Abstract:
Disclosed are systems, devices, and methods for interdigitation of waveforms for dual-output electrosurgical generators. Such methods may comprise outputting DC energy from a power supply, converting DC energy from the power supply, by a plurality of amplifiers coupled to the power supply, into a plurality of RF waveforms, and controlling the plurality of RF amplifiers to interdigitate the first and second RF waveforms.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
       [0001]    The present application claims the benefit of and priority to U.S. Provisional Application Ser. No. 62/141,594, filed on Apr. 1, 2015, the entire contents of which are incorporated herein by reference. 
     
    
     BACKGROUND 
       [0002]    1. Technical Field 
         [0003]    The present disclosure relates to an electrosurgical system and method for operating an electrosurgical generator. More particularly, the present disclosure relates to a system, method and apparatus for interdigitation of electrosurgical waveforms generated by radiofrequency resonant inverters. 
         [0004]    2. Background of Related Art 
         [0005]    Electrosurgery involves application of high radio frequency electrical current to a surgical site to cut, ablate, or coagulate tissue. In monopolar electrosurgery, a source or active electrode delivers radio frequency alternating current from the electrosurgical generator to the targeted tissue and a return electrode conducts the current back to the generator. A patient return electrode is placed remotely from the active electrode to conduct the current to the generator. 
         [0006]    In bipolar electrosurgery, return and active electrodes are placed in close proximity to each other such that an electrical circuit is formed between the two electrodes (e.g., in the case of an electrosurgical forceps). In this manner, the applied electrical current is limited to the body tissue positioned between the electrodes. Accordingly, bipolar electrosurgery generally involves the use of instruments where it is desired to achieve a focused delivery of electrosurgical energy between two electrodes positioned on the instrument, e.g. forceps or the like. 
         [0007]    Electrosurgical generators may have multiple outputs to power multiple electrosurgical instruments. When multiple instruments connected to a multiple output electrosurgical generator are activated, the generator delivers the programmed power to the parallel combination of connected instruments. However, prior art generators were not capable of equally distributing power to multiple instruments. Since it was unlikely that multiple instruments would be activated at the exact same time and used on the exact same impedances of tissue, it was not possible to obtain consistent performance with multiple instruments connected to multiple outputs of the electrosurgical generator. Thus, simultaneous activation of multiple instruments using existing generators resulted in poor performance, and in situations where multiple surgeons were operating on a patient simultaneously the results were unpredictable. As a result multiple electrosurgical generators were utilized to provide acceptable performance. Accordingly, there is a need for an electrosurgical generator configured to power multiple electrosurgical instruments that are usable simultaneously and to regulate individually the specified output power for each of the instruments coupled to the generator. 
       SUMMARY 
       [0008]    The present disclosure describes interdigitating waveforms corresponding to power output generated by a dual-output electrosurgical generator. Provided in accordance with the disclosure are devices, systems, and methods for interdigitating such waveforms. 
         [0009]    In an aspect of the present disclosure, an electrosurgical generator comprises a power supply configured to output DC energy, a plurality of RF amplifiers coupled to the power supply, each of the plurality of RF amplifiers being configured to convert DC energy from the power supply into an RF waveform, thereby generating a plurality of RF waveforms, and a controller coupled to the power supply and the plurality of RF amplifiers and configured to control the plurality of RF amplifiers to interdigitate the RF waveforms generated by the plurality of RF amplifiers. 
         [0010]    In a further aspect of the present disclosure, the electrosurgical comprises a plurality of sensors coupled to the plurality of RF amplifiers, each of the plurality of sensors configured to measure at least one property of a corresponding RF waveform of the plurality of RF waveforms supplied by a corresponding RF amplifier of the plurality of RF amplifiers. 
         [0011]    In yet a further aspect of the present disclosure, the controller is further coupled to the plurality of sensors and is further configured to control the plurality of RF amplifiers based on the at least one property of the corresponding RF waveform. 
         [0012]    In another aspect of the present disclosure, the plurality of RF waveforms are square waveforms. 
         [0013]    In yet another aspect of the present disclosure, the controller is further configured to adjust the DC energy supplied by the power supply to the plurality of RF amplifiers based on at least one property of at least one RF waveform of the plurality of RF waveforms. 
