. Tissue treatment can include ablation, coagulation, cutting, or other treatment methods.

[0020] The instrument 10 is connected to a device 11, which contains a gas source 12, for example, an argon source, and a generator 13 for supplying electrical power to the instrument 10. This generator is connected via appropriate connectors to a line 14 leading to the instrument 10, which is inserted into a line 15 through which the instrument 10 is supplied with gas. The generator 13 is also connected via appropriate connectors to a neutral electrode 16, which must be attached to the patient before using the instrument 10. The following description also applies to instruments with other neutral electrode configurations.

[0021] The instrument 10 has a distal end 17, which is separately in Figure 2This is illustrated. As can be seen, the instrument 10 includes a tube or hose 18 that surrounds a lumen 19, which is open at the distal end 17 of the hose 18. In the region of the distal end 17, the hose 18 may have an internal or external reinforcement, for example in the form of a ceramic sleeve, which is shown in Figure 2 The details are not shown. The tube 18 can therefore be single- or multi-layered. Examples of instruments with a ceramic sleeve inserted into the open end of the tube 18 can be found in WO 2005 / 046495 A1.

[0022] An electrode 20 is arranged in the lumen 19 and is electrically connected to a wire 21 belonging to the conductor 14, which extends through the lumen 19. The wire 21 can be welded to the electrode 20 or mechanically connected, for example by crimping.

[0023] The electrode 20 preferably has the following features: Figure 3The illustrated basic shape is shown. At its distal end, a sharp or at most slightly rounded tip 22 is formed on the electrode 20, the radius of curvature R ( Figure 2 ) is as small as possible and preferably less than one-tenth of the transverse dimension q, which is to be measured transversely to the axial direction and largely corresponds to the inner diameter of the lumen 19. The electrode 20 is preferably plate-shaped, i.e., its thickness is significantly less than its transverse dimension q. This results, for example, from Figure 4 , which define the cross-section of electrode 20 at the in Figure 3 The section line IV-IV is shown with a dashed line. The thickness d is less than 1 / 5, preferably less than 1 / 10, of the transverse dimension q.

[0024] What's next? Figure 4As can be seen, the electrode 20 has two flat sides 23, 24, which are connected by narrow sides 25, 26. This results in an overall quadrilateral, preferably rectangular, cross-section Q, which is bounded by the flat sides 23, 24 and the narrow sides 25, 26. The quadrilateral cross-section can also be bent once or several times, e.g., in an S-shape.

[0025] The electrode 20 has a tapered section at its distal end in which the otherwise parallel narrow sides 25, 26 are arranged convergently towards the tip 22. The convergent sections of the narrow sides 25, 26 can be, as Figure 3 They can be straight, convex, or concave. They define an angle α between each other, preferably in the range of 20° to 100°.

[0026] As cross-sections VV and VI-VI show, which are shown separately in the Figures 5 and 6As shown, the cross-section of the electrode 20 decreases towards the tip 22 in the distal direction D, or in other words, increases in the proximal direction P. The thickness d of the electrode 20 in the tapering region towards the tip 22 can be described as follows: Figures 5 and 6 The thickness d can, however, decrease towards the tip 22. In any case, the transverse dimension Q decreases in the tapered region towards the tip 22.

[0027] In a first embodiment, the electrode 20 consists entirely of a material with good thermal conductivity, such as tungsten, a hard metal, copper, aluminum, or a combination of these materials. Metals and non-metallic electrically conductive materials such as DLC or combinations of metals and such materials can be used. In any case, the material used has a thermal conductivity λ that is greater, preferably significantly greater, than the thermal conductivity of stainless steel. In particular, λ is ≥ 50 W / (m*K), ≥ 100 W / (m*K), ≥ 200 W / (m*K), ≥ 300 W / (m*K), ≥ 400 W / (m*K).

