DE10252325B4 - Radiofrequency thermal ablation probe and method of making the same - Google Patents

Abstract

Probe (14) for high-frequency thermal ablation with an insulating tube (18), at the distal end of which a metal electrode (16) is provided, the spatial extent of which can be changed from a cylindrical shape to a star-shaped shape, the metal electrode (16) being replaced by several flexible arms (26) are formed, the distal and proximal ends of which are connected to one another, the distal and / or the proximal ends of the arms (26) being electrically connected to a connection for supplying a high-frequency current, the flexible arms (26) themselves form the electrode and the shape of an arm (26) deviates approximately in the middle (M) from its shape at both ends, so that it has a bending stiffness which favors the star-shaped design of the metal electrode (16), the outer contour of an arm ( 26) approximately in the middle (M) is approximately spiral, zigzag, wavy or meandering and rectilinear at both ends.

Description

The present invention relates to an endoluminal probe for radiofrequency thermal ablation, also called radiofrequency induced thermotherapy, in which biological tissues are thermally denatured by heat generation by means of high-frequency electric fields and currents, and to a process for their production. The probe, which can also be used in combination with flexible endoscopy technology, is used for the minimally invasive thermal influence of diseased structures in hollow organs (eg intestine, bronchi, trachea, esophagus) or in larger veins or arteries by high-frequency energy in the frequency range of 300 kHz to 1 MHz.

US 5,681,280 discloses a steerable catheter having an elastically deflectable body member with an expandable row of electrodes at a distal end. Furthermore, a catheter with expansion parts is made DE 196 10 461 C2 known.

It is the object of the invention to provide a cost-producible endoluminal probe for Hochfrequnez-Thermoablation.

The solution of this object is achieved by the features of claim 1 and in particular in that the probe has an insulated tube, at the distal end of a metal electrode is provided, the spatial extent of a cylindrical shape to a star-shaped shape is variable. Due to the cylindrical shape of the metal electrode, a small-volume navigation of the probe within a biological lumen or via the instrumentation channel of an endoscope is possible. After positioning of the electrode in the target area, an electrode development to the star-shaped shape can subsequently take place. In particular, the star-shaped electrode particularly good effects are achieved in the thermal ablation, with an additional advantage of the variable diameter of the star-shaped electrode, This intraluminal a locally defined and electrically conductive electrode contact despite anatomically variable biological environment can be produced.

The metal electrode according to the invention is formed by a plurality of flexible arms whose distal and proximal ends are connected to each other, wherein the distal and / or proximal ends of the arms are electrically connected to a terminal for supplying a high-frequency current. According to the invention thus form the flexible arms themselves the electrode, d. H. no additional point electrodes or the like are required. As a result, on the one hand, the manufacture of the probe is simplified. On the other hand, this can be easily cleaned.

After the therapeutic Energieapplikation the deployment of the metal electrode can not be reversed, whereby a removal of the probe from the cavity is easily possible.

Further, the shape of an arm deviates approximately in the middle of its shape at both ends. As a result, a bending behavior is predetermined by the shape of the arm itself, which favors the star-shaped design of the metal electrode. The outer contour of an arm is approximately in the middle of approximately spiral, zigzag, wavy or meandering, the outer contour is straight at the two end portions of the arm. By means of such a trained middle region of an arm, the flexural rigidity can be adapted to the requirements.

Advantageous embodiments of the invention are described in the description, the drawings and the subclaims.

According to a further embodiment of the invention, the distal and proximal ends of the arms may be adjustable relative to one another by means of an actuating device provided at a proximal region of the hose. As a result, the outer diameter of the metal electrode can be varied and change the spatial extent of the cylindrical shape to the star-shaped shape.

According to another embodiment of the invention, the proximal ends of the arms are connected to a flexible cannula which is guided inside the tube. This embodiment has the advantage that flushing fluid and / or a further adjusting element for moving the arms can be guided within the flexible cannula. For example, the distal ends of the arms may be connected to a flexible actuator which is guided inside the tube or within the cannula. In this way, the outer diameter of the metal electrode can be changed, without necessarily the hose is moved along.

