Patent Description:
Electrosurgery involves the use of electricity to buildup heat within biological tissue to cause thermal tissue damage resulting in incision, removal or sealing of the tissue through one or more of desiccation, coagulation, or vaporization, for example. Benefits include the ability to make precise cuts with limited blood loss. Electrosurgical devices are frequently used during surgical procedures to help prevent blood loss in hospital operating rooms or in outpatient procedures. High-frequency electrosurgery typically involves radio frequency (RF) alternating current (AC) that is converted to heat by resistance as it passes through the tissue.

A typical electrosurgical signal generator uses a multi-stage voltage converter to convert AC line power to a controlled high frequency signal required to perform an electrosurgical procedure. This approach ordinarily includes converting an AC line input to direct current (DC) signal and converting the DC signal to an RF signal. The RF output is imparted to electrodes at a surgical instrument end effector that a surgeon manipulates to impart high frequency energy to seal or cut anatomical tissue.

A previous electrosurgical instrument has been provided that includes an end effector for both sealing and cutting vessels and/or tissue. The prior end effector includes a pair of opposing first and second jaws that are movable relative to one another from a first spaced apart position to a second position for grasping tissue therebetween. Each jaw includes an electrically conductive tissue sealing surface configured to be energized by an electrosurgical energy source and configured to contact a tissue surface. At least one of the jaws includes an electrically conductive cutting surface disposed within an insulator defined in the jaw. The cutting surface is configured to be energized by an electrosurgical energy source and is configured to contact a tissue surface.

<CIT> discloses an electrosurgical system with an electrosurgical generator with a multiple-phase RF output stage coupled to a multiple-electrode electrosurgical instrument. The instrument has three treatment electrodes each of which is coupled to a respective generator output driven from, for instance, a three phase output transformer.

<CIT> discloses an electrosurgical medical device having a handle a shaft coupled to the handle and an end effector coupled to the shaft. The end effector has at least one electrode for providing electrical signals to a tissue or vessel to be treated.

<CIT> discloses a method of ablating a tissue site including at least two stages. The first stage involving conducting bipolar ablation between a first pair of opposing first stage ablation regions extending from respective sides of the tissue towards the center. The second stage involving conducting bipolar ablation between a second pair of electrodes situated in a diametrical arrangement with respect to the first stage ablation regions, which forms a second stage ablation regions intermediate the pair of first stage ablation regions.

<CIT> discloses an apparatus and a method for producing a virtual electrode within or upon a tissue to be treated with radio frequency alternating electric current, such tissues including brain, liver, cardiac, prostate, breast, and vascular tissues and neoplasms.

<CIT> discloses an electrosurgical generator including an RF output stage configured to supply electrosurgical energy to tissue via at least one active electrode configured to apply electrosurgical energy to tissue; sensing circuitry configured to measure impedance of tissue; and a controller.

The present invention provides an electrosurgical system as set out in the appended independent claim. Optional features are defined in the appended dependent claims. According to a disclosure herein, a method is provided to seal and cut biological tissue. An alternating current (AC) sealing signal is imparted between a set of sealing electrodes. An AC cutting signal is imparted between a set of cutting electrodes in response to biological tissue impedance between the sealing electrodes reaching a first impedance threshold value. The AC sealing signal is halted at an end of a time interval, beginning while the AC cutting signal is imparted between the cutting electrodes, in response to impedance of biological tissue disposed between the set of sealing electrodes reaching a second impedance threshold value.

Also disclosed is an electrosurgical system. An electrosurgical signal generator sealing stage is configured to provide an AC sealing signal on a set of sealing electrodes. An electrosurgical signal generator cutting stage is configured to provide an AC cutting signal on a set of cutting electrodes. The set of sealing electrodes and the set of cutting electrodes share at least one electrode in common.

<FIG> is an illustrative plan view of a minimally invasive teleoperated surgical system <NUM> for performing a minimally invasive diagnostic or surgical procedure on a patient <NUM> who is lying on an operating table <NUM>. The system includes a surgeon's console <NUM> for use by a surgeon <NUM> during the procedure. One or more assistants <NUM> may also participate in the procedure. The minimally invasive teleoperated surgical system <NUM> further includes one or more patient-side cart <NUM> and an electronics cart <NUM>. The patient-side cart <NUM> can manipulate at least one surgical instrument <NUM> through a minimally invasive incision in the body of the patient <NUM> while the surgeon <NUM> views the surgical site through the surgeon's console <NUM>. An image of the surgical site can be obtained by an endoscope <NUM>, such as a stereoscopic endoscope, which may be manipulated by the patient-side cart <NUM> to orient the endoscope <NUM>. Computer processors located on the electronics cart <NUM> may be used to process the images of the surgical site for subsequent display to the surgeon <NUM> through the surgeon's console <NUM>. In some embodiments, stereoscopic images may be captured, which allow the perception of depth during a surgical procedure. The number of surgical instruments <NUM> used at one time will generally depend on the diagnostic or surgical procedure and the space constraints within the operative site among other factors. If it is necessary to change one or more of the surgical instruments <NUM> being used during a procedure, an assistant <NUM> may remove the surgical instrument <NUM> from the patient-side cart <NUM>, and replace it with another surgical instrument <NUM> from a tray <NUM> in the operating room.