[0028] In a preferred embodiment, the electrode 20 has a multilayer structure, as shown in the Figures 4 and 6The electrode 20 has an electrode base body 27, which is connected to a heat dissipation device 28 at least on its flat sides 23, 24, but optionally also on its narrow sides 25, 26. In the present embodiment, this heat dissipation device consists of a full-surface coating of the flat sides of the electrode base body 27 with thermally conductive coatings 29, 30. In this embodiment, the base body 27 can be made of stainless steel, while the coatings 29, 30 are made of another material with better thermal conductivity and / or better electrical conductivity. Silver has proven to be particularly suitable for this purpose. Other possible coatings include aluminum and / or copper and / or hard metal and / or DLC and / or tungsten and / or a layer, e.g., a metal layer with embedded CBN (cubic boron nitride), diamond powder, or a similarly well-conducting material.

[0029] The instrument described so far works as follows: As in Figure 7As illustrated, the lumen 19 of the instrument 10 is traversed by a gas stream 31 originating from the gas source 12. This gas stream (preferably an argon stream) flows along both flat sides 23, 24 of the electrode 20. The electrode 20 is simultaneously supplied with a high-frequency electric current via the wire 21. The operating frequency of the generator 13, and thus the frequency of the current, is preferably above 100 kHz, more preferably above 300 kHz, and more preferably above 500 kHz. At the tip 22 and an adjacent region thereof, the current exits the electrode 20 and forms a spark or plasma 32 that jumps to the patient's biological tissue (not further illustrated).The base 33 of the spark or plasma touches the narrow sides 25, 26, and especially the flat sides 23, 24 of the electrode 20, with this base region 33 occupying at least 1 / 10 of the axial (measured in the proximal direction) length of that region of the electrode 20 in which the narrow sides 25, 26 diverge from the tip 22. The coatings 29, 30 extend into this region and preferably to the tip 22. Thus, the spark or plasma current is electrically powered directly by the coating 29, 30. The thickness of the coatings 29, 30 can be relatively small. It has been shown that coatings with a thickness of 10 to 20 µm already lead to a significant increase in the service life of the electrode 20 and to a significantly reduced material removal from it. Preferably, the thickness of the coatings, which for example consist of silver, is 20 µm, 30 µm or 50 µm, which, with an electrode thickness of, for example,A thickness of 0.1 mm results in a thermal resistance of over 400 W / (m*K). The electrode 20, made of a stainless steel / silver material combination, therefore exhibits an exceptionally long service life.

[0030] In a modified embodiment, it is also possible to increase the electrode cross-section not continuously in the proximal direction, but abruptly, i.e., in one or more stages, unlike in the embodiments described above. Such an embodiment is described in Figure 8 illustrated. However, this embodiment also realizes the concept according to the invention, which is why, when describing this electrode 20', reference is made to the description of the embodiment according to Figures 1 to 7 Reference is made to the existing reference numerals. These are continued, each distinguished by an apostrophe. The foregoing description applies accordingly to the embodiment according to the following, with the exception of the following special features. Figure 8 .

[0031] The electrode 20' has a tip 22', which can be formed here by the pointed or blunt end of a wire-shaped electrode section. This wire-shaped electrode section 34 contains a core 35, which forms the base body 27' and can itself be designed as a thin cylindrical pin. The core 35 is provided with a coating 29', which, optionally in conjunction with an electrode holder 36, forms the heat dissipation device 28'. The electrode section 34 can be welded, crimped, or otherwise connected to the electrode holder 36. A metallurgical bond is preferred because of the improved heat transfer. The electrode holder 36 can be made of stainless steel or another material provided with a thermally conductive coating, such as tungsten, copper, aluminum, DLC, or the like, or formed from a thermally conductive material, such as tungsten, copper, aluminum, DLC, or the like.

