Electrosurgical system and method for tissue sensing based on time domain reflectometry

Abstract

A method of sealing tissue according to the present disclosure includes grasping tissue between a first jaw member and a second jaw member, applying a signal based on a tissue sensing algorithm to the grasped tissue for which a tissue treatment is scheduled, receiving reflected signals from the first and second jaw members, and determining tissue characteristics based on the reflected signals. An electrosurgical system configured to implement the method is also provided. In one embodiment, the method further includes adjusting a tissue sealing algorithm based on the determined tissue characteristics.

Description

Technical Field

[0001] The present disclosure relates to electrosurgery, and more particularly, to an electrosurgical system and method for treating tissue.

Background Art

[0002] In bipolar electrosurgery, an electric current is passed through tissue disposed between electrodes of different polarities to heat the tissue, thereby treating the tissue. Bipolar electrosurgery often involves the use of electrosurgical forceps, which are plier-like instruments that rely on mechanical movement between jaws to grasp, clamp, and compress tissue. More specifically, the electrosurgical forceps utilize a mechanical clamping action and electrical energy to treat the clamped tissue, such as cauterization, coagulation, and / or sealing.

[0003] Cauterization involves the use of heat to destroy tissue, coagulation is a process of drying the tissue such that tissue cells are ruptured and dried, whereas tissue sealing is a process that liquefies collagen, elastin, and the matrix in the tissue and causes them to reform into a melt having a significantly reduced boundary between opposing tissue structures. To form an effective tissue seal, it is necessary to precisely control two dominant mechanical parameters, namely the pressure applied to the tissue and the gap distance between the electrodes. In addition, the electrosurgical energy must be applied to the tissue under controlled conditions, for example, by controlling the intensity, frequency, and duration of the electrosurgical energy applied to the tissue, to ensure the formation of an effective tissue seal.

Summary of the Invention

Means for Solving the Problems

[0004] As used herein, the term "distal" refers to the portion that is described as being farther from the operator (whether a human surgeon or a surgical robot), while the term "proximal" refers to the portion that is described as being closer to the operator. Terms including "substantially", "about", "essentially", etc., when utilized herein, are intended to encompass, for example, manufacturing tolerances, material tolerances, use and environmental tolerances, measurement variations, design variations, and / or other variations of plus or minus 10 percent or less. Further, within non - conflicting ranges, any or all of the aspects detailed herein may be used in conjunction with any or all of the other aspects detailed herein.

[0005] A method of treating tissue according to the present disclosure includes grasping tissue between a first jaw member and a second jaw member, applying a signal based on a tissue sensing algorithm to the grasped tissue for which tissue treatment is scheduled, receiving reflected signals from the first and second jaw members at a plurality of frequencies, and determining tissue characteristics or a state in the first and second jaw members based on the reflected signals.

[0006] In one aspect of the present disclosure, the method may further include adjusting a tissue sealing algorithm based on the determined tissue characteristics.

[0007] In another aspect of the present disclosure, the method may further include applying energy to the grasped tissue according to a tissue sealing algorithm to seal the grasped tissue, and the tissue sealing algorithm is independent of the tissue sensing algorithm.

[0008] In still another aspect of the present disclosure, the tissue sensing algorithm may be controlled in a first manner, and the tissue sealing algorithm is controlled in a second different manner.

[0009] In yet another aspect of the present disclosure, the delay time and / or voltage of the reflected signals at a plurality of frequencies are utilized to determine tissue characteristics.

[0010] In yet another aspect of the present disclosure, the tissue characteristic is the impedance at each of a plurality of frequencies.

[0011] In one aspect of the present disclosure, at least a portion of the tissue sealing algorithm can adjust the energy output to track the impedance versus time trajectory.

[0012] In another aspect of the present disclosure, the states in the first and second jaw members can be either an open circuit state or a short circuit state.

[0013] In still another aspect of the present disclosure, determining the tissue characteristic can include determining the frequency components of the reflected signal and determining the tissue characteristic based on the determined frequency components of the reflected signal.

[0014] In yet another aspect of the present disclosure, the method can further include implementing a delay period during which no energy is applied, according to a tissue sensing algorithm, after applying energy to the grasped tissue and before applying energy to the grasped tissue according to a tissue sealing algorithm.

[0015] An electrosurgical system for treating tissue according to the present disclosure includes an electrosurgical forceps including first and second jaw members and an electrosurgical generator. The electrosurgical generator includes a processor and a memory. The memory includes instructions stored thereon that, when executed by the processor, cause the system to apply a signal based on a tissue sensing algorithm to tissue grasped between the first and second jaw members for which a tissue treatment is scheduled, receive reflected signals from the first and second jaw members at a plurality of frequencies, and determine a tissue characteristic or a state in the first and second jaw members based on the reflected signals.

