Tissue treatment facility

Description

[0001] The invention relates to an electrosurgical device for the electrothermal treatment of biological tissue. Furthermore, the invention relates to a method for positioning an instrument belonging to the device in the biological tissue.

[0002] It is generally known to detect and monitor the contact between a treatment electrode and biological tissue using electrical measurements. For this purpose, WO 2009 / 065140 A1 and US 2017 / 0312009 A1 disclose both an ablation system and a method that provides real-time feedback on the formation of a lesion. For this purpose, the degree of electrical coupling between an ablation electrode and the biological tissue is determined. Based on this, the volume of the resulting lesion can be estimated. To determine the degree of contact, the phase relationship between the applied voltage and the resulting current can be used. A phase measurement circuit is provided for this purpose.

[0003] EP 2 612 612 A1 also proposes detecting the phase relationship between voltage and current at the treatment electrode of an instrument. This method utilizes the knowledge that the phase relationships before contact, during contact, and after treatment are characteristically different from each other.

[0004] DE 10 2019 209 333 A1 discloses the determination of the type of tissue in contact with an instrument. For this purpose, alternating voltages of different frequencies are applied to the instrument and introduced into the tissue, and the resulting currents are monitored. This method is also known as impedance spectroscopy.

[0005] US 2021 / 0068895 A1 discloses a generator and an associated instrument for ablating lung tumors. The instrument is designed as a catheter and has a tip with electrodes that can be inserted into a tumor. The generator applies an ablation voltage to these electrodes that is suitable for heating and thereby killing the tumor tissue. The impedance measured at the electrodes is monitored. Impedance peaks indicate vapor bubble formation. However, vapor bubbles insulate the electrodes from the tissue, which is why such impedance peaks cause the ablation process to be shut down, at least briefly.

[0006] When coagulating specific tissue volumes in living human or animal patients, it is often crucial to position the instrument, and especially its electrodes, in the tissue to be treated, specifically the tissue to be coagulated, in such a way as to achieve a good treatment outcome. The surgeon's view of the tissue to be treated is typically limited. This is especially true if the tissue to be treated is not exposed but surrounded by and embedded in other tissue that should be protected during treatment.

[0007] This leads to the object underlying the invention of providing an electrosurgical device that supports the practitioner in placing the instrument in the tissue to be treated.

[0008] These objects are achieved with the electrosurgical device according to claim 1.

[0009] The electrosurgical device according to the invention includes an instrument that can be inserted into biological tissue and preferably has an elongated, needle- or pin-like basic shape. The instrument preferably has two or more electrodes that are arranged at an axial distance from one another on the instrument. For example, the instrument is a tube-like instrument that can be transferred into a body, for example through an endoscope, and has a distal end region in which the electrodes are arranged as spiral electrodes, cylindrical electrodes, or the like. The instrument can be cooled from the inside to prevent or limit heating of the electrodes. The electrodes, which are preferably arranged at an axial distance from one another, preferably serve as treatment electrodes and can be subjected to a treatment voltage U HF for this purpose.For this purpose, they are connected via appropriate cables to an electrosurgical generator which is designed to deliver such a treatment voltage U HF. The treatment voltage U HF is a high-frequency alternating voltage with a frequency typically greater than 100 kHz. In addition, the generator is designed to deliver a test voltage UT to the same electrodes, which is significantly lower than the treatment voltage U HF (e.g. a factor of 10 - 20) and therefore has no or only a very slight physiological effect. The test voltage UT is used to check and display the positioning of the instrument in biological tissue, for example in a target tissue such as a tumor, which, after the instrument has been correctly positioned, is then subjected to the treatment voltage U HF and thus thermally destroyed.

[0010] The invention takes advantage of the fact that tumorous tissue is very well supplied with blood, which makes it electrically distinct from adjacent healthy tissue. The device's instrument can be securely positioned within the tumor tissue using this property of the tumor, preventing misplacement.

