Probe electrode

Details Probe electrode Probe electrode

2001-06-18

2003-06-17

Peffley, Michael (Department: 3739)

Surgery

Instruments

Electrical application

C606S046000

Reexamination Certificate

active

06579289

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to a probe for electrosurgical treatment of tissues, in particular by way of an endoscope. Probe electrodes of this kind are used to stanch the bleeding of tissues, for example in the gastrointestinal tract in general or in the colon.
DESCRIPTION OF THE PRIOR ART
German patent DE 4139029 A1 describes a device for the coagulation of biological tissue, to be used in an endoscope with a working channel, which comprises an electrical lead to be connected to a HF voltage source in order to supply coagulation current to the tissue from the distal end of the endoscope. An ionizable gas can be passed through the working channel from a gas reservoir. Within the path along which the gas flows before emerging from the nozzle opening, there is disposed an electrode connected to the electrical lead, the purpose of which is to ionize the gas and provide the coagulation current. When the apparatus is within a specific ignition distance from the tissue to be treated, an electrical arc passes from the electrode through the ionized gas into the tissue and raises the temperature of the tissue to the level necessary to stop the bleeding. In this design the electrode has a cylindrical shape and is disposed at the inner edge just ahead of the opening of the connecting lead.
In U.S. Pat. No. 5,207,675 an apparatus is described in which the coagulation of biological tissue is achieved by means of a biocompatible, flexible tube that can be movably inserted into an endoscope. This tube conducts argon gas from a gas reservoir to the distal end of the tube. A wire running through the tube is connected to a HF voltage source from which coagulation current is supplied. This wire terminates in a tungsten tip that serves as an electrode; positioned at the distal end of the tube, it ionizes the gas that emerges there and enables a discharge to be conducted through the gas stream into the tissue. As a result of the HF energy applied through this arc, the tissue is brought to the temperature required to stop bleeding. The electrode here has the form of a wire with a tungsten tip. As alternatives to this tip, various surgical instruments such as a gripper, a scalpel or the like can be installed.
From the publication Farin G.; Grund K. E.: Technology of Argon-Plasma-Coagulation with particular regard to endoscopic application; in: Endoscopic surgery and allied technologies; Vol. 2, 1994, No. 1, pp. 71-77, it is known that the direction and extent of this arc, i.e. its overall geometric form, is determined less by the gas current than by the electrical relationships, in particular those of the tissue to be treated. Therefore in many cases in which plasma coagulation is employed, it is extremely problematic to treat precisely the places in the tissue that need to be treated, while leaving adjacent parts of the tissue unaffected. Owing to the special requirements of endoscopic treatment, these problems are exacerbated here.
In view of the circumstances outlined above, it is impossible to predict accurately the effect of such a treatment method, because of the limited precision with which the direction of the arc (also called “beam” below) can be determined. Furthermore, the extent and hence uniformity of the beam over the intended target region of the tissue to be treated is difficult to estimate, which in the end result forces the operator to position the electrode as close as possible to the target region in order to avoid missing it. But this increases the risk that the hot electrode will make contact with the tissue, with the result that the tissue will adhere to it and the source of bleeding will be torn open again.
According to the state of the art, as shown in
FIG. 6
, to avoid this risk appropriately shaped spacer pieces
80
made of poorly heat-conducting material, such as ceramic, have been placed onto the distal end of a tube
90
. However, this also increases it the distance between a distal tip
71
of an electrode, which as indicated in
FIG. 6
has the form of a helical discharge portion
70
of an electrical lead
30
, and the tissue to be treated, with the disadvantages described above for the efficiency of the beam. Furthermore, the distal tip
71
fitted in the distal end of the tube
90
makes it necessary for the correspondingly shaped electrode to be centered during its insertion from the proximal end
92
of the tube
90
into the exit opening
91
of the spacer piece. Such an elaborately constructed probe is expensive and its service life is limited by the tendency of the electrodes previously employed to burn away.
The problems just described are not satisfactorily solved by any of the devices known so far.
The object of the present invention is to provide a probe for the electrosurgical treatment of tissues which can be manufactured by a simple means and which can be easily manipulated in the operation area, in particular with respect to the distance from the tissue to be treated at which the distal end must be positioned and with respect to an associated reduction of the risk of injury. At the same time, it is intended to provide a probe with an enhanced efficiency of the beam, with respect for example to ease of ignition as well as more precise aiming and greater uniformity.
SUMMARY OF THE INVENTION
According to the present invention there is provided a probe for the electrosurgical treatment of tissues comprising a tubular supply device to guide a noble gas from a noble-gas source to a distal end of the supply device; and an electrode comprising a discharge portion and an electrical lead which can conduct a HF current from a HF source to the discharge portion, the discharge portion being formed as a flat structure that is disposed in the supply device such that the noble gas can flow over a substantial portion of its surface area to conduct away heat.
As the discharge portion of the probe is constructed with a suitably large surface area, heating of the probe is avoided. The discharge portion, which is disposed at the distal end of the supply device with its flat surfaces extending in the direction of flow, is thus completely surrounded by the stream of noble gas, as a result of which heat is conducted away.
Hence, there is no longer any need for structural features designed to avoid injury caused by the hot probe electrode, such as the elaborately designed tube tip with a spacer piece, at least in the case of disposable probes. Furthermore, a special centering of the discharge portion within the exit opening of a spacer piece is no longer required, which enables this portion to be constructed more simply and cost-effectively. In addition, the dissipation of heat makes it possible to minimize the rate at which the discharge portion of the probe burns away, which increases its service life.
Because the discharge portion defines a large, flat region parallel to the direction of gas flow, turbulence in the gas flow in this region is reduced, which increases the uniformity and directional precision of the gas stream.
Preferably, the discharge portion of the probe is so constructed that it comprises at least one tip or sharp edge that faces toward the distal end.
As a result of this construction, the electromagnetic field is condensed onto the tip or sharp edge that is closest to the tissue to be treated, which increases the field strength in this region. It can thus be ensured that the beam originates from the centered tip of the discharge portion. Hence the field strength is increased and the ionization of the gas is improved, as a result of which the ignition distance between discharge portion and tissue to be treated is enlarged.
Preferably, the discharge portion comprises a lamina, with dimensions such that opposed edges of the lamina are fixedly engaged with an interior wall of the supply device surrounding the discharge portion. In this case the thin plate of which the discharge portion is composed can either be flat or, if spinning and turbulence of the gas stream are desired, it can be twisted.
This arrangement offers the advanta

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