DE102008004843B4 - Plasma applicators for plasma surgical procedures - Google Patents

Abstract

Plasma applicator for flexible endoscopy with a device for insertion into the working channel of an endoscope, in which a probe line (12) is present for transmitting electrical energy from an electrosurgical HF generator (1), which is connected to the via a connection line (11) Probe line (12) is connected to an electrode (13) which is arranged at the distal end of the flexurally flexible probe (10) and further via a path or arc (14) of ionized gas that passes through the flexurally flexible probe (10) to the distal Electrode (13) is passed into a biological target tissue (4) and via a neutral electrode (2) back to the electrosurgical generator (1), with a resistance element (20) between the connecting line (11) and the distal electrode (13) predetermined impedance is arranged, which is dimensioned such that after the ionization of the gas, the treatment current is limited to a certain value, characterized in that for s To limit the treatment current, the resistance element (20) on ...

Description

The invention relates to plasma applicators for the application of plasma surgery in open surgery or in rigid endoscopy and plasma probes for the application of plasma surgical procedures in flexible endoscopy according to the preamble of claim 1. Plasma surgery refers to high-frequency surgical procedures in which, such as in 6 shown schematically, high-frequency electrical alternating current (HF current, IHF) by ionized and consequently electrically conductive gas (plasma), such as argon plasma, targeted to or in to be treated biological tissue (target tissue, A, B, C, D) is applied to produce on or in the target tissue medically beneficial thermal effects, in particular the devitalization effect (D), coagulation effect (C), desiccation effect (B) and / or shrinkage effect (A), but without collateral tissue (collateral tissue, G) more than inevitable and tolerable damage. The ionization of the gas between an ionization electrode (E) and the target tissue arises at a sufficiently high electric field strength (F _e ) corresponding to the function F _e = U _HF : d. For ionization of argon at atmospheric pressure about 500 V / mm are required. The structural design of various plasma applicators or plasma probes (R) is described in detail below.

Plasma surgical procedures and plasma applicators as well as devices for their application are not new. For more than 50 years, a known under the name fulguration or spray coagulation plasma surgical procedure is used in particular for thermal hemostasis in surgical operations. Here, the plasma is generated exclusively in air, d. H. it mainly produces oxygen plasma and nitrogen plasma. Both plasmas are known to be chemically very reactive and produce at the tissue surface Karbonisationseffekte, pyrolysis effects and consequently also vaporization of tissue and smoke. These unintentional side effects of fulguration or spray coagulation disturb or hinder the use of this plasma surgical procedure, especially in endoscopic operations.

The US 4,060,088 A has, inter alia, the avoidance of the above-mentioned side effects of fulguration or spray coagulation the subject. There it is proposed to replace the air between the active electrode and the tissue to be treated by a chemically inert gas or inert gas. As inert gas helium or argon and mixtures thereof are proposed. Because of its relatively low price, however, argon is predominantly used today, and this process has been called argon plasma coagulation (APC) for about 20 years to distinguish it from airborne fulguration or spray coagulation. A clinically applicable facility for this has been in the US 4,781,175 A and exclusively for use in open surgery and in rigid endoscopy for thermal haemostasis proposed.

Devices and methods suitable for APC have been described for the first time in 1994 by G. Farin and KE Grund (G. Farin, KE Reason: Technology of Argon Plasma Coagulation with Particular Regard to Endoscopic Applications, Endoscopic Surgery and Allied Technologies, No. 1 Volum , 1994: 71-77, and KE Grund, D. Storek, G. Farin: Endoscopic Argon Plasma Coagulation (APC): First Clinical Experiences in Flexible Endoscopy, Endoscopic Surgery and Allied Technologies, No. 1 Volum 2, 1994: 42- 46). The range of application of APC in flexible endoscopy has been described previously (KE Grund, C. Zindel, G. Farin: Argon plasma coagulation in flexible endoscopy: evaluation of a new therapeutic method after 1606 applications.) (German Medical Weekly Journal 122, 1977: 432-438) and is now standard worldwide, not only in flexible endoscopy.