<FIG> is a perspective view of the surgeon's console <NUM>. The surgeon's console <NUM> includes a viewer display <NUM> that includes a left eye display <NUM> and a right eye display <NUM> for presenting the surgeon <NUM> with a coordinated stereoscopic view of the surgical site that enables depth perception. The console <NUM> further includes one or more hand-operated control inputs <NUM> to receive the larger-scale hand control movements and includes one or more foot pedal controls <NUM>. One or more surgical instruments installed for use on the patient-side cart <NUM> move in smaller-scale distances in response to surgeon <NUM>'s larger-scale manipulation of the one or more control inputs <NUM>. The control inputs <NUM> may provide the same mechanical degrees of freedom as their associated surgical instruments <NUM> to provide the surgeon <NUM> with telepresence, or the perception that the control inputs <NUM> are integral with the instruments <NUM> so that the surgeon has a strong sense of directly controlling the instruments <NUM>. To this end, position, force, and tactile feedback sensors (not shown) may be employed to transmit position, force, and tactile sensations from the surgical instruments <NUM> back to the surgeon's hands through the control inputs <NUM>, subject to communication delay constraints.

<FIG> is a perspective view of a patient-side cart <NUM> of a minimally invasive teleoperated surgical system <NUM>, in accordance with embodiments. The patient-side cart <NUM> includes four mechanical support arms <NUM>. A surgical instrument manipulator <NUM>, which includes motors to control instrument motion, is mounted at the end of each support arm assembly <NUM>. Additionally, each support arm <NUM> can optionally include one or more setup joints (e.g., unpowered and/or lockable) that are used to position the attached surgical instrument manipulator <NUM> in relation to the patient for surgery. While the patient-side cart <NUM> is shown as including four surgical instrument manipulators <NUM>, more or fewer surgical instrument manipulators <NUM> may be used. A teleoperated surgical system will generally include a vision system that typically includes an endoscopic camera instrument <NUM> for capturing video images and one or more video displays for displaying the captured video images. User inputs provided at the control console <NUM> to control either the instrument as a whole or the instrument's components are such that the input provided by a surgeon or other medical person to the control input (a "master" command) is translated into a corresponding action by the surgical instrument (a "slave" response).

<FIG> is a perspective view of a surgical instrument <NUM>, which includes an elongated hollow tubular shaft <NUM> having a centerline longitudinal axis <NUM>, a distal (first) end portion <NUM> for insertion into a patient's body cavity and proximal (second) end portion <NUM> coupled adjacent a control mechanism <NUM> that includes multiple actuator motors <NUM>, <NUM> (shown with dashed lines) that exert force upon wire cables coupled to impart motion to the end effector <NUM> such as opening or closing of jaws and (x, y) wrist motion of a wrist. The surgical instrument <NUM> is used to carry out surgical or diagnostic procedures. The distal portion <NUM> of the surgical instrument <NUM> can provide any of a variety of end effectors <NUM>, such as the forceps shown, a needle driver, a cautery device, a cutting tool, an imaging device (e.g., an endoscope or ultrasound probe), or the like. The surgical end effector <NUM> can include a functional mechanical degree of freedom, such as jaws that open or close, or a knife that translates along a path or a wrist that may move in x and y directions. In the embodiment shown, the end effector <NUM> is coupled to the elongated hollow shaft <NUM> by a wrist <NUM> that allows the end effector to be oriented relative to the elongate tube centerline axis <NUM>. The control mechanism <NUM> controls movement of the overall instrument and the end effector at its distal portion.

<FIG> is an illustrative block diagram representing an electrosurgical signal generator circuit <NUM> in accordance with some embodiments. The electrosurgical signal generator <NUM> includes an electrosurgical signal generator sealing stage <NUM> and an electrosurgical signal generator cutting stage <NUM>. The sealing stage <NUM> produces a high frequency (HF) AC sealing signal between a set of sealing electrodes <NUM>, <NUM> (seal+, seal-). The cutting stage <NUM> produces a HF AC cutting signal between a set of cutting electrodes <NUM>, <NUM><NUM> (cut+, cut-). Typically, the frequency is in a range of approximately <NUM>-<NUM>. In some embodiments, the set of sealing stage electrodes <NUM>, <NUM> and the set of cutting stage electrodes <NUM>, <NUM> each shares at least one electrode <NUM>, <NUM> (seal-, cut-) in common, which may be referred to collectively herein as the return electrode.

