Electrosurgical Instruments

Abstract

To avoid radiation problems and problems concerning electromagnetical compatibility caused by transmitting radio frequency voltages and currents over long lines.SOLUTION: An electrosurgical instrument 11 according to the invention comprises at least one electrode 15, 16 for electrically acting on a biological tissue. The electrode is coupled with a radio frequency generator that is arranged in direct proximity of the electrode 15 and / or 16. The radio frequency generator oscillates in a self-controlled manner with a frequency between 100 kHz and 10 MHz and is preferably supplied by a constant or timely varying direct voltage. The instrument 11 is thus connected via a line supplying a low frequency voltage or direct voltage with a supplying source, e.g. an apparatus 19.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] FIELD OF THE INVENTION The present invention relates to an electrosurgical instrument having an energized electrode for performing electrosurgical intervention on a human or animal patient. [Background technology]

[0002] Electrosurgical instruments, probes, and the like typically require an electrosurgical generator to supply the instrument with radio-frequency alternating current. For this purpose, German Patent Application Publication No. 602004009293 discloses an electrosurgical system having a generator to which an instrument can be connected, the instrument being supplied with radio-frequency current from the generator. In one embodiment, the instrument includes a coagulation electrode and a cutting electrode that are alternately supplied in rapid sequence for simultaneous operation therewith. For this purpose, the instruments themselves are provided with respective electronic selector switches.

[0003] U.S. Patent No. 7,896,875 and U.S. Patent Application Publication No. 2011 / 0112530 each describe an RF instrument in which an external generator is supplied by a battery. U.S. Patent No. 9,155,585 further describes a battery-powered electrical medical generator with an externally controlled transistor. A battery-powered and generator-powered instrument is evident from U.S. Patent Application Publication No. 2015 / 0305798.

[0004] Furthermore, the use of microwaves for medical procedures is known from EP 2572668 and EP 2572669. Each instrument comprises a microwave antenna located at the distal end of a longitudinal shaft, which is fed by a microwave amplifier located within the instrument. The instrument is connected via a cable to a microwave signal generator, the signal of which is transmitted to the microwave amplifier. In a modified embodiment, the microwave signal generator is located within the handle of the instrument. A selector makes it possible to switch between the microwave signal of an external signal generator and the microwave signal of an internal signal generator.

[0005] A generator-equipped device with monopolar electrodes for treating a patient and which closes a current circuit capacitively via the therapist is also known from U.S. Pat. No. 6,039,734. The operating frequency is higher than 5 MHz. Finally, further prior art is evident from U.S. Patent Applications 2017 / 238987, 2017 / 202607, 2017 / 079710, 2016 / 0270841, 2014 / 148803, German Utility Model No. 202008001365, and Canadian Patent Application No. 2286835.

[0006] While microwave generators affect tissue by heating it with microwave radiation, high-frequency surgical instruments operate at significantly lower frequencies. The frequency of the current delivered by such instruments is typically around several hundred kilohertz. Such instruments operate on the flow of radio-frequency current through the tissue and always require two electrodes in contact with the tissue for this purpose. The instruments perform different procedures, such as cutting, coagulation, fusion, and ablation, directly linked to the flow of current through the tissue. The desired surgical effect can be precisely influenced by the geometry and use of the respective electrodes. This allows for the use of different RF voltages and currents, as well as different modulation forms, such as unmodulated RF (CW—"continuous wave"), amplitude modulation, and modulation with or without pulse-width modulation. Furthermore, the current / voltage dependence can be defined by the respective generator output characteristic curve, which is beneficial for the success of the surgery.

[0007] However, operation of such surgical instruments typically requires an external surgical generator that must provide the required modes from which radio frequency power is transmitted to the instrument via a cable, distinguished, for example, by voltage, current, power, modulation, etc.

[0008] DE 2901153 A1, US 2010 / 0137854 A1, US 2011 / 0245826 A1 and EP 1599146 A1 disclose generators with externally controlled switches for exciting one or more resonant circuits.

[0009] In addition to medical applications, self-oscillating generators are used in telecommunications, for example, as known from German Patent Applications DE 19780481 A1, DE 19780470 A1, DE 19719440 A1, and DE 19719441 A1. These generators are configured as voltage-controlled push-pull oscillators for the ultra-high frequency range of 1 to 20 GHz. As a result, the generators operate at very low operating voltages, for example, only 4.5 V. Circuits are suitable for the milliwatt range. In contrast, in the field of electrosurgery, generators operate at significantly higher voltages, higher powers, and substantially higher voltages. This presents a risk of voltage overload of individual components. Summary of the Invention [Problem to be solved by the invention]

[0010] It is an object of the present invention to provide an improved instrument. [Means for solving the problem]

[0011] This object is solved by an appliance according to claim 1 and additionally by a device according to claim 12 or 13.

