Plasma probe with improved ignition behavior

Abstract

To provide a plasma probe with improved ignition behavior for forming good plasma discharge.SOLUTION: A plasma probe (10) has a fluid line which is preferably configured as a hose, and an electrode arranged therein, the tip of the electrode being located in the vicinity of an outflow opening. The electrode has a hydrophobic surface area. Additional elements of the plasma probe (10), in particular in the vicinity of the outflow opening, can optionally be equipped with hydrophobic surfaces. Such a probe has significantly improved quickness of ignition and, due to the constancy of the resulting discharge base point, improved stability.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a plasma probe, in particular for plasma coagulation of living tissue. Furthermore, the present invention relates to a plasma probe, in particular for use in an endoscope. [Background technology]

[0002] A plasma probe consisting of a tube made of a bendable material is known from DE 69636399 A1. This tube is guided through the working channel of an endoscope inside the patient's body. The tube comprises an end piece made of a heat-resistant material, such as PTFE or ceramic. Likewise, the tube may also consist of PTFE (polytetrafluoroethylene). An electrode is arranged in the channel surrounded by the tube and the end piece, the tip of which does not protrude from the opening of the tube or the end piece. The electrode is connected to a voltage source. An inert gas, for example argon, flows through the channel surrounded by the tube so that a plasma jet is output from the probe. The regulating unit thereby allows the regulation of the volumetric flow rate of the gas, which can provide at least two different amounts of gas flow. In standby operation, the gas flow is low. In order to ensure that during plasma ignition the fluid that has entered the probe is expelled from the probe, the gas flow is increased during operation. In doing so, it is possible to avoid blood residues accumulating in the tube and causing a risk of infection during a later operation on another patient.

[0003] Another plasma probe consisting of a thin hose with a heat-resistant distal end piece and an electrode arranged in the lumen of the hose is known from DE 10030111 A1. The electrode is in particular formed by sheet metal with a distal tip, the longitudinal edge of which is supported on the inside of the hose.

[0004] A plasma probe with a hose made of PTFE or a similar material is known from EP 0957793. The hose is provided at its distal end with an end piece made of PTFE or ceramic. An electrode is arranged in the hose around which a noble gas flows, which is guided by the hose to form a plasma jet. Here too, the gas flow can be reduced in the standby phase and increased during operation in order to avoid the ingress of body fluids by the probe and the transfer of body fluids to other patients.

[0005] Furthermore, EP 0957793 proposes a plasma probe in which the end piece is made of ceramic. The tubular electrode is directly connected to the proximal end of the hollow shank of the ceramic end piece, so that the inner diameter of the electrode corresponds to the inner diameter of the ceramic end piece. This arrangement is useful for coagulating larger tissue areas.

[0006] In practical operation, the above-mentioned probes sometimes show poor ignition behavior, which means that either particularly high voltages have to be used for the formation of the plasma discharge or the probe has to be brought close to the tissue to be treated. Summary of the Invention [Problem to be solved by the invention]

[0007] Starting from the above, it is an object of the present invention to provide a plasma probe with improved ignition behavior. [Means for solving the problem]

[0008] This object is solved by a plasma probe according to claim 1.

[0009] The plasma probe of the present invention comprises a flexible fluid line, which may be formed by a hose made of a suitable plastic material such as PTFE or another suitable plastic. The fluid line defines at least one channel. Its proximal end may be connected to a gas source. The gas source serves to supply a defined gas flow to the channel that exits an outlet opening formed at the distal end of the fluid line.

[0010] Furthermore, the plasma probe comprises an electrode that can be connected to a power source via an electric wire. The electric wire can be a wire or strand or the like extending through the channel or a conductor guided on or inside the wall of the hose. The power source can be a radio frequency generator, since it is provided in the medical device for the supply of such a probe. The electrode is preferably arranged in the vicinity of the outlet opening. The end of the electrode, which is preferably formed sharp, is preferably arranged so that it does not protrude from the outlet opening. In this way, damage to the living tissue due to the mechanical effect of the electrode can be avoided. Alternatively, the electrode can extend through the outlet opening and carry at its end a round body, which is preferably electrically insulating to avoid damage to the tissue. Such a probe is suitable for an omnidirectional lateral plasma output.