The electrosurgical signal generator <NUM> includes an AC-to-DC power supply <NUM> to convert an AC line voltage to a DC voltage on a voltage bus line <NUM>. The voltage bus line <NUM> is coupled to provide a DC input voltage signal to the sealing stage circuit <NUM>. The voltage bus line <NUM> also is coupled to provide the DC input voltage signal to the cutting stage circuit <NUM>. In some embodiments, the DC input voltage signal is approximately 48V, for example.

The sealing stage <NUM> includes a first buck regulator circuit <NUM> to convert the DC input voltage signal to a first controlled DC voltage signal and includes a first output transformer <NUM> coupled to produce the AC sealing signal based upon the first controlled DC voltage signal. The first output transformer <NUM> is coupled to provide the sealing signal to the set of sealing electrodes <NUM>, <NUM>. More particularly, the first output transformer <NUM> includes a first terminal <NUM> electrically coupled to the first sealing electrode <NUM> and includes a second terminal <NUM> electrically coupled to the second sealing electrode <NUM>. The first controlled DC voltage signal is provided to a first output stage <NUM>, which is configured to provide the first controlled voltage across the terminals <NUM>, <NUM> of the first output transformer <NUM> in either polarity direction. In some embodiments, the first output stage includes a first H-bridge switch circuit. The first and second sealing electrodes <NUM>, <NUM> are electrically coupled via an output socket <NUM> to a surgical instrument end effector <NUM>, which includes a jaw end effector described below with reference to <FIG>. A first voltage and current monitoring circuit <NUM> is configured to monitor current and voltage across the set of sealing electrodes. A first micro-controller <NUM> is configured to provide a pulse width modulated (PWM) signal to the first buck regulator circuit <NUM> to determine the voltage conversion imparted by the first buck regulator circuit <NUM>. ) The first micro-controller <NUM> also is configured to produce a control signal to control switching of the output stage switch circuit <NUM> to thereby determine the HF sealing signal waveform pattern, including duty cycle and frequency, for example. First signal conditioning and acquisition circuitry <NUM> acquire the voltage and current measurements used to calculate RMS V, I, and average power. The first micro-controller <NUM> also is configured to determine a first impedance between the set of sealing electrodes <NUM>, <NUM> based upon the monitored voltage and current across them.

Similarly, the cutting stage <NUM> includes a second buck regulator circuit <NUM> to convert the DC input voltage signal to a second controlled DC voltage signal and includes a second output transformer <NUM> coupled to produce the cutting signal based upon the second controlled DC voltage signal. The second output transformer <NUM> is coupled to provide the AC cutting signal to the set of cutting electrodes <NUM>, <NUM>. More specifically, the second output transformer <NUM> includes a first terminal <NUM> electrically coupled to the first cutting electrode <NUM> and includes a second terminal <NUM> electrically coupled to the second cutting electrode <NUM>. The second controlled DC voltage signal is provided to a second output switching circuit <NUM>, which is configured to provide the second controlled voltage across the terminals <NUM>, <NUM> of the second output transformer <NUM> in either polarity direction. The set of cutting electrodes <NUM>, <NUM> are electrically coupled via the output socket <NUM> to the surgical instrument end effector <NUM>, which includes a jaw end effector described below with reference to <FIG>. A second current and voltage monitoring circuit <NUM> is configured to monitor current and voltage across the set of cutting electrodes <NUM>, <NUM>. A second micro-controller <NUM> is configured to provide a pulse width modulated (PWM) signal to the second buck regulator circuit <NUM> to determine the voltage conversion imparted by the second buck regulator circuit <NUM>. The second micro-controller <NUM> also is configured to produce a control signal to control switching of the output stage switching circuit <NUM> to thereby determine the cutting? signal waveform pattern, including duty cycle and frequency, for example. Second signal conditioning and acquisition circuitry <NUM> acquire the voltage and current measurements used to calculate RMS V, I; and average power. The second micro-controller <NUM> also is configured to determine a second impedance between the set of cutting electrodes <NUM>, <NUM> based upon the monitored voltage and current across them.

A user interface circuit (UI) block <NUM>, which may be incorporated in the control console <NUM>, may include one or more of hand controls and foot pedal controls and a display console to receive user input commands to start and stop sealing and cutting activities and to indicate parameters to use for sealing and cutting signal waveforms such as voltage, current, signal frequency, and dwell time, for example. The UI circuit block <NUM> also may provide feedback information to the user such as amount of power delivered, whether a seal was successfully completed, whether an error condition occurred. A surgeon may use the UI to provide user input to select voltage and current levels or sealing signal patterns and cutting signal patterns based upon requirements of a particular patient or surgical procedure, for example. A main controller <NUM>, which may be incorporated in the electronics cart <NUM>, is coupled to exchange information with the UI block <NUM> and to communicate with the first and second micro-controllers <NUM>, <NUM>. The main controller <NUM> may be configured to produce control signals to determine waveforms of the sealing and cutting signals under control of the first and second micro-controllers, including current and voltage levels, for example. The main controller <NUM> also may produce control signals to determine start and stop times of sealing and cutting operations under control of the first and second micro-controllers. In some embodiments, the main controller <NUM> also may be configured to provide control signals to the first and second micro-controllers for arc suppression and other time dependent functions. Values may change, for example, as a function of user settings or depending on what happens in the other stage.

