Tumor ablation soft antenna for nanoknife

Abstract

The application discloses a tumor ablation soft antenna for a nanometer knife, which comprises a handle and an elongated antenna soft body, the rear end of the antenna soft body is connected with the handle, the antenna soft body is flexible and can be bent and deformed, at least two spaced electrodes are arranged at the front end of the antenna soft body, the antenna soft body is internally provided with electrode channels with the same number as the electrodes, each electrode channel is arranged along the axial direction of the antenna soft body, and each electrode channel is independently separated, an electrode wire is arranged in each electrode channel, an insulating sleeve is arranged on the outer side of the electrode wire for insulation, both ends of the electrode wire are exposed from the insulating sleeve, one end of the electrode wire is electrically connected with a corresponding electrode, the other end of the electrode wire is inserted into the handle and is electrically connected with the handle, each electrode wire is arranged in an independent electrode channel, so that interference between the electrode wires is avoided, and the antenna soft body can reach a tumor position to be ablated through a human body pipeline such as an intestinal tract, a trachea, a blood vessel and the like.

Description

Technical Field

[0001] This invention relates to a tumor ablation soft antenna, and more particularly to a tumor ablation soft antenna for use with NanoKnife. Background Technology

[0002] Tumor ablation therapy is a new type of precise minimally invasive surgery that uses image guidance to precisely puncture the tumor target area with energy such as radiofrequency, microwave, cryotherapy, laser, and electric field to perform precise ablation and in situ inactivation of the tumor.

[0003] Physical ablation of tumors destroys tumor cells by heating or freezing the tumor tissue. Currently, widely used physical ablation techniques include argon-helium cryoablation, radiofrequency ablation, microwave ablation, and laser ablation. While these techniques are effective, their main drawback is the non-selective nature of tissue destruction; that is, within the ablation zone, normal tissues and organs such as blood vessels, nerves, bile ducts, and pancreatic ducts are completely destroyed, in addition to the tumor tissue. This drawback is a major cause of post-ablation complications, such as post-ablation hemorrhage, biliary system injury, intestinal perforation, and neurological dysfunction. Furthermore, because blood flow carries away heat, the effectiveness of thermal ablation is severely affected by blood perfusion. Moreover, thermal ablation causes tissue necrosis, which is difficult to expel from the body.

[0004] The NanoKnife tumor ablation device consists of two parts: a pulse generator and ablation electrode needles. The pulse generator outputs treatment pulses according to the parameters set by the doctor. The ablation electrode needles are inserted around the tumor, creating a strong electric field inside the tumor. During treatment, under imaging guidance, the doctor percutaneously inserts the ablation electrode needles parallel to the tumor site and applies a high-intensity, short-pulse electric field to the two ablation electrode needles. This causes irreversible pores to form in the tumor cell membrane, inducing tumor cell apoptosis and achieving the goal of ablating the tumor cells. NanoKnife ablation is a non-thermal ablation technique that utilizes irreversible electroporation to achieve tissue ablation.

[0005] Existing nanoknife ablation needle technology involves directly puncturing the tumor site percutaneously with electrode ablation needles, and then releasing high-voltage electrical pulses between the two electrode needles to ablate the tumor. These electrode ablation needles are all rigid and cannot be bent. In contrast, the ablation of some existing tumors requires reaching the tumor site through human tubes such as the intestines, trachea, or blood vessels, which is inconvenient to use.

[0006] A multi-angle nanoknife device has appeared on the market, such as the one published in patent CN113440244A. It includes a long tube with a handle at one end. The tube contains several mutually insulated electrode wires. The handle has a slider that can push the electrode wires out of the front end of the tube. When the electrode wires extend out of the front end of the tube, they are evenly spaced and arranged in an umbrella shape. The electrode wires are exposed in the extended area, while the remaining areas are covered with an insulating film. The front end of the tube is connected to a needle through which the electrode wires can pass. The long tube allows the nanoknife to enter the tumor site through the body's channels for ablation.