[0012] The electrosurgical instrument according to the present invention comprises two electrodes for acting on living tissue. If only one electrode is provided for acting on tissue, at least one second electrode is provided, which is attached to the patient as an indifferent electrode spaced from the surgical site. The instrument can thus be configured as a monopolar instrument, having an electrode for performing the surgical intervention and an indifferent electrode (or a connection for the indifferent electrode) attached to the patient to close the electrical circuit for the treatment current. A radio frequency generator is disposed on or within the instrument, which is configured as a self-excited oscillator. The radio frequency generator provides the power required for the surgical intervention.

[0013] On the input or primary side, the radio frequency generator is connected or connectable to a DC voltage source or a low-frequency AC voltage source (e.g., 50 Hz or 60 Hz). On the output or secondary side, the radio frequency generator is connected to the electrodes. The electrodes can be two active electrodes at the distal end of the instrument or a single active electrode and a neutral electrode connected to the radio frequency output of the radio frequency generator. The radio frequency generator oscillates at a frequency between 100 kHz and 10 MHz, typically several hundred kHz, e.g., 350 kHz, 500 kHz, or another frequency within the specified range (e.g., 4 or 5 MHz). Radio frequency generation in electrosurgical instruments eliminates the need to transmit radio frequency voltage and current over long lines (several meters long), thereby eliminating issues, particularly those related to radiation and electromagnetic compatibility.

[0014] It is possible to oscillate a radio frequency generator at a single frequency so that the current flowing through the electrode contains a narrow spectrum. However, the current output from the radio frequency generator can also be modulated to produce a wide frequency spectrum, which typically results in interference with adjacent electrical devices due to the antenna effect of the associated radio frequency radiation during transmission over electrical wires. This is particularly true in the case of pulse-width modulation, which has very short impulses with very high voltages (several thousand volts). The direct proximity between the radio frequency generator and the electrode largely avoids radiation problems, even with broadband, powerful signals. It is sufficient to supply electrosurgical instruments with a direct current or low-frequency alternating current voltage so that the supply line emits low or no electromagnetic interference radiation. The cable for supplying the instrument's current can be an unshielded wire with two or more cores (conductors). Such a cable can be substantially more flexible than a shielded cable.

[0015] The radio frequency generator is preferably configured as a push-pull oscillator, in particular a free-running push-pull oscillator. "Free-running" means that the oscillation of the push-pull oscillator is maintained in the push-pull oscillator by positive feedback. Such a push-pull oscillator can be constructed with particularly high efficiency and very low power losses. This is particularly true when the push-pull oscillator comprises a push-pull flip-flop with two alternating transistors, each connected to a voltage amplifier at its output terminal. The output electrodes of the transistors are the collectors when PNP transistors are used. When field-effect transistors are used, the output electrodes are their drain electrodes. The downstream voltage amplifiers are, for example, bipolar transistors in a common base circuit or field-effect transistors in a common gate circuit. Essentially, NPN transistors, IGBTs, depletion-mode or enhancement-mode N- or P-MOSFETs, junction-gate field-effect transistors, gallium nitride transistors (GaN), etc. can be used as transistors. Due to the self-regulation of the RF generator, the transistors of the push-pull flip-flop do not switch redundantly, but rather switch independently in an idle state with no applied voltage and / or no current flow, thereby minimizing power loss in the transistors. The associated voltage amplifier keeps the high voltage provided at the RF generator output, typically over 100 V, away from the flip-flop. The flip-flop can operate at low voltages, i.e., only 10 or 20 volts.

[0016] The radio frequency generator preferably includes a parallel resonant circuit consisting of at least one inductor and at least one capacitor connected in parallel with each other, the parallel resonant circuit preferably forming the frequency determining component of the radio frequency generator, and feedback to the push-pull flip-flop is achieved by current flowing through two voltage amplifiers.