In operation, an AC sealing signal is provided via the first output transformer <NUM> across the set of sealing electrodes <NUM>, <NUM>, and an AC cutting signal is provided via the second output transformer <NUM> across the set of cutting electrodes <NUM>, <NUM>. In some embodiments, the first and second micro-controllers <NUM>, <NUM> cooperate to provide a single PWM master signal to the first and second H-bridge switches <NUM>, <NUM> to produce in-phase periodic sealing and cutting signals. Although the sealing and cutting signals are periodic signals that are in phase with each other, they typically have different peak-to-peak voltage potentials. The first and second output transformers <NUM>, <NUM> may have different turn ratios to produce different voltage levels for the sealing and cutting voltages, for example. In general, impedance is lower during a sealing activity than during a cutting activity due to the higher impedance associated with the plasma discharge required to resect tissue. Thus, in general, a lower voltage ordinarily may be used during sealing than is used during a cutting. In some embodiments, for example, the peak-to-peak voltage for a sealing activity is approximately <NUM>-150V and the peak-to-peak voltage for a cutting activity is approximately <NUM>-600V. Conversely, in general, a higher current may be used during sealing than is used during a cutting.

<FIG> is an illustrative perspective view of a pair of jaws <NUM>, <NUM> of an end effector <NUM> that include a set of tissue sealing surfaces <NUM>-<NUM> and a set of tissue cutting surfaces <NUM>, <NUM> and <NUM> shown in an open position in accordance with some embodiments. Thus, sealing surfaces <NUM>, <NUM> are shared between the sealing stage <NUM> and the cutting stage <NUM>. <FIG> is a distal end view of the pair of end effector jaws <NUM>, <NUM> of <FIG> shown in a closed position with biological tissue <NUM> grasped between them in accordance with some embodiments. Referring to <FIG>, the end effector <NUM> includes first and second jaws <NUM>, <NUM> having opposing working faces <NUM>, <NUM> and a pivot axis <NUM>. At least one of the first and second jaws <NUM>, <NUM> is mounted to rotatably pivot about the pivot axis <NUM> between the open position in which the first and second jaws <NUM>, <NUM> are spaced apart from each other and the closed position for grasping biological tissue <NUM> between them.

The first jaw <NUM> includes first and second electrically conductive tissue sealing surfaces <NUM>, <NUM> that are electrically coupled at the socket <NUM> to the active sealing electrode <NUM> and that extend longitudinally along outer portions of the first jaw <NUM>. The first jaw <NUM> also includes an electrically conductive tissue cutting surface <NUM> that is electrically coupled at the socket <NUM> to the active cutting electrode <NUM> and that extends longitudinally along the first jaw <NUM> between the first and second tissue sealing surfaces <NUM>, <NUM>. The second jaw <NUM> includes third and fourth electrically conductive tissue sealing surfaces <NUM>, <NUM> that are electrically coupled at the socket <NUM> to the shared return sealing electrode <NUM> and that extend longitudinally along outer portions of the second jaw <NUM> so as to align with the first and second tissue sealing surfaces <NUM>, <NUM> when the first and second jaws <NUM>, <NUM> are in the closed position. The second jaw <NUM> also includes a passive/insulative surface <NUM> that extends longitudinally along the second jaw <NUM> between the third and fourth tissue sealing surfaces <NUM>, <NUM> so as to align with the first tissue cutting surface <NUM> when the first and second jaws <NUM>, <NUM> are in the closed position.

Referring to <FIG>, during tissue sealing activity, the sealing signal is conducted through tissue portion <NUM> disposed between the first and third sealing surfaces <NUM>, <NUM> and through tissue portion <NUM> disposed between the second and fourth tissue sealing surfaces <NUM>, <NUM>. During tissue cutting, the cutting signal is conducted though a tissue portion <NUM> disposed between the first and second tissue cutting surfaces <NUM>, <NUM>, <NUM>. Often, it is beneficial to start a sealing activity before a cutting activity for reduced clinical risk. In this way, if biological tissue, such as a blood vessel, is sealed to some pre-determined extent before cutting begins, there is minimal risk of blood leakage during a later-started cutting activity.