[0016] In one aspect of the present disclosure, the instructions, when executed by the processor, can further cause the system to adjust a tissue sealing algorithm based on the determined tissue characteristic.

[0017] In another aspect of the present disclosure, when the instructions are executed by a processor, the system may be further caused to apply energy to the grasped tissue according to a tissue sealing algorithm to seal the grasped tissue, and the tissue sealing algorithm is independent of the tissue sensing algorithm.

[0018] In still another aspect of the present disclosure, when the instructions are executed by a processor, the system may be further caused to control a pretreatment algorithm in a first manner, and the tissue sealing algorithm is controlled in a second different manner.

[0019] In yet another aspect of the present disclosure, the delay time and / or voltage of the reflected signals at a plurality of frequencies may be utilized to determine tissue characteristics.

[0020] In one aspect of the present disclosure, the tissue characteristic may be the impedance at each of a plurality of frequencies.

[0021] In another aspect of the present disclosure, at least a portion of the tissue sealing algorithm may adjust the energy output to track the impedance versus time trajectory.

[0022] In still another aspect of the present disclosure, the states in the first and second jaw members may be either an open circuit state or a short circuit state.

[0023] In yet another aspect of the present disclosure, when determining tissue characteristics, when the instructions are executed by a processor, the system may be further caused to determine the frequency components of the reflected signal and to determine the tissue characteristics based on the determined frequency components of the reflected signal.

[0024] When executed by a processor, a non-transitory computer-readable medium storing instructions that cause the processor to perform a computer-implemented method of treating tissue includes gripping tissue between a first jaw member and a second jaw member, applying a signal based on a tissue sensing algorithm to the gripped tissue for which tissue treatment is scheduled, receiving reflected signals from the first and second jaw members at a plurality of frequencies, and determining tissue characteristics or a state in the first and second jaw members based on the reflected signals.

[0025] The above and other aspects of the present disclosure will become more apparent when considered in conjunction with the following detailed description and the accompanying drawings, where like reference numerals are considered to be like or identical elements.

Brief Description of the Drawings

[0026]

Figure 1

Figure 2A

Figure 2B

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DETAILED DESCRIPTION OF THE INVENTION

[0027] The present disclosure enables the sensing of the characteristics of tissue (and / or other objects) gripped between the jaw members of an electrosurgical forceps using pulse time domain reflectometry. In this way, determining the characteristics of tissue (and / or other objects) is rapid and provides the advantage of not requiring additional sensing electrodes. A single short pulse contains a wide band of (multiple) frequencies within the single pulse. By paying attention to the amplitude and phase of these signals, more information is available within a single pulse.

[0028] Sweeping individual frequencies over the same bandwidth as the frequency during the pulse takes time. However, a single pulse having all frequency components can be transmitted and processed much more quickly than sweeping individual frequencies that cover the same range. Using a single short pulse provides the additional advantage that no additional sensing electrodes are required because reflections are returned from the same electrodes used for energy delivery. Such pulses according to the present disclosure can be applied before, during (randomly, intermittently, in response to user input, in response to sensed feedback, based on the situation or stage of tissue treatment, between energy deliveries, etc.) and / or after energy delivery.

[0029] Referring to FIG. 1, an electrosurgical system according to the present disclosure is shown and is generally identified by reference numeral 2. The electrosurgical system 2 includes an electrosurgical forceps 10 and an electrosurgical generator 40. The electrosurgical forceps 10 are illustrated and described herein as a shaft-based manual device. However, any other suitable electrosurgical forceps may be utilized in accordance with the present disclosure, regardless of shaft-based, hemostatic forceps type, manual, partial power supply, full power supply, robotic, etc. Obviously, different connections and considerations apply to each of the specific types of instruments, but the aspects and features of the present disclosure regarding tissue treatment generally remain consistent for any suitable instrument.

[0030] Continuing to refer to FIG. 1, the forceps 10 includes a shaft 12, a housing 20, a handle assembly 22, a trigger assembly 25, a rotation assembly 28, and an end effector assembly 100. The shaft 12 has a distal end portion 16 configured to mechanically engage the end effector assembly 100 and a proximal end portion 14 configured to mechanically engage the housing 20. A cable 34 couples the forceps 10 to an electrosurgical generator 40 for transmitting energy and control signals between the generator 40 and the forceps 10. The cable 34 houses a plurality of wires 56 that are internally divided into wires 56a - 56c within the handle assembly 22 and / or the shaft 12, and the wires electrically interconnect the end effector assembly 100, the activation switch 30, and / or the generator 40 to each other.

