Patent Publication Number: US-11660136-B2

Title: Electrosurgical system

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is continuation of U.S. patent application Ser. No. 16/448,492, entitled “ELECTROSURGICAL SYSTEM”, filed Jun. 21, 2019, currently pending, which is a continuation of U.S. patent application Ser. No. 15/431,595, entitled “ELECTROSURGICAL SYSTEM”, filed Feb. 13, 2017, now U.S. Pat. No. 10,342,604, issued Jul. 9, 2019, which is a continuation of U.S. patent application Ser. No. 14/076,469, entitled “ELECTROSURGICAL SYSTEM”, filed Nov. 11, 2013, now U.S. Pat. No. 9,566,108, issued Feb. 14, 2017, which is a continuation of U.S. patent application Ser. No. 12/416,751, entitled “ELECTROSURGICAL SYSTEM”, filed Apr. 1, 2009, now U.S. Pat. No. 8,579,894, issued Nov. 12, 2013, which is a continuation of U.S. patent application Ser. No. 12/416,128, entitled “ELECTROSURGICAL SYSTEM”, filed Mar. 31, 2009, now U.S. Pat. No. 8,568,411, issued Oct. 29, 2013, which claims the benefit of U.S. Provisional Patent Application Ser. No. 61/040,980, entitled “FEEDBACK CONTROL MECHANISM FOR FUSING BIOLOGICAL TISSUE WITH HIGH FREQUENCY ELECTRICAL ENERGY”, filed Mar. 31, 2008; U.S. Provisional Patent Application Ser. No. 61/040,994, entitled “FUSING BIOLOGICAL TISSUE WITH HIGH FREQUENCY ELECTRICAL ENERGY”, filed Mar. 31, 2008; U.S. Provisional Patent Application Ser. No. 61/040,957, entitled “METHOD AND APPARATUS FOR BLOODLESS TISSUE DISSECTION”, filed Mar. 31, 2008; U.S. Provisional Patent Application Ser. No. 61/040,828, entitled “LAPAROSCOPIC BIPOLAR ELECTRICAL INSTRUMENT”, filed Mar. 31, 2008; U.S. Provisional Patent Application Ser. No. 61/040,890, entitled “APPARATUS AND METHOD FOR FUSION OF LIVING TISSUE”, filed Mar. 31, 2008; U.S. Provisional Patent Application Ser. No. 61/041,045, entitled “WELDING BIOLOGICAL TISSUE WITH HIGH FREQUENCY ELECTRICAL ENERGY”, filed Mar. 31, 2008; U.S. Provisional Patent Application Ser. No. 61/041,012, entitled “ELECTRICAL CONTROL CIRCUIT FOR FUSING OF BIOLOGICAL TISSUE WITH HIGH FREQUENCY ELECTRICAL ENERGY”, filed Mar. 31, 2008; U.S. Provisional Patent Application Ser. No. 61/115,756, entitled “METHOD AND APPARATUS FOR ELECTROSURGICAL TISSUE DISSECTION”, filed Nov. 18, 2008. All of these applications are incorporated herein by reference in their entireties. 
    