In general, the voltage and current density applied to a biological tissue determines whether cutting or sealing of the tissue occurs, as a higher voltage and current density is required to achieve the plasma discharge required for resection. A lower current density typically results in less rapid tissue heating, which may result in sealing, which as used herein, refers to tissue dehydration, vessel wall shrinkage and coagulation of blood constituents and collagen denaturatization and bonding. A higher current density typically results in the creation of a plasma discharge, which may result in cutting, which as used herein, refers to dissecting of tissue through vaporization, for example. Although electrosurgical sealing signals and electrosurgical cutting signals may deliver the same power, they ordinarily use different voltage and current levels to do so.

A typical electrosurgical procedure that involves both sealing and cutting activities may involve a sequence of "bites" in which a pair of jaws grasp a tissue portion, the electrosurgical generator provides sealing and cutting signals to seal it and cut it, and then a next portion of tissue is grasped, sealed and cut, etc. Each bite of sealing activity and each cutting activity may require only a short time interval, such as two seconds to seal and two seconds to cut, for example. The overall time required for an electrosurgical procedure increases with an increasing number of bites. For example, an electrosurgical procedure involving <NUM>-<NUM> bites in which sealing and cutting activities are performed in sequence may require <NUM>-<NUM> seconds. Moreover, if a single stage electrosurgical generator is used, then an additional time delay of perhaps <NUM>-<NUM> seconds per bite may be required, for example, to reconfigure the generator to generate a different signal pattern at each transition between a sealing and a cutting activity, which can further increase the overall time for an electrosurgical procedure by an additional <NUM>-<NUM> seconds, for example. Thus, there is need for simultaneous sealing and cutting to shorten the time required for an electrosurgical procedure.

<FIG> is an illustrative signal timing diagram showing example peak-to-peak current signal levels of simultaneous sealing and cutting signals in accordance with some embodiments. It will be appreciated that the drawing is illustrative and current level units and time units are arbitrary and for illustrative purposes only. The peak-to-peak current value of the RF sealing current signal <NUM> is greater than the peak-to-peak current value of the RF cutting current signal pulses <NUM>-<NUM> to <NUM>-N. The sealing signal <NUM> is provided as a continuous RF signal. Whereas, the cutting signal <NUM> is provided in discrete RF signal pulses <NUM>-<NUM> to <NUM>-N during discrete time intervals with a dead signal dwell time delay between each pulse during which no cutting signal is provided. Each RF signal pulse includes an RF cutting signal imparted continuously during the pulse time interval. Each dead signal dwell time delay includes a time interval during which no RF cutting signal is imparted. As explained below with reference to <FIG>, the number of cutting pulses may vary as required to achieve a satisfactory cut based upon a measure of impedance between the set of cut electrodes <NUM>, <NUM>. The sealing and cutting signals provide substantially the same power, and therefore, while the sealing signal current level is greater than the cutting signal current level, the sealing signal voltage level (not shown) is less than the cutting signal voltage level (not shown).

<FIG> is an illustrative example impedance versus time diagram representing a process to independently control sealing and cutting of biological tissue during simultaneous tissue sealing and tissue cutting activities in accordance with some embodiments. It will be understood that the impedance values and time units indicated in the drawing are arbitrary and for the purpose of illustration. During a first time interval T1, starting at time t=<NUM>, the sealing stage <NUM> produces a sealing signal having a sealing signal voltage level. During the first time interval T1, the current and voltage measured between the set of sealing electrodes <NUM>, <NUM> may be used to determine impedance between them. The monitored voltage and current between the sealing electrodes <NUM>, <NUM> indicates impedance of biological tissue captured between the first and second jaws <NUM>, <NUM> as shown in <FIG>, for example. Impedance may indicate tissue moisture content, for example. In general, tissue moisture content should be low enough to allow a suitable voltage and current density to be delivered to start cutting. The second micro-controller <NUM> is configured to cause the second output transformer <NUM> to produce the cutting signal based at least in part upon the impedance between the sealing electrodes <NUM>, <NUM> reaching a pre-determined start-cutting threshold. During a second time interval T2, starting in the example at approximately time t=<NUM>, when the impedance between the sealing electrodes <NUM>, <NUM> reaches a pre-determined start-cutting threshold, the cutting stage <NUM> produces the cutting signal. During the second time interval T2, the sealing stage <NUM> continues to produce the sealing signal while the cutting stage <NUM> simultaneously produces the cutting signal. As explained above with reference to the timing diagram of <FIG>, although the sealing signal and the voltage signal are in-phase with each other, the sealing signal ordinarily has a lower peak-to-peak voltage than the cutting signal because a higher voltage generally is required to cut as explained above. During the second time interval T2, voltage and current measured between the set of sealing electrodes <NUM>, <NUM> may be used to determine impedance between them. The first micro-controller <NUM> is configured to cause the first output transformer <NUM> to initiate a dwell mode in which the sealing signal is produced by the first output transformer for an additional pre-determined third time interval T3, based at least in part upon the impedance between the sealing electrodes <NUM>, <NUM> reaching a pre-determined stop-sealing threshold indicating a predetermined tissue level, for example. At an approximate time of t=<NUM> in the example, when the impedance between the sealing electrodes <NUM>, <NUM> reaches pre-determined stop-sealing threshold, the sealing stage <NUM> enters the dwell mode in which the seal stage <NUM> continues to deliver the sealing signal for the additional pre-determined third time interval, which in the example, extends to approximately t=<NUM>, and then first micro-controller <NUM> causes the sealing stage <NUM> to halt the sealing signal. The cutting stage <NUM> may continue to produce the cut signal for a predetermined time interval (not shown), following which the second micro-controller <NUM> causes the cutting stage <NUM> to halt the cutting signal. Persons skilled in the art will appreciate that a lower impedance indicates presence of moisture which indicates presence of tissue still present between cut electrodes. A higher impedance indicates absence/reduction of moisture, which indicates absence/reduction of tissue between the electrodes, which indicates absence/reduction of tissue between the electrodes and/or a clean cut. Alternatively, in some embodiments, at the end of the fourth time interval in response to the current and voltage measured between the set of cutting electrodes <NUM>, <NUM> indicating that impedance between them is less than a stop-cutting impedance threshold, the second micro-controller <NUM> may initiate additional cutting signal pulses to ensure satisfactory cutting of the biological tissue.