[0031] The handle assembly 22 includes a movable handle 24 and a fixed handle 26. The fixed handle 26 is integrally associated with the housing 20, and the movable handle 24 is movable relative to the fixed handle 26. The movable handle 24 is ultimately connected to a drive assembly 70, and together they mechanically cooperate such that one or both of the jaw members 110, 120 of the end effector assembly 100 move relative to each other between a spaced-apart position and a closer position to grip tissue therebetween. As shown in FIG. 1, the movable handle 24 is initially spaced apart from the fixed handle 26, and correspondingly, the jaw members 110, 120 are disposed in a spaced-apart position (see FIG. 2A). The movable handle 24 is movable from this initial position to one or more compressed positions corresponding to one or more closer positions of the jaw members 110, 120 (see FIG. 2B).

[0032] The drive assembly 70 can be configured to adjust the clamping force applied to tissue gripped between the respective surfaces 112, 122 of the jaw members 110, 120. More specifically, the handle assembly 22 and / or the latch assembly 27 can be configured to, in conjunction with the drive assembly 70, convey a specific clamping force or a clamping force within a specific clamping force range to the tissue gripped between the respective surfaces 112, 122 of the jaw members 110, 120. This can be achieved manually, for example, by moving the movable handle 24 from an initial position to a specific compressed position (or multiple positions), such as a fully compressed position, via a mechanical latch (where, for example, the latch assembly 27 is configured to latch the movable handle 24 in a specific position (or multiple positions)); via a power actuator using feedback-based control, for example, by driving or reversing a motor control actuator to a specific position (or multiple positions), and / or via any other suitable mechanism. The drive assembly 70 can include one or more passive adjustment components, such as springs, elastic features, etc., and / or active adjustment components, such as motors, manual drives, etc., in any of the configurations detailed above or any other suitable configuration.

[0033] For controlling the clamping force, suitable mechanisms for use as or in combination with the drive assembly 70 include those described in U.S. Patent Nos. 5,776,130, 7,766,910, 7,771,426, 8,226,650 and / or U.S. Patent Application Publication Nos. 2009 / 0292283, 2012 / 0172873 and 2012 / 0184988, the entire contents of all of which are incorporated herein by reference. Other suitable mechanisms may also be provided for applying a specific clamping force or a clamping force within a specific clamping force range to the tissue grasped between the jaw members 110, 120. For the tissue grasped between the jaw members 110, 120 under a specific clamping force or within a specific clamping force range, energy may be supplied to one or both of the tissue contact surfaces 112, 122 of the jaw members 110, 120, for example via actuation of the activation switch 30, so that the tissue can be sealed.

[0034] The jaw clamping force measured at an intermediate point along the length of the jaw members 110, 120 can be in the range of about 7.0 lbf to about 11.0 lbf (or the jaw force range can be from about 7.0 lbf to about 11.0 lbf), in other embodiments from about 8.0 lbf to about 10.0 lbf, and in still other embodiments from about 8.5 lbf to about 9.5 lbf.

[0035] The latch assembly 27 can be provided to selectively lock the movable handle 24 in various positions between an initial position and a compressed position relative to the fixed handle 26, and accordingly lock the jaw members 110, 120 in various different positions, such as one or more approaching positions, during pivoting. The rotation assembly 28 is rotatable in either direction to similarly rotate the shaft 12 and the end effector assembly 100 relative to the housing 20.

[0036] Referring also to FIGS. 2A and 2B, end effector assembly 100 is shown attached to the distal end portion 16 of shaft 12 and includes opposing jaw members 110 and 120. Each jaw member 110, 120 includes a conductive tissue contact surface 112, 122, respectively, which cooperate, for example, at one or more proximate locations of jaw members 110, 120 to grip tissue therebetween and facilitate sealing of the gripped tissue by conducting energy from generator 40 therebetween. More specifically, tissue contact surfaces 112, 122 are electrically coupled to generator 40, for example, via wires 56a, 56b, energized to different potentials, and configured such that conduction of radio frequency (RF) electrosurgical energy supplied by generator 40 between and through the tissue contact surfaces 112, 122 and the tissue gripped therebetween enables sealing of the tissue. The tissue contact surfaces 112, 122 can be defined by conductive plates fixed to the jaw members 110, 120, by the surfaces of the jaw members 110, 120 themselves, by deposition of material onto the jaw members 110, 120, or defined and / or formed in any other suitable manner.

[0037] One or both of the jaw members 110, 120 further include one or more stop members 124 (FIG. 2A) disposed on or associated with one or both of the tissue contact surfaces 112, 122 to maintain a minimum gap distance between the tissue contact surfaces 112, 122 when the jaw members 110, 120 are in a fully approximated position, and thus prevent an electrical short circuit. The stop members 124 are insulating, partially insulating, and / or may be electrically insulated from one or both of the tissue contact surfaces 112, 122. In an aspect, at the approximated position of the jaw members 110, 120, it is desirable to maintain the gap distance within a suitable gap distance range to ensure consistent and effective tissue sealing. The gap distance can be controlled by the stop members 124, the movable handle 24, the latch assembly 27, and / or the drive assembly 70, and can be, in one aspect, from about 0.001 inches to about 0.010 inches, in other aspects, from about 0.001 inches to about 0.008 inches, and in yet other aspects, from about 0.001 inches to about 0.006 inches. Other suitable gap distance ranges are also contemplated. The gap distance can be determined as the maximum gap distance at any point along the tissue contact surface between the tissue contact surfaces 112, 122.