[0017] Decoupling of the electrical radio frequency energy from the parallel resonant circuit is preferably achieved by a decoupling inductor coupled to the inductor of the parallel resonant circuit within a transformer. The transformer configured in this manner can be configured for potential isolation between the patient circuit and a standard-compliant radio frequency generator. Preferably, both ends of the decoupling inductor are directly connected to the electrodes in contact with the tissue. It is particularly preferred that no additional components, particularly no current or voltage measurement sensors, are arranged between the inductor and the electrodes. In this way, the loading of the radio frequency output of the radio frequency generator with stray capacitance and the generation of capacitive leakage currents are minimized. The omission of any current and voltage sensors on the RF side not only minimizes capacitive leakage currents, but also achieves a particularly simple circuit configuration. This means that measuring devices for detecting voltage, current, power, and / or frequency can be arranged on the DC voltage side. Therefore, the respective measuring devices can be arranged within the instrument or the supply device. The measuring devices can generate signals useful for open-loop or closed-loop control of the operation of the radio frequency generator. For example, the power, current, voltage, or another electrical parameter output to the tissue can be adjusted. The state of the tissue to which the current is applied can be determined based on the measured current or based on the measured frequency, and the instrument can be controlled accordingly. For example, when the tissue fusion process is complete, the radio frequency generator can be switched off. Completion can be detected based on the current when the current falls below a threshold. Alternatively or additionally, the radio frequency generator can be switched off in a time-controlled manner.

[0018] The supply voltage input of the radio frequency generator can further be connected to a voltage modulation device, which can be located within the instrument or supply, and can be connected to a measurement device to provide RF power with a desired current / voltage characteristic or desired modulation.

[0019] Thus, the DC voltage source can output a defined, unchanging DC voltage, an adjustable DC voltage that does not vary over time, or a DC voltage that varies with time or load. Because the (push-pull) oscillator has low losses and is substantially constant over the load range, the voltage and power on the primary side (DC voltage side) of the radio frequency oscillator indicate the voltage, current, and power on the secondary side (RF side) with sufficient accuracy to achieve simple effects such as bipolar coagulation, even completely avoiding closed-loop control of the radio frequency generator, particularly its power or voltage. For example, for this purpose, the internal resistance of the radio frequency generator can be adapted to the respective surgical application. Such adaptation can be achieved, for example, by sizing the generator or its components, or by means of generator adjustment. In particular, such adaptation can be achieved by appropriately defining the turns ratio of the resonant circuit inductor relative to the decoupling inductor.

[0020] The concept of the present invention allows operation at frequencies up to 5 MHz with extremely low power inputs, due to respective modulation of the RF voltage. For example, the power input can be made very low by pulse-pause modulation of the RF signal with a very low pulse-pause ratio, thereby keeping any plasma that may be generated at the electrodes cool enough that its chemical effects are medically effective and the thermal surgical effects are pushed into the background or disappear.

[0021] Further details of advantageous embodiments of the invention emerge from the claims and from the figures and the respective description. [Brief explanation of the drawings]

[0022] [Figure 1] FIG. 1 is an illustration of an apparatus having an instrument and a delivery device. [Figure 2] FIG. 2 is a block diagram showing the device of FIG. 1. [Figure 3] FIG. 2 is a block diagram illustrating a modified embodiment of the device of FIG. [Figure 4]2 is a block diagram illustrating a further modified embodiment of the device of FIG. 1. FIG. [Figure 5] FIG. 5 is a diagram showing the circuit principle of the device of FIGS. 1 to 4 to clarify the circuit concept of the radio frequency generator. [Figure 6] FIG. 5 is a detailed diagram of the circuit of the device according to FIGS. 1 to 4. [Figure 7] 2 is a block diagram illustrating a further modified embodiment of the device of FIG. 1. FIG. [Figure 8] 2 is a block diagram illustrating a further modified embodiment of the device of FIG. 1. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0023] An apparatus 10 for surgical intervention on a patient is shown in FIG. 1. An instrument 11, shown here for clarity as a laparoscopic bipolar instrument, is part of the apparatus 10. Starting from its handle, configured as a housing, a shank 13 extends to its distal end, at which a tool with, for example, two jaws is supported, which can be opened and closed in the style of forceps by actuation of a hand lever 14. For example, electrodes 15, 16 are arranged on either side of the opposing jaws, suitable for applying an electric current directly to tissue 17 located therebetween and compressed by actuation of the hand lever 14, i.e., a current flow is enabled between the electrodes 15, 16 via the tissue 17. The tissue 17 is indicated in FIGS. 2, 3, and 4, respectively, by an ohmic resistor shown in dashed lines.