[0011] According to the invention, a hydrophobic surface portion is formed on the electrode. Preferably, the hydrophobic surface portion refers in particular to a portion of the electrode that is near or adjacent to the distal end of the electrode. The surface of the electrode can also be configured to be hydrophobic as a whole.

[0012] The hydrophobic configuration of the electrode's surface significantly improves its firing behavior. If during the introduction of the plasma probe into the endoscope, a liquid, for example a flushing liquid, wets the plasma probe, such liquid tends to enter the open exit opening of the plasma probe. Such droplets can affect the gas flow, creating turbulence and asymmetry in the gas flow and can hinder electron emission at the tip of the electrode. However, if the electrode is water-repellent (hydrophobic), such effects are reduced or avoided.

[0013] The hydrophobic surface of the electrode also prevents biological tissue, tissue fluids or products coming from biological tissue from accumulating on the electrode and modifying its surface conductivity during the operation of the plasma probe. In this way, the movement of the discharge origin, in particular the movement of the discharge origin away from the electrode tip into the channel of the probe, is also prevented. In this way, the otherwise imminent thermal overload of the probe is also avoided. Such excessive thermal distortions would also otherwise result in deformation of the fluid lines, thus significantly hindering the generation of further gas and plasma flows. Also, in the case of the respective probe damage, direct contact between the electrode and the tissue may occur. The consequences of the movement of the discharge origin are largely or completely avoided by the present invention.

[0014] In addition, the water-repellent construction of the electrode, particularly of its surface portion near the tip, provides for increased rapidity of ignition, particularly in adverse, i.e., wet, conditions of use.

[0015] The plasma probe of the invention may comprise a fluid line, which may itself consist of a heat-resistant material or which is provided at its distal end with a heat-resistant end piece through which the channel extends. The end piece may have an inner diameter which corresponds to or is slightly smaller than the inner diameter of the hose. Preferably, the electrode extends at least partially into the end piece such that the origin of discharge is located just before the outlet opening inside the end piece.

[0016] In addition to the hydrophobic surface portion formed on the electrode, additional hydrophobic surface portions can be provided. In doing so, the capillary effect can be avoided. This means, on the one hand, that the liquid can be blown out more easily and that the liquid absorption can be reduced due to the reduced capillary effect. For this purpose, the end piece and / or the hose can comprise hydrophobic surface portions, in particular on the inside adjacent to the channel, but also around the outlet opening if necessary and / or on the outside of the end piece and / or the hose. By these measures, the rapidity and stability of the ignition of the probe can be significantly supported.

[0017] In addition, the electrode can be constructed hollow so that it contains channels through which gas can flow. The electrode can be provided with a hydrophobic surface, particularly near its distal end, or entirely on its exterior. It is also possible to provide a hydrophobic surface on the channel surrounded by the electrode.

[0018] In addition, it is possible to provide flow directing elements made of metal or electrical insulators such as plastic or ceramic to support the electrodes and / or to influence the gas flow in the channel, so that the flow directing elements can be configured to reduce the gas flow in the center of the cross section, i.e. in the vicinity of the electrodes, compared to the peripheral areas of the cross section. This measure also helps to improve the rapidity of ignition. The flow directing elements can also be provided with a hydrophobic surface and can be provided with a hydrophobic surface structure or coating for this purpose.

[0019] In order to configure the desired surface parts hydrophobic, these surface parts can be provided with a hydrophobic coating, for example silicone oil, fluoropolymers such as polytetrafluoroethylene, parylene, PFA (perfluoroalkoxy), polyamide, polyethylene, silicone elastomers, etc. The hydrophobic coating can be applied, for example, by PVD or CVD processes. In addition, or as an alternative, it is possible to achieve a water-repellent effect of the respective surface parts by microstructuring of the surface. For this, each surface part can be provided with a plurality of intersecting finest grooves, which ensure a pattern of small protrusions that direct the liquid droplets away from the groove bottom by their surface so that the liquid can easily drip off.