According to a further embodiment of the invention, a temperature sensor may be arranged in the region of the distal ends of the arms. Such an arrangement additionally allows a temperature control or an automatic temperature control via a high-frequency generator designed for this purpose.

Furthermore, it may be advantageous if a proximal end of the probe is provided with a connection for rinsing liquid. This flushing fluid can through the tube or provided in the tube cannula in the direction of Metal electrode are promoted to prevent dehydration and electrical conductivity loss in the ablation zone.

An electrode for a probe of the type described above can be advantageously prepared by providing a sheet blank or a cylindrical cannula of electrically conductive material with mutually parallel microcuts, the ends of which are each not up to the edge of the blank or the cannula extend. In this way, individual webs are formed between the micro sections, which serve as arms of the probe. In this case, it may be advantageous if the microsections are formed in a central section in a spiral, meandering, wave or zigzag shape. This results in the middle region of the arms bending elastic metal webs. In order to make the central portions of the arms particularly flexible, it may also be advantageous to increase the thickness of the microsections in a middle section and to make them smaller in the end sections.

Hereinafter, the present invention will be described by way of example with reference to an advantageous embodiment and with reference to the accompanying drawings. Show it:

1 a schematic view of a device for high-frequency thermal ablation;

2 a partially sectioned view of a distal end of a probe, wherein the metal electrode has a cylindrical shape; and

3 the probe of 2 wherein the metal electrode is deployed to a star shape.

1 schematically shows a system for high frequency thermal ablation with a high frequency generator 10 , a neutral electrode 12 and an endoluminal probe 14 , at its distal end a metal electrode shown only schematically 16 is provided. The metal electrode 16 located at the distal end of an insulating tube 18 , at the proximal end of a handpiece 20 is provided. The hand piece 20 has a connection for a high-frequency cable 22 on, that the high frequency generator 10 electrically with the metal electrode 16 combines. The neutral electrode 12 is via a neutral electrode cable 24 with the high frequency generator 10 electrically connected.

2 shows in perspective view the distal region of the probe 14 wherein the metal electrode 16 folded into a cylindrical shape and into the interior of the tube 18 withdrawn. For better illustration is a part of the hose 18 shown broken.

3 shows the probe from 2 but where the metal electrode 16 from the hose 18 is pushed out and is deployed to a star-shaped figure. As in the 2 and 3 can be seen, is the metal electrode 16 by, for example, six flexible arms 26 formed in 2 coaxial with the axis of the hose 18 run, however, in 3 protrude predominantly radially and in a star shape from the central axis of the probe. All arms 26 are at their distal ends via a pot-like tail 28 connected with each other. The distal ends of the arms 26 are about a sleeve-shaped tail 30 also connected with each other. The poor 26 as well as the end pieces 28 and 30 , which are all integrally connected to each other, thus forming the metal electrode 16 Due to its extremely compact design, it can be guided through the instrumentation channel of an endoscope.

As in particular in the 2 and 3 it can be seen, there is every arm 26 made of a thin strip of metal with rectangular cross section, the shape of each arm 26 approximately in the middle M deviates from the shape at the two ends of the arm. The outer contour of each arm 26 is approximately wavy in its center M, while adjoining the wave-shaped region in the middle M on both sides of a section with a straight outer contour. In this case, the section with wavy outer contour about one third of the total length of the arm 26 on.

Due to the wavy outer contour of the arms 26 in the middle region M, the arms can be moved to the in 3 bend shown arrangement in which the wave-shaped portion is U-shaped and the arms protrude approximately at right angles from the central axis of the probe. In contrast, the metal electrode has 16 in the 2 illustrated state in which it is retracted into the interior of the tube, a cylindrical shape in which the individual arms 26 parallel to each other and abut each other with only a small distance.