In some embodiments, the start cutting impedance threshold is less than the initiate dwell time impedance threshold and the stop cutting impedance threshold is greater than the initiate dwell time impedance threshold. In particular, for example, in some embodiments, a typical start cutting impedance threshold may be in a range <NUM>-<NUM> ohms, a typical initiate dwell time impedance threshold may be in a range <NUM>-<NUM> ohms, and a typical stop cutting impedance threshold may be in a range <NUM> - <NUM> ohms. In accordance with some embodiments, a start cutting impedance is measured across seal electrodes and dwell time impedance threshold is also measured across seal electrodes. However, a stop cutting impedance will be measured across cut electrodes.

In alternative embodiments a phase angle between voltage, current or power delivered between the first and second jaws may also be used to determine a start-cutting threshold and a stop-sealing threshold. This alternative approach allows the reactive impedance to be considered, which generally is lower as the start of a seal and increases as the tissue dessicates.

<FIG> are illustrative flow diagrams representing a first process to perform simultaneous sealing and cutting activities in accordance with some embodiments. The first and second micro-controllers <NUM>, <NUM> and the main controller <NUM> may be configured with instructions to cause the first and second stages <NUM>, <NUM> of the electrosurgical system <NUM> of <FIG> to perform the simultaneous sealing and cutting activities. At block <NUM>, user input is received at a foot pedal UI actuator, for example, indicating a user command to start an electrosurgical procedure. At block <NUM>, one or more bite parameters are measured including at least one of a test voltage and/or current between the sealing or cutting electrodes, jaw angle and jaw grip strength. A test signal may be provided between the sealing or cutting electrodes to produce the test voltage or current. The jaws <NUM>, <NUM> may be configured with sensors (not shown) to determine jaw angle and grip force. At decision block, <NUM>, a determination is made as to whether biological tissue is appropriately grasped between the jaws. At block <NUM>, in response to a determination that tissue is not properly disposed between the jaws, a message is provided to the user via the UI to indicate insufficient or inappropriately positioned tissue between the jaws, for example.

At block <NUM>, the first micro-controller <NUM> starts a sealing activity in response to a determination that tissue is properly disposed between the jaws <NUM>, <NUM>. The sealing activity includes the sealing stage providing a sealing signal to the set of sealing electrodes <NUM>, <NUM> to impart a sealing signal within tissue <NUM> disposed between the first and third sealing surfaces <NUM>, <NUM> and transmission of the sealing signal within tissue disposed between the second and fourth sealing surfaces <NUM>, <NUM>. At block <NUM>, the first voltage and current monitoring circuit <NUM> monitors voltage and current at the set of sealing electrodes <NUM>, <NUM>. At decision block <NUM>, the first micro-controller <NUM> determines whether the second micro-controller <NUM> has started to impart the cutting signal.

At decision block <NUM>, in response to a determination that the cutting signal has started, the first micro-controller determines whether the monitored current and voltage between the set of sealing electrodes is greater than a stop-sealing impedance threshold. In response to the monitored impedance not reaching the stop-sealing impedance threshold, control returns to block <NUM> and current and voltage monitoring continues. At block <NUM>, in response to the monitored impedance reaching the stop-sealing impedance threshold, the first microcontroller continues to propagate the sealing signal for a pre-determined sealing signal dwell time interval (T3). At block <NUM>, at the end of the sealing signal dwell time interval, the first micro-controller halts the sealing process.