[0020] Further details of preferred embodiments of the invention are the subject of the dependent claims as well as the drawings of the specification. [Brief description of the drawings]

[0021] [Figure 1] FIG. 1 is a schematic diagram of a medical device having a plasma probe attached thereto. [Diagram 2] 2 is a longitudinal cross-sectional view of the distal end of the plasma probe of FIG. 1. [Figure 3A] 3 is an enlarged longitudinal cross-sectional view of a distal end of an embodiment of an electrode of the plasma probe according to FIG. 2. [Figure 3B] 3 is an enlarged longitudinal cross-sectional view of a distal end of another embodiment of an electrode of the plasma probe according to FIG. 2. [Figure 3C] 3 is an enlarged longitudinal cross-sectional view of a distal end of another embodiment of an electrode of the plasma probe according to FIG. 2. [Figure 3D] 3 is an enlarged longitudinal cross-sectional view of a distal end of another embodiment of an electrode of the plasma probe according to FIG. 2. [Figure 4] FIG. 2 is a longitudinal cross-sectional view of the distal end of a modified embodiment of the plasma probe of the present invention. [Diagram 5] FIG. 2 is a longitudinal cross-sectional view of a distal end of another embodiment of a plasma probe of the present invention. [Figure 6] FIG. 6 is a view of the plasma probe of FIG. 5 as viewed from the distal end. [Figure 7] 13 is a longitudinal cross-sectional view of a distal end of an additional embodiment of a plasma probe of the present invention. FIG. [Figure 8] FIG. 13 is a longitudinal cross-sectional view of a distal end of another additional embodiment of the plasma probe of the present invention. [Figure 9] FIG. 9 is a diagram of the plasma probe according to FIG. 8 showing the flow profile. [Figure 10] FIG. 2 is a longitudinal cross-sectional view of a distal end of one embodiment of a plasma probe of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0022] 1 shows a plasma probe 10 that can be used in a not shown endoscope for carrying out plasma treatments on a patient. For this, the plasma probe 10 is connected to a supply device 11 or to an arrangement of equipment that serves to supply the plasma probe 10 with electric current and an inert gas. For this, the equipment comprises a generator, for example an RF generator 12, configured to output a radio frequency alternating voltage sufficient to ignite and maintain a plasma discharge.

[0023] A gas source 13 supplying a suitable gas, for example argon, serves to supply the inert gas, whereby the gas source 13 is configured to supply the gas in a dosed and controlled manner to provide a suitable volumetric gas flow to the plasma probe 10.

[0024] The plasma probe 10 is connected at its proximal end to an RF generator 12 and a gas source 13, for example via suitable connectors.

[0025] The plasma probe 10 essentially consists of a flexible fluid line 14, for example in the form of a plastic hose. The plasma probe can consist of PTFE or another plastic suitable for medical applications. The fluid line 14 surrounds a channel 14a which leads to an outlet opening 16 provided at the distal end 15 of the hose 14. An electrode 17, for example in the form of a metal pin or wire with a sharp end, is arranged at the distal end 15. The distal end of the electrode 17 is preferably approximately centrally arranged inside the channel 14a so as not to protrude from the outlet opening 16, while the proximal end of the electrode 17 is connected to a suitable electric wire 18 which leads to the generator 12.

[0026] To position the electrode 17 in the channel 14a, a suitable holding device can be provided, for example a plate-shaped holder 19 arranged diametrically in the channel 14a supported on both longitudinal edges of the inner wall of the hose 14. The electrode 17 can be clamped, welded or otherwise connected to the holder 19. It is also possible for the electrode 17 and the holder 19 to be constructed as a single part, for example a diamond-shaped sheet metal part, the tip of which takes the position of the tip 20 of the electrode 17 and the longitudinal edges of which are supported inside the hose 14.

[0027] According to the invention, the electrode 17 comprises at least one hydrophobic surface portion 21. The hydrophobic surface portion preferably surrounds at least the distal end of the electrode 17. The hydrophobic surface portion 21 can in particular cover the cylindrical outer circumferential surface of the electrode 17. FIG. 3A shows a hydrophobic surface portion 21 which can be produced by a water-repellent coating of the electrode 17. The electrode 17, for example made of tungsten or another metal, is provided on its outer circumferential surface with a layer of water-repellent material, for example made of PTFE, silicone oil, etc. However, preferably, the tip 20 or a part thereof remains bare, i.e. uncoated, so that the expression "tip" means that it is generally tapered, for example the conical part of the electrode 17.