[0007] The existing nanoknife devices have the following problems: 1. The electrode wires are placed in the same pipe, which can easily cause interference between the electrode wires. In addition, the insulation between the electrode wires is poor, which can easily affect the use of the device and cause malfunctions. 2. The existing nanoknife devices cannot deliver liquid to the tumor ablation site through the tubing. Summary of the Invention

[0008] Based on the shortcomings of the above-mentioned electrode wires being arranged in the same pipe, which easily leads to interference between the electrode wires and makes it impossible to deliver liquid to the tumor ablation site through the flexible tube, the present invention provides a tumor ablation soft antenna for NanoKnife, in which the electrodes are separated from each other and can deliver liquid to the tumor ablation site.

[0009] The technical solution adopted by the present invention to solve the above-mentioned technical problems is as follows: a tumor ablation soft antenna for nanoknife, comprising a handle and a slender antenna soft body, the rear end of the antenna soft body being connected to the handle, the antenna soft body being flexible and bendable, characterized in that the front end of the antenna soft body is provided with at least two spaced electrodes, the antenna soft body is provided with the same number of electrode channels as the electrodes, each electrode channel is arranged along the axial direction of the antenna soft body and each electrode channel is independently separated, electrode wires are laid in the electrode channels, an insulating sleeve for insulation is sleeved on the outside of the electrode wires, both ends of the electrode wires protrude from the insulating sleeve, one end of the electrode wire is electrically connected to a corresponding electrode, and the other end of the electrode wire extends into the handle and is electrically connected to the handle.

[0010] A further preferred embodiment of the present invention is as follows: the antenna software is provided with a liquid channel that is independently separated from the electrode channel. The liquid channel is arranged along the axial direction of the antenna software and is not connected to the electrode channel. The antenna software is provided with an inlet and an outlet that are connected to the liquid channel. The outlet is located between the two electrodes at the front end of the antenna software. The handle is provided with a liquid inlet that is connected to the inlet on the antenna software. The liquid inlet is used to supply liquid into the liquid channel.

[0011] A further preferred embodiment of the present invention is as follows: the handle includes a handle body and a Luer connector; the rear end of the antenna software is inserted into the handle body and connected to the handle body; the liquid inlet is located on the rear end of the antenna software inserted into the handle body; the number of Luer connectors is the same as the number of liquid channels; the Luer connectors are connected to the handle body; the handle body is provided with a drainage capillary corresponding to the Luer connector; one end of the drainage capillary is connected to the liquid inlet of the liquid channel; the other end of the drainage capillary is connected to the Luer connector; and the Luer connector has a liquid inlet.

[0012] A further preferred embodiment of the present invention is as follows: the antenna software is provided with two liquid channels, which are independently separated and not connected to each other; the handle body is connected to two Luer connectors, which are respectively connected to the two liquid channels through drainage capillaries.

[0013] A further preferred embodiment of the present invention is as follows: the electrode is sleeved on the outside of the antenna software, and a communication port communicating with the electrode channel is opened at the position where the electrode is installed in the antenna software. A conductive elastic ring is sleeved on the part of the electrode wire that protrudes from the insulating sleeve. The elastic ring extends out of the communication port and contacts the electrode. The elastic ring is used for electrical connection between the electrode wire and the electrode.

[0014] A further preferred embodiment of the present invention is as follows: the elastic ring is a non-closed-loop structure, a local protrusion of the elastic ring forms a pointed head, an opening is provided on the pointed head, and the pointed head extends out of the communication port to elastically contact the electrode.

[0015] A further preferred embodiment of the present invention is as follows: the handle includes a handle body and an input connector; the rear end of the antenna software is inserted into the handle body and connected to the handle body; the number of input connectors is the same as the number of electrode channels; the input connectors are connected to the handle body; the electrode wire extends from the rear end of the antenna software inserted into the handle body and is electrically connected to a corresponding input connector; the input connector is used to connect to an external high-voltage pulse power supply.

[0016] A further preferred embodiment of the present invention is as follows: a conductive transition terminal is installed inside the handle body, and both ends of the transition terminal are provided with insertion slots. An input wire is provided on the input connector, and the input connector is connected to the handle body through the input wire. One end of the input wire extends into the handle body and is inserted into the insertion slot at one end of the transition terminal. The part of the electrode wire that protrudes from the insulating sleeve extends into the handle body and is inserted into the insertion slot at the other end of the transition terminal.

[0017] A further preferred embodiment of the present invention is as follows: the handle body is provided with wiring channels for corresponding electrode wires, each wiring channel is independently separated, and the electrode wires extending from the rear end of the antenna software are inserted into the corresponding wiring channels and run along the wiring channels.