    
     BACKGROUND 
     Field 
     The present application relates generally to electrosurgical systems and methods. More specifically, the present application relates to an electrosurgical system including an electrosurgical unit with a feedback circuit and an electrosurgical tool. 
     Discussion of the Relevant Art 
     Surgical procedures often involve cutting and connecting bodily tissue including organic materials, musculature, connective tissue and vascular conduits. For centuries, sharpened blades and sutures have been mainstays of cutting and reconnecting procedures. As bodily tissue, especially relatively highly vascularized tissue is cut during a surgical procedure, it tends to bleed. Thus, medical practitioners such as surgeons have long sought surgical tools and methods that slow or reduce bleeding during surgical procedures. 
     More recently, electrosurgical tools have become available that use electrical energy to perform certain surgical tasks. Typically, electrosurgical tools are hand tools such as graspers, scissors, tweezers, blades, needles, and other hand tools that include one or more electrodes that are configured to be supplied with electrical energy from an electrosurgical generator including a power supply. The electrical energy can be used to coagulate, fuse, or cut tissue to which it is applied. Advantageously, unlike typical mechanical blade procedures, application of electrical energy to tissue tends to stop bleeding of the tissue. 
     Electrosurgical tools typically fall within two classifications: monopolar and bipolar. In monopolar tools, electrical energy of a certain polarity is supplied to one or more electrodes on the tool. A separate return electrode is electrically coupled to a patient. Monopolar electrosurgical tools can be useful in certain procedures, but can include a risk of certain types of patient injuries such as electrical burns often at least partially attributable to functioning of the return electrode. In bipolar electrosurgical tools, one or more electrodes is electrically coupled to a source of electrical energy of a first polarity and one or more other electrodes is electrically coupled to a source of electrical energy of a second polarity opposite the first polarity. Thus, bipolar electrosurgical tools, which operate without separate return electrodes, can deliver electrical signals to a focused tissue area with a reduced risk of patient injuries. 
     Even with the relatively focused surgical effects of bipolar electrosurgical tools, however, surgical outcomes are often highly dependent on surgeon skill. For example, thermal tissue damage and necrosis can occur in instances where electrical energy is delivered for a relatively long duration or where a relatively high-powered electrical signal is delivered even for a short duration. The rate at which a tissue will achieve the desired coagulation or cutting effect upon the application of electrical energy varies based on the tissue type and can also vary based on pressure applied to the tissue by an electrosurgical tool. However, even for a highly experienced surgeon, it can be difficult for a surgeon to assess how quickly a mass of combined tissue types grasped in an electrosurgical instrument will be fused a desirable amount. 
     Attempts have been made to reduce the risk of tissue damage during electrosurgical procedures. For example, previous electrosurgical systems have included generators that monitor an ohmic resistance or tissue temperature during the electrosurgical procedure, and terminated electrical energy once a predetermined point was reached. However, these systems have had shortcomings in that they have not provided consistent results at determining tissue coagulation, fusion, or cutting endpoints for varied tissue types or combined tissue masses. These systems can also fail to provide consistent electrosurgical results among use of different tools having different tool and electrode geometries. Typically, even where the change is a relatively minor upgrade to tool geometry during a product&#39;s lifespan, the electrosurgical generator must be recalibrated for each tool type to be used, a costly, time consuming procedure which can undesirably remove an electrosurgical generator from service. 
     SUMMARY 
     In view of at least the foregoing shortcomings of the previous electrosurgical systems, there is a need in the art to improve control of electrosurgical procedures to enhance consistency of electrosurgical results among electrosurgical tools and tissue types. Accordingly, there is a need for an improved electrosurgical system that can accurately assess an electrical energy application endpoint for a desired electrosurgical procedure. There is also a need for an electrosurgical system that monitors tissue properties during the electrosurgical procedure to assess the energy application endpoint. There is also a need for an improved electrosurgical system that can rapidly accommodate various electrosurgical tools with minimal impact on surgical outcome. To address some or all of these needs and provide various additional advantages as discussed below in greater detail, various embodiments, methods, systems, and apparatuses for electrosurgical procedures are provided. 
     In various embodiments, methods and apparatuses for bloodless dissection of connective and vascular tissue are provided. The various methods and apparatuses described herein can be used in minimally invasive surgery, particularly laparoscopic surgery. 
     In certain embodiments, an electrosurgical tool comprises a handle assembly, an elongate shaft, a jaw assembly, and a force regulation mechanism. The handle assembly comprises a stationary handle and an actuation handle movably coupled to the stationary handle. The elongate shaft extends distally from the handle. The elongate shaft has a proximal end and a distal end defining a central longitudinal axis therebetween. The jaw assembly is positioned on the distal end of the elongate shaft. The jaw assembly comprises a first jaw and a second jaw. The first jaw has an inner surface, an outer surface, and at least one electrode disposed on the inner surface. The second jaw has an inner surface, an outer surface, and at least one electrode disposed on the inner surface. The jaw assembly is actuatable by movement of the ff from an open configuration in which the inner surface of the first jaw is spaced apart from the inner surface of the second jaw to a closed configuration in which the inner surface of the first jaw is proximate the inner surface of the second jaw. The force regulation mechanism couples the handle assembly to the jaw assembly. The force regulation assembly is configured such that in the closed configuration, the jaw assembly delivers a gripping force between the first jaw and the second jaw between a predetermined minimum force and a predetermined maximum force. 
     In other embodiments, an electrosurgical tool is provided comprising a handle assembly, an elongate shaft, and a jaw assembly. The handle assembly comprises a moveable actuation handle. The elongate shaft extends distally from the handle. The elongate shaft has a proximal end and a distal end defining a central longitudinal axis therebetween. The jaw assembly is positioned on the distal end of the elongate shaft. The jaw assembly comprises a first jaw, a second jaw, and a blade. The first jaw has an inner surface, an outer surface, a proximal end and a distal end, and at least one electrode disposed on the inner surface. The second jaw has an inner surface, an outer surface, a proximal end and a distal end and at least one electrode disposed on the inner surface. The blade is advanceable along the inner surface of the first jaw along a cutting path defined between a retracted position adjacent the proximal end and an advanced position between the proximal end and the distal end. The jaw assembly is actuatable from an open configuration to a closed configuration by movement of the actuation handle. The at least one electrode on the first jaw and the at least one electrode on the second jaw define a sealing area enclosing the cutting path of the blade. 
     In other embodiments, an electrosurgical tool is provided comprising a handle assembly, an elongate shaft, and a jaw assembly. The elongate shaft extends distally from the handle assembly. The shaft having a proximal end and a distal end defining a central longitudinal axis therebetween. The jaw assembly is positioned on the distal end of the elongate shaft. The jaw assembly comprises a first jaw and a second jaw. The first jaw has an inner surface, an outer surface, a proximal end and a distal end, and at least one fusion electrode disposed on the inner surface. The second jaw has an inner surface, an outer surface, a proximal end and a distal end and at least one fusion electrode disposed on the inner surface and a cutting electrode disposed on the outer surface. 
     In certain embodiments, an electrosurgical system for performing surgical procedures on body tissue of a patient comprises an electrosurgical generator and an electrosurgical tool. The electrosurgical tool comprises a memory module storing tool data. The electrosurgical generator is configured to receive the tool data from the memory module and apply an electrosurgical signal profile to the electrosurgical tool based on the tool data. 
     In other embodiments, an electrosurgical generator for performing surgical procedures on body tissue of a patient comprises a power supply, a signal generation module, and a first tool port. The signal generation module is electrically coupled to the power supply. The signal generation module is configured to generate a radiofrequency signal. The first tool port is configured to interface with an electrosurgical tool having tool data stored therein. The first tool port is adapted to receive the tool data stored on the electrosurgical tool and to supply the radiofrequency signal from the signal generation module to the tool. 
     In some embodiments, a controller for electrosurgical tools comprises a first actuator, a second actuator, and a tool selector. The first actuator is movable between an on position and an off position for actuating a first electrosurgical action when in the on position. The second actuator is movable between an on position and an off position for actuating a second electrosurgical action when in the on position. The tool selector has a first state wherein the controller is adapted to be operatively coupled to a first electrosurgical tool and a second state wherein the controller is adapted to be operatively coupled to a second electrosurgical tool. 
     In certain embodiments, a surgical tool can comprise jaw elements having a plurality of electrodes to be used for both electrosurgical coagulation and cutting. The electrodes can be powered in a first configuration to provide coagulation—leading to hemostasis of small vascular vessels and tissue—and powered in a second configuration for electrosurgical cutting of the coagulated tissue. The two powered configurations can be generated by addressing different electrodes on the jaw elements and applying them with voltages appropriate for electrosurgical coagulation and/or cutting. In some embodiments, the surgical tool can initially be powered in the first configuration to provide coagulation, and then can be powered in the second configuration for electrosurgical cutting. In other embodiments, the electrosurgical tool can be powered only in a coagulating configuration to achieve tissue hemostasis, only in a cutting configuration to dissect tissue, or in a cutting configuration followed by a coagulation configuration. 
     At the same time, various embodiments of the surgical tools described herein can include different electrode configurations. I.e., while in one embodiment only the lower jaw is utilized to provide both coagulation and cutting functions, another embodiment can also employ the upper jaw element to be used in the coagulation and/or cutting process. In yet another embodiment, each jaw element can carry multiple electrode elements, greatly increasing the functionality of the tool. A specific electrode arrangement can allow for tools that are more suitable for particular surgical procedures. 
     Another aspect of the surgical tools described herein relates to activation and deactivation of one or multiple electrodes, based on the position of the jaw elements. This position-based actuation allows, for example, activation of the upper jaw electrodes only in a near-closed position of the tool (or, in other embodiments, in an opened or near-opened position of the tool). In some embodiments, electrical switches in the jaw element driving mechanism can be positioned in a hand-piece of the surgical tool to selectively activate and deactivate one or multiple electrodes based on a position of the jaw elements. In other embodiments, the activation and deactivation can be performed by sliding contacts that are assembled in the hand-piece. 
     Yet another aspect of the surgical tools described herein is the automated switching from coagulation to cutting, enabled by use of a multi-electrode generator. Here, a tissue feedback mechanism triggers both switching from one set of coagulation electrodes (applied with voltages appropriate for coagulation) to another set of cutting electrodes (applied with voltages appropriate for cutting). As such, each individual tool electrode can be relayed through a bus-bar connection to any polarity of choice of the power supply. In addition, tool position switches in the hand tool can provide with logic switching for the population of different coagulation and/or cutting settings, depending on the specific tool position. 
     In certain embodiments, an electrosurgical tool is provided comprising a first jaw, a second jaw, a first electrode, a second electrode, and a third electrode. The second jaw is pivotable with respect to the first jaw. The first electrode is positioned on the first jaw. The second electrode is positioned on the first jaw. The third electrode is positioned on the first jaw. The electrosurgical tool can be selectively configurable in a coagulation configuration such that at least one of the first, second, and third electrodes is electrically coupled with a source of electrical energy having a first polarity and at least one other of the electrodes is electrically coupled with a source of electrical energy having a second polarity generally opposite the first polarity and in a cutting configuration such that one of the first, second, and third electrodes is electrically coupled with a source of electrical energy having a cutting voltage and at least one other of the electrodes is configured to be a return electrode. 
     In other embodiments, an electrosurgical tool having a proximal end and a distal end is provided comprising a distal end-piece, an elongate shaft, a handle assembly, and a switching mechanism. The distal end-piece is positioned at the distal end of the tool. The distal end-piece comprises a first jaw element, a second jaw element, and a plurality of electrodes. The first and second jaw elements are movable relative to one another between an open position and a closed position. The plurality of electrodes is disposed on at least one of the first jaw element and the second jaw element. The plurality of electrodes is selectively configurable in one of a coagulation configuration and a cutting configuration. The elongate shaft has a distal end connected to the distal end-piece and a proximal end. The handle assembly is positioned at the proximal end of the tool and connected to the proximal end of the elongate shaft. The handle assembly comprises a hand-piece and a trigger. The trigger is pivotally coupled to the hand-piece and operably coupled to the distal end-piece such that movement of the trigger relative to the hand-piece moves the first and second jaw elements relative to one another. The switching mechanism is electrically coupled to the distal end-piece to selectively configure the plurality of electrodes in one of the coagulation configuration and the cutting configuration. 
     In other embodiments, a method for substantially bloodless dissection of biological tissue is provided. The method comprises positioning an electrosurgical tool adjacent tissue to be dissected, measuring tissue properties to determine the switching point from coagulation to cutting, applying electrical energy to the electrosurgical tool, assessing the tissue coagulation (phase shift) through a feedback loop, switching a configuration of the electrosurgical tool, and applying electrical energy to the electrosurgical tool in a cutting configuration. The electrosurgical tool comprises a plurality of electrodes configurable in one of a coagulation configuration and a cutting configuration. Applying electrical energy to the electrosurgical tool comprises applying electrical energy to the electrosurgical tool in the coagulation configuration to achieve hemostasis in the tissue. Switching the electrosurgical tool comprises switching the electrosurgical tool to the cutting configuration. 
     In some embodiments, a method for controlling an output of an electrosurgical generator operatively coupled to a bipolar electrosurgical device is provided. The method comprises measuring a phase angle, determining a target phase angle, measuring the phase angle of a second measurement signal, and ceasing delivery of a treatment signal. Measuring the phase angle comprises measuring a phase angle of a first measurement signal applied to tissue of a patient via at least one electrode of the electrosurgical device. The first measurement signal is applied to the tissue prior to treatment of the tissue by the electrosurgical device. Determining a target phase angle comprises determining a target phase angle using the phase angle of the first measurement signal. Following delivery of a treatment signal comprises following delivery of a treatment signal to the tissue. Measuring the phase angle of a second measurement signal comprises measuring the phase angle of a second measurement signal applied to the tissue. The treatment signal is capable of causing modification of the tissue. Ceasing delivery of the treatment signal comprises ceasing delivery of the treatment signal to the tissue when the phase angle of the second measurement signal reaches the target phase angle. 
     In other embodiments, a method for controlling an output of an electrosurgical generator operatively coupled to a bipolar electrosurgical device is provided. The method comprises determining permittivity and conductivity of tissue, determining a threshold phase angle, measuring a phase angle, and ceasing the delivery of the treatment signal. Determining permittivity and conductivity of tissue comprises determining permittivity and conductivity of tissue of a patient using a measurement signal. The measurement signal is applied to tissue of a patient via at least one electrode of the electrosurgical device. The measurement signal is applied to the tissue prior to modification of the tissue by the electrosurgical device. Determining a threshold phase angle comprises determining a threshold phase angle based on the permittivity and the conductivity of the tissue. Measuring a phase angle comprises measuring a phase angle of a signal applied to the tissue. Ceasing the delivery of the treatment signal comprises ceasing the delivery of the treatment signal to the tissue when the phase angle of the signal reaches the threshold phase angle. 