[0024] The instrument 11 can also be configured in other ways, not shown in the figures. It is particularly possible to configure the instrument as an open surgical instrument, such as an electrosurgical forceps instrument, or to provide one or more additional electrodes in addition to the electrodes 15, 16. For example, a cutting electrode or the like can be provided in addition to the electrodes 15, 16, which are preferably provided for coagulating the tissue 17. The instrument 11 can also be configured as a monopolar instrument with only one active electrode 15 (FIG. 7). In this case, a counter electrode 16 is assigned to the active electrode 15, and this counter electrode is configured, for example, as a large-area indifferent electrode attached to the patient to close the current circuit (FIG. 7).

[0025] The instrument 11 is connected to the device 19 via a line that serves to supply electrical current to the instrument 11, for example a preferably unshielded two or more core cable 18.

[0026] For further explanation, please refer to FIG. 2. The tool 11 and the device 19 are shown therein diagrammatically as dashed blocks. The tool 11 comprises a radio frequency generator 20 with a radio frequency output 21 and a supply voltage input 22. The radio frequency output supplies the at least two electrodes 15, 16 with a radio frequency voltage UHF (FIG. 5) and is connected to the at least two electrodes 15, 16 to supply them with respective radio frequency currents. The voltage applied to the electrodes 15, 16 is typically between 100 V and several hundred V. In individual cases, this can also have significantly higher values, for example, peak voltages of up to several thousand V, for example, for the supply of cutting electrodes.

[0027] The supply voltage input 22 is a DC voltage input or, if a rectifier block G is present, an AC low-frequency voltage input. In this case, the supply voltage input 22 can be configured to accept both DC and AC low-frequency voltages, depending on the rectifier circuit used. The supply voltage input 22 is connected via a respective line to a measuring device 23, which detects at least one physical or electrical parameter, such as the voltage applied to the supply voltage input 22, the current flowing through the supply voltage input 22, the power supplied to the supply voltage input 22, and / or the oscillation frequency of the radio frequency generator 20. To determine the oscillation frequency, the measuring device 23 can detect and evaluate the radio frequency ripple of the current flowing through the radio frequency generator. The frequency of the ripple depends on the oscillation frequency of the radio frequency generator 20. Thus, the measuring device 23 can detect one or more of the indicated physical parameters and provide the respective measured values ​​to the apparatus 19 via a signal line 24. The signal line 24 may be part of a cable 18 which in addition comprises at least two cores 25 , 26 for the current supply of the device 11 .

[0028] The device 19 comprises a voltage source 27 capable of outputting a supply voltage of typically 100 V, 150 V, 200 V, or another voltage in the range between 12 and 500 V. The voltage can be a DC voltage or a respective low-frequency AC voltage. The voltage source supplies the appliance with a voltage at the required power. The power to be supplied can thereby range from a few watts to several hundred watts, typically between 100 W and 300 W. Power is thereby supplied to the appliance 11 as DC or low-frequency power via cores 25, 26 of the cable 18.

[0029] A voltage modulation device 28 may be provided within the apparatus 19, configured to influence the amount of supply voltage output from the apparatus 19. The voltage modulation device 28 may be part of a voltage source 27 or may be configured as a separate block, as symbolically shown in Figure 2. The voltage source 27 may be a battery-operated voltage source 27 or a grid-operated voltage source 27. Preferably, the voltage source provides a standard-compliant potential separation between the power grid and the supply voltage provided at the appliance side.

[0030] The instrument 11 and device 19 shown in Figures 1 and 2 operate as follows.

[0031] Once the instrument 11 is connected to the device 19 via the cable 18, it is ready for use. The hand lever 14 allows the jaws carrying the electrodes 15, 16 to be moved, holding the tissue 17 between them. The radio-frequency generator 20 can then be activated by the switch 29. For example, the switch 29 can be connected to the measuring device 23 for this purpose, which then transmits a release signal to the device 19 via the signal line 24. The release signal can have the effect of activating the voltage source 27 and / or causing the voltage modulation device 28 to apply the provided DC or AC voltage to the cores 25, 26, thus supplying the instrument 11 with voltage and current. In the simplest case, the voltage modulation device 28 is simply a switch. Instead of the switch 29, a foot switch or the like can also be provided, which activates the device 19 or releases current to the cores 25, 26.

[0032] When the voltage source 27 is activated, the radio frequency generator 20 obtains a DC voltage or a low frequency AC voltage at its supply voltage input 22. The radio frequency generator starts to oscillate at a radio frequency and outputs a therapeutic voltage or current at its radio frequency output 21. This is therefore generated in direct proximity to the electrodes 15, 16 so that no electromagnetic interference in the environment is to be expected. This in particular avoids interference with other devices, for example during video endoscopy or robotics applications.