[0011] The generator has a control device that is designed to record the current i that the test voltage UT causes between the two electrodes of the instrument. Furthermore, the control device is designed to determine two characteristic quantities from the test voltage UT and the current i. One of the two quantities depends on the impedance effective between the electrodes. The other of the two quantities depends on the phase angle between the test voltage and the current. For example, the first quantity can be the magnitude of the impedance while the second quantity is the power factor or another quantity dependent on the phase angle phi between the current and the voltage. Power factor is the quotient of the effective power converted between the electrodes in the tissue to the apparent power.

[0012] The control unit monitors the change in both variables as the instrument penetrates the biological tissue and checks whether both changes exceed specified thresholds. The changes in both variables can be understood as a temporal change. The change in the respective variable is then measured as the difference in the variable between two consecutive points in time at a given interval.

[0013] The control device can be designed in various ways: In a first variant, it can be set up to emit a signal whenever the changes in the two variables exceed their two threshold values. In another variant, the control device can be set up to emit a first signal when the changes exceed their two threshold values in a first direction and a second signal when the changes then reverse their directions. In a further variant, the control device can be set up to define the two variables as reference variables when both changes exceed predetermined threshold values. The setting of the two reference variables can optionally be linked to the emission of a first signal which signals to the surgeon that the target tissue has been reached.Furthermore, the control device can be configured to emit a second signal if a difference arises between the two variables and the reference variables that exceeds a predetermined amount. Alternatively, the control device can be configured to emit the second signal if the changes reverse their directions after the reference variables have been established. The first signal and the second signal can be the same or different. It is also possible to generate a signal as long as the two variables do not deviate from the two reference variables (within a predetermined or predeterminable tolerance).

[0014] The emitted signal can be, for example, an acoustic, an optical or a combination of both, whereby the optical signal can be displayed, for example, visually on a display of the electrosurgical system containing the electrosurgical generator.

[0015] According to the inventive concept, the practitioner inserts the instrument into the tissue at a normal speed. Typical insertion speeds are approximately 0.5 cm / s. Using the example of treating lung tumors, healthy lung tissue exhibits an impedance Imp of more than 300 ohms and a power factor of LF = cos(phi) < 0.75. As soon as one of the two electrodes, particularly the distal electrode of the instrument, comes into contact with tumor tissue, both parameters change—for example, both the impedance and the power factor.If the instrument is now inserted further into the target tissue and the distal end of a proximal electrode touches the target tissue, the impedance drops by at least 60% compared to the previously measured impedance within a period of, for example, 2 seconds at the usual insertion speed and usual instrument size, while the power factor increases by, for example, 20% compared to the power factor before the specified period of time (e.g., two seconds). This applies in particular to conventional instruments with an electrode length measured in the axial direction of 8 to 9 mm and an axial electrode distance of 3 to 4 mm. The changes in both variables are recorded by the control device. This can then emit a signal from which the practitioner can conclude that both electrodes are in contact with the tumor tissue.According to the aforementioned alternative embodiments of the control device, instead of or in addition to the direct signal output, the control device can also store the values of the variables as reference variables and emit a signal when the variables change from the stored reference variables. For example, the position of the electrodes on the instrument in the target tissue can be displayed to the user on a display located on the device 15.

[0016] When measuring the two variables, for example the impedance and the power factor, preferably several consecutive values are measured and a moving average is determined from these. The first variable can be the moving average of the impedance, for example, while the second variable is the moving average of the power factor. The device according to the invention can be provided to compare the moving averages at different points in time and to determine which points in time belong to one another within a given time interval. This allows the practitioner to adapt the insertion speed to their individual needs. If they tend to insert the electrodes slowly, they should choose a longer time interval; if they tend to insert the instrument quickly, they should choose a shorter time interval.