As described in the publications cited above, argon plasma coagulation has not been used only for the coagulation of biological tissues. Today, this method is used in particular for thermal devitalization of pathological tissue and / or for desilication and consequently shrinkage of blood vessels and their collateral tissue for the purpose of hemostasis. The use of this method for the thermal devitalization of relatively thin tissue layers, such as the mucosa of the gastrointestinal tract or tracheobronchial system, is becoming increasingly important. This procedure is also becoming increasingly important for the thermal sterilization of tissue surfaces during transmural operations, for example in transgastric operations, in order to prevent germinal exudations from the stomach into the abdominal cavity. These applications are not adequately covered by the term argon plasma coagulation (APC). Since the subject of this invention is not limited only to the coagulation of biological tissues and not only to the gas argon, this method will be hereinafter called correspondingly more extensive "plasma surgery".

The wide range of applications of plasma surgery today, however, more differentiated application-specific requirements for the properties of the facilities required for this, in particular with respect to reproducibility of the intended thermal effects on or in target tissues and the prevention of unintentional thermal effects in both the target tissue and in collateral tissues than previously used in applications of fulguration or spray coagulation. This applies in particular to the use of plasma surgery on or in thin-walled hollow organs of the gastrointestinal tract or of the tracheobronchial system (see G. Farin, KE Reason: Principles of Electrosurgery, Laser, and Argon Plasma Coagulation with Particular Regard to Colonoscopy, In: Colonoscopy; Principles and Practice, Edited by JD Waye, DK Rex and CB Williams, Blackwell Publishing 2003: 393-409).

The spectrum of various plasma applicators for medical applications, in particular for plasma surgery and for endoscopically controlled interventions, is very broad. With regard to the access to the respective target organ or tissue to be treated, it is possible to differentiate the previously available plasma applicators into those designed for open surgery, for rigid endoscopy and for flexible endoscopy. The basic structure and the function of these various plasma applicators is, for example, the publication of G. Farin and K. E. Reason: Technology of Argon Plasma Coagulation with Particular Regard to Endoscopic Applications, Endoscopic Surgery and Allied Technologies, Thieme Verlag, Stuttgart, no. 1, Volume 2, 1994: 71-77.

An arrangement for the plasma surgery, namely for endoscopically controlled interventions, as also the subject of the present application, is in 7 shown. Such an arrangement typically includes a surgical radio frequency generator 1 , on the one hand, to a neutral electrode 2 and on the other hand a surgical instrument, in this case a probe 10 (or the discharge electrode, not shown) is connected. The probe 10 stuck in one of the working channels 6 an endoscope 5 , A lumen of the probe 10 becomes argon (or other noble gas) from a noble gas source 7 fed. The neutral electrode 2 is placed over a large area on a patient and thus stands with its biological tissue 3 in connection. In this way, the surgeon can use a target tissue 4 treated with an argon plasma to achieve the desired effects, based on 6 already described, to achieve there.

The available for plasma surgery RF generators can be differentiated in terms of their internal resistance. HF generators with high internal resistance are particularly suitable for the treatment of superficial lesions in which a low penetration depth of the thermal effects is expedient. HF generators with a low internal resistance are particularly suitable for the treatment of massive lesions in which a large penetration depth of the thermal effects is expedient. In DE 198 39 826 A1 is described an RF generator whose internal resistance between high and low adjustable.

The treatment of superficial lesions in which low penetration depths of the thermal effects are expedient or even required is problematic with HF generators with low internal resistance and known plasma applicators insofar as the penetration depth of the thermal effects is predominantly controlled by the duration of application, ie by the surgeon must become. Since the rate of penetration of the thermal effects during the beginning of the plasma application is relatively fast and decelerated over time to reach the maximum achievable penetration depth, a small and uniform penetration depth of the thermal effects in areal lesions is difficult or impossible to achieve. Although the penetration rate of the thermal effects can be influenced by varying the power or the RF current flowing through the plasma, this becomes due to the high RF voltage required for ionizing the gas in known RF generators by pulse modulation of the RF voltage or the HF current realized. However, pulse modulation can interfere with video signals from video endoscopes and cause neuromuscular stimuli, especially at modulation frequencies below 1 kHz. Another problem in the use of RF generators with low internal resistance for the treatment of superficial lesions are very high temperature of the plasma due to the high RF voltage required for ionization on the one hand and the low internal resistance of the RF generator and the low electrical resistance of the plasma path on the other. whereby a very high HF current density and consequently such a high temperature can be caused in the plasma path that the carbonization and pyrolysis effects disturbing this application can arise.