[0033] The measuring device 23 monitors the current supply to the radio frequency generator 20, which is closely related to the current output at the radio frequency output 21, for example. For example, if a desired dependence between treatment duration and power output between the electrodes 15, 16 is to be adjusted, the voltage modulation device 28 can switch off the current supply to the instrument 11 after a desired period of time. For example, if a pulse-width modulated RF signal is to be output at the radio frequency output 21, the DC voltage modulation device 28 can modulate the amount of DC (or AC) voltage supplied to the instrument 11, for example, by switching it on and off or alternating between two values, for example, 10 V and 150 V. The voltage modulation device 28 can also generate a desired internal resistance of the radio frequency generator 20, i.e., a desired voltage / current characteristic curve, in that the voltage output to the cores 25, 26 decreases with increasing current according to a desired function. If the measuring device 23 is a current measuring device and the signal line 24 transmits a current measurement signal to the voltage modulation device 28, the voltage modulation device 28 can adjust the voltage in response to the measured current in a desired manner, for example according to a desired curve. When the radio frequency generator 20 operates at a constant efficiency, a desired characteristic, i.e., a desired dependence between the RF output voltage and the RF output current, is thus adjusted at its radio frequency output 21.

[0034] The cable 28 conducts DC voltages and currents (or low-frequency AC voltages and currents) that can be modulated at low frequencies, for example, up to a few hertz or a few kHz or tens of kHz. No interference radiation or leakage of capacitive leakage currents occurs through the cable 18.

[0035] The presented concept can be varied in various ways. A first variant is shown in Figure 3. The device 11 according to Figure 3 comprises a radio frequency generator 20 and electrodes 15, 16. Apart from that, the above description applies accordingly, subject to the following deviations:

[0036] The measuring device 23 is located in the device 19, not in the instrument 11. As a result, the cable 18 actually includes cores 25, 26, but a signal line is not required. Therefore, the cable 18 can be a simple two-core, unshielded wire. The actuation switch is not shown in FIG. 3. It can be configured as a foot switch and connected directly to the device 19 to release or cut off the DC voltage output. It is also possible to attach the actuation switch 29 to the instrument 11 and control the device 19 via the signal line. Furthermore, it is also possible to place an actuation switch solely as an on / off switch in one or both cores 25, 26 to supply or cut off the voltage supplied by the device 19 to or from the supply voltage input 22 via the cable 18.

[0037] A further modification is shown in FIG. 4. In this embodiment, the radio frequency generator 20, as well as the measuring device 23 and the voltage modulation device 28, are arranged within the instrument 11. The apparatus 19 comprises only a voltage source 27 configured to output a constant DC voltage (or a low-frequency AC voltage). For example, the voltage source 27 can be a normal DC voltage source, e.g., a high-power USB power supply, or a voltage source provided on the operating table, e.g., a socket for DC voltage. It is also possible to provide an AC voltage source having, for example, a 50 Hz or 60 Hz AC voltage as the voltage source, with a rectifier block G connected upstream of the voltage modulation device 28. Apart from that, the above description with reference to the preceding embodiment applies accordingly with regard to the functioning of the system consisting of the instrument 11, the cable 18 and the apparatus 19.

[0038] The structure of the radio frequency generator 20 is essentially as illustrated in Figure 5. The radio frequency generator 20 is configured as a push-pull oscillator with a total of at least four switching transistors T1, T2, T3, T4, preferably configured as field effect transistors (and / or GaN transistors) (preferably n-channel, enhancement type, i.e. self-blocking). However, essentially other transistors can also be used in the same circuit configuration, for example in case of reverse voltage polarity, p-channel field effect transistors or bipolar transistors (npn or pnp), IGBTs, etc.

[0039] The source electrodes of the transistors T1 and T2 are connected to a common reference potential 30 (ground). The drain electrodes form taps Z1 and Z2, respectively. The gates of the two transistors T1 and T2 are each connected to the tap of the other transistor. Thus, together, the transistors T1 and T2 form a flip-flop with the two transistors T1 and T2 operating in push-pull mode. A square wave voltage between 0 and a few volts (e.g., 20 V) is applied to the taps Z1 and Z2, so that the transistors T1 and T2 are never on or off at the same time.

[0040] Taps Z1 and Z2 are connected to the current inputs of transistors T3 and T4, which operate as common-gate voltage amplifiers. The current inputs are realized by their source electrodes. The gates of transistors T3 and T4 are connected to a constant voltage provided by a constant voltage circuit 31.