[0018] A further preferred embodiment of the present invention is as follows: the number of electrodes is two, the two electrodes are arranged at an interval, one of the electrodes is located at the front end of the antenna software and the front end is hemispherical, the antenna software is provided with two electrode channels corresponding to the two electrodes, and the electrode lines in the two electrode channels are electrically connected to the two electrodes respectively.

[0019] Compared with the prior art, the advantages of the present invention are that the front end of the antenna software is provided with at least two spaced electrodes, the antenna software is provided with the same number of electrode channels as the electrodes, each electrode channel is arranged along the axial direction of the antenna software and each electrode channel is independently separated, electrode wires are laid in the electrode channels, and each electrode wire is arranged in an independent electrode channel so that the electrode wires do not interfere with each other. By sleeved with insulating sleeves on the electrode wires, the insulation between the electrode wires is further strengthened, and the size of the antenna software becomes thinner.

[0020] The slender antenna soft body is flexible and can be bent and deformed, allowing it to be bent arbitrarily. The antenna soft body can reach the tumor site that needs to be ablated through human channels such as the intestines, trachea, and blood vessels, thereby ablating the tumor and facilitating the use of the Nanoknife ablation device. Attached Figure Description

[0021] The present invention will be further described in detail below with reference to the accompanying drawings and preferred embodiments. However, those skilled in the art will understand that these drawings are drawn only for the purpose of explaining the preferred embodiments and therefore should not be construed as limiting the scope of the invention. Furthermore, unless specifically indicated, the drawings are only schematic representations of the composition or structure of the described objects and may contain exaggerated depictions, and the drawings are not necessarily drawn to scale.

[0022] Figure 1 This is a schematic diagram of the overall structure of the present invention. Figure 1 ;

[0023] Figure 2 This is a schematic diagram of the overall structure of the present invention. Figure 2 ;

[0024] Figure 3 This is a cross-sectional view of the present invention. Figure 1 ;

[0025] Figure 4 This is a cross-sectional view of the present invention. Figure 2 ;

[0026] Figure 5 This is a cross-sectional view of the present invention. Figure 3 ;

[0027] Figure 6 for Figure 3 A magnified view of part A;

[0028] Figure 7 for Figure 3 A magnified view of section B;

[0029] Figure 8 for Figure 4 A magnified view of a portion at point C;

[0030] Figure 9 for Figure 5 A magnified view of a portion of point D.

[0031] In the diagram: 1. Electrode; 2. Liquid outlet; 3. Antenna software; 4. Handle; 5. Handle body; 6. Luer connector; 7. Second damping sleeve; 8. Input line; 9. Input connector; 10. Wiring channel; 11. Electrode line; 12. Insulating sleeve; 13. Transition terminal; 14. Assembly cavity; 15. Insertion slot; 16. Second slot; 17. Drainage capillary; 18. Liquid channel; 19. Connecting port; 20. Elastic ring; 21. Pointed head; 22. Electrode channel; 23. First damping sleeve; 24. First slot; 25. Liquid inlet; 26. Liquid input port. Detailed Implementation

[0032] Preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings. Those skilled in the art will appreciate that these descriptions are merely descriptive and exemplary and should not be construed as limiting the scope of the invention.

[0033] It should be noted that similar labels in the following figures indicate similar items; therefore, once an item is defined in one figure, it may not be further defined and explained in subsequent figures.

[0034] Figures 1-9 As shown, the tumor ablation soft antenna for NanoKnife includes a handle 4 and a slender antenna soft body 3. The rear end of the antenna soft body 3 is connected to the handle 4. The antenna soft body 3 is flexible and can be bent and deformed. This allows the antenna soft body 3 to reach the tumor site that needs ablation through human channels such as the intestines, trachea, and blood vessels, thereby ablating the tumor and facilitating the use of the NanoKnife ablation device.

[0035] The handle 4 includes a handle body 5, and the rear end of the antenna software 3 is inserted into the handle body 5 from the front side and fixedly connected to the handle body 5.