HF generators with high internal resistance are not practical or even not applicable for endoscopic operations or interventions because the high RF voltage required for the ionization of the gas between ionization electrode and target tissue due to the so-called stray capacitance between active RF line and neutral RF line insufficiently or not at all can be transmitted from the RF generator to the ionization electrode. This is known, in particular in flexible endoscopy of the case.

HF generators accordingly DE 198 39 826 A1 are not available yet.

From the EP 1 148 770 A2 Another plasma applicator of this genus is known in whose Handpiece, which is connected via an external line to an RF generator, a capacitor is mounted in series with the outer line. To the handle, a probe is further fixed with a special line disposed therein, which is connected downstream of the capacitor and connects an electrode at the distal special tip with the RF generator.

Based on the above-mentioned prior art, the invention is based on the object to show a plasma applicator of the type mentioned in such a way that with low cost and yet with great certainty a sufficiently low penetration depth is achieved in the application in flexible endoscopy.

This object is achieved by a plasma applicator according to claim 1. Advantageous developments are the subject of the dependent claims.

In particular, the object is achieved by a plasma applicator for transmitting electrical energy from an electrosurgical RF generator via a lead, a downstream probe lead and an electrode connected at its distal end, and further via a flow path of ionized gas into a target biological tissue, between the distal End of the probe line and the electrode, a resistive element having a predetermined impedance is arranged, which is dimensioned such that after the ionization of the gas, a limitation of a treatment current is ensured.

An essential point of the invention lies in the fact that the entire arrangement, consisting of RF generator and all leads up to the electrode as "total generator" is considered, whose internal resistance is then determined by the resistive element, which is immediately upstream of the electrode. This resistance element can now be selected according to the requirements of the depth of penetration to be achieved or one can provide different instruments for different penetration depths. Of course, the treatment time still plays a role, but just the critical phase, namely the brief moment after the "ignition" of the arc, during which a high current can flow, defused.

The resistance element can in principle be an ohmic resistance, which ensures the desired current limitation. Preferably, however, the resistance element is formed as a capacitance or comprises such a capacitance, which has the voltage stability necessary here. The big advantage in this case is that this capacity forms a high pass, so that low-frequency portions of the current are attenuated. This, in turn, results in, among other things, a significant reduction in interference from video systems (as commonly used in endoscopes today) and in avoiding neuromuscular irritation, such as that which can occur through lower frequencies.

With sufficiently large plasma applicators, the capacitive resistance can be realized by commercially available components, for example high-voltage resistant ceramic capacitors. In the case of plasma applicators driven by narrow instrumentation channels of flexible endoscopes (as related to 7 described), such as plasma applicators or so-called argon plasma coagulation probes (APC probes), z. B. accordingly DE 198 20 240 A1 or DE 101 29 699 C1 respectively. EP 1 397 082 A1 However, those having an outer diameter of only 2 to 3.5 mm, these capacitive resistances must be developed specifically for these plasma applicators or constructively realized by appropriate design of the distal end of the APC probes.

Of course, since these so-called APC probes can be used not only with argon and not only for coagulation, but also with other gases or gas mixtures, for other thermal effects and, where appropriate, in other fields, these plasma applicators will become more general Called plasma probes (P probes).

In a preferred embodiment, the resistive element comprises a subsection of the probe lead and / or the electrode. Thus, portions of these components are used either to form an ohmic resistance or (optionally additionally) to form a capacitance. This can be done, for example, by the resistance element being formed by sections of the probe line electrically insulated from one another, parallel or twisted or coaxially arranged, and / or a supply line to the electrode and / or the electrode itself. Such a construction is relatively simple.

Preferably, the resistive element has a capacitance of 10 pF to about 1,000 pF. These are capacitance ranges that result in currents commonly used in high frequency surgery to ensure the desired relatively low penetration depth.

The dielectric used for the formation of the capacitance should have the highest possible dielectric constant. For this purpose, not only plastics, but above all ceramic material, which is introduced as insulation and / or dielectric are suitable. This can be rigid ceramic material or but (if greater flexibility is required) also be powdered ceramic material.

All the above points also apply to such electrosurgical arrangements where no "shielding gas" is used. Preferably, however, a protective gas, a noble gas (in particular argon) is used. In this case, the electrode is located in or near a tube, a tube or a probe and is positioned such that a noble gas, in particular argon, can be supplied as gas to be ionized into a space between the electrode and the target tissue. The resulting advantages have already been described above.