[0038] The activation switch 30 is disposed on the housing 20 and is coupled between the generator 40 and / or between or to the tissue contact surfaces 112, 122 via the wire 56c. The activation switch 30 is selectively activatable to initiate the supply of energy from the generator 40 to the tissue contact surfaces 112, 122 of the respective jaw members 110, 120 of the end effector assembly 100. More specifically, depressing the activation switch 30 is recognized by the generator 40 as, for example, a resistance drop and signals the generator 40 to supply energy to, for example, the jaw members 110, 120 to initiate tissue sealing.

[0039] The end effector assembly 100 is designed as a bilateral assembly such that, for example, both the jaw members 110 and 120 are movable relative to each other and about a pivot axis 19 relative to the shaft 12. However, the end effector assembly 100 may alternatively be configured as a unilateral assembly, for example, one of the jaw members 110, 120 is fixed relative to the shaft 12 and the other jaw member 110, 120 is movable about a pivot axis 19 relative to the shaft 12 and the fixed jaw member.

[0040] In some configurations, a knife assembly (not shown) is disposed within the shaft 12 and a knife channel 115 is defined in one or both of the jaw members 110, 120 to permit reciprocation of a knife blade (not shown) through the knife channel, for example via actuation of the trigger assembly 25, to mechanically cut tissue grasped between the jaw members 110, 120. In aspects, it is possible to supply energy to the knife blade to enable dynamic energy-based tissue cutting. Alternatively, the end effector assembly 100 may include, for example, a static energy-based tissue cutter (not shown) disposed on or within one of the jaw members 110, 120. The energy-based tissue cutter, whether static or dynamic, may be configured to supply any suitable energy, such as RF, microwave, infrared, light, ultrasound, etc., to the tissue for energy-based tissue cutting. Energy activation for tissue cutting may be initiated automatically via the trigger assembly 25 via a different (or further) activation of the switch 30, via a separate actuation button, via a foot switch (not shown), or in any other suitable manner after tissue sealing.

[0041] Referring to FIG. 3, a robotic surgical instrument provided by the present disclosure is shown and is generally identified by reference numeral 1000. Aspects and features of the robotic surgical instrument 1000 that are not closely related to the understanding of the present disclosure are omitted to avoid obscuring the aspects and features of the present disclosure with unnecessary detail.

[0042] The robotic surgical instrument 1000 includes a plurality of robotic arms 1002, 1003, a control device 1004, and an operating console 1005 coupled to the control device 1004. The operating console 1005 can include a display device 1006 that can be prepared in particular for displaying three-dimensional images, and manual input devices 1007, 1008 that can be used by a surgeon to remotely operate the robotic arms 1002, 1003 in the operating room. The robotic surgical instrument 1000 can be configured for use in a minimally invasive manner on a patient 1013 being treated lying on a patient table 1012. The robotic surgical instrument 1000 can further specifically include a database 1014 coupled to the control device 1004 or can be capable of accessing such a database, in which preoperative data from, for example, the patient 1013 and / or anatomical illustrations is stored.

[0043] Each of the robotic arms 1002, 1003 may include a plurality of members connected via joints and mounting devices 1009, 1011 to which end effector assemblies 1100, 1200, for example, can be respectively attached. The end effector assembly 1100 may be similar to, and may include, any of the features of the end effector assembly 100 (Figs. 1 - 2B), and together with the robotic arm 1002, functions in a manner similar to that described above with respect to the forceps 10, except that it operates and is controlled in a robotic manner. Other suitable end effector assemblies for coupling to the mounting device 1009 are also contemplated. The end effector assembly 1200 can be any end effector assembly, such as a surgical camera, other surgical tool. The robotic arms 1002, 1003 and the end effector assemblies 1100, 1200 can be driven by an electric drive, such as a motor, connected to the control device 1004. The control device 1004 (e.g., a computer) can be configured to activate the motor, particularly using a computer program, so that the robotic arms 1002, 1003, their mounting devices 1009, 1011 and the end effector assemblies 1100, 1200 perform desired movements and / or functions in response to corresponding inputs from each of the manual input devices 1007, 1008. The control device 1004 can be configured to control the movement of the robotic arms 1002, 1003 and / or the motor.