[0036] Figure 3As shown, the front end of the antenna software 3 is provided with at least two spaced electrodes 1. The antenna software 3 is provided with the same number of electrode channels 22 as the electrodes 1. Each electrode channel 22 is arranged along the axial direction of the antenna software 3 and each electrode channel 22 is independently separated. Electrode wires 11 are laid in the electrode channels 22. An insulating sleeve 12 for insulation is sleeved on the outside of the electrode wires 11. Both ends of the electrode wires 11 protrude from the insulating sleeve 12. One end of the electrode wires 11 is electrically connected to a corresponding electrode 1, and the other end of the electrode wires 11 extends into the handle body 5 and is electrically connected to the handle 4.

[0037] Figure 5 , Figure 6 As shown, each electrode channel 22 is independently separated, and each electrode wire 11 is laid in each electrode channel 22, so that there is less interference between each electrode wire 11, which facilitates better use. Furthermore, each electrode wire 11 is also covered with an insulating sleeve 12, which further strengthens the insulation between each electrode wire 11.

[0038] Preferably, the insulating sleeve 12 is a slender cylindrical high-voltage resistant thin-walled insulating sleeve, and the insulating sleeve 12 is also flexible and can be bent and deformed.

[0039] The electrode wire 11 is a slender cylindrical conductor, and it is also flexible and can be bent and deformed.

[0040] Figure 3 As shown, specifically, the handle 4 also includes an input connector 9, the same number as the electrode channels 22. The input connector 9 is connected to the tail end of the handle body 5. The electrode wire 11 extends from the rear end of the antenna software 3 inserted into the handle body 5. The extended electrode wire 11 is electrically connected to a corresponding input connector 9. The input connector 9 is used to connect to an external high-voltage pulse power supply, allowing the external high-voltage pulse power supply to conduct current to the electrode wire 11 through the input connector 9. The rear end face of the antenna software 3 is provided with an extension port for the electrode wire 11 to extend. The structure of the input connector 9 connecting to external devices is the same as the existing nanoknife ablation structure.

[0041] Preferably, a conductive transition terminal 13 is installed inside the handle body 5. Both ends of the transition terminal 13 have insertion slots 15. An input wire 8 is provided on the input connector 9, which is connected to the tail end of the handle body 5 via the input wire 8. One end of the input wire 8 connected to the handle body 5 extends into the handle body 5 and inserts into the insertion slot 15 at the rear end of the transition terminal 13. The portion of the electrode wire 11 protruding from the insulating sleeve 12 extends into the handle body 5 and inserts into the insertion slot 15 at the front end of the transition terminal 13, thus achieving electrical connection between the input connector 9 and the electrode wire 11. The transition terminal 13 facilitates the electrical connection between the electrode wire 11 and the input connector 9. The electrode wire 11 and the input wire 8 are inserted into the insertion slots 15 of the transition terminal 13 and welded to the slots 15 for fixation.

[0042] Figure 7 As shown, the handle body 5 is provided with wiring channels 10 corresponding to the electrode wires 11. Each wiring channel 10 is independently separated. The electrode wires 11 extending from the rear end of the antenna software 3 are inserted into the corresponding wiring channel 10 and run along the wiring channel 10. They extend from the other end of the wiring channel 10 and are plugged into the transition terminal 13. The independently separated wiring channels 10 ensure that the electrode wires 11 will not interfere with each other in the handle body 5, thereby improving the insulation between the electrode wires 11.

[0043] Figure 3 , Figure 7 As shown, specifically, the front end of the handle body 5 has a first slot 24 for the rear end of the antenna software 3 to be inserted. The rear end of the antenna software 3 is inserted into the first slot 24 and fixedly connected to the handle body 5. A first damping sleeve 23 is provided between the antenna software 3 and the inner wall of the first slot 24. The first damping sleeve 23 is fitted on the circumferential outer wall of the antenna software 3. The rear end of the handle body 5 has several second slots 16 for the insertion and connection of the input lines 8. The line of each input line 8 is inserted into a corresponding second slot 16 and fixedly connected to the handle body 5. A second damping sleeve 7 is provided between the line of each input line 8 and the inner wall of the second slot 16. The second damping sleeve 7 is fitted on the circumferential outer wall of the line of the input line 8 and protrudes from the tail end of the handle body 5. The front end of each wiring channel 10 is connected to the same first slot 24. The rear end of each wiring channel 10 is connected to an assembly cavity 14. A transition terminal 13 is fixedly installed in the assembly cavity 14. The rear end of each assembly cavity 14 is connected to a corresponding second slot 16.