The invention will be explained in more detail with reference to figures. Show here

1 a schematic representation of an embodiment of the electrosurgical instrument,

2 - 5 schematized representations as resistive elements formed as capacitive elements and the associated electrodes,

6 the above-mentioned representation to explain the processes in argon plasma coagulation and

7 an overall arrangement for endoscopic treatment of tissues by APC.

In the following description, the same reference numerals are used for the same and the same acting objects.

In 1 is shown very schematically an arrangement that in principle of those 7 equivalent. This in 7 shown endoscope is not visible in this arrangement.

As in 1 As shown, a high-frequency generator is provided which has a voltage source with a voltage U ₀ and an internal resistance 8th having a resistance R _i . Thus stands at an output current I _HF1 at the output of the generator 1 a voltage U ₁ U ₁ = U _{0 -R i} * I _{HF 1} at the output terminals of the generator 1 at. The generator 1 is via a supply line 11 with a probe lead 12 connected within a tube of the probe 10 is arranged. The probe line 12 is at its distal end via a resistance element 20 and an electrode lead 24 with an electrode 13 connected. Through the hose of the probe 10 argon gas Ar is passed, leaving a space between the distal end of the probe 10 and the biological tissue 3 filled with argon gas, so normally air is displaced there. When the voltage between the tip of the electrode 13 and the biological tissue 3 is high enough, the gas (argon) in this space between the electrode 13 and the biological tissue 3 ionized, leaving an arc 14 arises. Then, a current IHF4 flows through the target tissue 4 and the biological tissue 3 to the neutral electrode 2 ,

The supply line 11 is usually formed as a monopolar line. Furthermore, the neutral electrode is located 2 at ambient potential (as well as an optionally provided endoscope), so that a relatively large stray capacitance 15 between the supply line 11 as well as a stray capacity 16 between the probe lead 12 and the environment forms. Through these stray capacities 15 and 16 Currents I _HF2 or I _{HF3 flow} . Due to this stray capacitance sinks before igniting an arc 14 the voltage (U _Z ) that is between the electrode 13 and the target tissue 4 used for igniting plasma: U _Z = U _{0 -R i} (I _{HF 2} + I _{HF 3} )

To start the ignition of the plasma 14 at the largest possible distance between the electrode 13 and the target tissue 4 To ensure it is advantageous if the amount R _{i of} the internal resistance 8th is low. On the other hand, in this case, when the arc is ignited 14 which has a very low resistance, as well as due to the fact that the resistance between the target tissue 4 and the neutral electrode 2 is also relatively low, a very large current I _HF4 flow, so that in a short time the target tissue 4 is influenced to a relatively large depth. As a result, now that the resistance 20 between the distal end of the (lossy) probe lead 12 and the electrode 13 is arranged, even at a high, at the electrode 13 available ignition voltage, after the ignition of the arc 14 generates a high voltage drop, so that the current I _HF4 can be limited. Such a limitation of the current is only by a resistance element 20 possible at this point. However, it should be underlined here that the resistance element 20 by no means must be a locally limited resistance element. This resistance element 20 can in various ways extend over a certain length to the tip of the electrode 13 extend.

Hereinafter, various embodiments of the resistance element based on 2 - 5 explained.

At the in 2 shown embodiment is a distal end of the probe lead 12 shown a probe lead wire 21 which has an insulating material 22 is isolated. Parallel to this distal end of the probe lead 12 is the inside of the probe 10 electrode lead 24 arranged with the electrode 13 connected and with insulation 22 ' is provided. Through this parallel guidance of the two lines 12 and 24 a capacitance is formed, which serves as a resistance element 20 acts.

In the 3 The embodiment shown differs from that according to FIG 2 in that both the distal end of the probe lead wire 21 as well as the end of the electrode lead 24 in a common insulation material 22 are embedded.

In addition, the electrode lead is 24 designed bifilar, so that any resulting Leitungsinduktivitäten be compensated. As insulation material is just in such a case, a ceramic material (designed as solid or powdered ceramic) to achieve the highest possible capacity with a small size of the arrangement.

At the in 4 In the embodiment shown, the capacitance is increased by the fact that the electrode feed line 24 around the end of the probe lead 12 is wound. Again, a bifilar arrangement to avoid inductance can be chosen again.