         [0014]    In another aspect of the present disclosure, at least one of the plurality of RF amplifiers is a non-resonant RF amplifier. 
         [0015]    In an aspect of the present disclosure, a system for interdigitating waveforms for a dual-output electrosurgical generator comprises the dual-output electrosurgical generator which comprises a power supply configured to output DC energy, a plurality of RF amplifiers coupled to the power supply, each of the plurality of RF amplifiers being configured to convert DC energy from the power supply into an RF waveform, thereby generating a plurality of RF waveforms, and a controller coupled to the power supply and the plurality of RF amplifiers and configured to control the plurality of RF amplifiers to interdigitate the RF waveforms generated by the plurality of RF amplifiers, and at least two electrosurgical instruments operatively coupled to the dual-output electrosurgical generator, wherein each of the electrosurgical instruments is coupled to one of the plurality of RF amplifiers. 
         [0016]    In another aspect of the present disclosure, the electrosurgical generator further comprises a plurality of sensors coupled to the plurality of RF amplifiers, each of the plurality of sensors configured to measure at least one property of a corresponding RF waveform of the plurality of RF waveforms supplied by a corresponding RF amplifier of the plurality of RF amplifiers. 
         [0017]    In a further aspect of the present disclosure, the controller is further coupled to the plurality of sensors and is further configured to control the plurality of RF amplifiers based on the at least one property of the corresponding RF waveform. 
         [0018]    In another aspect of the present disclosure, the plurality of RF waveforms are square waveforms. 
         [0019]    In yet another aspect of the present disclosure, the controller is further configured to adjust the DC energy supplied by the power supply to the plurality of RF amplifiers based on at least one property of at least one RF waveform of the plurality of RF waveforms. 
         [0020]    In another aspect of the present disclosure, at least one of the plurality of RF amplifiers is a non-resonant RF amplifier. 
         [0021]    In an aspect of the present disclosure, a method for interdigitating waveforms for a dual-output electrosurgical generator comprises outputting DC energy from a power supply, converting DC energy from the power supply, by a plurality of amplifiers coupled to the power supply, into a plurality of RF waveforms, and controlling the plurality of RF amplifiers to interdigitate the first and second RF waveforms. 
         [0022]    In another aspect of the present disclosure, the method further comprises measuring at a plurality of sensors coupled to the plurality of RF amplifiers at least one property of a corresponding RF waveform of the plurality of RF waveforms supplied by a corresponding RF amplifier of the plurality of RF amplifiers. 
         [0023]    In a further aspect of the present disclosure, the method further comprises controlling the at least one of the plurality of RF amplifiers based on the at least one property of an RF waveform generated by the at least one of the plurality of RF amplifiers. 
         [0024]    In another aspect of the present disclosure, the plurality of RF waveforms are square waveforms. 
         [0025]    In yet another aspect of the present disclosure, the method further comprises adjusting the DC energy supplied by the power supply to the plurality of RF amplifiers based on at least one property of at least one RF waveform of the plurality of RF waveforms. 
         [0026]    In another aspect of the present disclosure, at least one of the plurality of RF amplifiers is a non-resonant RF amplifier. 
         [0027]    Any of the above aspects and embodiments of the present disclosure may be combined without departing from the scope of the present disclosure. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0028]    Various embodiments of the present disclosure are described herein with reference to the drawings wherein: 
           [0029]      FIG. 1  is a perspective view of an electrosurgical system according to an embodiment of the present disclosure; 
           [0030]      FIG. 2  is a front view of the electrosurgical generator of  FIG. 1  according to an embodiment of the present disclosure; 
           [0031]      FIG. 3  is a schematic, block diagram of the electrosurgical generator of  FIG. 12  according to an embodiment of the present disclosure; 
           [0032]      FIG. 4  is a schematic, block diagram of a DC-DC converter and a DC-AC inverter of the electrosurgical generator of  FIG. 1  according to an embodiment of the present disclosure; 
           [0033]      FIG. 5  is a graphical representation of power output levels of the electrosurgical generator of  FIG. 1  having multiple outputs according to an embodiment of the present disclosure; 
           [0034]      FIG. 6  is another graphical representation of power output levels of the electrosurgical generator of  FIG. 1  having multiple outputs according to an embodiment of the present disclosure. 