[0044] Referring to FIG. 4, the generator 40 can be configured to be used with the forceps 10 (FIG. 1), the robotic surgical system 1000 (FIG. 3) and / or any other suitable surgical instrument or system. The generator 40 includes a sensor circuit 42, a controller 44, a high voltage DC power supply ("HVPS") 47 and an RF output stage 48. The HVPS 47 supplies a high voltage DC power supply to the RF output stage 48, and the RF output stage converts the high voltage DC power supply into RF energy for transmission to, for example, the respective tissue contact surfaces 112, 122 of the jaw members 110, 120 of the end effector assembly (FIGS. 1-2B) of the end effector assembly 100. Specifically, the RF output stage 48 generates a sine wave form of high frequency RF energy. The RF output stage 48 is configured to generate a plurality of waveforms having various duty cycles, peak voltages, crest factors and other parameters according to a specific operating mode.

[0045] The controller 44 includes a microprocessor 45 operably connected to a memory 46 which can be a volatile type memory (e.g., RAM) and / or a non-volatile type memory (e.g., flash media, disk media, etc.). The microprocessor 45 is operably connected to the HVPS 47 and / or the RF output stage 48 to enable the microprocessor 45 to control the output of the generator 40 according to feedback received, for example, from the sensor circuit 42. The sensor circuit 42 is operably coupled to wires 56a, 56b that supply energy to / from the tissue contact surfaces 112, 122 (FIGS. 1 - 2B). The sensor circuit 42 can determine one or more parameters, such as tissue impedance, output current, and / or voltage, etc., from the signals transmitted along the wires 56a, 56b, more specifically, the wires. The sensor circuit 42 provides feedback to the controller 44 based on, for example, the sensed parameters, and then the controller selects an energy transfer algorithm, modifies the energy transfer algorithm, and / or adjusts the energy transfer parameters based on the feedback. The sensor circuit 42 or the controller 44 also monitors the wire 56c to determine the activation (and / or deactivation) of the switch 30 (FIG. 1) and, accordingly, can start (or end) the supply of energy based thereon.

[0046] Referring to FIG. 5, a schematic diagram of the system 2 (FIG. 1) shows a generator 40 connected to the jaw members 110, 120 by a cable 34. A signal such as a pulse 502 is transmitted on the cable 34. The signal travels at a speed that is a function of the characteristic impedance of the cable 34. For example, the characteristic impedance of the cable can be 50 ohms. However, any suitable characteristic impedance can be used. The time required for the signal to travel the length of the cable (e.g., about 150 nS for a 10-foot cable) is obtained by dividing the speed per unit length by the physical length of the cable. The time to travel the length of the cable is called the electrical length "L". If the signal (i.e., pulse 502) has a duration shorter than the electrical length of the cable "L", the reflection returns to the generator 40 after the generator 40 has completed transmission. This enables a time discrimination scheme in which the receiver at the generator output is turned off during the time the signal is transmitted (i.e., the pulse width) and turned on for the time required for the signal to travel back and forth along the length of the cable 34.

[0047] To measure the characteristics, e.g., impedance, of tissue (and / or other objects) between the jaw members 110, 120, a short-duration pulse can be transmitted on the instrument cable 34 and the returned reflected signal is measured. As an example, impedance is used, but other characteristics are contemplated as well.

[0048] The difference between the characteristic impedance of the grasped tissue (and / or other object) and the characteristic impedance of the cable 34 and the generator 40 causes reflection of the signal (i.e., the pulse 502). The impedance between the jaw members 110, 120 reflects a part of the signal (i.e., the reflected pulse 506) back to the generator 40. The amount of reflection is a function of the impedance between the jaw members 110, 120 and the characteristic impedance of the cable 34. Since the characteristic impedance of the cable 34 is relatively constant, the change in the amplitude of the reflected signal is directly related to the impedance between the jaw members 110, 120. In an aspect, the voltage standing wave ratio (VSWR) mismatch between the grasped tissue and the characteristic impedance of the system (e.g., 50 ohms) can be determined from the amplitude of the reflected signal. The resulting VSWR can be used to determine the tissue impedance (and thereby the type of tissue, the thickness of the tissue, the moisture of the tissue, etc.) and / or other conditions inside and outside the jaw members 110, 120, such as whether the jaw members 110, 120 are immersed in saline, whether there is a conductive material in the vicinity, whether an open or short - circuit state exists, etc.

[0049] The impedance (and / or other characteristics) can be derived from the time - domain voltage measurement of the amplitude of the reflected pulse. The impedance can also be derived from the change in the frequency spectrum and / or frequency - domain measurements. In an aspect, the impedance, phase, and / or amplitude of the return signal at multiple frequencies can be measured to determine tissue characteristics. More specifically, by measuring the measured impedance, phase, and / or amplitude of the return signal at multiple frequencies, for example, a feedback spectrum of the impedance is provided, and it becomes possible to confirm tissue characteristics based not only on a single impedance measurement value but also on relative impedance measurement values at different frequencies. The same can be achieved using phase, amplitude, and / or time.