At the in 5 The arrangement shown is the electrode lead 24 formed as a sleeve which the distal end of the probe lead 12 surrounds telescopically and thus forms a capacity with this. In this case, the electrode is over a junction 25 with the sleeve-shaped electrode feed line 24 electrically connected. The sizing can also be similar to the following 4 take place, so that supplied argon gas is no longer through the sleeve-shaped electrode lead 24 but outside this past in the hose 9 the probe 10 flows.

Important in all arrangements is a corresponding insulation, so that no breakdown occurs between the elements formed by lines. Furthermore, it is also possible, the lines in a wall of the hose 9 embed the gas line of the probe 10 forms. It should also be noted that the working channel 6 of the endoscope 5 can be used as a gas line, as for example in the EP 0 954 246 A1 is described.

The physical parameters that determine the capacitance between the leads are described in detail in the pertinent literature and are known to one of ordinary skill in the art.

The arrangement and the shape of the gas outlet opening can of course not only, as shown in the embodiments, be aligned in the axial direction, they can also be arranged differently, as for example in the DE 198 20 240 A1 or the DE 101 29 699 C1 is shown.

Limiting the amplitude of the RF current flowing through the plasma not only serves to controllably limit the penetration depth of the thermal effects in the target tissue, but also has several other benefits, such as avoiding too high temperatures of the plasma and thereby avoiding or even carbonization Pyrolysis of the target tissue, the avoidance of thermal overloads of the distal end of the plasma probe, especially when the plasma is directly in contact with plastic, such as in plasma probes accordingly DE 101 29 699 C1 , as well as the possibility to avoid disturbances of video systems and neuromuscular irritation. Neuromuscular irritations are avoided when using plasma probes according to the invention by the capacitive resistance in front of the ionization electrode, in that this capacitive resistance in particular prevents low-frequency currents.

LIST OF REFERENCE NUMBERS

1

RF generator

2

neutral electrode

3

biological tissue

4

target tissue

5

endoscope

6

working channel

7

Inert gas source

8th

internal resistance

9

tube

10

probe

11

supply

12

probe cable

13

electrode

14

Electric arc

15

stray capacitance

16

stray capacitance

20

resistive element

21

Probe wire

22

isolation

24

electrode lead

25

junction

Claims (6)

Plasma applicator for flexible endoscopy with a bend-flexible tubular probe ( 10 ) which is intended for insertion into the working channel of an endoscope in which a probe line ( 12 ) is present for transmitting electrical energy from an electrosurgical HF generator ( 1 ), which is connected via a connecting cable ( 11 ) to the probe line ( 12 ) is connected to an electrode ( 13 ), which at the distal end of the bend-flexible probe ( 10 ) and further via a path or arc ( 14 ) of ionized gas passing through the flexible probe ( 10 ) to the distal electrode ( 13 ) into a biological target tissue ( 4 ) and via a neutral electrode ( 2 ) back to the electrosurgical generator ( 1 ), whereby between the connecting line ( 11 ) and the distal electrode ( 13 ) a resistance element ( 20 ) is arranged with a predetermined impedance, which is dimensioned such that after the ionization of the gas, the treatment current is limited to a certain value, characterized in that for safe limitation of the treatment current, the resistive element ( 20 ) at the distal end portion of the flexible probe ( 10 ) between the probe line ( 12 ) and the distal electrode ( 13 ) is connected in series. Plasma applicator according to claim 1, characterized in that the resistance element ( 20 ) in the form of a capacitor in the distal end portion of the flexible probe ( 10 ) is integrated or inserted. Plasma applicator according to claim 2, characterized in that the capacitor ( 20 ) in the probe axial direction parallel guided, spirally twisted or coaxially and telescopically nested portions of the probe line ( 12 ) at the distal end portion of the flexible probe ( 10 ) and preferably via a feed adapter ( 24 ) with the distal electrode ( 13 ) connected is. Plasma applicator according to claim 2, characterized in that the capacitor ( 20 ) through the distal electrode ( 13 ) itself is formed. Plasma applicator according to claim 2, 3 or 4, characterized in that the capacitor ( 20 ) has a capacity of 10 pF to 1000 pF. Plasma applicator according to one of claims 2 to 5, characterized in that the capacitor ( 20 ) forming sections of the probe line ( 12 ) are electrically insulated from each other by a ceramic material, which preferably has a powdery consistency.

Images