[0044] Preferably, the first damping sleeve 23 and the second damping sleeve 7 are both made of silicone material, the handle body 5 is made of engineering plastic material, and the input line 8 is a silicone high-voltage resistant wire.

[0045] The number of electrodes 1 on the antenna software 3 can be two, three, four or more. Preferably, the number of electrodes 1 is two, and the two electrodes 1 are arranged at intervals. One of the electrodes 1 is located at the front end of the antenna software 3, and the front end is hemispherical. The antenna software 3 has two electrode channels 22 corresponding to the two electrodes 1. The electrode lines 11 in the two electrode channels 22 are electrically connected to the two electrodes 1 respectively.

[0046] Figure 1 , Figure 5 As shown, preferably, electrode 1 is sleeved on the outside of antenna software 3. At the position where electrode 1 is installed, antenna software 3 has a communication port 19 that communicates with the inside of electrode channel 22. A conductive elastic ring 20 is sleeved on the part of electrode wire 11 that protrudes from the insulating sleeve 12. The elastic ring 20 extends out of the communication port 19 and contacts electrode 1. The elastic ring 20 is used for electrical connection between electrode wire 11 and electrode 1.

[0047] In addition, the elastic ring 20 is a non-closed-loop structure. The partial protrusion of the elastic ring 20 forms a pointed head 21. An opening is provided on the pointed head 21. The pointed head 21 extends out of the communication port 19 and makes elastic contact with the electrode 1. When the electrode 1 is installed on the antenna software 3, the electrode 1 squeezes the exposed pointed head 21, causing the pointed head 21 to deform elastically, so that the elastic ring 20 is fully connected to the motor, realizing the electrical connection between the electrode 1 and the electrode line 11.

[0048] When performing tumor ablation through electrode 1, the input connector 9 is connected to an external high-voltage pulse power supply, and the electrode line 11 is powered on, so that one electrode 1 is the positive electrode and the other electrode 1 is the negative electrode, and an electrical pulse is generated between the two electrodes 1 to ablate the tumor.

[0049] Figure 4 , Figure 8 As shown, the antenna software 3 is provided with a liquid channel 18 that is independently separated from the electrode channel 22. The liquid channel 18 is arranged along the axial direction of the antenna software 3 and is not connected to the electrode channel 22. The antenna software 3 is provided with an inlet 25 and an outlet 2 that are connected to the liquid channel 18. The outlet 2 is located between the two electrodes 1 at the front end of the antenna software 3. The handle 4 has a liquid input port 26, which is connected to the inlet 25 on the antenna software 3. The liquid input port 26 is used to supply liquid into the liquid channel 18.

[0050] Figure 9As shown, specifically, the handle 4 also includes a Luer connector 6. The liquid inlet 25 is located on the rear end face of the antenna software 3 inserted into the handle body 5. The number of Luer connectors 6 is the same as the number of liquid channels 18. The Luer connector 6 is connected to the rear end of the handle body 5. The handle body 5 is provided with a drainage capillary 17 corresponding to the Luer connector 6. One end of the drainage capillary 17 is connected to the liquid inlet 25 of the liquid channel 18, and the other end of the drainage capillary 17 is connected to the Luer connector 6. The Luer connector 6 has a liquid inlet 26, which can input liquid. The liquid flows into the liquid channel 18 through the drainage capillary 17.

[0051] Preferably, the antenna software 3 has two liquid channels 18, which are independently separated and not connected to each other. The handle body 5 is connected to two Luer connectors 6, which are connected to the two liquid channels 18 through drainage capillaries 17 respectively.

[0052] Physiological saline or liquid drugs can be injected between the two electrodes 1 through the liquid channel 18. Injecting physiological saline between the two electrodes 1 can expand the ablation range of the tumor during ablation, and injecting drugs can provide corresponding drug treatment for the tumor.

[0053] The aforementioned electrode wire 11, electrode 1, and elastic ring 20 are all made of conductive materials, the antenna soft body 3 is made of flexible engineering plastic material, the drainage capillary 17 is made of stainless steel capillary material, and the transition terminal 13 is made of conductive material.