[0032] In operation of an instrument 10 with an electrode 20' after Figure 8 An electrical discharge, and thus the resulting spark or plasma current, originates first from the tip 22 and then from at least a portion of the wire-shaped electrode section 34. The electrically and thermally conductive coating 29', which is preferably a silver coating, significantly reduces the electrical resistance of the electrode 20 or 20'. The high-frequency alternating current from the generator 13 concentrates in the outer layers of the electrode 20, 20' and thus flows essentially through the coating 29, 30, 29'. This minimizes the ohmic losses at the electrode 20, 20', and, moreover, the reduced amount of heat is conducted away from the discharge base much more effectively by the coating 29, 30 and distributed so that it can be transferred over a large area of ​​the gas flow.

[0033] In an improved instrument 10, the electrode 20, 20' is provided with a heat dissipation device 28, 28' such that the thermal resistance of the electrode 20, 20', measured in the longitudinal direction (in the distal or proximal direction), is preferably ≥ 300 W / (m*K). In a preferred embodiment, the heat dissipation device 28, 28' is formed by a coating 29, 30, 29' which has a higher electrical conductivity as well as a higher thermal conductivity compared to the material of the electrode base body 27, 27'. Reference symbol:

[0034] 10 Instrument 11 Device 12 Gas source 13 Generator 14 Line (for current) 15 Line (for gas) 16 Neutral electrode 17 Distal end of instrument 10 18 Hose 19 Lumen 20 Electrode 21 Wire 22 Tip q Electrode cross-sectional dimension 20 d Electrode thickness 20 23, 24 Flat sides of electrode 20 25, 26 Narrow sides of electrode 20 Q Electrode cross-section 20 α Angle between sections of narrow sides 25, 26 D Distal direction P Proximal direction λ Thermal conductivity 27 Electrode body 28 Heat dissipation device 29, 30 Coatings 31 Gas flow 32 Plasma 33 Base point 34 Wire-shaped electrode section 35 Core 36 Electrode holding section

Claims

1. Electrode arrangement for an electrosurgical instrument (10), particularly for plasma coagulation, having an electrode (20, 20') that comprises a tip (22) orientated in distal direction, starting therefrom the electrode cross-section (Q) is configured to increase in proximal direction (P) by a transverse dimension (q) that increases from the tip (22) in proximal direction, wherein the electrode (20, 20') consists of a base body (27, 27') an a thermally conductive overlay (29, 30) provided on a surface of the base body, wherein the electrode (20, 20') consists of a material combination having a thermal conductivity (λ) that is larger than 20 W / (m*K), wherein the electrode (20, 20') is configured as platelet that comprises two flat sides (23, 24) that are connected with each other by narrow sides (25, 26), wherein edges are formed between the narrow sides (25, 26) and the flat sides (23, 24).

2. Electrode arrangement according to claim 1, wherein the electrode (20, 20') has a maximum transverse dimension (q) and a radius of curvature (R) at its tip (22) that is smaller than 1 / 10 of the maximum transverse dimension (q).

3. Electrode arrangement according to claim 1, wherein the transverse dimension (q) is configured to continuously increase in proximal direction starting from the tip (22).

4. Electrode arrangement according to any of the preceding claims, wherein the electrode (20) comprises stepless configured edges starting from the tip (22).

5. Electrode arrangement according to any of the preceding claims, wherein the electrode (20) comprises at least one flat side (23, 24) and wherein the overlay is configured to cover the entire flat side (23, 24).

6. Electrode arrangement according to any of the preceding claims, wherein the overlay is made of a metallic material.

7. Electrode arrangement according to any of the preceding claims, wherein the overlay is made of a non-metallic material.

8. Electrode arrangement according to any of the preceding claims, wherein the overlay is configured and arranged to extend up to an area (33) that is provided for direct contact with a spark originating from the electrode (20, 20').

9. Electrode arrangement according to any of the preceding claims, wherein the overlay comprises an electrical conductivity that is larger than the electrical conductivity of the base body (27, 27').

10. Electrode arrangement according to any of the preceding claims, wherein the overlay has a thermal conductivity that is larger than the thermal conductivity of the base body (27, 27').