Low Eletromagnetic Field Electrosurgical Cable

Abstract

An electrosurgical cable that produces no electromagnetic (EM) field around its vicinity (zero-EM pollution). The cable is comprised of inner insulator with embedded conductor placed inside the outer insulator tube with embedded second conductor. Sizes and materials of conductors and insulators are chosen so that voltage applied to inner conductor is higher than the breakdown voltage while voltage applied to gas gap inside the electrosurgical cable is below than the breakdown voltage. Therefore, the cable is producing discharge at the surgical handpiece, but breakdown inside the cable is prohibited.

Claims

1. An electrosurgical cable comprising: an elongated outer conductor; an outer insulator surrounding said outer conductor, said outer conductor and said outer insulator forming a tube; an elongated inner conductor inside said tube; an inner insulator surrounding said inner conductor, wherein there is a channel between an interior surface of said tube and said inner insulator an electrical connector connected to said inner conductor for connecting said inner conductor to an electrosurgical power supply; an electrical connector connected to said outer conductor for connecting said outer conductor to a ground; and a fluid connector connected to said tube for connecting said tube to a fluid source.

2. An electrosurgical cable according to claim 1 wherein sizes and materials of conductors and insulators are chosen so a voltage applied to the inner conductor is higher than the breakdown voltage and a voltage applied to gas flowing within said channel is below than the breakdown voltage.

3. (canceled)

4. An electrosurgical cable comprising: an elongated outer conductor having an outer radius c; an outer insulator surrounding said outer conductor and having inner radius d and an outer radius e, said outer conductor and said outer insulator forming a tube; an elongated inner conductor inside said tube, said inner electrode having a radius a; and an inner insulator surrounding said inner conductor, said inner insulator having an outer radius b; wherein there is a channel between an interior surface of said tube and said inner insulator and the radii a, b, c, d, e are selected so a<b<c?d?e and wherein the radii a, b, c, d and 3 are selected so a total applied voltage (U.sub.0) is distributed between the inner insulator (U.sub.in) and gas gap between inner and outer insulators (U.sub.gas), so that U.sub.0=U.sub.in+U.sub.gas.

5. (canceled)

6. An electrosurgical cable according to claim 4 wherein a, b, c, d and e are selected so that U.sub.in?U.sub.gas.

7. An electrosurgical cable according to claim 5 wherein a=0.25 mm, b=2.5 mm, c=d=4 mm and e=5 mm.

8. An electrosurgical cable comprising: an elongated outer conductor having an outer radius c; an outer insulator surrounding said outer conductor and having inner radius d and an outer radius e, said outer conductor and said outer insulator forming a tube; an elongated inner conductor inside said tube, said inner electrode having a radius a; and an inner insulator surrounding said inner conductor, said inner insulator having an outer radius b; wherein there is a channel between and interior surface of said tube and said inner insulator and the radii a, b, c, d, e are selected so a<b<c<d?e and a=0.25 mm, b=2.5 mm, c=d=4 mm and e=5 mm.

9. An electrosurgical cable according to claim 8 further comprising: an electrical connector connected to said inner conductor for connecting said inner conductor to an electrosurgical power supply; an electrical connector connected to said outer conductor for connecting said outer conductor to a ground; and a fluid connector connected to said tube for connecting said tube to a fluid source.

10. An electrosurgical cable according to claim 4 further comprising: an electrical connector connected to said inner conductor for connecting said inner conductor to an electrosurgical power supply; an electrical connector connected to said outer conductor for connecting said outer conductor to a ground; and a fluid connector connected to said tube for connecting said tube to a fluid source.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0010] For a more complete understanding of the present invention and the advantages thereof, reference is now made to the following description and the accompanying drawings, in which:

[0011] FIG. 1 is a perspective view of an electrosurgical cable in accordance with a preferred embodiment of the present invention with connectors on one end of the cable and an electrosurgical handpiece on the other end of the cable.

[0012] FIG. 2 is a perspective view of a portion of a cable in accordance with a preferred embodiment of the present invention.

[0013] FIG. 3 is a cross-section of a cable in accordance with a preferred embodiment of the present invention showing relationships of dimensions and voltage drops of various component parts of the cable.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0014] In describing a preferred embodiment of the invention illustrated in the drawings specific terminology will be resorted to for the sake of clarity. However, the invention is not intended to be limited to the specific terms so selected, and it is to be understood that each specific term includes all technical equivalents that operate in similar manner to accomplish a similar purpose. The preferred embodiment of the invention is described for illustrative purposes, it being understood that the invention may be embodied in other forms not specifically shown in the drawings.

[0015] The present invention presents a novel concept of an electrosurgical cable which produces no EM-field or only negligible EM-field around itself (zero-EM pollution) and offers operation without risk of electric shock for human subjects involved in the electrosurgical procedure.

[0016] As shown in FIG. 1, a cable in accordance with the present invention can be used in an electrosurgical system, which, for example, may be a cold plasma electrosurgical system, a hybrid plasma electrosurgical system, or an argon coagulation electrosurgical system. The cable 200 of the present invention may have an electrical connector 400 and a gas supply connector 500 on one end and a handpiece 300 on its other end. The electrical connector will have wiring 410 from the cable 200 and the gas connector will have a tube 510 from the cable 200. Various known connectors 400 and 500 may be used with the present invention.