     In other embodiments, a method of characterizing tissue prior to the delivery of electrosurgical energy to the tissue via a bipolar electrosurgical device is provided. The method comprises measuring phase angle, determining the product of the relative permittivity and conductivity, and characterizing the tissue. Measuring phase angle comprises measuring phase angle of a measurement signal applied to tissue of a patient via at least one electrode of the electrosurgical device. The measurement signal is applied to the tissue at a predetermined frequency prior to modification of the tissue by the electrosurgical device. Determining the product of the relative permittivity and conductivity comprises determining the product of the relative permittivity and conductivity of the tissue using the phase angle measurement and the predetermined frequency. Characterizing the tissue comprises characterizing the tissue based on the product of the relative permittivity and conductivity of the tissue. 
     In other embodiments, a method of characterizing tissue prior to the delivery of electrosurgical energy to the tissue via a bipolar electrosurgical device is provided. The method comprises generating a measurement signal, determining a treatment endpoint condition, and stopping delivery of a treatment signal. Generating a measurement signal comprises generating a measurement signal applied to tissue of a patient positioned between at least two jaw members of an electrosurgical device. At least one of the jaw members comprises an electrode. The measurement signal is delivered to the tissue via the electrode and applied to modification of the tissue by the electrosurgical device. Determining a treatment endpoint condition comprises determining a treatment endpoint condition using the measurement signal. The treatment endpoint condition is determined substantially independently of the dimensions of the tissue positioned between the at least two jaw members. Stopping delivery of a treatment signal comprises stopping delivery of a treatment signal to the tissue when the treatment endpoint condition is reached. The treatment signal is capable of causing modification of the tissue. 
     In other embodiments, an electrosurgical system for application of treatment energy to a patient involved in bipolar electrosurgery is provided. The system comprises an electrosurgical generator, an electrosurgical control unit, and an electrosurgical tool. The electrosurgical generator is configured to generate and output a treatment energy along with a measurement signal. The electrosurgical control unit is configured to direct the output of treatment energy and a measurement signal. The electrosurgical tool is removably connected to one of the electrosurgical generator and the electrosurgical control unit and arranged to contact tissue and apply the treatment energy and the measurement signal to the tissue. The electrosurgical control unit measures permittivity and conductivity of the tissue through the application of the measurement signal. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present inventions may be understood by reference to the following description, taken in connection with the accompanying drawings in which the reference numerals designate like parts throughout the figures thereof. 
         FIG.  1 A  is a schematic block diagram of an embodiment of electrosurgical system. 
         FIG.  1 B  is a schematic block diagram of another embodiment of electrosurgical system. 
         FIG.  2 A  is a perspective view of components of one embodiment of an electrosurgical system. 
         FIG.  2 B  is a perspective view of components of one embodiment of an electrosurgical system. 
         FIG.  2 C  is a perspective view of components of one embodiment of electrosurgical system. 
         FIG.  3 A  is a perspective view of an electrosurgical unit for use in an electrosurgical system. 
         FIG.  3 B  is a front view of the electrosurgical unit of  FIG.  3 A . 
         FIG.  3 C  is a rearview of the electrosurgical unit of  FIG.  3 A . 
         FIG.  4 A  is an exemplary screenshot of a display of the electrosurgical unit of  FIG.  3 A . 
         FIG.  4 B  is another exemplary screenshot of the display of the electrosurgical unit of  FIG.  3 A . 
         FIG.  5    is a block diagram of various embodiments of an electrosurgical unit. 
         FIG.  6    is a front view of a user interface of an electrosurgical unit. 
         FIG.  7    is a front view of a user interface of an electrosurgical unit. 
         FIG.  8    is a front view of a user interface of an electrosurgical unit. 
         FIG.  9    is a block diagram of an electrosurgical unit. 
         FIG.  10    is a block diagram of an electrosurgical unit. 
         FIG.  11    is a graphical representation of a high voltage driving signal at low frequency relative to a low voltage measurement voltage at a high frequency. 
         FIG.  12    is a graphical representation of filtered measurement and current signals for a time near the end of the fusion process. 
         FIG.  13    is a block diagram of an electrosurgical unit. 
         FIG.  14    is a block diagram of an electrosurgical unit. 
         FIG.  15    is a schematic diagram of an external measurement circuitry of an electrosurgical unit. 
         FIG.  16    is a schematic diagram of switch circuitry of an electrosurgical unit. 
         FIG.  17    is a schematic diagram of a phase comparator or detection circuitry of an electrosurgical unit. 
         FIG.  18    is a schematic diagram of a battery power circuitry of an electrosurgical unit. 
         FIG.  19    is a schematic diagram of an input interface of an electrosurgical unit. 
         FIG.  20    is a graphical representation of experimental data for the voltage applied to the tissue during a typical a vessel fusion process. 
         FIG.  21    is a graphical representation of experimental data for the voltage applied to the tissue during the measurement cycle. 
         FIG.  22    is a graphical representation of experimental data for the voltage applied to the tissue during the RF measurement cycle to determine the phase shift through the tissue. 
         FIG.  23    is a graphical representation of a sample of experimental data for a typical vessel sealing process, showing a temporal showing a temporal snapshot of applied voltage, electrical current, and dissipated power at 1 second into the fusion. 
         FIG.  24    is a graphical representation of a sample of experimental data for a typical vessel sealing process, showing the peak voltage and peak electrical current as function of fusion time. 
         FIG.  25    is a graphical representation of a sample of experimental data for a typical vessel sealing process, showing the vessel impedance as function of fusion time. 
         FIG.  26    is a graphical representation of a vessel sealing and tissue welding process in accordance with various embodiments of the present invention showing the relative impedances of various tissues as a function of time. 
         FIG.  27    is a graphical representation of a fusion/vessel sealing process in accordance with various embodiments of the present invention showing a temporal snapshot of applied voltage, electrical current, and dissipated power at 4 seconds into the fusion process. 
         FIG.  28    is a graphical representation for a fusion/vessel sealing process showing a temporal snapshot of applied voltage, electrical current, and dissipated power at 7 seconds into the fusion process. 
         FIG.  29    is a graphical representation of bursting pressure as a function of phase shift used in end point determination. 
         FIG.  30    is a table of dielectric constants or permittivity and conductivities for various types of biological tissue, arranged by increasing values of the product of dielectric constants and tissue conductivity. 
         FIG.  31    is a graphical representation of empirically determined phase shifts to adequately fuse and/or weld various types of biological tissue. 
         FIG.  32    is a graphical representation of endpoint phase shifts relative to initial phase shift measurements of various types of biological tissue. 
         FIG.  33    is a graphical representation of a phase diagram of two electrosurgical tools and their associated capacitance and resistance. 
         FIG.  34    is a graphical representation of a phase diagram of an electrosurgical tool in tissue contact and the associated capacitance and resistance. 
         FIG.  35    is a graphical representation of the ohmic resistance of a porcine renal artery during the electrosurgical fusion process. 
         FIG.  36    is a graphical representation of phase shift during the electrosurgical fusion process. 
         FIG.  37    is a graphical representation of the derivate of the phase shift during the electrosurgical fusion process. 
         FIG.  38    is a graphical representation of phase shift during the electrosurgical fusion process. 
         FIG.  39    is a graphical representation of the derivate of the phase shift during the electrosurgical fusion process. 
         FIG.  40    is a block diagram of a fusion or welding process of an electrosurgical unit. 
         FIG.  41 A  is a perspective view of an embodiment of laparoscopic sealer/divider. 
         FIG.  41 B  is a disassembled view of a laparoscopic sealer/divider of  FIG.  1 A . 
         FIGS.  42 A- 42 C  are views of an actuator of the laparoscopic sealer/divider of  FIG.  41 A . 
         FIG.  43    is a top cross-sectional view of an actuator of a laparoscopic sealer/divider of  FIG.  41 A . 
         FIGS.  44 A,  44 B,  44 C- 1 ,  44 C- 2 ,  44 C- 3 , and  44 D  are views of a shaft assembly of a laparoscopic sealer/divider of  FIG.  41 A . 
         FIGS.  45 A,  45 B- 1 ,  45 B- 2 ,  45 C- 1 , and  45 C- 2    are views of a jaw assembly of a laparoscopic sealer/divider of  FIG.  41 A . 
         FIGS.  46 A,  46 B,  46 C,  46 D,  46 E- 1 ,  46 E- 2 ,  46 F, and  46 G  are cross-sectional side views of a laparoscopic sealer/divider of  FIG.  41 A . 
         FIGS.  47 - 1  and  47 - 2    are perspective views of a controller of a laparoscopic sealer/divider of  FIG.  41 A . 
         FIG.  48 A  is a side view of a jaw assembly of a laparoscopic sealer/divider of  FIG.  41 A . 
         FIGS.  48 B- 48 C  are graphical representations of exemplary vessel sealing pressures provided by a laparoscopic sealer/divider of  FIG.  41 A . 
         FIGS.  49 - 1 ,  49 - 2 , and  49 - 3    are top level views of electrode configurations of a laparoscopic sealer/divider of  FIG.  41 A . 
         FIG.  50    is a top level view of a jaw assembly of a laparoscopic sealer/divider of  FIG.  41 A . 
         FIG.  51    is a side view of a jaw assembly of a laparoscopic sealer/divider of  FIG.  41 A . 
         FIGS.  52 - 1  and  52 - 2    provide views of a jaw assembly of a laparoscopic sealer/divider of  FIG.  41 A . 
         FIG.  53 A  is a perspective view of a jaw assembly of a laparoscopic sealer/divider of  FIG.  51 A . 
         FIG.  53 B  is a perspective view of an actuator of a laparoscopic sealer/divider of  FIG.  41 A . 
         FIGS.  54 - 1 ,  54 - 2 , and  54 - 3    provide views of portions of a shaft assembly of a laparoscopic sealer/divider of  FIG.  41 A . 
         FIGS.  55 - 1  and  55 - 2    provide views of a jaw assembly of a laparoscopic sealer/divider of  FIG.  41 A . 
         FIG.  56    is a perspective view of an embodiment of surgical tool for use in a laparoscopic surgical procedure. 
         FIG.  57    is a perspective drawing of the distal end of an exemplary tissue fusion/cutting devices. 
         FIGS.  58 A-D  are schematic drawings of various embodiments of distal end configurations for an electrosurgical bloodless tissue dissection device. 
         FIGS.  59 A-C  are schematic drawings of active electrode switching circuitries in the hand tools. 
         FIG.  60    is a schematic drawing of the inside of the hand-piece, illustrating the embodiment of active electrode switching mechanism based on the opening of the jaw elements. 
         FIG.  61    depicts another embodiment of an active electrode switching mechanism, also based on the opening of the jaw elements. 
         FIG.  62    depicts an embodiment of a passive switching mechanism, also based on the opening of the jaw elements. 
         FIG.  63    depicts another embodiment of a passive switching mechanism, based on both the opening and closing of the jaw elements. 
         FIG.  64    depicts a schematic circuitry that connects five electrodes through relays to a bus bar which is relayed to a measurement circuit, or an electrosurgical power plant. 
         FIG.  65    schematically illustrates one embodiment of a method for substantially bloodless dissection of biological tissue. 
         FIG.  66    is a perspective view of an electrosurgical instrument in a closed condition. 
         FIG.  67    is a perspective view of an electrosurgical instrument in an open condition. 
         FIG.  68    is a side view of an electrosurgical instrument in an open condition. 
         FIG.  69    is an enlarged perspective view of a clamping portion of an electrosurgical instrument in an open condition. 
         FIG.  70    is a side section view of an electrosurgical instrument in an open condition. 
         FIG.  71    is an enlarged perspective view of a clamping jaw portion with the top clamping jaw removed. 
         FIG.  72    is an enlarged perspective view of an actuator for advancing electrodes. 
         FIG.  73    is an enlarged side view of clamping jaws in an open condition with electrodes extended. 
         FIG.  74    is an enlarged side section view of clamping jaws in an open condition and having electrodes extended. 
         FIG.  75    is an enlarged perspective view of an actuator sled and associated electrical contacts. 
         FIG.  76    is an enlarged perspective view of an electrode. 
         FIG.  77    illustrates a relationship between clamping jaws and tissue to be fused in a first, grasping condition. 
         FIG.  78    illustrates a relationship between clamping jaws and tissue to be fused in a second, compressing condition. 
         FIG.  79    illustrates a relationship between clamping jaws and tissue to be fused in a third, electrode-extending condition. 
         FIG.  80    illustrates a relationship between clamping jaws and tissue to be fused in a final, electrode-extending condition. 
         FIG.  81    is a perspective cut-out view of a body conduit showing an electrosurgical instrument moving into position to occlude a lumen of a conduit. 
         FIG.  82    is a perspective view of a body conduit showing an electrosurgical instrument in position to occlude a lumen of a conduit. 
         FIG.  83    is a perspective view of a body conduit showing an electrosurgical instrument occluding a lumen of a conduit. 
         FIG.  84    is a schematic diagram illustrating current concentration through tissue in a first, non-contact condition. 
         FIG.  85    is a schematic diagram illustrating current concentration through tissue in a full-contact condition. 
         FIG.  86    illustrates electrosurgical energy radiation associated with penetrating electrodes. 
         FIG.  87    illustrates a thermal zone associated with penetrating electrodes. 
         FIG.  88    illustrates a thermal zone associated with penetrating electrodes with the electrodes withdrawn. 
         FIG.  89    illustrates electrosurgical energy radiation associated with penetrating electrodes within approximated tissue. 
         FIG.  90    illustrates a thermal zone associated with penetrating electrodes within approximated tissue. 
         FIG.  91    illustrates a thermal zone associated with penetrating electrodes with electrodes withdrawn. 
         FIG.  92    is an end view of a conduit closed or occluded using a suturing technique. 
         FIG.  93    is an end view of a conduit closed or occluded using a stapling technique. 
         FIG.  94    is an end view of a conduit closed or occluded using a compressive fusion technique. 
         FIG.  95    is an end view of a conduit closed or occluded using a compressive fusion technique with inserted electrodes. 
         FIG.  96    is a graphical representation of exemplary burst pressure data of an occlusion using a compressive fusion technique with inserted electrodes 
         FIG.  97    is an enlarged perspective view of a clamping jaw showing an associated cutting element. 
         FIG.  98    is an enlarged perspective view of a clamping jaw showing an associated cutting element comprising an electrosurgical wire electrode. 
         FIG.  99    is an enlarged perspective view of a clamping jaw showing an associated cutting element comprising an electrosurgical or mechanical wedge electrode-knife. 
         FIG.  100    is an enlarged perspective view of a clamping jaw showing an associated cutting element comprising an electrosurgical or mechanical double edge knife. 
         FIG.  101    is an enlarged perspective view of a clamping jaw showing a plurality of current intensifying elements comprising holes. 
         FIG.  102    is an enlarged perspective view of a clamping jaw showing a plurality of current intensifying elements comprising extended posts. 
         FIG.  103   a    is an enlarged perspective view of a clamping jaw showing a plurality of current intensifying elements comprising extended arcs. 
         FIG.  103   b    is an enlarged perspective view of a clamping jaw showing a plurality of current intensifying elements comprising extended squares. 
         FIG.  103   c    is an enlarged perspective view of a clamping jaw showing a plurality of current intensifying elements comprising extended rods. 
         FIG.  103   d    is an enlarged perspective view of a clamping jaw showing a plurality of current intensifying elements comprising extended “ball-and-cups”. 
         FIG.  104    is an enlarged perspective view of a clamping jaw showing a plurality of current intensifying elements comprising extended rectangles. 
         FIG.  105 A  is an enlarged perspective view of a clamping jaw showing a plurality of current intensifying elements comprising extended ridges. 
         FIG.  105 B- 1    is an enlarged perspective view of a clamping jaw showing a plurality of current intensifying elements comprising linear “spicket-and-sockets”.  FIG.  105 B- 2    is a cross-sectional view of the clamping jaw of  FIG.  105 B- 1   . 
         FIG.  106    is an enlarged perspective view of a clamping jaw showing a plurality of current intensifying elements comprising extended pyramids or cones. 
         FIG.  107    shows a cross-section view of a clamping jaw with an exemplary compressed artery with an application of electrical or thermal energy. 
         FIGS.  108   a  and  b    are views of an exemplary portion of an artery sealed and cut ( 108   a  top plan view,  108   b  along 8-8). 
         FIGS.  109   a  and  b    are views of an exemplary portion of tissue sealed and cut ( 109   a  top plan view,  109   b  along 9-9). 
         FIG.  110    shows a cross-sectional view of a clamping jaw with an exemplary compressed artery with an application of ultrasonic energy. 
         FIG.  111    shows a cross-sectional view of a clamping jaw with an exemplary compressed artery with an application of UV or IR radiant energy. 
     
