DE102008004843A1 - Electrosurgical instrument i.e. plasma applicator, for applying argon plasma on or in biological tissue during e.g. open surgery, has resistor element dimensioned such that delimitation of treatment current is ensured after ionizing of gas - Google Patents

Abstract

The instrument has a tubular or hose shaped sensor (10) transmitting electrical energy from a high frequency generator (1) by a connection line (11), an electrode (13), a path or an arc load (14) of ionized gas and by a neutral electrode (2). The electrode (13) is attached to a distal end of the line. A resistor element (20) e.g. standard resistor, with a preset impedance is arranged between the distal end and the electrode (13), and is dimensioned such that a delimitation of a treatment current is ensured after ionizing of the gas. The resistor element comprises a ceramic material.

Description

The invention relates to plasma applicators for the application of plasma surgery in open surgery or rigid endoscopy and plasma probes for the use of plasma surgical procedures in flexible endoscopy. By plasma surgery is meant high frequency surgical procedures in which, as in 6 shown schematically, high-frequency electrical alternating current (RF current, I _HF ) by ionized and consequently electrically conductive gas (plasma), such as argon plasma, specifically applied to or in to be treated biological tissue (target tissue, A, B, C, D) in order to produce medically beneficial thermal effects on or in the target tissue, in particular the devitalization effect (D), coagulation effect (C), desiccation effect (B) and / or shrinkage effect (A), but without collateral tissue (collateral tissue, G) being more than unavoidable 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 _c ) corresponding to the function F _c = 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 Processes and plasma applicators and devices for their use are not new. For more than 50 years, one of the Designation fulguration or spray coagulation known plasma surgical procedure in particular for thermal haemostasis in surgical Operations applied. Here, the plasma is exclusive generated in air, d. H. it mainly produces oxygen plasma and nitrogen plasma. Both plasmas are chemically very well known reactive and produce carbonization effects on the tissue surface, Pyrolysis effects and consequently vaporization of tissue and smoke. These unintentional side effects of fulguration or spray coagulation disturb or hinder the application of this plasma surgical procedure especially in endoscopic operations.

The US 4,060,088 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 exclusively for use in open surgery and in rigid endoscopy for thermal haemostasis.

For the APC suitable facilities and procedures are the first time 1994 by G. Farin and KE Grund been described ( G. Farin, KE Reason: Technology of Argon Plasma Coagulation with Particular Regard to Endoscopic Applications. Endoscopic Surgery and Allied Technologies, No. 1 volume 2, 1994: 71-77 ; such as KE Grund, D. Storek, G. Farin: Endoscopic Argon Plasma Coagulation (APC): First Clinical Experiences in Flexible Endoscopy. Endoscopic Surgery and Allied Technologies, No. 1 volume 2, 1994: 42-46 ). The range of applications 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 procedure after 1606 applications. German Medical Weekly 122, 1977: 432-438 ) and is today the standard worldwide not only in flexible endoscopy.

As described in the publications cited above, argon plasma coagulation not only used for coagulation of biological tissues. today This method is especially used for thermal devitalization pathological tissues and / or desilication and consequently shrinkage of Blood vessels and their collateral tissue for Used for the purpose of hemostasis. The more important is the Application of this method for thermal devitalization relative thin tissue layers, such as the mucosa that Gastrointestinal Tract or Tracheobronchial System. Increasingly important This procedure is also used for the thermal sterilization of tissue surfaces in transmural operations, such as transgastric surgery, to germinal diseases from the stomach into the abdominal cavity to avoid. These applications are called Argon Plasma Coagulation (APC) not adequately recorded. As the subject of this invention not only on the coagulation of biological tissues and not limited only to the gas argon, this procedure is hereafter according to comprehensive "plasma surgery" called.

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 col lateral tissues than previously used in applications of fulguration or spray coagulation. This is especially true when using plasma surgery on or in thin-walled hollow organs of the gastrointestinal tract or 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 from the publication of G. Farin and KE 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 , known.

An arrangement for the plasma surgery, for endoscopically controlled interventions 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 is described an RF generator whose internal resistance between high and low adjustable.