       
    
    
     DETAILED DESCRIPTION 
       [0035]    Particular embodiments of the present disclosure are described hereinbelow with reference to the accompanying drawings. In the following description, well-known functions or constructions are not described in detail to avoid obscuring the present disclosure in unnecessary detail. 
         [0036]    According to embodiments of the present disclosure, an electrosurgical generator including at least a power supply and a plurality of amplifiers may be configured to power multiple instruments simultaneously. As described in more detail below, by interdigitating the waveforms corresponding to the energy output by each of the plurality of amplifiers, a peak power output, and thus the load on the power supply in, may be reduced. 
         [0037]    A generator according to the present disclosure is configured to output electrosurgical energy suitable for performing monopolar and/or bipolar electrosurgical procedures, including, but not limited to, cutting, coagulation, ablation, and vessel sealing procedures. The generator may include a plurality of outputs for interfacing with various electrosurgical instruments (e.g., a monopolar instrument, return electrode, bipolar electrosurgical forceps, footswitch, etc.). Further, the generator includes electronic circuitry configured to generate radio frequency energy specifically suited for various electrosurgical modes (e.g., cut, blend, coagulate, division with hemostasis, fulgurate, spray, etc.) and procedures (e.g., monopolar, bipolar, vessel sealing). 
         [0038]      FIG. 1  is a schematic illustration of a bipolar and monopolar electrosurgical system  1  according to the present disclosure. System  1  may include one or more monopolar electrosurgical instruments  2  having one or more active electrodes  3  (e.g., electrosurgical cutting probe, ablation electrode(s), etc.) for treating tissue of a patient. Electrosurgical alternating current is supplied to instrument  2  by a generator  200  via a supply line  4  that is connected to an active terminal  230   a ,  230   b  ( FIG. 3 ) of generator  200 , allowing instrument  2  to cut, coagulate, ablate and/or otherwise treat tissue. The alternating current is returned to generator  200  through a return electrode  6  via a return line  8  at a return terminal  232   a ,  232   b  ( FIG. 3 ) of generator  200 . For monopolar operation, system  1  may include a plurality of return electrode pads  6  that, in use, are disposed on a patient to minimize the chances of tissue damage by maximizing the overall contact area with the patient. In addition, generator  200  and return electrode pads  6  may be configured for monitoring so-called “tissue-to-patient” contact to ensure that sufficient contact exists therebetween to further minimize chances of tissue damage. 
         [0039]    System  1  may also include one or more bipolar electrosurgical instruments, for example, a bipolar electrosurgical forceps  10  having one or more electrodes for treating tissue of a patient. Electrosurgical forceps  10  includes a housing  11  and opposing jaw members  13  and  15  disposed at a distal end of a shaft  12 . Jaw members  13  and  15  have one or more active electrodes  14  and a return electrode  16  disposed therein, respectively. Active electrode  14  and return electrode  16  are connected to generator  200  through a cable  18  that includes supply and return lines  4 ,  8  coupled to active and return terminals  230   a ,  230   b , and  232   a ,  232   b , respectively ( FIG. 3 ). Electrosurgical forceps  10  is coupled to generator  200  at a connector having connections to active and return terminals  230  and  232  (e.g., pins) via a plug disposed at the end of cable  18 , wherein the plug includes contacts from supply and return lines  4 ,  8  as described in more detail below. 
         [0040]    With reference to  FIG. 2 , a front face  240  of generator  200  is shown. Generator  200  may be any suitable type (e.g., electrosurgical, microwave, etc.) and may include a plurality of connectors  250 - 262  to accommodate various types of electrosurgical instruments (e.g., electrosurgical forceps  10 , etc.). 
         [0041]    Generator  200  includes a user interface  241  having one or more display screens or information panels  242 ,  244 ,  246  for providing the user with variety of output information (e.g., intensity settings, treatment complete indicators, etc.). Each of screens  242 ,  244 ,  246  is associated with a corresponding connector  250 - 262 . Generator  200  includes suitable input controls (e.g., buttons, activators, switches, touch screen, etc.) for controlling generator  200 . Display screens  242 ,  244 ,  246  are also configured as touch screens that display a corresponding menu for the electrosurgical instruments (e.g., electrosurgical forceps  10 , etc.). The user then adjusts inputs by simply touching corresponding menu options. 