    
    
     DETAILED DESCRIPTION 
     The following description is provided to enable any person skilled in the art to make and use the surgical tools and perform the methods described herein and sets forth the best modes contemplated by the inventors of carrying out their inventions. Various modifications, however, will remain apparent to those skilled in the art. It is contemplated that these modifications are within the scope of the present disclosure. 
     Electrosurgical System 
       FIG.  1 A  illustrates a schematic diagram of an electrosurgical system  2 . The electrosurgical system  2  can comprise an electrosurgical unit (ESU)  10  and an electrosurgical tool  40 . The electrosurgical tool  40  can be electrically coupled to the electrosurgical unit  10 . In some embodiments, an electronic coupler  30  such as an electrical wire, wire bundle, or cable can electrically couple the electrosurgical tool  40  to the ESU  10 . In some embodiments, the electrosurgical system  2  can optionally further comprise an external tool controller  80 . 
     With continued reference to  FIG.  1 A , the electrosurgical unit  10  can comprise a generator  12  and a feedback circuit  20 . The generator  12  can include an actuator  16  such as a power supply and a signal processor configured to generate a radiofrequency (RF) electrosurgical signal. The generator  12  can further comprise a display  14 . The display  14  can be configured to indicate the status of the electrosurgical system  2 , including, among other information, the status of the actuator  16  and the status of the electrosurgical tool  40  electrically coupled to the electrosurgical unit  10 . 
     With continued reference to  FIG.  1 A , the feedback circuit  20  of the ESU  10  can comprise a phase discriminator  22 , a tissue identifier  24 , and an encryption module  26 . In some embodiments, the phase discriminator  22  can be electrically coupled to the tissue identifier  24 . The phase discriminator  22  can be configured to receive information from the electrosurgical tool  40  electrically coupled to the ESU  10 . In some embodiments, the information from the electrosurgical tool  40  comprises information regarding an applied voltage and a supplied current to the electrosurgical tool, and the phase discriminator  22  can be configured to calculate a phase difference between the applied voltage and the supplied current. The encryption module  26  can be configured to transmit and receive data formatted in an encrypted protocol. The encrypted protocol can be one of several commercially-available encryption protocols, or, in some embodiments can be a purpose developed encryption protocol. 
     With continued reference to  FIG.  1 A , In some embodiments, the feedback circuit  20  can be one or more integrated circuits, printed circuit boards, or other processor collocated with the generator  12  within an integrated ESU  10 . As Illustrated in  FIG.  1 B , In other embodiments, the feedback circuit  20 ′ can be electrically coupled to a stand-alone generator  12 ′ to form an ESU  10 ′. The tool  40  can be electrically coupled to the feedback circuit  20 ′. Other aspects of electrosurgical systems having a stand-alone generator  12 ′ and feedback circuit  20 ′ can be substantially similar to systems having an integrated ESU discussed with respect to  FIG.  1 A . 
     With continued reference to  FIG.  1 A , the tool  40  can comprise an indicator  42 , a tissue selector  50 , an actuator  60 , and a memory  70 . In some embodiments, the indicator  40  can comprise an audio indicator  44  such as a speaker, a chime, a clicker device, or another audio generation device. In some embodiments, the indicator  40  can comprise a visual indicator  46  such as a lamp, an LED, a display, a counter, or another visual indication device. In some embodiments, the visual indicator  46  comprises a multi-color LED. In some embodiments, the tool  40  comprises both an audio indicator  44  and a visual indicator  46 . 
     The tissue selector  50  can comprise an electrode assembly  52  and a cutting tool  54 . In various embodiments, various electrode assemblies can be configured to perform a desired electrosurgical procedure such as, for example, coagulation, cutting, or fusion, on a particular tissue. In some embodiments, the electrode assembly  52  can be configured for use as a vascular sealer. In other embodiments, the electrode assembly  52  can be configured for use as a bariatric stapler. In still other embodiments, the electrode assembly  52  can be configured for use as a tissue cutting device. In some embodiments, the cutting tool  54  can be a mechanical element such as a stationary or moveable blade or sharpened edge. In other embodiments, the cutting tool  54  can be an electrosurgical element such as an energizable wire or filament. 
     With continued reference to  FIG.  1 A , the actuator  60  can be operatively coupled to the tissue selector  50  to selectively select tissue. For example, in some embodiments, the tissue selector  50  can include a jaw-based grasper, and the actuator can comprise an actuation mechanism to selectively move the grasper from an open position to a closed position. In other embodiments, it is contemplated that other tissue selectors can be used in the electrosurgical system  2 . In some embodiments, the actuator  60  can also be configured to selectively energize the electrodes. For example, the actuator  60  can comprise a switch or button on the tool. 
     With continued reference to  FIG.  1 A , the tool  40  can further comprise a memory  70 . In some embodiments, the memory  70  comprises an encryption module  72  and a configuration device module  74 . The encryption module  72  can be configured to facilitate an encrypted information exchange with the encryption module  26  on ESU  10 . The configuration device module  74  can store operational parameter information about the tool  40 . For example, in some embodiments, the configuration device module  74  can store information regarding the electrode assembly, the number of uses and total operational time of use of the tool, and other operational parameters. 
     With continued reference to  FIG.  1 A , the electrosurgical system  2  can further comprise an external tool controller  80  electrically coupling the ESU  10  to the tool  40 . In some embodiments, the external tool controller  80  comprises a tool selector  82  such as a switch. The external tool controller  80  can allow for multiple devices to connect thereto. A tool selector  82  allows selection of one of the multiple devices to be energized. For example the tool selector  82  can comprise a dial, switch, or toggle. The tool actuator  84  can selectively electrically couple the selected tool  40  with the ESU  10 . 3 
     With reference to  FIG.  2 A , an exemplary embodiment of electrosurgical system  102  is illustrated including an ESU  110 , and an electrosurgical fusion tool  120 . The electrosurgical fusion tool  120  can be electrically coupled to the ESU  110  by an electrical coupler  130  such as with an cabled connection to a tool port  112  on the ESU  110 . In the illustrated embodiment, the electrosurgical fusion tool  120  comprises a tissue sealer and divider, as discussed in further detail below with respect to  FIGS.  41 A- 55   . The electrosurgical fusion tool  120  comprises visual indicators  122  such as multi-color LEDs positioned there on to apprise a user of the status of the tool. In other embodiments, the electrosurgical fusion tool  120  can be electrically coupled to a generator or a different electrosurgical unit. In some embodiments, a manual controller such as a hand of foot switch can be electrically coupled to the ESU  110  or the electrosurgical fusion tool  122  to allow selective control of the tool. 
     With reference to  FIG.  2 B , an exemplary embodiment of electrosurgical system  202  is illustrated including an ESU  210 , and an electrosurgical tool  220 . The electrosurgical tool  220  can be electrically coupled to the ESU  210  such as with a cabled connection to a tool port  212  on the ESU  210 . In the illustrated embodiment, the electrosurgical tool  220  comprises an electric cutting and coagulation tool, as discussed in further detail below with respect to  FIGS.  56 - 65   . The electrosurgical tool  220  comprises visual indicators  222  such as multi-color LEDs positioned there on to apprise a user of the status of the tool. In other embodiments, the electrosurgical tool  220  can be electrically coupled to a generator or a different electrosurgical unit. In some embodiments, a manual controller such as a hand of foot switch can be electrically coupled to the ESU  210  or the electrosurgical fusion tool  222  to allow selective control of the tool. 
     With reference to  FIG.  2 C , an exemplary embodiment of electrosurgical system  2302  is illustrated including an ESU  310 , and an electrosurgical tool  320 . The electrosurgical tool  320  can be electrically coupled to the ESU  310  such as with a cabled connection to a tool port  312  on the ESU  310 . In the illustrated embodiment, the electrosurgical tool  320  comprises an electrosurgical stapling tool, as discussed in further detail below with respect to  FIGS.  66 - 111   . The electrosurgical tool  320  comprises visual indicators  322  such as multi-color LEDs positioned thereon to apprise a user of the status of the tool. In other embodiments, the electrosurgical tool  320  can be electrically coupled to a generator or a different electrosurgical unit. In some embodiments, a manual controller such as a hand of foot switch can be electrically coupled to the ESU  310  or the electrosurgical tool  322  to allow selective control of the tool. 
     Integrated Electrosurgical Unit 
     With reference to  FIGS.  3 A- 3 C , of electrosurgical unit  410  is illustrated in perspective, front, and rear views. The electrosurgical unit  410  can be an integrated ESU as discussed above with respect to  FIG.  1 A , and can comprise a generator and a feedback circuit. In some embodiments, the housing or console of the electrosurgical unit  410  can be sized and configured to fit on a standard operating room cart or storage rack. In some embodiments, the housing or console of the electrosurgical unit  410  can be configured to be stackable with other surgical electrical equipment. 
     With reference to  FIGS.  3 A- 3 B , a perspective view of the electrosurgical unit  410  is illustrated. In the illustrated embodiment, the electrosurgical unit  410  comprises two dedicated tool ports  412 , one bipolar tool port  414 , and one electrical power port  416 . In other embodiments, electrosurgical units can comprise different numbers of ports. For example, in some embodiments, an electrosurgical unit can comprise more or fewer than two dedicated teleports  412 , more or fewer than one bipolar tool port  414 , and more or fewer than one power port  416 . 
     With continued reference to  FIGS.  3 A- 3 B , each dedicated tool port  412  is configured to be coupled to electrosurgical tool having a memory, as described above with respect to  FIG.  1 A . Thus the dedicated tool ports  412  can be electrically coupled to the feedback circuit of the electrosurgical unit  410  as well as the generator. In some embodiments, the dedicated tool ports  412  can comprise multi-pin connectors comprising a plurality of electrical connection pins or pin receptacles. In some embodiments, the connectors can comprise more than 10, for example 20 pins or pin receptacles. As discussed above with respect to  FIG.  1 A , and discussed in further detail below, the dedicated tool ports  412  can be configured for encrypted transmission and reception of data from an electrically coupled electrosurgical tool. 
     With continued reference to  FIGS.  3 A- 3 B , the bipolar tool port  414  can include a plug configured to receive a conventional bipolar electrosurgical tool. The bipolar tool port  414  can be coupled to the generator of the electrosurgical unit  410 . In some embodiments, the bipolar tool port  414  is not coupled to the feedback circuit of the electrosurgical unit  410 . Thus, advantageously, the electrosurgical unit  410  can energize both specialized electrosurgical tools, as described in further detail here and, conventional bipolar electrosurgical tools. Accordingly, the electrosurgical unit  410  can be used in place of a standalone bipolar electrosurgical generator without requiring additional rack or cart space in a surgical workspace. 
     With continued reference to  FIGS.  3 A- 3 B , the electrical power port  416  can be coupled to the generator of the electrosurgical unit  410 . The electrical power port  416  can be configured to supply direct current. For example, in some embodiments, the electoral power port  416  can provide approximately 12 Volts DC. The electrical power port  416  can be configured to power a surgical accessory, such as a respirator, pump, light, or another surgical accessory. Thus, advantageously, in addition to replacing electrosurgical generator for standard bipolar tools, the electrosurgical unit  410  can also replace a surgical accessory power supply. In some embodiments, replacing presently-existing generators and power supplies with the electrosurgical unit  410  can reduce the amount of storage space required on storage racks cards or shelves in the number of mains power cords required in a surgical workspace. 
     With continued reference to  FIGS.  3 A- 3 B , the electrosurgical unit  410  can comprise a display  420 . In some embodiments, the display can comprise a multi-line display capable of presenting text and graphical information such as for example an LCD panel display, which, in some embodiments can be illuminated via backlight or sidelight. In some embodiments, the display  420  can comprise a multi-color display that can be configured to display information about a particular tool electrically coupled to the electrosurgical unit  410  and a color that corresponds to a standard color associated with a surgical procedure (such as, for example cutting operations displayed in yellow text and graphics, fusion or welding operations displayed in purple, and coagulation displayed in blue, bloodless dissection operations can be displayed in yellow and blue). In some embodiments, as discussed in further detail below, the display can be configured to simultaneously indicate status data for a plurality of tools electrically coupled to the electrosurgical unit  410 . In some embodiments, a user can toggle the display  420  between presenting status of multiple electrically connected tools and status of a single electrically connected tool. Further exemplary aspects of the display are discussed generally with respect to  FIGS.  4 A and  4 B , and more specifically with respect to operation of the system below. 
     With continued reference to  FIGS.  3 A- 3 B , the electrosurgical unit can comprise a user interface such as, for example a plurality of buttons  422 . The buttons  422  can allow user interaction with the electrosurgical unit such as, for example, requesting an increase or decrease in the electrical energy supplied to one or more tools coupled to the electrosurgical unit  410 . In other embodiments, the display  420  can be a touch screen display thus integrating data display and user interface functionalities. In some embodiments, the electrosurgical unit  410  can comprise an audible indicator, such as a speaker or chime to alert a user of a possible error, the termination of electrical energy supplied, or other conditions. In some embodiments, the electrosurgical unit  410  can be configured such that the audible indicator can sound a particular sound during cutting operations, a different sound during fusion or welding operations, and another distinct sound during coagulation operations to provide audible feedback to a user. 
     With reference to  FIG.  3 C , a rearview of the electrosurgical unit  410  is illustrated. In the illustrated embodiment, the rear of the electrosurgical unit  410  includes a rear panel  430 . The rear panel  430  can include various ports, such as a controller port  432  configured to be electrically coupled to an external controller such as a foot pedal controller, as described above with respect to  FIG.  1 A . The rear panel  430  can also include a grounding lug. In other embodiments, one or more controller ports and/or the grounding lug can be located on another face of the electrosurgical unit  410 , for example on the front face or a side face. The rear face of the electrosurgical unit  410  can include a power module  440  including a mains power port configured to be plugged into an AC power mains such as a wall socket and a master power switch for powering the electrosurgical unit  410  on and off. In other embodiments, the master power switch can be positioned on another face of the electrosurgical unit  410 , for example on the front face or a side face. The rear phase of the electrosurgical unit  410  can also include a heat exchange feature, such as, for example slots, a grill, or a plurality of louvers  450 . In other embodiments, the heat exchange feature can be positioned on another face of the electrosurgical unit  410 , for example on the front face or a side face. The heat exchange feature can enhance air or other fluid cooling of the generator, the feedback circuit, and other electrical components housed within the electrosurgical unit  410  console. 