The Treatment of superficial lesions in which a low penetration depths of the thermal effects appropriate or even prerequisite, is with HF generators with low Internal resistance and known plasma applicators insofar problematic as the penetration depth of the thermal effects mainly by the duration of the application, ie by the surgeon, must be checked. Since the penetration rate of thermal effects during the beginning of the plasma application is relatively fast and over the time degressive until reaching the maximum achievable penetration depth slower, is a small and even Penetration depth of thermal effects in planar Lesions difficult or impossible to realize. The Penetration rate of the thermal effects can indeed by Variation of the power or the flowing through the plasma RF current This will be with regard to the Ionizing the gas required high RF voltage in known HF generators by pulse modulation of the RF voltage or the HF current realized. However, the pulse modulation can produce video signals from video endoscopes disturb and cause neuromuscular stimuli, the latter in particular at modulation frequencies below 1 kHz. Another Problem when using RF generators with low internal resistance to treat superficial lesions are very high temperature of the plasma due to the ionizing required high RF voltage on the one hand and the low internal resistance of HF generator and the low electrical resistance of the plasma path on the other hand, resulting in a very high RF current density in the plasma path and consequently such high temperature can be caused that the disturbing in this application carbonation and Pyrolysis can occur.

RF generators With high internal resistance are for endoscopic operations or interventions not appropriate or even not applicable because of the ionization of the gas High RF voltage required between the ionization electrode and the target tissue due to the so-called stray capacitance between active HF line and neutral RF line only insufficient or not transferred from the HF generator to the ionisation electrode can be. This is known, especially in the flexible Endoscopy of the case.

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

Based on the above-mentioned prior art, the invention is based on the object to show an electrosurgical instrument of the type mentioned in that ge ringem effort and yet with great certainty a sufficiently low penetration depth can be achieved.

These Task is by an electrosurgical instrument according to claim 1 solved.

Especially The object is achieved by an electrosurgical instrument for transmitting electrical Energy from an electrosurgical HF generator over a connecting lead and a connected at the distal end Electrode and further via a current path of ionized Gas reaches into a biological target tissue, whereby between the distal end of the lead and the electrode is a resistance element is arranged with a predetermined impedance, which dimensions such is that after the ionization of the gas, a limitation of a treatment stream is ensured.

One The essential point of the invention is therefore that the entire Arrangement consisting of HF generator and all supply lines up towards the electrode as a "total generator" considered whose internal resistance is then determined by the resistance element is. This resistance element can now according to the requirements be selected to the penetration depth to be achieved or You can use different instruments for different penetration depths provide. Of course plays The treatment time is still a factor, but that is just the critical phase, namely the brief moment after the "ignition" of the Arc, during which a high current flow can, defused.

The Resistance element can be an ohmic resistance, the desired Current limitation ensures. Preferably, however, the resistance element designed as a capacity or comprises such a capacity, which has the here required dielectric strength. the big advantage In this case, this capacity is one High pass forms so that low frequency portions of the current are muted become. This in turn leads to a significant reduction of interference from video systems (as in endoscopes commonly used today) and to avoid of neuromuscular irritation, as indicated by lower Frequencies can occur.

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 rigid or 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 or DE 101 29 699 respectively. EP 1 397 082 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.

There these so-called APC probes of course not just with argon and not just for coagulation, but also with other gases or gas mixtures, for other thermal Effects and, if applicable, also applied in other fields These plasma applicators are below commonly called plasma probes (P probes).

at a preferred embodiment comprises the resistive element a section of the connecting cable and / or the electrode. So it will be sections of these components either to form a ohmic resistance or (possibly additionally) to Forming a capacity used. This can be, for example be done by that the resistive element by electric isolated, parallel or twisted or Coaxially arranged portions of the connecting line and / or a Supply line to the electrode and / or the electrode itself is formed. Such a construction is relatively simple. In this case too should be taken to ensure that no inductances arise, which, for example, by using biphilar piping arrangements can happen.

Preferably the resistance element has a capacity of 10 pF to about 1,000 pF up. These are capacity areas that are included the frequencies commonly used in high frequency surgery lead to currents that the desired ensure relatively low penetration depth.