[0050] FIG. 6 shows a flowchart of an exemplary computer-implemented method for sealing tissue. The steps of FIG. 6 are shown in a particular order, but not all steps need to be performed in the specified order and certain steps may be performed in a different order. In various aspects, the operations of FIG. 6 may be performed, in whole or in part, by the controller 44 of the generator 40 of FIG. 4. In aspects, the operations of FIG. 6 may be performed, in whole or in part, by another device, such as a mobile device and / or a client computer system. These variations are intended to be within the scope of the present disclosure.

[0051] First, at step 602, tissue is grasped between the first and second jaw members 110, 120 (FIG. 5).

[0052] Next, at step 604, the controller 44 applies a signal to the grasped tissue where a tissue treatment is scheduled. The signal is based on a tissue sensing algorithm. For example, the signal may include a short pulse having an amplitude of about 500 mV and a pulse duration of about 100 nS. The signal is configured to reflect from the first and second jaw members 110, 120 and return through the cable 34. The tissue sensing algorithm may include the amplitude of the signal, the duration of the signal, and / or the repetition rate of the signal.

[0053] Next, at step 606, the controller 44 receives a reflected signal from the first and second jaw members 110, 120. For example, the reflected signal may have an amplitude of about 30 mV.

[0054] Next, at step 608, the controller 44 determines tissue characteristics and / or other conditions based on the reflected signal. For example, the controller 44 can determine, based on the reflected signal, that the tissue is a particular type of tissue, such as a blood vessel, muscle, organ, etc. The determined tissue type can be used to select and / or adjust a tissue sealing algorithm or to allow or prevent subsequent application of energy. The impedance of the tissue (or the impedance spectrum of the tissue over a plurality of frequencies of the reflected signal) can be utilized to determine the tissue type.

[0055] The delay time and / or voltage of the reflected signal can, in addition or alternatively, facilitate determining tissue characteristics, such as the type of tissue. In an aspect, other tissue characteristics can be determined based on, for example, the impedance of the tissue (or the impedance spectrum of the tissue over a plurality of frequencies of the reflected signal), such as the thickness of the tissue, the water content of the tissue, the conductivity of the tissue.

[0056] The controller 44 can determine the tissue characteristics based on determining the frequency components of the reflected signal and then determining the tissue characteristics based on the determined frequency components of the reflected signal. A fast Fourier transform (FFT) can be performed on the reflected signal (e.g., the reflected pulse). An ideal short pulse has an infinite series of harmonics with equal amplitudes. In practice, due to the rising edge of the generated pulse and due to various parasitic capacitances and / or inductances, the harmonic series is not infinite and attenuates as the frequency increases. An FFT can be performed on a known short pulse having a known duration to determine the initial frequency domain response. The controller 44 can perform an FFT on the received reflected signal to determine the frequency domain response regarding the reflected pulse. The controller 44 can compare the initial frequency domain response and the reflected frequency domain response and determine the tissue characteristics based on the comparison.

[0057] In an aspect, the controller 44 may adjust the tissue sealing algorithm based on the determined tissue characteristics. More detailed tissue sealing algorithms suitable for use in accordance with the present disclosure can be found, for example, in U.S. Patent No. 8,920,421, filed Nov. 29, 2010, as U.S. Patent Application No. 12 / 995,042, entitled "SYSTEM AND METHOD FOR TISSUE SEALING," the entire content of which is incorporated herein by reference, and in U.S. Patent No. 8,147,485, filed Feb. 23, 2009, as U.S. Patent Application No. 12 / 391,036, entitled "SYSTEM AND METHOD FOR TISSUE SEALING," the entire content of which is incorporated herein by reference.

[0058] In yet another aspect, the tissue sensing algorithm may be executed during and / or after the tissue sealing algorithm, in addition to or instead of.

[0059] In an aspect, the controller 44 may apply energy to the grasped tissue according to the tissue sealing algorithm to seal the grasped tissue. The tissue sealing algorithm may be independent of the tissue sensing algorithm, or the tissue sensing algorithm may be incorporated into the tissue sealing algorithm. In an aspect, the tissue sensing algorithm is controlled in a first manner, and the tissue sealing algorithm is controlled in a second different manner.

[0060] In an aspect, the controller 44 may apply a signal during the treatment of the tissue to determine a change in tissue characteristics. At least a portion of the tissue sealing algorithm may adjust the energy output to track the impedance versus time trajectory.

[0061] In an aspect, the controller 44 may determine whether the tissue sensing algorithm is complete before applying energy to the grasped tissue according to the tissue sealing algorithm.