     With reference to  FIG.  4 A , an exemplary screen shot of the display is illustrated. In the illustrated embodiment, the display  420  can be portioned to display status information for ADC tools  460 , a bipolar tool  470 , a first radiofrequency electrosurgical tool  480 , and a second radiofrequency electrosurgical tool  490 , corresponding to the four ports on the front panel of the electrosurgical unit  410  discussed above with respect to  FIGS.  3 A,  3 B  in the illustrated screenshot, a first section  462  displays information regarding the DC tool  460 . A second section  472  displays information regarding the bipolar electrosurgical tool  470 . A visual indicator such as a status bar graph  474  can be used to illustrate a proportion of total available electrical energy to be applied to the bipolar electrosurgical tool  470  when actuated. As discussed above, the visual indicator can be color-coded to indicate a surgical procedure to be performed. A third section  482  can display information regarding a first radiofrequency electrosurgical tool  480  with a visible indicator such as a status bar graph  484 . A fourth section  492  can display information regarding a second radiofrequency electrosurgical tool  490  with separate visual indicators or bar graphs  494 ,  496 ,  498  for each type of surgical operation that can be performed for that tool. For example an electrosurgical tool operable to cut, coagulate, or fuse tissue could have three color-coded bar graphs. The display  420  can also include a controller icon, such as a foot pedal icon  476  positions in a section corresponding to a tool to which a foot pedal is electrically coupled. 
     With reference to  FIG.  4 B , another exemplary screen shot of the display  420  is illustrated. It is illustrated, the display has been configured to maximize information presentation of the section  492  corresponding to the second of electrosurgical tool. As discussed above, in some embodiments electrosurgical unit can be configurable display status information regarding a single tool electrically coupled thereto. In some embodiments, the electrosurgical unit can allow user manipulation of energy levels applied to electrosurgical tool. In one configuration, energy levels for an electrosurgical tool can be adjusted proportionally for each type of electrosurgical procedure to be performed by the tool. For example, a user can increase or decrease a master energy level which correspondingly increases or decreases the energy levels supplied to you electrosurgical operation performed by the tool, which can be reflected in the bar graphs  494 ,  496 ,  498  on the display  420 . In another configuration, energy levels for electrosurgical tool can be manipulated in a procedure-specific manner. For example, a user can increase or decrease in energy level corresponding to one of the electrosurgical procedures performed by specific electrosurgical tool while leaving energy levels for other electrosurgical procedures unchanged. This change can be reflected in one of the bar graphs on the display  420 , for example, the cut bar graph  494 . 
     Electrosurgical System Phase Angle Operation 
     Electrosurgical Unit 
     Generally, an electrosurgical unit is provided that includes an electrosurgical generator, an electrosurgical controller and one or more electrosurgical tool. The controller can be incorporated in or attached to the generator with the tool attached to the controller. 
     In one embodiment, a controller is attachable to various electrosurgical generators. The generator attached to the controller provides the supply of RF energy as directed by the controller. The controller provides feedback control and preprogrammed settings for the various attachable generators. This is largely enabled by using an internal measurement signal that is independent from the attached generator. In other words, regardless of the driving frequency of the drive signal the generator generates (which has an impact on the end point measurement, e.g., the phase shift), the measurement signal and hence the final phase shift remains the same. 
     Referring to  FIG.  5   , in one embodiment, an electrosurgical generator includes an RF amplifier, pulse width modulator (PWM) and relays. The electrosurgical generator is coupled to a 120 Hz Voltage main input. The main input is isolated with a low leakage isolation transformer of a power supply  631 . The power supply provides operational voltages for the control processor  637  and the RF amplifier  633 . Additionally, the power supply includes two 50 VDC output modules connected in series to provide a total output of 100 VDC and 8 Amps. RF power is generated by the RF amplifier, e.g., a switched mode low impedance RF generator that produces the RF output voltage. In one embodiment, a 600 peak cut voltage for cutting and 10 Amp current for coagulation/fusing is generated. 
     Fusing tissue in one embodiment involves applying RF current to a relatively large piece of tissue. Because of the potentially large tool contact area tissue impedance is very low. Accordingly, to deliver an effective amount of RF power, the current capability of the RF amplifier is large. As such, where a typical generator might be capable of 2 to 3 amps of current, the RF amplifier of the generator can supply more than 5 Amps RMS into low impedance loads. This results in rapid tissue fusion with minimal damage to adjacent tissue. 
     The RF amplifier circuitry has redundant voltage and current monitoring. One set of voltage and current sensors are connected to the PWM circuitry and are used for servo control. The voltage and current can also be read by the processor  637  using an analog to digital converter (ADC) located on the PWM circuitry. The PWM circuitry also has an analog multiplier, which calculates power by computing the product of the voltage and current. The PWM circuitry uses the average value of voltage and current and does not include a phase angle and thus is actually calculating Volt Amps Reactive (VAR) rather than actual power. A second set of voltage and current sensors are also connected to the Telemetry circuitry  642 . The signals are connected to an ADC for redundant monitoring of the voltage and current. The processor multiplies the voltage and current readings to verity that power output does not exceed 400 Watts. The Telemetry circuitry has monitoring circuits that are completely independent of the PWM circuitry. This includes the ADC, which has an independent voltage reference. 
     The RF amplifier in one embodiment is a switching class D push pull circuitry. As such, the amplifier can generate large RF voltages into a high tissue impedance, as well as large RF currents into low tissue impedance. The output level of the RF amplifier is controlled by Pulse Width Modulation (PWM). This high voltage PWM output signal is turned into a sine wave by a low pass filter on the RF amplifier. The output of the filter is the coagulation output of the RF amplifier. The output is also stepped up in voltage by an output transformer resulting in the cut output of the RF amplifier. Only one output is connected to the control servo on the PWM circuitry at a time and only one output is selected for use at a time. 
     Coupled to the RF amplifier is the PWM circuitry  634 . The PWM  634  in one embodiment receives voltage and current set points, which are input by the user through a user interface, to set the output level of the RF amplifier. The user sets points are translated into the operating levels by digital to analog converters of the PWM. The user sets points are translated into the operating levels by digital to analog converters of the PWM. The set points in one embodiment include a maximum voltage output, maximum current output, maximum power output, and a phase stop. The servo circuit of the PWM circuitry controls the RF output based on the three set points. The servo circuit as such controls the output voltage of the RF amplifier so that the voltage, current, and power set points are not exceeded. For example, the output of the ESG is restricted to be less than 400 watts. The individual voltage and current set point can be set to exceed 400 watts depending on the tissue impedance. The power servo however limits the power output to less than 400 watts. 
     The RF output voltage and current are regulated by a feedback control system. The output voltage and current are compared to set point values and the output voltage is adjusted to maintain the commanded output. The RF output is limited to 400 Watts. Two tool connections are supported by using relays  635  to multiplex the RF output and control signals. The EMI line filter  636  limits the RF leakage current by the use of an RF isolation transformer and coupling capacitors. 
     The cut and coagulation output voltages of the RF amplifier are connected to the relay circuitry  635 . The relay circuitry in one embodiment contains a relay matrix, which steers the RF amplifiers output to one of the three output ports of the electrosurgical unit. The relay matrix also selects the configuration of the tool electrodes. The RF output is always switched off before relays are switched to prevent damage to the relay contacts. To mitigate against stuck relays steering RF to an idle output port each output port has a leakage current sensor. The sensor looks for unbalanced RF currents, such as a current leaving one tool port and returning through another tool port. The current sensors on are located on the Relay PCB, and the detectors and ADC are on the Telemetry PCB. The CPU monitors the ADC for leakage currents. Any fault detected results in an alarm condition that turns off RF power. 
     The relay circuitry also contains a low voltage network analyzer circuit used to measure tool impedance before RF power is turned on. The circuit measures impedance and tissue phase angle. The processor  637  uses the impedance measurement to see if the tool is short-circuited. If a Tool A or B output is shorted the system warns the user and will not turn on RF power. The RF amplifier is fully protected against short circuits. Depending on the servo settings the system can operate normally into a short circuit, and not cause a fault condition. 
     Voltage and current feedback is provided using isolation transformers to insure low leakage current. The control processor  637  computes the power output of the RF amplifier and compares it to the power set point, which in one embodiment is input by the user. The processor also monitors the phase lag or difference between current and voltage. Additionally, in one embodiment, the processor matches the different phase settings, which depend on tissue types to the monitored phase difference. The processor as such measures a phase shift of tissue prior to any application of RF energy. As will be described in greater detail below, the phase measurement is proportional to tissue permeability and conductivity that uniquely identifies the tissue type. Once the tissue type is identified, the phase angle associated with an end point determination of that tissue type can be determined. The generator in one embodiment has three RF output ports (Tool A, Tool B and generic bipolar). The tool A and B ports  639  are used to connect smart tools, while the generic bipolar port  640  supports standard electro surgical tools. Audible tones are produced when the RF output is active or an alarm condition exists. 
     The hand and foot controls are also isolated to limit leakage current. The control processor checks the inputs for valid selections before enabling the RF output. When two control inputs from the switches are simultaneously activated the RF output is turned off and an alarm is generated. Digital to analog converters are used to translate control outputs into signals useable by the Analog Servo Control. The control set points are output voltage and current. The analog to digital converter is used to process the analog phase angle measurement. Voltage RMS, current RMS, and power RMS information from the controller is also converted into a form usable for presentation to the user. The digital I/O bus interface  638  provides digital communication between the user, controller and hand/foot switches. Isolation circuitry is used to eliminate a possible leakage path from the electrosurgical generator. It also provides communication between the user and the generator though a data channel protocol. 
     In one embodiment, there are four tool Interface circuits in the unit. These circuits are used to electrically isolate the user input switches from mains power inside the system. The four tool interface circuits are identical and have an on board microprocessor to read the user switch inputs as well as the tool crypto memory and script memories. The switch closure resistance is measured with an ADC to eliminate a contaminated switch contact being read as a closure. Switch closures below 300 Ohms are valid, while any reading above 1000 Ohms is open. Readings between 300 and 1000 Ohms are considered to be faulty inputs. 
     The four tool interface circuits communicate with the processor using an RS485 network. Each tool interface circuit has jumpers to select its address and location in the unit. The RS485 interface is isolated to eliminate any potential leakage current paths. One tool interface circuit is connected to each of the Tool A and B ports. A third tool interface circuit is connected to the DC output port, and the fourth circuit is connected to the rear panel foot switch inputs. The processor is the network master and each of the four circuits is a network slave. The processor polls each circuit for input. The tool interface circuitry can only reply to commands. This makes the network deterministic and prevents any kind of dead lock. Each Tool Interface circuit is connected to a System OK logic signal. If a system error is detected by a Tool Interface circuit, this signal is asserted. The processor monitors this signal and indicates a fault. This signal also has a hardware connection to the PWM circuit and will disable the RF amplifier when asserted. A system error could be two input switches activated at the same time, or a loss of communication with the processor. The Tool A &amp; B ports as well as the DC port have a micro switch that detects when a tool is plugged into the receptacle. Until this switch is depressed the Tool Interface circuit front panel connections are configured off to prevent any leakage current flowing from front panel connections. Once the switch is depressed the Tool Interface allows the processor to initiate reads and writes to the tool crypto memory and script memory. Once a tool is detected a window opens in the user interface display showing the type of tool connected and status. The generic bipolar port supports legacy tools, which do not have any configuration memory. The tissue measurement circuitry is used to monitor the bipolar connection contacts. When a bipolar tool is connected the tool capacitance is detected and the processor opens the bipolar tool window on the user interface display and shows status for the bipolar tool. The DC port is used to interface with 12 Volt DC powered custom surgical tools. When a tool is plugged into this port a window opens in the user interface display showing the type of tool connected and status. When the DC tool script commands power on, the processor closes a relay on the Power Control and Isolation circuitry  643  turning on the isolated 12 Volt tool power. 
     The power control and isolation circuitry  643  has two other features. It controls the 100 Volt power supply that drives the RF amplifier. This power supply is turned on by a relay controlled from the PWM circuitry. The processor commands this power supply on via the PWM circuitry. If the PWM circuitry is reset or detects a fault condition, the relay will not operate leaving the 100 Volt power supply off. Also located on the power control and isolation circuitry is a RS485 isolation circuit that adds an extra layer of isolation. 
     The front panel interface circuitry  641  is used to connect the front panel control switches and LCD display to the processor. The front panel interface circuitry also contains a microprocessor, which is powered by an isolated standby power supply, which is on whenever the main power switch is on. When the front panel power switch is pressed, the microprocessor uses a relay on the Power Control and Isolation circuitry to turn on the main logic power supply. When the button is pressed to turn power off, the microprocessor signals a power off request to the processor. When the processor is ready for power to be turned off it signals the microprocessor to turn off power. The power control relay is then opened, turning off the main power supply. 