[0017] Furthermore, it is possible to automate the piercing process by providing a drive device that moves the instrument in the distal direction at a known, e.g., constant speed and / or in a path-controlled manner. The drive device can generate position data that characterize the respective position of the instrument with respect to its longitudinal direction. In this case, the changes can be determined as temporal changes or, alternatively, as position-dependent changes. The latter is also possible when manually piercing an instrument if it is connected to a suitable path-measuring device. Such a path-measuring device can, for example, provide data that indicate how far the instrument has been moved in the distal axial direction.In the simplest case, such a distance measuring device can be provided on an endoscope or bronchoscope, in which, for example, a measuring wheel is provided at its proximal end, which is in contact with the instrument body (the probe) and is rotated when the probe is advanced axially.

[0018] Further advantageous details of the invention are the subject of subclaims as well as the description and accompanying drawings. They show: Figure 1 the device according to the invention in the treatment of biological tissue, in a schematic representation, Figure 2 that belongs to the institution Figure 1 appropriate instrument when penetrating tissue requiring treatment. Figure 3 the instrument after Figure 2 , in a schematic, partial longitudinal section, Figure 4 Voltage and current on the instrument during insertion and treatment, Figure 5various quantities determined from the voltage and current in a time course as a diagram.

[0019] In Figure 1 Illustrated is a device 10 used to treat biological tissue 11, such as lung tissue, which, for example, consists of healthy lung tissue 12 and a tumor 13 embedded therein. The device 10 comprises at least one instrument 14 and a device 15 for supplying the instrument 14 with the necessary operating media, e.g., cooling medium and power. The instrument 14 can be a flexible probe 16, which is guided to the target tissue 11, for example, through a bronchoscope 17.

[0020] When treating other tissues, other instruments may also be used, such as endoscopes, laparoscopic instruments, or even open surgical instruments. The invention is not limited to bronchoscopy.

[0021] The instrument 14 is in Figure 2and 3 further illustrated. It comprises an elongated body 18, for example, designed as a tube, on which a distal electrode 19 and a second electrode 20 spaced apart in the proximal direction are arranged. The electrodes 19, 20 are typically between 7 and 10 mm long in the axial direction and electrically insulated from one another. For this purpose, they are arranged, for example, at a distance of 3 mm to 5 mm in the axial direction. The electrodes 19, 20 are formed, for example, by cylindrical sleeves, coils, or the like and have a diameter of, for example, 2 to 3 mm.

[0022] The electrodes 19, 20 can be supplied with voltage and current via electrical lines that preferably extend through the probe 16 and are connected to the device 15. The device 15 in Figure 1For this purpose, it has an RF generator 23 which is controlled by a control device 24 in order to deliver either a test voltage UT or a treatment voltage U HF to the electrodes 19, 20.

[0023] The instrument 14 may enclose a lumen 25, to which a cooling medium is supplied via a capillary 26 arranged in the lumen 25. This cooling medium may serve to cool the electrodes 19, 20 to prevent the tissue in contact with the electrodes 19, 20 from drying out during treatment.

[0024] Optionally, the bronchoscope 17 can be connected as shown in Figure 1For example, as shown, a position measuring device 27 can be provided, by means of which the current position of the probe 16 can be determined when it is inserted into the bronchoscope 17 and when it is inserted into the biological tissue 11. The position measuring device can include, for example, a wheel 28 that is in frictional engagement with the probe 16 and a resolver 29. Alternatively, position markers can be attached to the casing of the probe 16, which can be read by the position measuring device 27. Furthermore, it is possible to insert the probe 16 into the tissue 11 in an automated manner. For this purpose, a motor 30 can be provided, which is drive-connected to the wheel 28. The resolver 29 or the other position measuring device 27 and, if present, the motor 30 are then connected to the control device 24.

[0025] The control device 24 can have input means 31, such as a keyboard, a touchscreen, or the like, to influence its operation. The input means can be provided for entering preset values, e.g., for durations, voltages, currents, powers, threshold values, and the like, and transmitting them to the control device.

[0026] The generator 23 is designed to generate a treatment voltage U HF and alternatively a Figure 4 The test voltage UT shown in the diagram can be a few volts, for example, as low as 10 volts. The test voltage UT is preferably an alternating voltage, in particular a high-frequency alternating voltage with a frequency above 100 kHz. It is transmitted to the electrodes 19, 20 via the lines 21, 22.