[0017] As shown in FIG. 2, the cable 200 has an inner electrode 230 to be connected to an electrosurgical generator, surrounded by insulation 240. When the cable is in use, this inner electrode 230 would be connected to a power supply through connector 400. In the preferred embodiment, the electrode 230 is made of cylindrical stainless steel wires of 0.25 mm radius embedded in silicon rubber insulator with radius about 2.5 mm. Material and diameter of the wire is not limited to utilization of stainless steel and other electrically conducting materials can be used as well. Preferentially, diameter (a) of the wire 230 should be chosen depending on precise maximal current requirements of the specific electrosurgical system. Radius (b) of insulator 240 and its material can be varied in wide range as well. In the preferred embodiment silicon rubber was used as material for insulator 240 having relative dielectric permittivity ??3, however dielectrics with other values of can be utilized as well. Preferentially, flexible electrically insulating material should be used to provide electrical insulation along with good flexibility of the electrosurgical cable as a whole.

[0018] The cable further has an outer electrode 210 to be connected to a ground, surrounded on its exterior by electrical insulator 220. As shown in FIGS. 2-3, the outer conductor is cylindrical and forms a tube within which the inner conductor and inner insulation are placed such that a fluid channel is formed between the outer conductor 210 and the inner insulator 240. In the preferred embodiment, the outer electrode 210 is made of stainless steel braided sleeving embedded into outer insulating tube 220. Transparency of the braided shield can be varied depending on requirements of maximal cable weight. Lighter electrosurgical cables can be obtained by reducing diameter of the wire used in the braid and increasing of its transparency. Thin foil or other form of outer conductor can be used as well. Minimal cross-section of the outer conductor 210 should be limited by maximal electric current values required to be drawn through the particular electrosurgical cable. Inner radius (c) of the outer conductor 210 and outer radiuses (e) of insulator 220 and its material can be varied. Preferentially, flexible electrically insulating material should be used to provide electrical insulation along with good flexibility of the electrosurgical cable. The braided shield can be embedded inside the outer conductor and can have radius (d) in the range c?d?e. Note, FIG. 3 shows the case when inner diameter of the outer conductor 210 is shown to be exactly equal to diameter of outer conductor 220 (c=d) and inner electrode 230 and the outer tube are coaxial.

[0019] In a preferred embodiment, the inner conductor and outer conductor are cylindrical but other shapes may be sued with the invention.

[0020] In preferred embodiment Helium was used as working gas while other gases such as Argon can be used as well.

[0021] Relative sizes of the conductors 210, 230 and insulators 220, 240 should be chosen so that a<b<c?d?e. In preferred embodiment it was chosen a=?0.25 mm, b=2.5 mm, c=d=4 mm and e=5 mm.

[0022] The total applied voltage (U.sub.0) is distributed between the inner insulator (U.sub.in) and gas gap between inner and outer insulators (U.sub.gas), so that U.sub.0=U.sub.in+U.sub.gas as shown in FIG. 2. Ratio of voltages U.sub.in and U.sub.gas, can be expressed as:

[00001]$\frac{U_{\mathrm{in}}}{U_{\mathrm{gas}}}=\frac{\ln .Math.\frac{b}{a}}{\mathrm{.Math.ln}.Math.\frac{c}{b}}$

[0023] In preferred embodiment, the ratio

[00002]$\frac{U_{\mathrm{in}}}{U_{\mathrm{gas}}}=1.1$

meaning that U.sub.in?U.sub.gas and thus using U.sub.0=U.sub.in+U.sub.gas one can obtain the that

[00003]$U_{\mathrm{in}}?U_{\mathrm{gas}}?\frac{U_0}{2}.$

In preferred embodiment, U.sub.0?4 kV was used and U.sub.BD was about 2.5 kV. Therefore, U.sub.in?U.sub.gas?2 kV and thus U.sub.gas<U.sub.BD providing that breakdown inside the electrosurgical cable prohibited. At the same time, U.sub.0>U.sub.BD and thus the voltage is sufficient to produce breakdown at the surgical handpiece. Various combinations of radiuses and dielectric permittivity can be used, however, it is critical to choose theses parameters so that two conditions are simultaneously satisfied: [0024] 1. U.sub.0>U.sub.BDvoltage is sufficient to produce breakdown at the surgical handpiece [0025] 2. U.sub.gas<U.sub.BDbreakdown inside the electrosurgical cable is prohibited

[0026] In the preferred embodiment, the inner electrode with insulator was freely placed inside the outer tube. However, relative location of the inner electrode with insulator with respect to the outer tube could be different such as coaxial or any other relative positioning. Also, inner insulator can be either permanently attached or not attached to the inner wall of the outer insulator.

[0027] The embodiment was chosen and described in order to explain the principles of the invention and its practical application to enable one skilled in the art to utilize the invention in various embodiments as are suited to the particular use contemplated. It is intended that the scope of the invention be defined by the claims appended hereto, and their equivalents. The entirety of each of the aforementioned documents is incorporated by reference herein.