The proximal tail 30 the metal electrode 16 is with a guided inside the tube, flexible cannula 32 connected with a push handle 34 ( 1 ) of the handpiece 20 communicates. The distal end piece 28 the metal electrode 16 is with a flexible actuator 36 connected within the cannula 32 is guided and its proximal end with a push handle 38 communicating, which is also on the handpiece 20 is provided. The actuator 36 and the cannula 32 are inside the handpiece 20 mechanically releasable with the push handles 34 and 38 connected, wherein the push handles can be operated with one hand individually and relative to each other. The proximal end of the tube 18 is with the Housing of the handle 20 releasably connected. Within the handle, which is not shown in detail, is an electrically conductive connection between the cannula 32 and the metal electrode cable 22 intended.

By relative movement of the push handles 34 and 38 to each other and relative to the handpiece 20 can the metal electrode 16 from the in 2 shown position in which they are completely inside the tube 18 located in the in 3 shown arrangement are shifted, wherein the metal electrode 16 from the distal end of the tube 18 protrudes and has a star-shaped shape.

In the area of the handpiece 20 can also have a connection 40 be provided for rinsing liquid, for example, by the physiological saline solution in the region of the metal electrode 16 can be brought.

The hose 18 the probe 14 consists of flexible, insulating material. The metal electrode 16 and the cannula 32 consist of a super-elastic material that conducts electrically, for example, a nickel-titanium alloy. The actuator 36 may optionally be wire or cannula shaped and made of flexible metal or plastic. The handle 20 and the push handles 34 . 38 consist of insulating plastic.

The probe 14 may have a different total length depending on the application up to about 200 mm and a probe diameter to about 3 mm. The metal electrode 16 may have a length of about 20 to 35 mm. The outer diameter of the metal electrode 16 can be for example 1.8 mm. From the in 2 As illustrated, the metal electrode may be compressed by compression into that shown in FIG 3 illustrated, star-shaped arrangement can be converted, in which the electrode star has an axial length of about 8 mm and a diameter of up to 30 mm.

The preparation of the metal electrode according to the invention 16 can be done for example by a flat blank, such as a thin metal foil, or a cylindrical cannula, each made of electrically conductive material with mutually parallel microcuts are provided, wherein the cuts at their ends not to the edge of the blank or the Extend cannula. If these cuts are distributed uniformly over the circumference of the cannula or over the extension of the blank, strip-like material sections, which form the arms, are produced between the individual cuts 26 form. These micro-cuts can be spiral, meander, zigzag or wave-shaped in a central section (cf. 2 and 3 ), whereby the above-described central portions of the arms can be formed. The blank can then be formed into a sleeve.

In addition, it may be advantageous to vary the thickness of the micro-cuts along their longitudinal extent. For example, the thickness of the micro-cuts in the middle section M may be greater than in the region of the end sections, whereby an additional variation of the elastic behavior of the arms is possible.

The operation of the probe described above is described below using the example of endoluminal radiofrequency thermal ablation: After the patient to be treated with an adhesive and large-area neutral electrode 12 contacted on the skin, resulting in the shortest possible body distance to the metal electrode 16 should be done, the patient is after connecting the neutral electrode cable 24 to the neutral electrode 12 and to the high frequency generator 10 an integral part of the high frequency circuit.

Subsequently, the probe according to the invention is navigated via the instrumentation channel of a flexible endoscope - or in interventional therapies under image control (sonography, computed tomography, magnetic resonance tomography) via body cavities or vessels to the target area. Subsequently, the metal electrode 16 by pressing the push handles 34 and 38 extended and unfolded, so that this contacted the treated or pathogenic biological tissue, for example, within the esophagus. Subsequently, a high frequency current is activated at the RF generator for a defined time or until reaching a predetermined electrical impedance level or energy level or temperature level. In this case, the high-frequency current flows inside the probe 14 over the star-shaped unfolded metal electrode 16 to the contacted biological tissue and via the neutral electrode 12 back to the HF generator 10 , With the square of the RF current intensity and proportional to the current electrode electrode biofertiliseand proportional to the activation time, localized thermal effects arise, whereby at temperatures above 50 ° C., preferably in the range 60 ° C. to 100 ° C., the biological tissue is thermally denatured. After a few seconds of exposure to the HF current, bio-tissue shrinkage and drying are achieved in the narrow contact area of the electrodes. Thus, even malignant biological tissue (primary tumors, metastases) can be thermally destroyed or it can be a thermal hemostasis or therapeutic tissue shrinkage produced with tolerable scarring.