[0027] When the tissue 11 is punctured, a current i flows between the electrodes 19, 20. The generator 23 contains appropriate measuring devices to measure the current i both in terms of its magnitude and its phase position relative to the test voltage UT. The measuring devices can, for example, measure the phase angle phi between the test voltage UT and the resulting current i, or a value dependent on the phase angle phi (e.g., the power factor).

[0028] The generator 23 is further configured to deliver the treatment voltage U HF , which may be, for example, 100 volts or several hundred volts (but preferably < 200 Vp). The generator 23 may additionally be configured to detect the resulting current. However, this is not mandatory.

[0029] The control device 24 is configured to supply the electrodes 19, 20 with test voltage via the generator 23 when the instrument 14 is inserted into the tissue 11. The control device 24 is further configured to determine a first variable G1 from the voltage UT and the current i, which is dependent on the impedance Imp acting between the electrodes 19, 20. This variable G1 can be, for example, the complex impedance Imp, its real part R=Re{Imp}, its absolute value |Imp|, or another variable derived therefrom, for example the conductance Imp -1<. The first variable G1 can also be represented by other variables derived from the impedance Imp.

[0030] Furthermore, the control device 24 is configured to determine a second variable G2, which depends, for example, on the phase angle phi between the current i and the test voltage UT. The second variable G2 can be, for example, the power factor LF = cos(phi). The power factor LF can also be the quotient of the active power P transmitted into the tissue 11 and the apparent power S, LF = P / S.

[0031] Furthermore, the control device 24 is set up to determine the change V1 in the first variable G1 and the change V2 in the second variable G2. The change can be the change over time, for example. For this purpose, a moving average can be formed from the first variable G1 and the difference between this average between two points in time can be determined. The two points in time t1, t2 can be spaced apart by a fixed, predetermined time interval Δt. The time interval Δt can be a time interval that can be entered, for example, using the input device 31. This can be between 0.1 and 5 seconds, for example, and can be set to 2 seconds, for example. The first change V1 is therefore the difference between the variable G1 at a point in time t2 and a point in time t1, which are spaced apart from each other by the time interval Δt.

[0032] The conditions are in Figure 5illustrated. Likewise, the second change V2 can be understood as the difference in the second variable G2 between two different times t1, t2. This difference is again preferably formed between averaged values of the second variable G2. For example, the second variable G2 is the moving average of the power factor. In this example, the difference is formed from the moving average of the power factor LF at time t2 and the moving average of the power factor LF at time t1.

[0033] The control device 24 is designed to determine the two changes V1 and V2 when the instrument 14 is inserted into the tissue 11. In Figure 5 This is illustrated in the following. Figure 5On the far left, both electrodes 19, 20 are in lung tissue 12. The impedance, or its magnitude, and thus the quantity G1, is at a relatively high value above 300 ohms. The power factor LF is in a range of cosine phi < 0.75.

[0034] At a time t0, the electrode 19 begins to touch the tumor 13. As the instrument 14 continues to penetrate the tumor 13, the impedance begins to gradually decrease. At the same time, the power factor LF gradually increases. As soon as the second electrode 20 also penetrates the tumor 13 (time t1), the impedance Imp begins to decrease more rapidly and the power factor LF begins to increase more rapidly. This is shown in Figure 5 in section A by the steeper decline of the curve of G1 and the steeper rise of the curve of G2 in the time window Δt. (It is noted that in Figure 5the course of the quantities G1 and G2 is illustrated using the moving average, ie to determine the quantity G1 and the quantity G2, a series of measured values, for example within an interval of one second, are processed into an average).