     In one embodiment, the generator accepts only single switch input commands. With no RF active, e.g., RF energy applied, multiple switch closures, either from a footswitch, tool, or a combination of footswitch and tool are ignored. With RF active, dual closures shall cause an alarm and RF shall be terminated. The footswitch in one embodiment includes momentary switches providing activation of the application of RF energy. The switches for example when manipulated initiates activation of the RF energy for coagulation, for cutting and/or sequenced coagulation or cutting. A two-position pushbutton on the foot pedal switch allows toggling between different tools. The active port is indicated on the display of the generator and an LED on the hand tool. 
     In one embodiment, all RF activation results in a RF ON Tone. Activation tone volume is adjustable, between 40 dBA (minimum) and 65 dB (maximum) with a rear panel mounted control knob. The volume control however does not affect audio volume for alarms. Also, in one embodiment, a universal input power supply is coupled to the generator and operates over the input voltage and frequency range without the use of switches or settings. A programming port in one embodiment is used to download code to the generator and is used to upload operational data. 
     The generator in one embodiment provides output power has a 12V DC at 3 Amps. Examples of such tools that use DC power are, but are not limited to, a suction/irrigation pump, stapler, and a morcellator (tool for dividing into small pieces and removing, such as a tumor, etc.). The DC connector has intuitive one-way connection. Similar to the other tool receptacles, a non-sterile electronic chip module is imparted into the connector of the appropriate DC-powered hand tool by a one-time, one-way locking mechanism. Tool-specific engravings on both the connector and chip module ensure that the chip module fits only to the type of tool for which it has been programmed. The chip connector allows tool recognition and the storage of data on tool utilization. The DC connector is also configured to prevent improper insertion. The generator is also configured to recognize the attached DC-powered tool. The generator reads configuration data from the tool connector, allowing tool recognition and the storage of tool utilization data. 
     The controller in one embodiment recognizes the tool upon the tool being attached to the controller. Based on the recognized tool, the generator accesses and initiates specific operations and setting parameters utilized to configure the controller to properly apply RF energy as desired by the tool. For example, parameters set includes but not limited to an automatic preset of the output voltage, activation of specific output pins (connected to tool) or determination of the feedback cycle. 
     In one embodiment, the controller supplies control signals and/or power to a connected tool to indicate when they are active via a LED and/or a distinctive audio tone. The controller is also arranged to display when and/or which specific tool is active. The controller also prevents the tool from being reused after certain expiration of the tool shelf life, or a specific time period after the first tool activation. 
     In one embodiment, phase measurement is a relative measurement between two sinusoidal signals. One signal is used as a reference, and the phase shift is measured relative to that reference. Since the signals are time varying, the measurement cannot be done instantaneously. The signals must be monitored long enough so that difference between them can be determined. Typically the time difference between two know points (sine wave cross through zero) are measured to determine the phase angle. In the case of the phase controller, the device makes the output sine wave with a precise crystal controlled clock. That exact same clock is use to read the input samples with the analog to digital converter. In this way the output of the phased controller is exactly in phase with the input of the phase controller. The phase controller in one embodiment compares the input sine wave signal to a reference sine wave to determine the amount of phase shift. 
     The phase controller does this comparison using a mathematical process known as a Discreet Fourier Transform (DFT). In this particular case 1024 samples of the input signal are correlated point by point with both a sine function, and a cosine function. By convention the cosine part is called real, and the sine part is called imaginary. If the input signal has no phase shift the result of the DFT is 100% real. If the input signal has a 90-degree phase shift the result of the DFT is 100% imaginary. If the result of the DFT has both a real and imaginary component, the phase angle can be calculated as the arctangent of ratio of the imaginary and real values. 
     It should be appreciated that the phase angle calculation is independent of units of the real and imaginary numbers. Only the ratio matters. The phase results of the phase controller are also independent of gain and no calculation of impedance is made in the process of calculating the phase angle. By performing a DFT, the phase controller encodes the phase measurement as a pair of numbers. 
     A user interacts with the electrosurgical unit via a graphical panel display and associated switches  641 . The front panel switches allow interaction with LCD display menus generated on the graphical panel display. The menus allow language selection, and modification of tool set points. In one embodiment, only when a tool is plugged in and detected by the unit, parameters can be changed for that tool. 
     The electrosurgical unit as described above includes one or more receptacles in which electrosurgical tools connect to the unit. Through this connection, a tool and unit communicate with each other. Connecting the tool also causes the controller to update the display of the system to show tool information and current intensity. 
     An example of a display or user interface  641  is shown in  FIG.  6   . The user interface provides tool information such as tool status for each connected tool and allows a user to modify set points, e.g., the application or intensity of the RF energy. The user interface in one embodiment also shows the tool settings for functions for each connected tool. In the illustrated embodiment, three tools are connected to the generator. Accordingly, a suction/irrigation pump display  621 , a Kii fusion tool display  622  and a spatula tool display  623  are shown. Associated operations or actions available for each tool are also provided in which the suction/irrigation pump has an on/off setting  624 ; the Kii fusion tool has relative power settings for cut  625 , coagulation  626  and fuse  627 ; and the spatula tool has relative power settings for cut  628  and coagulation  629 . 
     In one embodiment, the user interface allows a simultaneous change to all settings for a selected tool (indicated by the highlighted rim  631 ) by pushing single button from the navigation buttons  632 . For example, as shown in  FIG.  7   , pushing the “up” button  633  will simultaneously change the cut, coagulation and fuse relative power settings for the connected Kii fusion tool. Additionally, the settings can be changed individually by navigating into a sub menu, as shown in  FIG.  8   . In the illustrated case, the coagulation level of the Kii fusion tool is changed without changing the cut and/or fuse relative power setting. By selecting the default button  634 , the settings for all tool functions of the selected tool are returned to the default setting. Also, as warranted by the context, an associated button operation and corresponding label can vary as shown in button  635  being a menu button in  FIG.  7    and a back button in  FIG.  8   . 
     A block diagram illustrating a controller in accordance with various aspects of the invention is shown in  FIG.  9   . As shown, the output of a generator is fed into circuitry that determines the frequency of the driving signal and circuitry to measure the phase shift between voltage and current applied to the tissue. The voltage applied by the generator is sent through a buffer/level shifter  541  that reduces the amplitude of the output voltage. The signal is processed to deliver the frequency of the generator output via frequency measurement  542  and fed into a microcontroller  543 . The frequency of the driving signal can directly impact the phase shift. Similarly, the generator output is sent through a signal conditioning circuitry  544  to reduce high-frequency noise, and then conditioned via voltage and current conditioning  545   a - b  and filtered by multi-pole low pass filter  546   a - b  to deliver signals to represent applied voltage and current. Both signals representing voltage and current are measured for phase shift using a phase comparator  547 . The output of the phase comparator is fed into the microcontroller  543 . Depending on the frequency of the electrosurgical unit used, which can determine the final phase shift to be reached, the microcontroller compares the output of the phase comparator with the trigger level determined by the driving frequency of the generator. When such trigger level is achieved, i.e., the tissue fusion or welding is completed, the microcontroller  543  causes the tissue to be disconnected from the generator and indicates that state by acoustical or visual indicators  548  (buzzer, display, lights, etc.). An over-voltage detector  549  is also provided that is supplied the generator output to detect excessive voltage the condition of which is supplied to the microcontroller  543 . 
       FIG.  10    shows a block diagram of a controller in accordance with various embodiments of electrosurgical unit utilizing the phase shift between voltage and current to determine the end-point of the fusion process. A microcontroller  553  delivers a low-voltage square-wave signal  551  at 5 MHz, which is converted by a 4-pole low pass filter  550  into a low-voltage sin-wave signal  552  at 5 MHz. The low-voltage 5 MHz signal is superimposed to the output of the generator, which is typically in the 100 to 200V range at frequencies of 300 to 500 kHz. As an example, the superimposed voltage signal of a 200V driving voltage at 500 kHz and a 5V measurement voltage at 5 MHz is shown in  FIG.  11   . 
     The combined voltages are then applied to the tissue and, just as in the previous example, also conditioned through a buffer/level shifter circuitry for processing. Similarly, the current through the tissue is measured and also conditioned for processing. The processed voltage (and current) signal containing the high voltage (and high current) signal at 300 to 500 kHz from the ESU, as well as low voltage (low current) signal at 5 MHz are sent through a multi-pole band pass filter centering at 5 MHz. The filter discriminates the signal from the ESU, leaving only the two signals at 5 MHz for measuring the phase shift in a phase comparator. The filtered signals for both the voltage and current at 5 MHz are illustrated in  FIG.  12    at a time near the end of the fusion process. 
     The measured phase shift is fed into a microcontroller, which compares the reading with a pre-determined level indicative to the completion of the fusion process at 5 MHz frequency. Again, when such a trigger level is achieved, i.e., the tissue fusion or welding is completed, the microcontroller  553  will cause the tissue to be discontinued from the generator and indicate that state by acoustical or visual indicator  548  (buzzer, display, lights, etc.). 
       FIG.  13    shows a schematic block diagram of one aspect of a controller. As shown, a microprocessor  561  times the switching of the tissue between the output of a generator and an internal measurement circuit. As a result, the tissue is periodically assessed for the status of the fusion process by measuring the phase shift of a low-voltage and low-current measurement signal. Depending on the value of the obtained phase shift, the tissue is either switched back to the high-voltage output of the generator for further fusion, or permanently disconnected from the generator. As such, the internal circuit comprises of a microprocessor  561  generating a low-voltage square wave signal  562  at 500 kHz that is transferred into a low-voltage sinusoidal wave  563  at 500 kHz. This signal is applied to the tissue, and analyzed by a phase comparator  564  only when it electrically disconnected from the generator during regular measurement intervals. 
     In one embodiment, the phase shift is derived directly from the driving signal, i.e., the voltage and current supplied by the electrosurgical generator to the tissue. In one embodiment, an electrical circuit modifies the driving voltage having one (sinusoidal) frequency by superimposing a measurement signal at a vastly different frequency. As a result, electrical energy for the fusion process is provided at one frequency, while simultaneously applying as second signal at a second frequency for measurement. Separation of the two different signals by using band pass filters in the measurement circuit allows continuous measurement of the phase shift during the electrosurgical fusion or welding process. In one embodiment, the controller periodically interrupts the supply of electrosurgical energy to assess the status of the fusion or welding process by applying a low-voltage measurement signal. Depending on the phase shift obtained during the measurement cycle, the controller switches the driving signal from the generator back to the tissue or isolates the tissue. In one embodiment, the controller interrupts the tissue fusion or welding process at a pre-determined level of phase shift by terminating the supply of RF energy from the generator to the tissue. 
       FIG.  14    depicts a controller or control unit in accordance with aspects of the present invention for the controlled fusion or welding of biological tissue. As shown, the control unit is connecting the bipolar power outlet of a generator  507  to the tool  508  that is arranged to compress vessels or tissue. The tool also houses a switch  509  that activates the fusion process. If the generator is equipped with an input for hand activation (rather than using a foot pedal  511  or other intermediary device), a third connection  512  from the control unit to the generator allows activation of the generator with the same hand switch. 
     The controller in one embodiment includes a processor  513  that controls the switching of the tissue between the direct output of the generator and an internal measurement circuit, e.g., switch  515 . It is powered with an internal battery power module  514 . The timed switching causes the tissue to be fused in intervals while periodically measuring the status of the tissue. As such, the measurement signal is a 500 kHz sinusoidal low voltage signal, generated by a signal generator  518  when fed with a 500 kHz square wave from the microprocessor  513 . When the low-voltage sinusoidal measurement signal is applied to the tissue, a phase comparator  516  measures the phase shift between the applied measurement voltage and the current caused by application of the measurement voltage. Depending on the result analyzed or processed by the processor, the tissue will be either be switched back to the generator, or disconnected from the generator accompanied by an acoustical and/or visual indication via LEDs/buzzers  517 . 
       FIG.  15    shows in one embodiment of the external measurement circuit that generates the low-voltage sinusoidal signal used to measure the phase shift. It is generated by passing a 500 kHz square wave through a 4-pole low-pass active filter  531 . The 4-pole low pass filter removes higher harmonic components and passes the sinusoidal fundamental frequency. The 500 KHz square wave is generated via the PWM peripheral  522  in the microcontroller  524 . 
       FIG.  16    illustrates switch  515  configured to switch between the application of the drive signal and the measurement signal, e.g., the 500 kHz, 5 Volt peak-to-peak sine wave reference signal, from the generator. Although the use of a solid-state switch to implement the switching offers a long operational life and inherent current surge control, it can be difficult to block the relatively high voltage (−200 VAC) and high frequency (−500 KHz) signal generated by a typical generator in bipolar coagulation mode. As such, two double pole, double-throw mechanical relays  527 , 528  are used. The first relay  527  switches between the generator and the reference signal. The second relay  528  limits the current surge, which can damage the relay and create an electromagnetic interference (EMI) pulse that can disrupt the low-voltage circuitry. Additionally, this protects the tissue against complications or issues caused by electrical arcing. Since most generators are constant power devices, the highest voltages occur during conditions of no load. By first switching in the generator through a series resistor, the output voltage of the generator is shared across the resistor, limiting the voltage imparted to the tissue. Furthermore, the resistor serves as an energy limiter, enabling high conductive channels in the tissue to fuse before the full power of the generator is applied. 