[0062] In accordance with the tissue sensing algorithm, after applying energy to the grasped tissue and before applying energy to the grasped tissue in accordance with the tissue sealing algorithm, the controller 44 may implement a delay period during which no energy is applied.

[0063] FIG. 7 shows a simulation of a signal (i.e., pulse 502) having a duration of 150 nS and a delay of 150 nS between the reflection and the measured reflected pulse 506. The impedance of the load from which the pulse is reflected was varied from 1 ohm to 1000 ohms. The simulation shows how the amplitude of the return pulse changes with the impedance change.

[0064] Referring to FIG. 8, an oscilloscope trace is provided showing the transmitted signal (i.e., pulse 502) and the reflected signal (i.e., reflected pulse 506) when the first and second jaw members 110, 120 of FIG. 5 are in the open position and not grasping tissue. As can be seen from the oscilloscope trace, the applied signal is a pulse having a duration of about 60 nS and an amplitude of about 400 mV peak. The cable length results in a delay of about 10 nS. In an "ideal" open circuit, the reflected pulse 506 has an amplitude equal to the transmitted pulse 502. The observed reflected pulse 506 indicates that the first and second jaw members 110, 120 of FIG. 5 have an impedance other than 50 ohm characteristic impedance. Thus, in addition to detecting tissue characteristics, other conditions associated with the first and second jaw members 110, 120, such as an open circuit condition, can be detected. Similarly, it can be determined whether a sufficient volume of tissue is grasped between the first and second jaw members 110, 120 or whether a minimum volume of tissue insufficient to establish proper tissue sealing is grasped. Additionally, the presence of other materials, such as bone, staples, other instruments, etc., can also be detected.

[0065] FIG. 9 shows an oscilloscope trace showing a transmission pulse 502 and a reflection pulse 506 to an impedance of about 100 ohms. FIG. 10 shows a simulation of an ideal reflection pulse from a 100-ohm load. As can be seen from the oscilloscope trace of FIG. 9, the amplitude of the reflection pulse 506 is close to the simulated theoretical amplitude of about 138 mV peak in FIG. 10.

[0066] FIG. 11 shows an oscilloscope trace showing a transmission pulse 502 and a reflection pulse 506 when the first and second jaw members 110, 120 of FIG. 5 grip a load of about 50 ohms. From the oscilloscope trace, the amplitude of the reflection pulse 506 is close to about 0 volt peak which is the theoretical amplitude of the 50-ohm system. The characteristic impedance of the coaxial cable is 50 ohms, and thus the reflected signal should be nearly zero. The trace of the actual reflection pulse 506 shows a non-zero voltage of a fraction, which is due to the parasitic capacitance and inductance of the first and second jaw members 110, 120 of FIG. 5. The voltage reaches about 0 volts at the end of the pulse.

[0067] Referring to FIGS. 12-14, frequency domain plots of the frequency domain responses of the transmission pulse 502 and the reflection pulse 504 are shown for three exemplary impedance conditions: a short circuit (FIG. 12), an open (FIG. 13), and a 50-ohm impedance (FIG. 14) between the first and second jaw members 110, 120. A very low amplitude pulse 502 having a peak of about 40 mV and a short duration of about 60 nS is applied to the first and second jaw members 110, 120 of FIG. 5, and the frequency spectrum is shown.

[0068] From the results, it can be seen that the spectra are different for different conditions. Two frequencies were selected to show the changes. Markers were placed at about 6.19 MHz and about 10.19 MHz. It can be seen that the amplitudes at these two frequencies change as summarized in the following table.

[0069] From the results, it can be seen that the spectrum does not change according to the impedance, which indicates that the impedance change can be determined using the frequency domain response or the frequency response for short pulses, and the tissue type and / or other tissue characteristics can be distinguished.

[0070] FIG. 12 is a trace showing the frequency spectrum when there is a short circuit between the first and second jaw members 110, 120 of FIG. 5. FIG. 13 is a trace showing the frequency spectrum when there is an open circuit between the first and second jaw members 110, 120. FIG. 14 is a trace showing the frequency spectrum when the first and second jaw members 110, 120 are gripping a load of about 50 ohms.

[0071] FIG. 15 is a table showing the impedance vs. amplitude at different frequencies for the return pulse under the load conditions shown in FIGS. 12-14. For example, for the short circuit load shown in FIG. 12, an amplitude of about -56 dBm is measured at about 6.19 MHz. An amplitude of about -74 dBm is measured at a frequency of about 10.19 MHz. For the open circuit load of FIG. 13, an amplitude of about -78 dBm is measured at about 6.19 MHz. An amplitude of about -58 dBm is measured at a frequency of about 10.19 MHz. For the 50 ohm load of FIG. 14, an amplitude of about -58 dBm is measured at about 6.19 MHz. An amplitude of about -64 dBm is measured at a frequency of about 10.19 MHz.