         [0042]    Screen  242  controls monopolar output and the devices connected to connectors  250  and  252 . Connector  250  is configured to couple to a monopolar electrosurgical instrument (e.g., electrosurgical instrument  2 ) and connector  252  is configured to couple to a foot switch (not shown). The foot switch provides for additional inputs (e.g., replicating inputs of generator  200 ). Screen  244  controls monopolar and bipolar output and the devices connected to connectors  256  and  258 . Connector  256  is configured to couple to other monopolar instruments. Connector  258  is configured to couple to a bipolar instrument (not shown). 
         [0043]    Screen  246  controls bipolar sealing procedures performed by forceps  10  that may be plugged into connectors  260  and  262 . Generator  200  outputs energy through connectors  260  and  262  suitable for sealing tissue grasped by forceps  10 . In particular, screen  246  outputs a user interface that allows the user to input a user-defined intensity setting. The user-defined setting may be any setting that allows the user to adjust one or more energy delivery parameters, such as power, current, voltage, energy, etc. or sealing parameters, such as energy rate limiters, sealing duration, etc. The user-defined setting is transmitted to controller  224  where the setting may be saved in memory  226 . In embodiments, the intensity setting may be a number scale, for example, from one to ten or one to five. In embodiments, the intensity setting may be associated with an output curve of generator  200 . The intensity settings may be specific for each forceps  10  being utilized, such that various instruments provide the user with a specific intensity scale corresponding to forceps  10 . 
         [0044]    Generator  200  according to the present disclosure is a non-resonant generator and may include dual or multiple outputs to simultaneously power multiple instruments. 
         [0045]    The generator  200  may be configured to operate in any of a constant voltage limit mode, a constant current limit mode, a constant power mode, and combinations thereof. The mode selection is generally based on the impedance associated with the tissue being cut. Different types of tissue, such as muscle and fat, have different impedances. In terms of electrosurgical operations, constant power output tends to uniformly vaporize tissue, resulting in clean dissection. Whereas constant voltage output tends to explosively vaporize or carbonize tissue (“black coagulation”), and constant current output tends to thermally coagulate tissue without vaporization (“white coagulation”). Carbonization is surgically useful if the surgeon wishes to rapidly destroy surface tissue, and thermal coagulation is regularly coupled with mechanical pressure to seal hepatic or lymphatic vessels shut. However, the surgeon generally desires to operate using constant power output and importantly, return to using constant power output as quickly as possible if there is deviation. 
         [0046]    With respect to the AC output of the generator  200  and in exemplary embodiments, “constant power” is defined to mean the average power delivered in each switching cycle is substantially constant. Likewise, “constant voltage” and “constant current” are defined as modes where the root mean square (RMS) value of the AC voltage or current, respectively, is regulated to a substantially fixed value. An exemplary graphical representation of the desired output characteristics is illustrated in  FIG. 5 . In an exemplary embodiment, as the load impedance increases and voltage increases, the corresponding increasing output voltage triggers a transition from a constant current mode shown as region A to a constant power mode shown as region B and to a constant voltage mode shown as region C. Similarly, in an exemplary embodiment, as the load impedance decreases and current increases, the corresponding decreasing output voltage triggers the opposite transition from the constant voltage region C to the constant power region B and to the constant current region A. 
         [0047]      FIG. 3  shows a schematic block diagram of generator  200  configured to output electrosurgical energy. Generator  200  includes a controller  224 , a power supply  227 , radio-frequency (RF) amplifiers  228   a ,  228   b , and sensors  280   a ,  280   b . Power supply  227  may be a high voltage, DC power supply connected to an AC source (e.g., line voltage) and provides high voltage, DC power to RF amplifiers  228   a ,  228   b , which then converts high voltage, DC power into treatment energy (e.g., electrosurgical or microwave) and delivers the energy to active terminals  230   a ,  230   b , respectively. The energy is returned thereto via return terminals  232   a ,  232   b . RF amplifiers  228   a ,  228   b  are configured to operate in a plurality of modes, during which generator  200  outputs corresponding waveforms having specific duty cycles, peak voltages, crest factors, etc. It is envisioned that in other embodiments, generator  200  may be based on other types of suitable power supply topologies. RF amplifiers  228   a ,  228   b  may be non-resonant RF amplifiers. A non-resonant RF amplifier, as used herein, denotes an amplifier lacking any tuning components, i.e., conductors, capacitors, etc., disposed between the RF inverter and the load. 