[0054] The foregoing has described the tumor ablation soft antenna for Nanoknife provided by this invention. Specific examples have been used to illustrate the principles and implementation methods of this invention. The descriptions of the embodiments above are merely for the purpose of helping to understand this invention and its core ideas. It should be noted that those skilled in the art can make various improvements and modifications to this invention without departing from its principles, and these improvements and modifications also fall within the protection scope of the claims of this invention.

Claims

1. A flexible antenna for tumor ablation using a nanoknife, comprising a handle and an elongated antenna body, the rear end of the antenna body being connected to the handle, the antenna body being flexible and bendable, characterized in that, The antenna software has at least two spaced electrodes at its front end. The antenna software has the same number of electrode channels as the electrodes, each electrode channel is arranged along the axial direction of the antenna software and is independently separated. Electrode wires are laid within the electrode channels, and insulating sleeves are fitted over the outer sides of the electrode wires. Both ends of the electrode wires protrude from the insulating sleeves. One end of the electrode wire is electrically connected to a corresponding electrode, and the other end extends into the handle and is electrically connected to the handle. The electrodes are fitted over the outside of the antenna software. A communication port connecting to the electrode channels is provided at the location where the electrodes are installed in the antenna software. A conductive elastic ring is fitted over the portion of the electrode wire protruding from the insulating sleeve. The elastic ring extends out of the communication port and contacts the electrode. The elastic ring is used for electrical connection between the electrode wire and the electrode. The elastic ring has a non-closed-loop structure, with a local protrusion forming a pointed head. An opening is provided on the pointed head, which extends out of the communication port and elastically contacts the electrode. The antenna software has a liquid channel that is independently separated from the electrode channel. The liquid channel is arranged along the axial direction of the antenna software and is not connected to the electrode channel. The antenna software has an inlet and an outlet that communicate with the liquid channel. The outlet is located between the two electrodes at the front end of the antenna software. The handle has a liquid inlet that communicates with the inlet on the antenna software and is used to supply liquid into the liquid channel.

2. The tumor ablation soft antenna for Nanoknife according to claim 1, characterized in that, The handle includes a handle body and a Luer connector. The rear end of the antenna software is inserted into the handle body and connected to it. The liquid inlet is located on the rear end of the antenna software inserted into the handle body. The number of Luer connectors is the same as the number of liquid channels. The Luer connectors are connected to the handle body. The handle body is provided with a drainage capillary corresponding to the Luer connector. One end of the drainage capillary is connected to the liquid inlet of the liquid channel, and the other end of the drainage capillary is connected to the Luer connector. The Luer connector has a liquid inlet.

3. The tumor ablation soft antenna for Nanoknife according to claim 2, characterized in that, The antenna software has two liquid channels that are independent and separate from each other. The handle body is connected to two Luer connectors, which are connected to the two liquid channels through drainage capillaries.

4. The tumor ablation soft antenna for Nanoknife according to claim 1, characterized in that, The handle includes a handle body and an input connector. The rear end of the antenna software is inserted into the handle body and connected to it. The number of input connectors is the same as the number of electrode channels. The input connectors are connected to the handle body. The electrode wires extend from the rear end of the antenna software inserted into the handle body and are electrically connected to a corresponding input connector. The input connectors are used to connect to an external high-voltage pulse power supply.

5. The tumor ablation soft antenna for Nanoknife according to claim 4, characterized in that, The handle body is equipped with a conductive transition terminal, and both ends of the transition terminal are provided with insertion slots. The input connector is provided with an input wire, and the input connector is connected to the handle body through the input wire. One end of the input wire extends into the handle body and is inserted into the insertion slot at one end of the transition terminal. The part of the electrode wire that protrudes from the insulating sleeve extends into the handle body and is inserted into the insertion slot at the other end of the transition terminal.

6. The tumor ablation soft antenna for Nanoknife according to claim 4 or 5, characterized in that, The handle body is provided with wiring channels for corresponding electrode wires. Each wiring channel is independently separated. The electrode wires extending from the rear end of the antenna software are inserted into the corresponding wiring channels and run along the wiring channels.

7. The tumor ablation soft antenna for Nanoknife according to claim 1 or 4, characterized in that, The antenna has two electrodes, which are spaced apart. One electrode is located at the very front of the antenna software and is hemispherical. The antenna software has two electrode channels corresponding to the two electrodes, and the electrode lines in the two electrode channels are electrically connected to the two electrodes respectively.

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