[0028] The electrodes 17 can also be provided with a coating that extends into the region of the tip forming the hydrophobic surface portion 21. Thereby, the coating can extend with a thickness that does not decrease up to its end 21a, or it can extend towards its end 21a with a continuous or stepwise decreasing thickness, as shown in FIG. 3C. In addition, each of the above-mentioned electrodes 17 can support an electrically good conducting layer 17a, for example a layer of silver, as shown in FIG. 3D as an example of an electrode according to FIG. 3B. This layer 17a is covered by a coating of the hydrophobic surface portion 21 up to the tip or into the region of the tip 20. The electrodes 17 themselves can consist of stainless steel, steel, tungsten, hard metal or another heat-resistant material.

[0029] The water repellency effect in the hydrophobic surface portion 21 is preferably 20 mJ / m 2 This can be achieved by the low surface energy of the materials used, which is less than 100 nm. Additionally or alternatively, the hydrophobic effect in the surface portion 21 can be achieved by surface microstructuring. For this purpose, the surface portion 21 is formed in such a way that a large number of very small peak-like projections project radially therefrom. For example, this can be achieved in that the surface portion 21 is first provided with a spiral groove and then with an axial groove, for example by means of a laser. Thereby, the length of the remaining projections and their distance from each other are coordinately adjusted, so that a water drop placed at the tip of the projection does not come into contact with the bottom of the groove, a meniscus then being formed between the projections due to the inherent surface tension. Also, other methods for microstructuring or influencing surface roughness can be applied, such as dry etching or application of nanoparticles.

[0030] Tip 20 can be made hydrophobic due to its conical surface and the large curvature of its tip.

[0031] In addition, the holder 19 can have hydrophobic surface portions 22 which completely or partially cover the surface of the holder 19. Here too, the hydrophobic surface portions 22 can be obtained by suitable microstructuring of the surface or by coating said surface with a water-repellent material. The above explanations regarding the electrodes 17 and the hydrophobic surface portions 21 apply accordingly to the structuring of the surface or coating material.

[0032] In addition, the hose 14 can be configured hydrophobic on the inside and / or outside and can have respective hydrophobic surface portions 23, 24. Likewise, the faces can also be made hydrophobic. This hydrophobicity can be achieved by appropriate material selection, for example in that the hose 14 is made of PTFE. The hydrophobic effect of the surfaces can be increased by microstructuring and / or coatings or material selection as explained above.

[0033] The plasma probe 10 described thus far operates as follows.

[0034] During operation, a gas flow having a defined volume, for example an argon flow, flows through the channel 14a. An alternating voltage, for example a high frequency voltage, is applied to the electrode 17. The patient is connected to the neutral electrode. A plasma flow is formed which emanates from the tip 20 and impinges on the tissue.

[0035] During interruptions in operation or before the start of operation, liquids, such as water, body fluids, flushing liquids, etc., may reach the outlet opening 16. However, the hydrophobic surface portions 21 and also 22, 23, 24 prevent the ingress of liquids into the channel 14a or at least the deposition of droplets in the channel 14a and on the electrode 17. Thus, already a very low gas flow is sufficient to free the electrode 17 and the channel 14a from the ingressing liquid. The electrode 17, which thus remains dry, can easily ignite at a large distance to the tissue. The gas flow, which is thereby kept low, aids the rapidity of ignition.

[0036] The same is true during the introduction of the plasma probe 10 into the patient through the endoscope before the start of the procedure, and in this case a liquid may be advanced into the channel 14a which can be flushed from the electrode 17 beforehand with a very low gas flow.

[0037] Numerous modifications can be made to the invention as generally described above.