         [0048]    Controller  224  includes a processor  225  operably connected to a memory  226 , which may include transitory type memory (e.g., RAM) and/or non-transitory type memory (e.g., flash media, disk media, etc.). Processor  225  includes an output port that is operably connected to power supply  227  and/or RF amplifiers  228   a ,  228   b  allowing processor  225  to control the output of generator  200  according to either open and/or closed control loop schemes. A closed loop control scheme is a feedback control loop, in which a plurality of sensors  280   a ,  280   b  measure a variety of tissue and energy properties (e.g., tissue impedance, tissue temperature, output power, current and/or voltage, etc.), and provide feedback to controller  224 . Controller  224  then signals power supply  227  and/or RF amplifiers  228   a ,  228   b , which adjusts the DC and/or power supply, respectively. Those skilled in the art will appreciate that processor  225  may be substituted for by using any logic processor (e.g., control circuit) adapted to perform the calculations and/or set of instructions described herein including, but not limited to, field programmable gate array, digital signal processor, and combinations thereof. 
         [0049]    Generator  200  according to the present disclosure includes a plurality of sensors  280   a ,  280   b , i.e., RF current sensors and RF voltage sensors. Various components of generator  200 , namely, RF amplifiers  228   a ,  228   b , and sensors  280   a ,  280   b , may be disposed on a printed circuit board (PCB). An RF current sensor may be coupled to active terminals  230   a ,  230   b  and provide measurements of the RF current supplied by RF amplifiers  228   a ,  228   b . An RF voltage sensor may be coupled to active terminals  230   a ,  230   b  and return terminals  232   a ,  232   b  provides measurements of the RF voltage supplied by RF amplifiers  228   a ,  228   b.    
         [0050]    Sensors  280   a ,  280   b  provide the sensed RF voltage and current signals, respectively, to controller  224 , which then may adjust output of power supply  227  and/or RF amplifiers  228   a ,  228   b  in response to the sensed RF voltage and current signals. Controller  224  also receives input signals from the input controls of generator  200 , instrument  2  and/or forceps  10 . Controller  224  utilizes the input signals to adjust power outputted by generator  200  and/or performs other control functions thereon. 
         [0051]    With reference to the schematic shown in  FIG. 4 , the generator  200  includes a DC-DC buck converter  101 , a DC-AC boost converter  102 , an inductor  103 , a transformer  104 , and controller  224 . In embodiments, the DC-AC boost converter  102  is part of each of the RF amplifiers  228   a ,  228   b . Accordingly, for simplicity only one of the RF amplifiers  228   a ,  228   b  is discussed herein below. In the exemplary embodiment, a DC voltage source Vg, such as power supply  227 , is connected to DC-DC buck converter  101 . Furthermore, inductor  103  is electrically coupled between DC-DC buck converter  101  and DC-AC boost converter  102 . The output of DC-AC boost converter  102  transmits power to the primary winding of transformer  104 , which passes through the secondary winding of transformer  104  to the load Z (e.g., tissue being treated). 