[0041] The drain electrodes of the two transistors T3, T4 form the amplifier output, which is connected to a parallel resonant circuit 32. This consists of a capacitor 33 (or several capacitors, for example arranged in series) and an inductor 34 (or several inductors connected in series). The inductor 34 has a tap 35 connected to the positive potential of the supply voltage input 22.

[0042] The decoupling inductor 36 serves to decouple RF power from the parallel resonant circuit 32 and is coupled to the inductor 34 in a transformer-coupled manner. The inductor 36 is connected to the electrodes 15, 16 without any additional intervening components, thereby outputting RF power to them. If necessary, an additional decoupling inductor 36' can be provided to supply an additional electrode (not shown in further detail), such as a cutting electrode S. For example, this electrode can be located within the jaw of the instrument 11. The inductor 36' can be connected in series with the inductor 36 to output an increased voltage. It is also possible to select a different inductor configuration. Preferably, the decoupling inductor forms a branchless galvanic circuit with the tissue 17 held between the electrodes 15, 16.

[0043] Transistors T1 and T3 together form a cascode circuit. Similarly, transistors T2 and T4 together form a cascode circuit. The parallel resonant circuit 32, together with the two cascode circuits, forms a push-pull oscillator that determines the oscillation frequency of the push-pull flip-flops T1 and T2. The push-pull oscillator can be perfectly symmetrical, or it can be configured to be slightly asymmetrical in terms of structure and dimensions, as desired. Asymmetry can exist due to component variations, especially with regard to the transistors, slight inductor asymmetry (the resonant inductor tap is not exactly centered), different stray capacitances, etc. This can support the onset of oscillation in a radio frequency oscillator, for example.

[0044] FIG. 6 shows the radio frequency generator 20 of FIG. 5 in slightly more detail. Based on the circuit description of FIG. 5 above, it can be seen that the push-pull flip-flop formed by transistors T1 and T2 can include capacitive coupling in that taps Z1 and Z2 are connected to the gates of transistors T1 and T2 via capacitors 37 and 38, respectively. Furthermore, the two gates can be connected to each other via resistor 39 to maintain the same potential over time. Preferably, capacitors 37 and 38, together with resistor 39, define a flip-flop frequency for the push-pull flip-flop realized by transistors T1 and T2 that is lower than the oscillation frequency set by the parallel resonant circuit. Transistors T1 through T4 can be arranged in a common housing and typically do not require cooling. They are not cooled.

[0045] The parallel resonant circuit can be connected to a reference potential 30 via two Z diodes ZD1 and ZD2 to avoid overvoltages in the parallel resonant circuit 32.

[0046] The constant voltage circuit 31 can be realized by connecting a Z diode ZD3 and a capacitor 40 to which a current is supplied via a resistor 41 in parallel.

[0047] 6 also comprises, in addition to the radio frequency generator 20, a measuring device 23, represented here by way of example by a shunt 42. This is realized by a low ohmic resistor located in the line leading from the voltage source 27 to the radio frequency oscillator 20. Furthermore, a block 43 is part of the measuring device 23, which detects the voltage applied on the shunt 42 for current measurement and supplies a respective control signal to the voltage modulation device 28. Via a line 44, the block 43 can also detect the voltage applied at the voltage input 22.

[0048] The voltage modulation device 28 may be realized by a transistor T5, whose drain-source connection (or collector-emitter connection) is disposed in the line leading from the voltage source 27 to the supply voltage input 22. A signal line 24 may be connected to the gate of the transistor T5.

[0049] To smooth the current supplied by the voltage source 27 to the radio frequency generator 20, a reactor D may be provided in the line leading to the tap 35. Additionally, a buffer capacitor may be provided at the voltage input (downstream of the rectifier block G, if present).

[0050] Block 43 can control the desired function of the radio frequency generator 20. As long as the radio frequency generator 20 receives a constant voltage via transistor T5, it provides a specific radio frequency voltage at its output for applying current to the electrodes 15 and 16. The current flowing through the electrodes 15 and 16 is detected by shunt 42 and block 43. Block 43 can define the desired current / voltage dependence. Different current / voltage dependences can be provided and selected. For example, if the generator output voltage is to decrease with increasing current, block 43 can control transistor T5 accordingly via line 24. Block 43 can be connected to the supply voltage input 22 via a dashed line in FIG. 6 and can measure the voltage applied thereto. The measured voltage can be used to control transistor T5. Transistor T5 can operate in analog or pulse (on / off) operating mode. By opening or blocking transistor T5 via line 24, respectively, the radio frequency generator 20 can be switched on or off, or switched between high and low power. Other types of modulation are possible.