[0038] FIG. 4 shows a modified plasma probe 10, which, compared to the plasma probe 10 according to FIG. 2, further comprises a ceramic insert 30 in the distal end 15 of the hose 14. This insert 30 comprises an elongated shank 31, configured hollow, which is inserted into the hose 14. The channel 14a extends through the hose 14 and the shank 31 to the outlet opening 16. The tip 20 of the electrode 17 is arranged inside the insert 30, preferably in the vicinity of the outlet opening 16. The shank 31 serves for the distribution and dissipation of heat. The insert 30 can be provided on its outside within the area of ​​its distal end with a hydrophobic surface portion 25. Similarly, the insert can also include a hydrophobic surface portion 26 on the inside of its wall. The water-repellent effect of the surface portions 25, 26 can be achieved by each of the above-mentioned methods by appropriate material selection and / or structuring of the surfaces. Apart from this, the explanations provided with reference to FIGS. 1 and 2 apply accordingly.

[0039] The plasma probe 10 according to FIG. 2 is again shown separately in FIG. 5 and FIG. 6. The holder 19 can be configured as a cooling element and can have one or more recesses at its hose-side edge that minimize the contact surface with the hose. The holder 19 can be made of metal, ceramic material or plastic material or elastomer, for example silicone. As shown in FIG. 6, flow channels 33, 34 are provided on both sides of the holder 19, through which a gas, for example argon, can flow towards the open hose end. FIG. 9 shows the outflow gas flow 35 and the plasma formed therein.

[0040] Again, as shown in Fig. 5, the electrode 17 may comprise a hydrophobic surface portion 21, preferably extending from the tip 20 to the holder 19. The holder 19 may also comprise hydrophobic surface portions 27, 28 on its surface and / or in the flow channels 33, 34. The surface portions 27, 28 may be hydrophobic because the holder 19 itself consists of a hydrophobic material, because it is covered with a hydrophobic material and / or because its surface is microstructured to provide a lotus effect. With regard to the microstructuring, the explanations provided in the context of the electrode 17 apply accordingly. Apart from this, the explanations given above with reference to Figs. 1 to 4 also apply supplementarily to the embodiment according to Figs. 5 and 6.

[0041] A further modified embodiment of the plasma probe 10 is shown in FIG. 7. In this embodiment, firstly the description of the plasma probe 10 according to FIGS. 5 and 6 applies. However, in contrast to the above description, the electrode 17 is hollow and therefore configured without a tip. The electrode surrounds a narrow channel 36. The electrode 17 thus configured as a thin tube is again connected with a wire 18 or another conductor. The distal end of the electrode does not protrude through the outlet opening 16. The electrode 17 carries on its outside, for example, again a hydrophobic coating. The surface portion 21 can be hydrophobic, because the electrode 17 itself consists of a hydrophobic material, because it is coated with a hydrophobic material and / or because its surface is microstructured to provide a lotus effect.

[0042] A further modification of the plasma probe 10 of the invention is evident from Fig. 8. The plasma probe 10 shown there comprises two holders 19a, 19b for supporting an electrode 17 which extend across the lumen of the hose and can be arranged to rotate relative to each other around the electrode 17. Each of the illustrated elements, in particular the electrode 17 as well as one or even both of the holders 19a, 19b, can have a hydrophobic surface and, for this purpose, can consist of a hydrophobic material or be configured in a hydrophobic manner by coating or surface structuring with a hydrophobic material.

[0043] The electrode 17 is not necessarily in a retracted position behind the exit opening 16 in the channel 14a. As is evident from the plasma probe 10 according to FIG. 10, it is also possible for the electrode 17 to extend outside the exit opening 16. In this case, the electrode 17 is preferably provided with a round, preferably insulating body 37, for example a ceramic ball, which avoids direct galvanic contact between the electrode 17 and the surrounding biological tissue as well as mechanical damage of the tissue by the electrode 17. The electrode 17 can be supported by a holder 19 as shown in FIG. 10 or by a number of holders similar to FIG. 8. The electrode 17 can have a tip 38 as a discharge base point, which is arranged in front of the exit opening 16 and extends radially away from the electrode 17. The electrode 17 can again include a hydrophobic surface portion 21. A further hydrophobic surface portion 29 can be formed on the insulator 37, which can completely or partially cover the insulator. Surface portion 29 may be hydrophobic because insulator 37 itself consists of a hydrophobic material, because it is coated with a hydrophobic material and / or because its surface is microstructured to provide a lotus effect. Apart from this, the above explanations apply accordingly, particularly with regard to the configuration of hydrophobic surface portions 21 to 27.