LIST OF REFERENCE NUMBERS

10

RF generator

12

neutral electrode

14

probe

16

metal electrode

18

tube

20

handpiece

22

Metal electrode cable

24

Neutral electrode cable

26

poor

28

distal end piece

30

proximal tail

32

cannula

34

push handle

36

actuator

38

push handle

40

Connection for rinsing fluid

M

Middle area

Claims (12)

Probe ( 14 ) for high-frequency thermal ablation with an insulating tube ( 18 ), at its distal end a metal electrode ( 16 ) is provided whose spatial extent is variable from a cylindrical shape to a star-shaped shape, wherein the metal electrode ( 16 ) by a plurality of flexible arms ( 26 ) whose distal and proximal ends are connected to each other, wherein the distal and / or the proximal ends of the arms ( 26 ) are electrically connected to a terminal for supplying a high-frequency current, wherein the flexible arms ( 26 ) itself form the electrode and the shape of an arm ( 26 ) deviates in its middle (M) from its shape at both ends, so that it has a flexural rigidity, the star-shaped formation of the metal electrode ( 16 ), whereby the outer contour of an arm ( 26 ) approximately in the middle (M) is approximately spiral, zigzag, wavy or meandering shape and is rectilinear at its two ends. A probe according to claim 1, wherein the metal electrode ( 16 ) has a length of 20 to 35 mm and by compression in the star-shaped arrangement has an axial length of about 8 mm and a diameter of up to 30 mm. Probe according to one of the preceding claims, characterized in that by means of a at a proximal portion of the tube ( 18 ) ( 34 . 38 ) the distal and proximal ends of the arms ( 26 ) are adjustable relative to each other. Probe according to one of the preceding claims, characterized in that the proximal ends of the arms ( 26 ) with a flexible cannula ( 32 ), which are inside the hose ( 18 ) is guided. Probe according to one of the preceding claims, characterized in that the distal ends of the arms ( 26 ) with a flexible actuator ( 36 ), which are inside the hose ( 18 ) is guided. Probe according to one of the preceding claims, characterized in that in the region ( 28 ) of the distal ends of the arms ( 26 ) A temperature sensor is arranged. Probe according to one of the preceding claims, characterized in that its proximal end is connected to a connection ( 40 ) is provided for rinsing liquid. Probe according to one of the preceding claims, wherein a distal end piece ( 28 ) of the metal electrode ( 16 ) with a flexible actuator ( 36 ), which within a cannula ( 32 ) is guided. A probe as claimed in claim 8, wherein a proximal end of the flexible actuator (10). 36 ) with a push handle ( 38 ) connected is. Method for producing an electrode for a probe ( 14 ) for high-frequency thermal ablation with an insulating tube ( 18 ), at its distal end a metal electrode ( 16 ) is provided, whose spatial extent is variable from a cylindrical shape to a star-shaped shape, the method comprising the steps of: forming the metal electrode ( 16 ) by a plurality of flexible arms ( 26 ) and connecting their distal and proximal ends together, so that the flexible arms ( 26 ) itself form the electrode, and forming the arm ( 26 ) such that the shape of the arm ( 26 ) deviates in its middle (M) from its shape at both ends, so that the flexural rigidity of the star-shaped formation of the metal electrode ( 16 ) favors; where the outer contour of an arm ( 26 ) approximately in the middle (M) is approximately spiral, zigzag, wavy or meander-shaped and formed at its two ends straight. Process for producing an electrode for a sand ( 14 ) for high-frequency thermal ablation according to claim 10, characterized in that in a flat blank or a cylindrical cannula made of electrically conductive material parallel micro-cuts are introduced, which do not extend at their ends in each case to the edge of the blank or the cannula. A method according to claim 10 or 11, characterized in that the thickness of the microsections in a larger middle section and lower in end sections.

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