[0035] If the absolute value of the difference between the moving averages of G1 in interval A, i.e. the change V1, exceeds 60% and the change V2 (i.e. the absolute value of the difference between the moving averages of G2 in interval A) exceeds 20%, the control device 24 can carry out various actions depending on its design. A first option is the immediate emission of a signal which indicates to the operator that both electrodes 19, 20 are sufficiently placed in the tumor 13. This enables treatment of the tumor. A second option is the emission of the signal after a fixed or adjustable waiting time. This takes into account the fact that the changes V1 and V2 usually already fulfill the above conditions before the proximal electrode has fully penetrated the tumor. The waiting time of 1 s, for example, allows the user to push the probe somewhat deeper into the tumor.The practitioner can now switch the generator from test mode to treatment mode and thus apply the treatment voltage to the electrodes 19, 20. This can be done manually or, in a modified embodiment, automatically by the control device 24.

[0036] In another variant, the control device 24 can also store the quantities G1 and G2 at the end of phase A as reference quantities G1B, G2B and only emit a signal when the quantities G1, G2 start to move in the opposite direction, as in Figure 5 shown in Section B.

[0037] The device 10 described so far works as follows: After connecting the instrument 14 to the device 15, the instrument 14 is guided through the bronchoscope 17 to the tissue 11 to be treated. The instrument 14 is then pushed out of the bronchoscope 17 in the distal direction and inserted into the tissue 11. As soon as the electrodes 19, 20 of the instrument 14 are no longer visible to the user through the bronchoscope, the practitioner activates the generator 23 in test mode so that it delivers the test voltage UT to the electrodes 19, 20 of the instrument 14. The generator 23 applies a low sinusoidal alternating voltage of, for example, less than 10 V p (volt peak) with a frequency of, for example, 350 kHz and a power limit of 1 watt to the instrument 14. The test voltage UT and the resulting current i have no thermal effect on the tissue 11 due to their low power.

[0038] In test mode, the instrument 14 is advanced further into the tissue 11, with the impedance Imp and the phase angle phi, or derived quantities G1, G2, such as the power factor LF, being determined and stored at specified time intervals (e.g., every 0.1 milliseconds). As long as the instrument 14 is located in the lung tissue 12, the impedance Imp is in the range above 300 ohms, and the power factor LF is typically less than 0.75.

[0039] As soon as the distal electrode 19 of the instrument 14 comes into contact with the tumor tissue 13, both the impedance Imp and the power factor LF begin to change characteristically. However, the ablation instrument 14 continues to penetrate the tumor tissue 13.

[0040] If the change V1 of the current impedance value Imp compared to the impedance Imp a given time period ago (e.g., Δt = 2 seconds) is greater than a threshold S1 (e.g., 60%), and at the same time the change V2 of the current power factor LF compared to the power factor LF 2 seconds ago is greater than a threshold S2 (e.g., 20%), these instantaneous values of the impedance Imp and the power factor LF are declared as tumor values. The control device can be configured to store the current values G1 and G2 as reference values G1B and G2B.

[0041] Instead of the time period Δt of two seconds, other time periods can also be set and used depending on the practitioner. This time period Δt can be changed using input device 31.

[0042] The user now pushes the instrument 14 further through the tumor 13. However, as soon as the control device 24 detects an increase in the currently calculated mean of the moving average impedance value and a decrease in the moving average of the power factor ( Figure 5, Section B), the control device gives the user a signal indicating that the instrument is now back in contact with the lung tissue. This means that the instrument 14 with its electrodes 19, 20 is located asymmetrically in the tumor 13 or has pierced the tumor 13. The user recognizes this from the signal, which is shown, for example, on the display on the device 15, and can withdraw the ablation instrument. In this way, the user finds a position suitable for treatment. The signal can be emitted in Section B when the changes V1, V2 exceed a respective threshold value. The threshold values can be identical to or different from the threshold values S1 and S2.

[0043] In a modified embodiment, the control device outputs in section A ( Figure 5) a first signal and in section B a second signal, so that the user finds the correct position of the instrument 14 between sections A and B.