[0044] In all the embodiments according to figures 5 to 10, a hollow cylindrical insert for thermal protection of the hose 14 can be inserted into the distal end 15 of the hose 14. The inner diameter of this insert can correspond to the inner diameter of the channel 14a or can also be slightly smaller than said inner diameter. The insert can be hydrophobic, in particular on its inner wall and / or on at least one of its faces. For this, the insert itself can consist of a hydrophobic material, can be coated with a hydrophobic material and / or can be microstructured on the surface to provide a lotus effect.

[0045] The plasma probe 10 according to the invention comprises a fluid line 14, preferably configured as a hose, and an electrode 17 arranged therein, the tip 20 of which is arranged in the vicinity of the outlet opening 16. The electrode 17 comprises a surface portion 21 configured to be hydrophobic. Optionally, additional elements of the plasma probe 10, in particular in the vicinity of the outlet opening 16, can be provided with a hydrophobic surface. Such a probe has a significantly improved rapidity of ignition and an improved stability due to the resulting durability of the discharge origin. [Explanation of symbols]

[0046] 10 Plasma Probe 11 Equipment 12 RF Generator 13 Gas Source 14 Fluid lines (plastic hoses) Channel 14a 15 Distal end of fluid line 16 Outlet opening 17 electrodes 18 lines 19 Holder 20 Tip of electrode 17 21-29 Hydrophobic surface part 21a End of hydrophobic surface portion 30 Insert 31 Shank 32 Recess 33 Flow Channel 34a Flow Channel 35 Gas Flow 36 Channels 37 Insulators 38 Tip

Claims

1. A plasma probe (10) for plasma coagulation of living tissue, comprising: a fluid line (14) defining at least one channel (14a) connectable to a gas source (13), said channel (14a) running to a distal end (15) of said fluid line (14) and terminating in an outlet opening (16) of said distal end (15); an electrode (17) adjacent said outlet opening (16) connected to a power source (12) via a wire (18); The electrode (17) is disposed within the channel (14a) through which gas flows; A plasma probe, characterized in that a hydrophobic surface portion (21) is formed on said electrode (17) near or adjacent to a distal end of said electrode (17).

2. 2. The plasma probe of claim 1, wherein the fluid line (14) is a flexible hose made of an electrically insulating material, and wherein an electrically insulating, heat resistant end piece (30) is carried within the distal end (15) of the fluid line (14) and through which the channel (14a) extends.

3. The plasma probe of claim 2, characterized in that the electrode (17) is at least partially disposed inside the end piece (30).

4. 4. The plasma probe according to claim 2 or 3, characterized in that a hydrophobic surface portion (26) is further formed on the end piece (30) and / or on the hose (14).

5. A plasma probe according to any one of claims 1 to 4, characterized in that the electrode (17) is hollow and comprises a hydrophobic surface portion (21) on the outside of the electrode (17).

6. 6. The plasma probe of claim 1, further comprising a holder (19) disposed on or within the distal end (15), the holder (19) being connected to the electrode (17) and fixing the electrode (17) within the fluid line (14).

7. A plasma probe according to claim 6, characterized in that, in addition, hydrophobic surface portions (27, 28) are formed on the holder (19).

8. A plasma probe according to any one of the preceding claims, characterized in that the hydrophobic surface portion (21) defines a wetting contact angle (α) with water of greater than 90°.

9. The surface energy of the hydrophobic surface portion (21) is 20 mJ / m ２ A plasma probe according to any one of claims 1 to 8, characterized in that it is less than

10. A plasma probe according to any one of the preceding claims, characterized in that the hydrophobic surface portion (21) is formed by a hydrophobic material.

11. 7. The plasma probe according to claim 6, characterized in that the holder (19) comprises at least two channels (33, 34) extending along the electrode (17).

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