[0072] Although some aspects of the present disclosure are shown in the drawings, the present disclosure is not intended to be limited thereto, and the present disclosure is intended to be as broad in scope as is permitted by the art and as such is to be read herein. Accordingly, the above description should not be construed as limiting, but should be construed merely as an exemplification of a particular configuration. Those skilled in the art will envision other modifications within the scope and spirit of the appended claims.

Claims

1. A method of treating tissue, comprising: grasping tissue between a first jaw member and a second jaw member; applying a signal based on a tissue sensing algorithm to the grasped tissue for which tissue treatment is scheduled; receiving reflected signals from the first and second jaw members at a plurality of frequencies; determining tissue characteristics or a state in the first and second jaw members based on the reflected signals The method includes.

2. The method according to claim 1, further comprising adjusting a tissue sealing algorithm based on the determined tissue characteristics.

3. The method according to claim 1, further comprising applying energy to the grasped tissue according to a tissue sealing algorithm to seal the grasped tissue, wherein the tissue sealing algorithm is independent of the tissue sensing algorithm.

4. The method according to claim 1, wherein the tissue sensing algorithm is controlled in a first manner and the tissue sealing algorithm is controlled in a second different manner.

5. The method according to claim 1, wherein the delay time and / or voltage of the reflected signals at the plurality of frequencies are utilized to determine the tissue characteristics.

6. The method according to claim 5, wherein the tissue characteristics are impedances at each of the plurality of frequencies.

7. The method according to claim 1, wherein at least a part of the tissue sealing algorithm adjusts the energy output to track the impedance vs. time trajectory.

8. The method according to claim 1, wherein the state in the first and second jaw members is one of an open circuit state or a short circuit state.

9. Determining the tissue characteristics includes: determining frequency components of the reflected signals; determining tissue characteristics based on the determined frequency components of the reflected signals The method according to claim 1, including.

10. The method according to claim 1, further comprising implementing a delay period during which no energy is applied after applying energy to the grasped tissue according to the tissue sensing algorithm and before applying the energy to the grasped tissue according to the tissue sealing algorithm.

11. An electrosurgical system for treating tissue, comprising: electrosurgical forceps including first and second jaw members; an electrosurgical generator, comprising: a processor, A memory including instructions stored thereon, which, when executed by the processor, cause the system to apply a signal based on a tissue sensing algorithm to tissue grasped between the first jaw member and the second jaw member, wherein tissue treatment is scheduled receive reflected signals from the first and second jaw members at a plurality of frequencies determine tissue characteristics or states of the first and second jaw members based on the reflected signals A memory that causes the above to be performed An electrosurgical generator including An electrosurgical system including **Claim 12** The electrosurgical system according to claim 11, wherein the instructions, when executed by the processor, further cause the system to adjust a tissue sealing algorithm based on the determined tissue characteristics. **Claim 13** The electrosurgical system according to claim 11, wherein the instructions, when executed by the processor, further cause the system to apply energy to the pre-treated grasped tissue according to a tissue sealing algorithm to seal the pre-treated grasped tissue, and the tissue sealing algorithm is independent of the pre-treatment algorithm. **Claim 14** The electrosurgical system according to claim 11, wherein the instructions, when executed by the processor, further cause the system to control the tissue sensing algorithm in a first manner, and the tissue sealing algorithm is controlled in a second different manner. **Claim 15** The electrosurgical system according to claim 11, wherein the delay time and / or voltage of the reflected signals at the plurality of frequencies are used to determine the tissue characteristics. **Claim 16** The electrosurgical system according to claim 15, wherein the tissue characteristics are impedances at each of the plurality of frequencies. **Claim 17** The electrosurgical system according to claim 11, wherein at least a part of the tissue sealing algorithm adjusts the energy output to track the impedance vs. time trajectory. **Claim 18** The electrosurgical system according to claim 11, wherein the state of the first and second jaw members is one of an open circuit state or a short circuit state. **Claim 19** When determining the tissue characteristics, the instructions, when executed by the processor, cause the system to determine the frequency components of the reflected signals determining tissue characteristics based on the determined frequency components of the reflected signal The electrosurgical system according to claim 11, further causing the above to be performed. [

20. ] A non-transitory computer-readable medium storing instructions that, when executed by a processor, cause the processor to perform a computer-implemented method of treating tissue, the computer-implemented method comprising: grasping tissue between a first jaw member and a second jaw member; applying a signal based on a tissue sensing algorithm to the grasped tissue for which tissue treatment is scheduled; receiving reflected signals from the first and second jaw members at a plurality of frequencies; determining tissue characteristics or a state in the first and second jaw members based on the reflected signals A non-transitory computer-readable medium including the above.

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