At decision block <NUM>, in response to a determination that the cutting signal has not started, the second micro-controller <NUM> determines whether the monitored voltage and current between the set of sealing electrodes <NUM>, <NUM> indicates an impedance greater than a start-cutting impedance threshold. Control flows to decision block <NUM> in response to a determination that the impedance between the set of sealing electrodes is not greater than a start-cutting impedance threshold. At block <NUM> the second micro-controller <NUM> starts a cutting activity in response to an indication that the tissue impedance has reached the start-cutting threshold. The cutting activity includes the cutting stage providing a cutting signal to the set of cutting electrodes <NUM>, <NUM> to impart a cutting signal within tissue <NUM> disposed between the first and second cutting surfaces <NUM>, <NUM> and <NUM>. At block <NUM>, the second voltage and current monitoring circuit <NUM> monitors voltage and current at the set of cutting electrodes <NUM>, <NUM>. At decision block <NUM>, the second micro-controller <NUM> determines whether the cut time exceeds a cut-time threshold. In response to a determination that the cut-time threshold has not been reached, control flows back to block <NUM>. At decision block <NUM>, in response to a determination that the cut-time threshold has been reached, the second micro-controller <NUM> determines whether the monitored impedance between the set of cutting electrodes <NUM>, <NUM> is greater than a stop-cutting impedance threshold. At block <NUM>, in response to a determination that the impedance between the set of cutting electrodes <NUM>, <NUM> is not greater than a stop-cutting impedance threshold, the second microcontroller <NUM> determines that additional cut-pulses are required to complete the cut. In accordance with some embodiments, the second micro-controller <NUM> determines the number of additional cut pulses to be provided based upon At block <NUM>, the second micro-controller delays initiation of the additional cut pulses for a pre-determined dead time delay time during which no cutting signal is provided to allow the plasma to dissipate, and a new discharge be created at subsequent pulses, which can prevent a discharge from hanging at one specific location rather than making a complete cut. At block <NUM>, following the delay, the second micro-controller reinitiates the cutting signal and control flows back to block <NUM>. At decision block <NUM>, in response to a determination that the cut-time threshold has been reached, the second-micro-controller <NUM> determines that additional cut pulses are not needed. At block <NUM>, the second micro-controller <NUM> halts the cutting process.

In some embodiments, thresholds used to initialize dwell within seal output stage and initialize cut output stage start may be varied based upon jaw angle, grip force or other similar measurements. Measurements such as jaw angle and grip force can provide additional information on the status of tissue between the jaws. For example, a reduction in jaw angle implies loss of moisture or tissue desiccation or a clean cut Moreover, the timing of the cut output stage and seal output stage can be varied based on jaw angle, grip force or other similar measurements.

Furthermore, in some embodiments, instead of performing a single cut sequence with a predefined time, multiple shorter cut activations may be performed, with a period of dead time being introduced between each shorter activation. This can result in more reliable cutting performance, since the starting, stopping and restarting the sequence is more likely to vaporize residual tissue strands at the cut electrode that could cause an incomplete cut. Also, it may be desirable to suspend the activation of the seal sequence for some predetermined time to allow the tissues to cool and any vapor barrier between the tissue cutting surface and the tissue to dissipate, prior to starting the cut activation. This may result in a more uniform cut discharge and improved cut performance. Moreover, when the cut activation is terminated, it also may be desirable to suspend the seal activation for a predefined period of time, to allow the tissue to recover from the energy delivered during the cut activation, and allow a more accurate measurement of the electrical parameters being used to determine when the sealing sequence should advance to the next stage of the sequence. It will be appreciated that seal and cut signals are provided independently and in some situations, the seal signal may always end after the cut signal ends.

<FIG> is an illustrative flow diagram representing a second process to suppress arcs during simultaneous sealing and cutting activities in accordance with some embodiments. The first and second micro-controllers <NUM>, <NUM> and the main controller <NUM> may be configured with instructions to cause the first and second stages <NUM>, <NUM> of the electrosurgical system <NUM> of <FIG> to perform the simultaneous sealing and cutting activities. Decision block <NUM> determines whether the cutting signal is active. In response to a determination that the cutting signal is active, at decision block <NUM> the second micro-controller <NUM> determines whether the monitored current between the set of cutting electrodes <NUM>, <NUM> is greater than a cut arc threshold. At block <NUM>, in response to a determination that the monitored current between the set of cutting electrodes <NUM>, <NUM> is greater than a cut arc threshold, the second micro-controller <NUM> halts the cutting signal. Control flows to decision block <NUM> following block <NUM>, or following a determination at decision block <NUM> that the cut signal is not active, or following a determination at decision block <NUM> that the monitored current between the set of cutting electrodes <NUM>, <NUM> is not greater than a cut arc threshold. Decision block <NUM> determines whether the sealing signal is active. In response to a determination that the sealing signal is active, at decision block <NUM> the first micro-controller <NUM> determines whether the monitored current between the set of sealing electrodes <NUM>, <NUM> is greater than a seal arc threshold. At block <NUM>, in response to a determination that the monitored current between the set of sealing electrodes <NUM>, <NUM> is greater than a seal arc threshold, the first micro-controller <NUM> halts the sealing signal and the second micro-controller <NUM> halts the cutting signal. It will be appreciated that cutting without sealing may result in bleeding, which is a reason to halt both cutting and sealing in response to a seal arc but not in response to a cut arc. Control flows to decision block <NUM> following a determination at decision block <NUM> that the seal signal is not active or following a determination at decision block <NUM> that the monitored current between the set of cutting electrodes <NUM>, <NUM> is not greater than a seal arc threshold.