[0051] The concept according to the present invention has various advantages. The push-pull oscillator according to FIGS. 5 and 6 allows for a particularly compact implementation. No cooling is required for transistors T1 to T4, even when the radio-frequency generator outputs a power exceeding 100 W. Furthermore, any current or voltage sensors can be omitted in the patient circuit, i.e., on the radio-frequency side of the radio-frequency generator 20. The patient circuit is a non-branch circuit. The measuring device 23 (and additional measuring devices, if necessary) can be provided in the DC circuit. Even the oscillation frequency of the radio-frequency generator 20 can be detected at the shunt 42, for example, by the current ripple occurring there. The current, voltage, and power on the primary side provide a sufficiently accurate indication of the RF voltage on the patient side. This is because the losses of the radio-frequency generator 20 are low and essentially constant over its load range. Thus, closed-loop control of the RF voltage, RF current, or RF power can be achieved by primary measurements determined on the DC side. The omission of current and voltage sensors on the RF side also reduces the coupling capacitance between the DC and RF circuits over the very long insulation distances required by the standards. Thus, the radio frequency leakage current of the system is reduced.

[0052] To achieve simpler effects, such as bipolar coagulation, closed-loop control can be omitted entirely. For example, the power curve of a non-closed-loop controlled radio frequency generator 20 can be adapted for surgical applications for this purpose. The load impedance (i.e., the resistance of the biological tissue 17) then determines the flowing current. Corresponding adjustments can be made by changing the generator's output circuit, e.g., the winding ratio of the inductors 34 and 36 relative to each other, or by defining the coupling coefficient between the inductors 34 and 36, respectively. By appropriately dimensioning the reactor D and the coupling coefficient between the resonant circuit inductor 34 and the decoupling inductor 36 using the L / C ratio of the resonant circuit, the dependence of the RF current from the load formed by the tissue 17 on the internal resistance of the radio frequency generator can be determined.

[0053] Such adjustments can also be made by interference at another point, for example, by changing the gate bias of the gates of transistors T3 and T4. Additionally, complex monitoring of specific load conditions, such as short circuits or idling, is not required. This results in a substantially simplified design compared to known generators. Furthermore, complex frequency tracking by the control, as in known generators, is not required. The self-oscillating system, i.e., the radio frequency generator 20, does not require an external clock generator or specific monitoring circuitry.

[0054] As shown in Figure 7, the radio frequency generator 20 can also be located on the neutral electrode 16 and therefore must be considered part of the device 11. The above description of the embodiments according to Figures 1 to 6 therefore applies based on the reference numbers already introduced. In all embodiments, the location of the radio frequency generator 20 in or next to the device 11 offers the possibility of rationally using a higher frequency generator, for example 4 MHz. Even with such high radiation frequencies, the concept according to the invention generates low interference and capacitive leakage currents.

[0055] FIG. 8 shows an advantageous embodiment of the present invention having an instrument 11 releasably connected to a radio frequency generator 20, which can be configured, for example, to be plugged directly into the housing of the instrument 11 or can be arranged in an extension of the cable 18. For example, the radio frequency generator 20 can also be arranged in the proximal connector of the cable 18, through which the cable 18 is connected to the device 19. The instrument according to FIG. 8 can have a radio frequency generator 20 operating under non-closed-loop control, the internal resistance of its RF output side adapted to the desired surgical effect, such as coagulation or tissue fusion. The internal resistance of the radio frequency generator 20 can be linear or nonlinear. This can be determined as needed by the respective dimensioning of the coupling coefficient between the inductors 34 and 36 (FIGS. 5 and 6), the appropriate dimensioning of the reactor D (FIG. 6), or the respective setting of the internal resistance of the voltage source 18. In the embodiment according to FIG. 8, the measuring device 23 and the voltage modulation device 28 can be omitted. However, as is the basis of FIG. 3, it is also possible to arrange the measuring device 23 and the voltage modulation device 28 directly on the radio frequency generator 20 or alternatively in the apparatus 19. In all such variations based on the embodiment according to FIG. 8, the generator can be detached from the instrument 11 and thus mounted in a reusable instrument cable 18. The instrument 11 can then be provided for single use only and then discarded. The generator 20 can also be provided in a separate housing as an intermediate connector or intermediate cable mounted between the instrument 11 and its cable 18 and the apparatus 19. The radio frequency generator 20 can also be provided in a separate, removable housing on or near the neutral electrode 16, as envisioned in FIG. 7.