     In one embodiment, switching takes place in the following sequence. When switching from the low voltage measurement or reference signal to the generator, the first relay  528  switches out both ends of the reference and switches in one generator lead directly and one through a 100 Ohm resistor. The 100 Ohm resistor limits the surge current to two amps for a 200 Volt source. If a shorted output occurs, 400 watts are dissipated in the 3 Watt resistor, which would quickly burn up. However, approximately 50 milliseconds after the first relay  528  switches in the generator, a second relay  527  switches out the 100 Ohm resistor, keeping it from burning up and allowing the full power of the generator to be delivered to the tissue. When the device switches the other way (from the ESU to the reference signal), it first switches in the 100 Ohm resistor, reducing the current, and then switches out the generator entirely. This sequence reduces inductive kickback and EMI generation. 
     The relays  527 , 528  in one embodiment are of a latching type. Most mechanical relays draw a fair amount of power in their non-default state (an electrical current is needed to fight the force of the returning spring). Since the controller is equipped with a battery of limited power capacity, two latching type relays are used. These relays only use current to transition between two stable states and can operate at a much lower power level. 
     The phase detection circuitry  530  is shown in  FIG.  17   , which measures the phase shift between the two above-mentioned sine waves. The first part of the circuit level-shifts the sine wave to the same DC value as a reference voltage. The level-shifted signal is then sent to the negative input of a comparator  531 . The positive input is connected directly to the DC reference voltage. A small amount of hysteresis is used to reduce switching noise. The output of the comparator is a square wave with the same phase as the input sine wave. These two signals are sent to an exclusive “OR” gate  532 . The output of the gate is high when one of the two inputs is high, and low otherwise. The duty cycle of the output is therefore linearly related to the phase of the two input square waves. The duty cycle is converted to a DC voltage through a low pass filter, which is measured by the analog to digital converter peripheral of the microcontroller. 
       FIG.  18    shows the battery power circuit that is powering the control circuit by two low-capacity coin cells. The battery provides a life of 500 fusing cycles over a 5-hour time span. When a specific number of seals, or a specific time limit have been reached, the controller issues a warning and ceases operating. The controller manages its power demand around the power characteristics of the specific batteries used. The controller includes management controls that prevent specific operations from occurring simultaneously that may exceed the power capacity of the batteries, power down selected portions of the circuit between fusing cycles, and slow the microcontroller oscillator down from 4 MHz to 32 kHz between fusing cycles. 
       FIG.  19    shows an input port  534  adapted for connecting to a tool. With engagement of a switch on the tool, the controller takes initial measurements on the tissue (shorting, etc.) and based on the initial measurements activates the generator to supply electrosurgical power that is passed and controlled by the controller. 
     As many generators can exclusively (but also alternatively, with the surgeons preference) be activated with a foot-pedal, the controller accommodates such a scenario. For example, if the generator is activated with a foot switch while subsequent activation of the hand switch on the tool occurs, the controller allows switching-in of the output of the generator. 
     The result of using the control circuit described above is shown in  FIG.  20   , showing the effective voltage applied to the biological tissue as function of time. As shown in this specific example of porcine renal arteries, the tissue is being exposed to 6 high-power fusion intervals of about 850 ms time duration, interrupted by 5 measurement cycles of about 300 ms. 
     In one embodiment, the fusion process starts with depressing a switch on the tool, which starts an initial measurement sequence. This point in time is marked start (switch on)  535 . The tool in one embodiment checks the resistance between the two electrodes and if the phase shift is within an acceptable range. Verifying the phase shift prevents an attempt to re-fuse already fused tissue. Based on the results of the initial check, the controller switches-in the activated output of the generator to the tissue. This starts the application of RF energy to the compressed tissue. After about 850 ms, the controller disconnects the tissue from the generator and switches back to the first tissue assessment phase. Depending on the result, the tissue gets heated further, or remains disconnected from the generator to remain on the measurement circuit. The latter case is marked “power stop (switch on)”  536 . In this case, an acoustical and/or visual signal is given off the unit, indicated that the tissue is sealed (or that shorting of the electrodes has occurred). The supply of the measurement signal to the tissue is ended when the switch on the tool is released, marked “manual stop (switch off)”  537 . At this point, all supply of energy to the tissue is terminated. 
     A more detailed analysis of the measurement cycle  538  is shown in  FIGS.  21  and  22   , showing that additional measurements (other than the phase shift) can be included in that measurement period. Such measurements, for example, could prevent attempting to fuse already fused tissue, or powering of electrically shorted electrodes. 
     In  FIG.  22   , a more detailed analysis of the measurement plateau  539  of 2V in  FIG.  21   . As shown, a detailed view of the low-voltage measurement signal  540  at 500 kHz used to determine the phase shift through the tissue during the RF measurement cycle. 
     Electrosurgical Systems and Processes 
     Electrosurgical systems and processes in various embodiments apply monopolar or bipolar high-frequency electrical energy to a patient during surgery. Such systems and processes are particularly adapted for laparoscopic and endoscopic surgeries, where spatially limited access and visibility call for simple handling, and are used to fuse blood vessels and weld other biological tissue and in one aspect to cut, dissect and separate tissue/vessels. In particular embodiments, the systems and processes include the application of RF energy to mechanically compressed tissue to (a) desiccate the tissue, and (b) to denature collagens (type I-III) and other proteins, which are abundant in most biological tissue. As heating of collagens to an appropriate temperature causes them to unfold, shrink or denature, the system enables the sealing of capillaries and blood vessels during surgery for permanent occlusion of the vessels. As described in greater detail below, as an example, arteries up to seven millimeters can be occluded and dissected by radio frequency (RF) energy and mechanical pressure. 
     When concurrently applying controlled high-frequency electrical energy to the compressed tissue, the tissue is compressed with a relatively high pressure (about 10-20 kg/cm2), and the tissue is supplied with sufficient electrical energy to denature proteins and remove sufficient water in the tissue. During this process, the applied voltages are sufficiently reduced to avoid electrical arcing (typically &lt;200V RMS). 
     When applying electrical energy in the described manner stated above, the tissue quickly moves through the following fusion/welding process. Starting at body temperature the tissue (a) heats quickly, leading to (b) cell rupture, expelling of juices (mainly water and salt ions), (c) unraveling and “activation” of collagens and elastin in the blood vessels at about 60-650 C, and (d) desiccation of the vessel. Here, the desiccation process can be seen by the release of water in form of steam where the vessel temperature has reached about 1000 C. The reduction of water in presence of unraveled collagen and elastin strands leads to formation of bonds between collagen strands, leading to a strong and elastic seal of the tissue. As confirmed by measurements, the strongest (highest burst pressure) vessel fusions are obtained when the vessels have been heated to at least 70° C., pressurized with about 10-20 kg/cm2, and then desiccated by about 40-50% of their original water content. 
     Electrically, the tissue can be characterized during the fusion process by its impedance, which is typically starting at 10-100 Ohms purely ohmic resistance. During the fusion process, the purely ohmic resistance reduces by 20-50% before it increases by two orders of magnitude. As the resistance approaches a final value, the impedance of the tissue gradually increases in capacitive behavior with a phase shift of about 20 degrees. The tissue will exhibit a pronounced capacitive behavior at the end of the fusion process with a phase shift of about 40 degrees, even though the ohmic component will remain nearly unchanged during this phase. 
     Referring now to  FIG.  23   , graphical representation exemplifying experimental data for the sealing of a four-millimeter diameter porcine renal artery in accordance with various embodiments of electrosurgical system is shown. The fusion process is performed by compressing the artery with 0.75 millimeter wide electrodes with a compression load of three pounds, and by energizing it with a voltage-stabilized electrosurgical power supply using 200V at 60 W maximum power setting. Voltage  501 , current  502  and electrical power  503  in the beginning of the fusion process (1 second) are shown. As can be seen, the sinusoidal voltage and current are substantially in-phase, e.g., the phase difference or angle equals zero. At this time, the impedance of the artery is purely ohmic with a value of about 100 Ohms. 
     The temporal progression of the applied peak voltage and peak current for the same-sized artery is provided in  FIG.  24   . The applied voltage quickly stabilizes to a constant value, which is an artifact of the voltage-stabilized power supply. Regardless of the applied load, voltage-stabilized electrosurgical power supplies regulate the output voltage to a pre-set value since the voltage has a dominant impact on the electrosurgical effect. In contrast to the voltage, the current driven through the artery increases from an initial 1 A to 1.5 A at 0.5 s, and then gradually reduces over the next three seconds to about 0.2 A. For the remaining 4 seconds of the fusion time the peak value of the current remains nearly unchanged. 
     Another way to depict the information from  FIG.  24    is shown in  FIG.  25   , showing the impedance  506  of the artery as function of fusion time. The initial impedance of the harvested artery is 75 Ohms. With application of high frequency electrical energy the artery heats quickly, leading to shrinkage of collagens, rupture of cell membranes, and the ultimate expelling of trapped liquid (mainly water and ions). As a result, the impedance has reduced to about 54 Ohms. Further supply of electrical energy starts to desiccate the artery, resulting in an impedance increase. At about 4 seconds into the fusion process the impedance of the artery starts to stabilize, with a slow increase of the impedance from about 800 Ohms to about 1,200 Ohms. 
     The fusion process could be terminated (a) at a fixed and absolute resistance (for example 2 k Ohms), which would neglect both the size and type of tissue, (b) at a specific multiple of the time where the ohmic resistance is minimal, (c) at a specific multiple of the time where the ohmic resistance is the same as the initial one, or (d) at a specific multiple of the time where the ohmic resistance is a certain factor of the minimal one. However, considering burst pressure of fused arteries and thermal spread, the termination of the fusion process is determined to be in the flattened part of the impedance curve. As can be seen in  FIG.  25   , however, this region is also an inexact range for impedance measurements. Similarly, each succession of (a) to (d) becomes better in determining the end-point of the fusion time (resulting in the highest desired bursting pressure with the least desired thermal spread). Utilizing the ohmic resistance only as termination criterion can lead to incomplete results. This can be more pronounced when fusing differently sized tissues (even of same nature), also exemplified in  FIG.  26    showing the relative resistance (relative to the initial resistance) of various-sized arteries and other tissue as a function of fusion time. 
     Termination of the fusion process for same-material tissue (i.e., arteries) cannot be controlled with desired precision by specifying one relative ohmic load (e.g., when the resistance reaches 3 times the initial resistance). Instead, the relative change in resistance depends on the size of the vessel, i.e., &lt;2 mm arteries seal in fractions of a second (where the resistance about doubles compared to the initial resistance), about 3 mm arteries seal in about 2 seconds (where the resistance about triples), and 15 mm arteries/veins seal in about 7 seconds (where the resistance increases by a factor of 5). At the same time, some arteries may not follow that characterization (e.g., a 3-4 mm artery would not reach more than 2.5 times the initial resistance). Instead, the fusion process should end within the flat region in  FIG.  25   . As previously described, precision is difficult in the flat region with the function of time at different fusion times. 
     Phase Based Monitoring 
     In one aspect, the determination of the end-point of the fusion process is given by monitoring the phase shift of voltage and current during the fusion process. Unlike impedance, the phase shift changes much more pronounced at times where the artery desiccates and the fusion completes, and hence offers a more sensitive control value than the impedance. This can be seen when monitoring the voltage and current as function of time at different fusion times, as is shown in  FIG.  23    for the beginning of the fusion process. 
     In  FIG.  23   , the beginning of the fusion shows that the applied voltage and current are in phase (with a shift of about −3 degrees), revealing that the artery behaves dominantly like an ohmic load of about 75 ohms. Further supply of energy leads to heating of the artery, an initial reduction in impedance (caused by shrinking of collagens, cell membrane rupture and expelling of mainly water and dissolved ions), and a subsequent increase in impedance. During this period of vessel fusion, the phase difference between voltage and current remains small with minimal changes, indicating that the artery is purely ohmic. 
     The artery is not fully desiccated, and thus the seal is not complete. Referring to  FIG.  27   , at 4 seconds into the fusion process, the phase difference slowly increases to −10 degrees (current leads). While further supply of electrical energy does not significantly change the value of the resistance (see  FIG.  24   ), it does cause a pronounced increase in phase difference between voltage and current. This can be seen in  FIG.  28    at 7 seconds into the fusion process, showing a phase difference of about 25 degrees. The vessel fusion process continues and yields the desired burst pressures at the least desired thermal spread when the phase difference or angle reaches about 35-40 degrees as shown in  FIG.  29   . Also, as shown the phase angle reaches about 20 to 40 degrees. Similarly, the phase difference or angle necessary to result in welding of other tissue reaches about 45-50 degrees for lung tissue, and 60 to 65 degrees for small intestine. However, for all types of tissue, reaching a high end of the phase range can lead to excessively long sealing times. Accordingly, as will be described in greater detail below, the application of RF energy, i.e., drive signal, via an electrosurgical generator in conjunction with the measuring or monitoring of phase shift, i.e., a measurement signal, via an electrosurgical controller are provided to fuse or weld vessels and tissue in accordance with various embodiments of electrosurgical system. 
     Endpoint Determination Based on Tissue Properties 
     Using the phase difference between voltage and current as a control value in the fusion or welding process, instead of the impedance, can be further shown when characterizing the tissue electrically. When considering vessels and tissue to be a time-dependent ohmic resistor R and capacitor C in parallel (both of which depend on the tissue size and type) the phase difference can be obtained with 
               R   =       ρ   ·   d     A       ,         
where R is the ohmic resistance, ρ the specific resistance, A the area, and d the thickness of the fused tissue,
 