The Dielectric used for capacitance formation should have the highest possible dielectric constant exhibit. Not only plastics are suitable for this, but also especially ceramic material that as insulation and / or dielectric is introduced. This can be rigid ceramic material or (if a higher flexibility is required) also powdered Be 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. The electrode is located in or near a tube, a tube or a probe and is positi so oniert that a noble gas, in particular argon, is supplied as a gas to be ionized in a space between the electrode and the target tissue. The resulting advantages have already been described above.

following 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 will be for the same and the same acting objects the same reference numerals used.

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. It should be noted, however, that such arrangements are also suitable for open surgery, in which no endoscope is needed.

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 HF1 at the output terminals of the generator 1 at. The generator 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 I _{HF4 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 HF2 + I HF3 )

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) lead 11 . 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 electrode lead 24 arranged with the electrode 13 connected and with insulation 22 ' is provided. Through this parallel guidance of the two lines 12 / 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 formed biphilar, 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 biphilic arrangement to avoid inductance can be selected 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 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 also 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 representing the capacity between determine the lines are in the relevant literature described in detail and are known to those 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 A1 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 , 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.

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

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited patent literature

• - US 4060088 [0003]
• US 4781175 [0003]
• - DE 19839826 [0009, 0012]
• - DE 19820240 [0018]
• - DE 10129699 [0018, 0043]
• - EP 1397082 [0018]
• EP 0954246 A1 [0040]
• - DE 19820240 A1 [0042]
• - DE 10129699 A1 [0042]

Cited non-patent literature

• - 1994 by G. Farin and KE Grund [0004]
• - G. Farin, KE Reason: Technology of Argon Plasma Coagulation with Particular Regard to Endoscopic Applications. Endoscopic Surgery and Allied Technologies, No. 1 Volum 2, 1994: 71-77 [0004]
• - KE Reason, 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 [0004]
• - KE Reason, C. Zindel, G. Farin: Argon plasma coagulation in flexible endoscopy: evaluation of a new therapeutic procedure after 1606 applications. German Medical Weekly 122, 1977: 432-438 [0004]
• - 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 [0006]
• - G. Farin and KE 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 [0007]

Claims (10)

Plasma applicator with a tubular or tubular probe ( 10 ) for transmitting electrical energy from an electrosurgical RF generator ( 1 ) via a connecting line ( 11 . 12 ) and an electrode connected to the distal end thereof ( 13 ) and continue through a path or arc ( 14 ) of ionized gas into a biological target tissue ( 4 ) and via a neutral electrode ( 2 ) back to the electrosurgical generator ( 1 ), wherein between the distal end of the connecting line ( 11 . 12 ) and the electrode ( 13 ) a resistance element ( 20 ) is arranged with a predetermined impedance, which is dimensioned such that after the ionization of the gas, a limitation of a treatment current is ensured. Electrosurgical instrument according to claim 1, characterized in that the resistance element ( 20 ) comprises a capacity. Electrosurgical instrument according to one of the preceding claims, characterized in that the resistance element ( 20 ) is designed as a commercially available component, in particular as a commercially available resistor or capacitor. Electrosurgical instrument according to one of the preceding claims, characterized in that the resistance element ( 20 ) a subsection of the connecting line ( 12 ) and / or the electrode ( 13 ). Electrosurgical instrument according to one of the preceding claims, in particular according to claim 4, characterized in that the resistance element ( 20 ) by parallel or twisted or coaxially arranged sections of the connecting line ( 12 ) and a supply line ( 24 ) to the electrode ( 13 ) and / or the electrode ( 13 ) itself is formed. Electrosurgical instrument according to one of the preceding Claims, in particular according to claim 5, characterized that the sections a lowest possible inductance have, in particular as biphilic arrangements are formed. Electrosurgical instrument according to one of the preceding Claims, characterized in that the resistance element a capacity of 10 pF to 1,000 pF. Electrosurgical instrument according to one of the preceding claims, characterized in that the resistance element ( 20 ) comprises a ceramic material as insulation and / or dielectric. Electrosurgical instrument according to one of the preceding claims, characterized in that the electrode ( 13 ) in or near a pipe or hose ( 9 ) of a probe ( 10 ) is mounted such that a noble gas, in particular argon, as gas to be ionized into a space between the electrode ( 13 ) and the target tissue ( 4 ) can be fed. Electrosurgical instrument according to claim 8, characterized in that the ceramic material is powdered is.