         [0052]    DC-DC buck converter  101  includes a switching element  101   a  and DC-AC boost converter  102  includes a plurality of switching elements  102   a - 102   d  arranged in an H-bridge topology. In embodiments, DC-AC boost converter  102  may be configured according to any suitable topology including, but not limited to, half-bridge, full-bridge, push-pull, and the like. Suitable switching elements include voltage-controlled devices such as transistors, field-effect transistors (FETs), combinations thereof, and the like. In an exemplary embodiment, controller  224  is in communication with both DC-DC buck converter  101  and DC-AC boost converter  102 , in particular, the switching elements  101   a  and  102   a - 102   d , respectively. Controller  224  is configured to output control signals, which may be a pulse-width modulated signal, to switching elements  101   a  and  102   a - 102   d  as described in further detail in co-pending application published as US 2014/0254221, entitled CONSTANT POWER INVERTER WITH CREST FACTOR CONTROL, filed on Dec. 4, 2013 by Johnson et al., the entire contents of which is incorporated by reference herein. In particular, controller  224  is configured to control the duty cycle d 1  of the control signal supplied to switching element  101   a  of DC-DC buck converter  101  and duty cycle d 2  of the control signals supplied to switching elements  102   a - 102   d  of DC-AC boost converter  102 . Additionally, controller  224  is configured to measure power characteristics of generator  200 , and control generator  200  based at least in part on the measured power characteristics. Examples of the measured power characteristics include the current through inductor  103  and the voltage at the output of DC-AC boost converter  102 . In an exemplary embodiment, controller  224  controls buck converter  101  by generating the duty cycle d 1  based on a comparison of the inductor current and a nonlinear carrier control current for every cycle. 
         [0053]      FIG. 5  is a plot showing the power output levels of the generator  200 . In response to one of the instruments  310   a  or  310   b  being activated, a corresponding RF amplifier  228   a  or  228   b  generates the programmed treatment energy for the instrument. To generate treatment energy, RF amplifiers  228   a ,  228   b  draw DC power from shared power supply  227 . 
         [0054]    In response to both instruments  310   a  and  310   b  being activated simultaneously, each of the RF amplifiers  228   a  and  228   b  generates energy for each of the instruments  310   a  and  310   b . The non-resonant RF amplifiers  228   a  and  228   b  according to the present disclosure are configured to generate square waveforms as shown in  FIG. 5 , rather than sine waveforms, which are generated by resonant networks that are absent from the RF amplifiers  228   a  and  228   b . With continued reference to  FIG. 5 , output generated by RF amplifier  228   a  is represented by a first waveform  502  having peaks  510  and  512 , and output generated by RF amplifier  228   b  is represented by a second waveform  504  having peaks  514  and  516 . The combined output of RF amplifiers  228   a ,  228   b  is represented by peaks  518 , each of which is a combination of peaks  510  and  514  and peaks  512  and  516 . 
         [0055]    Thus, when instruments  310   a ,  310   b  are activated simultaneously, with treatment energy being delivered in-phase, the total peak power sourced by shared power supply  227  is the sum of individual outputs, requiring shared power supply  227  to be rated for this higher peak power. To avoid this, the power levels drawn from shared power supply  227  may be interspersed such that peak power levels are not drawn by multiple RF amplifiers  228   a  and  228   b  simultaneously. One method of interspersing power drawing levels is by interdigitating the waveforms. Interdigitation, as used herein, denotes outputting two or more waveforms at a specific phase relationship in which the power draw from the power supply  227  is substantially uniform. In one embodiment, waveforms may be interdigitated such that their respective peaks are evenly spaced and occur out of phase. The peaks of one waveform may be aligned with the valleys of the other waveform. By doing so, the power levels drawn balance out, and results in a constant level of power drawn instead of peaks and valleys. 
         [0056]      FIG. 6  is a plot showing the power output levels of generator  200  when the waveforms generated by RF amplifiers  228   a ,  228   b  are interdigitated. Output of the RF amplifier  228   a  is represented by a first waveform  602  having peaks  610 ,  612  and output of the RF amplifier  228   b  is represented by a second waveform  604  having peaks  614  and  616 . The combined output of RF amplifiers  228   a ,  228   b  when the respective output waveforms  602  and  604  are interdigitated may be represented by a single, continuous waveform  618 , without any peaks, because the power output level remains constant. Thus, when dual output waveforms are interdigitated, as shown in  FIG. 6 , the peak power delivered by shared power supply  227  may be reduced as compared to the output illustrated in  FIG. 5 . 
         [0057]    While several embodiments of the disclosure have been shown in the drawings and/or described herein, it is not intended that the disclosure be limited thereto, as it is intended that the disclosure be as broad in scope as the art will allow and that the specification be read likewise. Therefore, the above description should not be construed as limiting, but merely as exemplifications of particular embodiments. Those skilled in the art will envision other modifications within the scope and spirit of the claims appended hereto.