<FIG> is an illustrative flow diagram representing a third process to halt sealing and cutting activity in response to absence of biological tissue between the tissue sealing surfaces in accordance with some embodiments. The first and second micro-controllers <NUM>, <NUM> and the main controller <NUM> may be configured with instructions to cause the first and second stages <NUM>, <NUM> of the electrosurgical system <NUM> of <FIG> to perform the simultaneous sealing and cutting activities. The third process occurs while the sealing signal is active. At block <NUM>, the first voltage and current monitoring circuit monitors current and voltage between the set of sealing electrodes <NUM>, <NUM>. At block <NUM>, the first micro-controller <NUM> determines whether the monitored voltage and current between the set of sealing electrodes <NUM>, <NUM> indicates direct electrical contact between any of the tissue sealing surfaces <NUM>-<NUM>, i.e. between the first and third tissue sealing surfaces <NUM>, <NUM> or between the second and fourth tissue sealing surfaces <NUM>, <NUM>. Direct contact between the tissue sealing surfaces, which may cause a short circuit, may result from an absence of biological tissue between the sealing surfaces. Control flows back to block <NUM> in response to a determination that the monitored voltage and current between the set of sealing electrodes <NUM>, <NUM> does not indicate direct electrical contact between any of the tissue sealing surfaces <NUM>-<NUM>. At decision block <NUM>, in response to a determination that the monitored voltage and current between the set of sealing electrodes <NUM>, <NUM> does indicate direct electrical contact between any of the tissue sealing surfaces <NUM>-<NUM>, the second micro-controller <NUM> determines whether the cutting signal is active. At block <NUM>, in response to a determination that the cutting signal is active, the second micro-controller <NUM> halts the cutting signal. At block <NUM>, following block <NUM> or following a determination at block <NUM> that the cutting stage is not active, the first micro-controller <NUM> halts the sealing signal. It will be appreciated that the high energy delivered from an arc could damage the instrument itself, and make it ineffective; e.g. poor sealing performance.

Claim 1:
An electrosurgical system for sealing and cutting biological tissue comprising:
a signal generator (<NUM>) configured to impart an alternating current, AC, sealing signal between a set of sealing electrodes (<NUM>, <NUM>) and to impart an AC cutting signal between a set of cutting electrodes (<NUM>, <NUM>);
a first controller (<NUM>) configured to determine impedance of biological tissue (<NUM>) disposed between the set of sealing electrodes (<NUM>, <NUM>) while the AC sealing signal is imparted between the set of sealing electrodes (<NUM>, <NUM>);
wherein the first controller (<NUM>) is configured to control the signal generator (<NUM>) to impart a continuous AC sealing signal between the set of sealing electrodes (<NUM>, <NUM>) starting before imparting the AC cutting signal
in response to the impedance of biological tissue (<NUM>) disposed between the sealing electrodes (<NUM>, <NUM>) reaching a first impedance threshold value, a second controller (<NUM>) is configured to control the signal generator (<NUM>) to impart the AC cutting signal between the set of cutting electrodes (<NUM>, <NUM>) during discrete pulse time intervals;
wherein the first controller (<NUM>) is configured to determine impedance of biological tissue (<NUM>) disposed between the set of sealing electrodes (<NUM>, <NUM>) while the AC cutting signal is imparted between the set of cutting electrodes (<NUM>, <NUM>);
wherein the first controller (<NUM>) is configured to control the signal generator (<NUM>) to halt the AC sealing signal between the set of sealing electrodes (<NUM>, <NUM>) in response to impedance of the biological tissue (<NUM>) disposed between the set of sealing electrodes (<NUM>, <NUM>) reaching a second impedance threshold value;
wherein the second controller (<NUM>) is configured to control the signal generator (<NUM>) to halt the AC cutting signal; and
wherein the AC sealing signal is in phase with the AC cutting signal.