[0056] The electrosurgical instrument 11 according to the present invention comprises at least one electrode 15, 16 for electrically influencing living tissue. The electrodes are coupled to a radio-frequency generator 20 arranged in direct proximity to the electrode 15 and / or 16. The radio-frequency generator oscillates in a self-regulating manner at a frequency between 100 kHz and 10 MHz and is preferably supplied by a constant or time-varying DC voltage. The instrument 11 is therefore connected to a source, e.g., device 19, via lines supplying a low-frequency or DC voltage. [Explanation of symbols]

[0057] 10 equipment 11 Equipment 12 Handle 13 Shank 14 Hand lever 15 electrodes 16 Electrode or Neutral Electrode 17 Biological Tissue 18 Cable 19 Equipment 20 Radio Frequency Generator 21 Radio Frequency Output 22 Supply voltage input G Optional commutation block UHF radio frequency voltage 23 Measuring Devices 24 signal line 25, 26 Cable 18 cores 27 Voltage Source 28 Voltage Modulation Device 29 Switch 30 Reference potential T1~T4 transistors 31 Constant voltage circuit 32 parallel resonant circuit 33 Capacitor 34 Inductor 35 taps 36, 36' Decoupling inductor S cutting electrode 37, 38 Capacitor 39 Resistance ZD1~ZD4 Z diodes 40 capacitor 41 Resistance 42 Shunt T5 transistor D Reactor 43 Block, measuring device 44 Conduit

Claims

1. An electrosurgical instrument (11) for treating a human or animal patient, comprising: at least two electrodes (15, 16) for applying a current to the biological tissue (17); at least one radio frequency generator (20) configured as a push-pull oscillator with a supply voltage input (22) and a radio frequency output (21) connected to said electrodes (15, 16), said radio frequency generator (20) configured to convert a time-constant or time-varying supply voltage into a radio frequency alternating voltage; At the supply voltage input (22) of said radio frequency generator (20) there is a line (18) connectable to a voltage source (27) for supplying current to said radio frequency generator (20); Electrosurgical instrument, wherein the radio frequency generator (20) comprises a push-pull flip-flop having two alternatingly switching transistors (T1, T2), at the output electrodes of which one voltage amplifier (T3, T4) is connected respectively.

2. 2. The device according to claim 1, characterized in that the radio frequency generator (20) is configured to provide a voltage (UHF) having a frequency ranging between 100 kHz and 10 MHz.

3. An apparatus as described in claim 1 or 2, characterized in that the voltage amplifiers (T3, T4) are connected in a common gate or common base circuit, respectively.

4. 4. The device according to claim 1, wherein the radio frequency generator (20) comprises a parallel resonant circuit (32) consisting of at least one inductor (34) and at least one capacitor (33) connected in parallel with each other, and wherein the radio frequency generator (20) comprises a decoupling circuit exclusively connected to the electrodes (15, 16) for electrically acting on the biological tissue (17).

5. 5. The apparatus of claim 4, wherein the at least one inductor (34) of the radio frequency generator (20) is in a transformer coupled configuration with a decoupling inductor (36, 36'), the decoupling inductor (36, 36') being connected to the two electrodes (15, 16).

6. 6. The device according to any one of claims 1 to 5, characterized in that the radio frequency generator (20) is releasably connected to the device (11).

7. An apparatus as described in any one of claims 1 to 6, characterized in that the non-closed loop controlled radio frequency generator (20) includes a current / voltage characteristic in which the voltage output decreases with increasing current.

8. said supply voltage input (22) being connected to at least one measuring device (23); 8. An instrument according to any one of claims 1 to 7, characterized in that the measuring device (23) comprises a current measuring device (42) and / or a voltage measuring device (42) and / or a power measuring device (43) and / or a frequency measuring device (42, 43).

9. 9. An apparatus according to any one of claims 1 to 8, characterized in that the supply voltage input (22) of the radio frequency generator (20) is connected to a voltage modulation device (28).

10. 10. Apparatus according to claim 9, when dependent on claim 8, characterized in that the voltage modulation device (28) is connected to the measuring device (23).

11. 11. An apparatus comprising a device according to any one of claims 1 to 10, The apparatus comprises a device (19) having a voltage source (27) that can be connected to the instrument (11) by a cable (18).

12. A device comprising a device (11) according to claim 8, An apparatus (19) is provided comprising a controllable voltage source (27) to which the instrument (11) can be connected by a cable (18), Apparatus, characterized in that the voltage source (27) can be connected to the measuring device.

13. 13. Apparatus according to claim 12, characterized in that the measuring device (23) is arranged in the apparatus (19) connected to the voltage source (27).

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