[0044] An instrument 14 suitable for the treatment of lung tumors and other tissues and an associated device 15 detect the correct positioning of the instrument 14 and its two electrodes 19, 20 in suitable target tissue by observing two variables G1, G2 and, in particular, their temporal changes. If the change V1, V2 of the two variables G1, G2 exceeds the given limit values S1, S2, this can be used to determine the contact between the instrument and the tissue to be treated and thus also the positioning of the instrument in a desired position. The invention thus contributes significantly to increasing treatment safety. Reference symbol:

[0045] 10Device 11Biological tissue 12Healthy lung tissue 13Tumor 14Instrument 15Device 16Probe 17Bronchoscope 18Main body 19First electrode 20Second electrode 21, 22Leads 23Generator 24Control device 25Lumen 26Capillary 27Displacement measuring device 28Wheel 29Resolver 30Motor 31Input device

Claims

1. An electrosurgical device (10) for the electrothermal treatment of biological tissue (11), having an instrument (14) that can be penetrated into biological tissue and that has a body (18) with a first electrode (19) and at least one second electrode (20) arranged at a proximal distance from the first electrode (19), which can be supplied with a radio frequency test voltage (UT) and with a radio frequency treatment voltage (UHF), wherein the test voltage (UT) is significantly lower than the treatment voltage (UHF) and therefore has no or only a very low physiological effect, wherein the treatment voltage (UHF) is suitable for the thermal destruction of the biological tissue (11), having an apparatus (15) comprising an electrosurgical generator (23) that is configured to supply the electrodes (19, 20) of the instrument (14) with the test voltage (UT) and to detect the resulting current (i) thereby, having a control device (24) that is configured to detect from the test voltage (UT) and the current (i) a first parameter (G1) that is dependent on the effective impedance (Imp) between the electrodes (19, 20) and a second parameter (G2) that is dependent on the phase angle (phi) between the test voltage (UT) and the current (i), wherein the control device (24) is further configured to determine whether a) a first change (V1) in the first parameter (G1) exceeds a first threshold value (S1) and b) a second change (V2) in the second parameter (G2) exceeds a second threshold value (S2).

2. The device according to claim 1, characterized in that the first change (V1) and the second change (V2) are in each case changes in the parameters (G1, G2) measured between different points in time.

3. The device according to claim 2, characterized in that the control device is configured to determine the first change (V1) by determining the first parameter (G1) at different points in time (t1, t2) defined at a time interval (Δt) from one another, wherein the first change (V1) is determined from the difference of the first parameter (G1) determined at the different points in time (t1, t2).

4. The device according to any of the preceding claims, characterized in that the control device is configured to determine the parameters (G1, G2) in each case as averages from several successive measurements.

5. The device according to claim 3 or 4, characterized in that the control device (24) is connected with an input means (31) by means of which the time interval (Δt) can be adjusted.

6. The device according to any of the preceding claims, characterized in that the control device is configured to set the value of the first and the second parameter (G1, G2) as reference parameter (G1B, G2B) if both changes (V1, V2) have exceeded the defined threshold values (S1, S2) in respective first directions.

7. The device according to claim 6, characterized in that the control device (24) is configured to output a signal, if the first and the second parameter (G1, G2) change in a respective second direction, which is opposite to the respective first direction, starting from the reference parameters (G1B, G2B).

8. The device according to any of the preceding claims, characterized in that a displacement measurement device (27) is assigned to the instrument and that the control device (24) is configured to detect the changes (V1, V2) as a function of displacement, wherein the control device (24) is configured to determine the changes (V1, V2) by the differences between parameters (G1, G2) determined in different instrument positions.

9. The device according to claim 8, characterized in that the different instrument positions are different positions of the instrument (14) during penetration.

10. The device according to any of the preceding claims, characterized in that the first parameter (G1) is the impedance (Imp) and the second parameter (G2) is the power factor (LF).

11. The device according to claim 10, characterized in that the first change (V1) is a drop in the impedance (Imp) by a predetermined first value.

12. The device according to claim 11, characterized in that the predetermined first value is 60%.

13. The device according to claim 10 or 11, characterized in that the second change (V2) is an increase in the power factor (LF) by a predetermined second value.

14. The device according to claim 13, characterized in that the predetermined second value is 20%.