                 X   c     =     1     ω   ·   C         ,         
where X c  is the capacitive impedance, ω the frequency, and C the capacity of the tissue, and
 
               C   =       ε   ·     ε   0     ·   A     d       ,         
where ε and ε 0  are the relative and absolute permittivity.
 
     The phase difference φ can then be expressed as 
     
       
         
           
             φ 
             = 
             
               
                 arctan 
                 ⁡ 
                 ( 
                 
                   
                     X 
                     c 
                   
                   R 
                 
                 ) 
               
               = 
               
                 
                   arctan 
                   [ 
                   
                     
                       ( 
                       
                         ω 
                         · 
                         ε 
                         · 
                         
                           ε 
                           0 
                         
                         · 
                         ρ 
                       
                       ) 
                     
                     
                       - 
                       1 
                     
                   
                   ] 
                 
                 . 
               
             
           
         
       
     
     As such, the difference between monitoring the phase difference φ as opposed to the (ohmic) resistance R is that φ depends on the applied frequency ω and material properties only (namely, the dielectric constant ε and the conductivity ρ), but not on tissue dimensions (namely the compressed tissue area A and tissue thickness d). Furthermore, the relative change in phase difference is much larger at the end of the fusion process than the change in tissue resistance, allowing for easier and more precise measurement. 
     In addition, with measurement of the initial dielectric properties of the tissue (dielectric constant ε and conductivity ρ) at a certain frequency, the type of tissue can be determined. The dielectric properties for various types of biological tissue, arranged by increasing values of the product of dielectric constant ε and conductivity ρ) are given in  FIG.  30    at a frequency of 350 kHz (which is in the frequency range of a typical electrosurgical generator). By measurement of the product of dielectric constant ε and conductivity ρ of the tissue (which are material characteristics and independent of tissue dimensions) before the actual tissue fusion or welding process, the phase shift required to adequately fuse or seal the specific biological tissue can be determined from  FIG.  30   . The phase shift required to reliably fuse or seal the respective type of tissue is measured as function of the product of dielectric constant ε and conductivity ρ of the tissue (at 350 kHz).  FIGS.  31  and  32    further emphasize this function in which in  FIG.  31   , endpoint determination is shown as a function of an initial phase reading and in  FIG.  32   , end point determination is shown as a function of tissue properties (conductivity times relative permittivity). The function of tissue properties can also be expressed as ϕend=38+29[1−exp(−0.0091ρε)]. 
     As a result, (a) measurement of the dielectric properties of the tissue and (b) control and feedback of the phase difference allows for a precise control and feedback mechanism for various tissue types, regardless of the tissue size and allows employing standard electrosurgical power supplies (which individually run in a very close range of frequencies). It should be noted that however that specific frequency of the tissue properties measurement is performed can be the same or different from the specific frequency of the phase If the tissue measurement is based on the driving frequency of the generator, and various generators are used (all of which run in a close range of frequencies) though, the end points will be different. Hence, for such a case, it can be desirable to (1) use an external measurement signal (which is at the same frequency), or (b) utilize a stand-alone generator. 
     As such, the controller is configured to determine the product of dielectric constant and conductivity, as well as the phase difference between the applied voltage and current to monitor and control the tissue fusion or welding process. In particular, control and feedback circuitry of the controller determines when the phase difference reaches the phase shift value determined by the result of the dielectric and conductivity measurements. When this threshold is reached, the fusion or welding process is terminated. An indicator, e.g., visual or audible, is provided to signal the termination and in one aspect the controller restricts (completely, nearly completely or to a predetermined minimum) further delivery of electrical energy through the electrodes. As such, the tool generating the seal, weld or connection of the tissue provides atraumatic contact to the connecting tissue and provides enough burst pressure, tensile strength, or breaking strength within the tissue. 
     Capacitive Load Compensation of Connected Tools 
     In one embodiment, measuring and accounting for the tool capacitance and tool resistance is provided for consistent initial tissue assessment (conductivity and permittivity) which provides the tissue-specific endpoint of the process (i.e., coag, fuse, or weld). In another aspect of the invention, measuring and accounting for the tool capacitance and tool resistance is provided for consistent tissue feedback measurements (phase shift) which ensures consistent tissue modification results (i.e., coag, fuse or weld). 
       FIG.  33    shows phase diagrams of two electrosurgical tools. As can be seen, both tools are electrically represented as a resistive or ohmic load (originating mainly from the wire harness  1500  connecting the hand tool to the generator, as well as the connections within the hand tools), as well as a capacitive load (originating mainly from the tool jaws, as well as the wire harness  1500  connecting the hand tool to the generator). In a phase diagram, the tool can be characterized by a phase angle α. 
     The values of the ohmic and capacitive impedances found in typical arrangements of tools are in the range of 1-10 Ohms for the ohmic load and 1-100 kOhms for capacitive resistances (several ten to several hundred pF capacitance at several 100 kHz). Even for two equal tools variations in the tool characteristics (such as wire connections, harness length, etc.) can lead to different phase angles α and α′ for the same tool. As will be shown in the following, these variations can lead to different tissue measurement results, used both before and during tissue assessment. 
     As shown in  FIG.  34   , the phase diagram of an electrosurgical tool that is in contact with tissue composes of the resistive and capacitive component of the tool (dotted arrows) which add to the ohmic and capacitive component of the tissue (solid arrows) to present a total load to the electrosurgical generator (dashed line). For tissue measurement techniques that rely on the phase shift of voltage and current, the presence of the tool significantly alters the results of the intended tissue measurement by the apparent phase. 
     In this context, the presence of the tool (impedance) does not pose an actual problem if the tissue measurement before powering (to determine end point of fuse/weld), or during powering (to determine the end point of the fuse/weld) has been defined with the very same tool (i.e., tool impedance). Instead, variances of the tool impedances lead to different results in both the initial tissue assessment (pointing to an inaccurate endpoint) and tissue feedback measurement (determining the end point of the fuse/weld). 
     As such, the controller used to measure the phase shift during the tissue modification process can be used to initially determine the initial tool impedance (e.g., during plug-in of the tool connector to the electrosurgical generator), where tolerances/changes in the tool characteristics are then accounted for in the tissue measurement algorithm. This will allow for tissue measurement values which are independent of the ohmic and capacitive values and/or tolerances of the specific electrosurgical tool. 
     Accordingly, generally speaking, when tool capacitance increases, the endpoint phase shift decreases. In particular, when the tool capacitance increases, the capacitive impedance decreases (X=1/ωC). Decreased capacitive impedance leads to a smaller or decreased end point phase shift. Similarly, when tool resistance increases, the end point phase shift decreases. 
     Also, from an initial tissue determination perspective, generally speaking, when tool capacitance increases, the apparent initial phase shift decreases compared to the “ideal” value. The “ideal” value being a tool having zero or near zero capacitance. Similarly, when tool resistance increases, the apparent initial phase shift decreases compared to the “ideal” value. As such, when the tool capacitance (C=εε 0  A/d) and/or the tool resistance (R=ρ d/A) increase, there is an increase in permittivity and/or conductivity which reflects a decrease in tan φ, i.e., a decrease in phase. In one example, an electrosurgical tool having a capacitance of 160 pF had an initial phase shift of 9-59 degrees versus a tool having a capacitance of 230 pF having an initial phase shift of 6-23 degrees. Additionally with tissue permittivity and conductivity product values being inversely proportional with the initial phase shift, when tool capacitance and/or resistance increases, the apparent tissue permittivity and conductivity product value increases compared to the “ideal” value. 
       FIG.  35    shows the ohmic resistance of a porcine renal artery during the electrosurgical fusion process. As was shown previously, the fusion process of blood vessels and/or welding of tissue can be better controlled when the phase difference or angle between applied voltage and incurred current is measured and used to interrupt the fusion/sealing process. Depending on the type of tissue, the end point has been found to be ideal at about 40 degrees (blood vessels) or 60 degrees (intestines), respectively. 
     Instead of the tissue quickly reaching a pre-determined phase (ranging from 40 to 60 degrees, depending on type of tissue), the measured phase shift approaches the cut-off threshold asymptotically. This is shown in  FIG.  36    for the same seal as given in  FIG.  35   . As can be seen, the phase shift quickly increases during the initial fusion process, but then increases slowly for the remainder of the seal. The asymptotic approach can require a significant amount of time to reach the final phase threshold (e.g., 40 degrees). As such, instead of depending on the phase value to reach a definite value alone, additionally the derivate of the phase can be used to avoid asymptotic approaches to a finalized phase value. The derivative of the phase value of the same seal is shown in  FIG.  37   . As shown, the phase changes (increases) strongly during the first 0.5 s into the seal and changes little for the remainder of the seal. After about 1.5 s sealing time, the derivative of the phase dp/dt reaches a pre-determined value of 0.1 degrees/second to terminate the seal (independent of the actual phase reading). 
     Additionally, the determined phase value can be overshot without being detected, for example, when the phase trip level is reached during the read out time of the processor controlling the power supply. In such cases, the processor may not recognize that the final phase stop has been reached. This is shown in  FIG.  38    for welding of porcine intestines. As can be seen, the phase shift overshoots a pre-determined phase threshold of 60 degrees, but instead reaches an asymptotic steady-state level of 50 degrees. Instead of relying on the phase value to reach a definite value alone, the derivate of the phase is also used to ensure the seal to end. 
     The derivative of the phase value of the same seal is shown in  FIG.  39   . As shown, the phase changes (increases) strongly during the first 0.25 s into the weld and changes only little for the remainder of the seal. At about 1.5 s into the weld, the derivative of the phase dp/dt reaches a pre-determined value of 0.1 degrees/second and terminates the weld (independent of the actual phase reading). The derivate of the phase in one embodiment is set to 0.02 degrees per second. A range of phase derivate from 0.2 to 0.01 degrees per second has also been found to be acceptable. In the latter case, the derivate of the phase angle reading provides a safety feature for terminating a seal/weld. 
     As previously described and described throughout the application, the electrosurgical generator ultimately supplies RF energy to a connected electrosurgical tool. The electrosurgical generator ensures that the supplied RF energy does not exceed specified parameters and detects faults or error conditions. In various embodiments, however, an electrosurgical tool provides the commands or logic used to appropriately apply RF energy for a surgical procedure. An electrosurgical tool includes memory having commands and parameters that dictate the operation of the tool in conjunction with the electrosurgical generator. For example, in a simple case, the generator can supply the RF energy but the connected tool decides how much energy is applied. The generator however does not allow the supply of RF energy to exceed a set threshold even if directed to by the connected tool thereby providing a check or assurance against a faulty tool command. 
     In one embodiment, each tool comes with an integrated circuit that provides tool authentication, configuration, expiration, and logging. Connection of tools into the receptacles or ports initiates a tool verification and identification process. Tool authentication in one embodiment is provided via a challenge-response scheme and/or a stored secret key also shared by the controller. Other parameters have hash keys for integrity checks. Usages are logged to the controller and/or to the tool integrated circuit. Errors in one embodiment can result in unlogged usage. In one embodiment, the log record is set in binary and interpreted with offline tools or via the controller. 
     In one embodiment, connection of a standard bipolar tool into the standard bipolar outlet will not actively check the tool. However, the controller recognizes a connection so that the information on the bipolar outlet can be displayed on the monitor or user interface of the unit. The display reserves a field for the bipolar outlet before the outlet is activated. In one embodiment, the controller uses time measurement components to monitor a tool&#39;s expiration. Such components utilize polling oscillators or timers, real-time calendar clocks and are configured at boot time. Timer interrupts are handled by the controller and can be used by scripts for timeouts. Logging also utilizes timers or counters to timestamp logged events. 
     The tool in one embodiment has memory integrated with or removable from the tool. A tool algorithm or script within the tool&#39;s memory is loaded into a script interpreter of the generator. The script provides commands and parameters readying the tool for use when connected to the generator. Upon activation of a switch coupled to the tool, the controller detects the switch closure, and authenticates the tool, checks the tool&#39;s expiration status, and initializes internal data structures representing the receptacle&#39;s tool. A subsequent activation of the tool switch initiates an event that causes the script to direct the generator to supply RF energy. The controller logs the usage to both the tool and the generator. When the tool is disconnected from the receptacle of the generator, the controller resets the information associated with the receptacle. The controller constantly monitors the generator for proper operation. Unrecoverable errors and faults are announced and further operation of the system is prevented. All faults are stored in the controller&#39;s memory and/or the tool&#39;s memory. 
     Data from a specific procedure (e.g., from power-up to power-down) is stored on each tool. The tool additionally holds the data from a procedure, i.e., the number of tool uses, the power setting and faults. Each tool in one embodiment holds the information from all other tools as well. Tool memory includes but is not limited to the following parameters: serial number of generator, time stamp, tissue assessment and endpoint setting for each tool use, cut, coagulation, weld, power setting, duration of RF and endpoint (auto stop, fault, manual stop, etc.). 
     The generator logs usage details in an internal log that is down loadable. The generator has memory for storage of code and machine performance. The generator has reprogrammable memory that contains instructions for specific tool performance. The memory for example retains a serial number and tool use parameters. The generator stores information on the type of tools connected. Such information includes but is not limited to a tool identifier, e.g., a serial number of a connected tool, along with a time stamp, number of uses or duration of use of the connected tool, power setting of each and changes made to the default setting. The memory in one embodiment holds data for about two months or about 10,000 tool uses and is configured to overwrite itself as needed. 
     In one embodiment, the controller includes a state machine interpreter module that parses tool scripts. Tool scripts represent a tool process for a specific or given tool. The tool scripts are stored on memory connected to or integrated with a tool, the controller or a combination thereof. The state machine interpreter module responds to specific events, such as a switch activation/de-activation, tool positions or exceeding measurement thresholds. The module upon response controls the output of RF energy and/or electrode activation. In one embodiment, an interpreter module is provided for each tool input receptacle. The controller detects tool events and forwards the detected event to the appropriate interpreter module. The module in turn requests actions of the controller based on the detected event which provides output to the connected tool associated with the appropriate tool input receptacle and also the appropriate interpreter module. 
     In one embodiment, the controller has a specific or predetermined fixed tool script for a specific input receptacle. As such, only this tool script is used for the tool connected to the particular input receptacle. The interpreter module includes an event detector and a script parser. The event detector receives and identifies tool events, such as a switch activation/de-activation event or a measurement event (e.g., phase threshold exceeded). The event detector formulates requests to the controller to control RF output, output selection and/or selection of outputs, changes to the display and audio tones. Other events detected include detecting hand and foot switches, jaw switches, phase over and phase under-after-over events, shorts and opens, tool script states. The script parser interprets the tool scripts. Keywords in the scripts assist the script parser to extract operational commands and data for tool operation based on a detected event identified by the event detector. In addition to the voltage, current, etc. set points, a tool script specifies the RF source as from the CUT or the COAG source. The script also specifies which electrodes get connected to RF+, RF−, or allowed to float. Because the script controls the electrode configuration, and can set thresholds that trigger events, a script can completely reconfigure tool during its use. 
     The script controls the voltage and current output settings as well as sequences of voltage and current settings. For example the permittivity and conductivity of blood vessels is the same independent of size. A small blood vessel will fuse very rapidly while a large vessel may take several seconds. Applying a large amount of current to a small vessel may cause excess tissue damage, while using a small amount of current will take an unacceptably long time to perform the fusion function. So to modify tool performance the script can initially command a small amount of RF current, and if fusion endpoint is not reached in less than one second, a high current is commanded to speed the fusion of a large vessel. Another script usage to modify tool performance to switch from one operation (coagulation) to another operation (cut) is to reconfigure the tool electrodes and ESG output to simplify a multistep process such as fuse and cut. When the clinician starts the process the script will first setup the unit for the fusion, measure the tissue phase angle that indicates the fusion endpoint. RF power is then turned on until the fusion endpoint is reached. The unit will then turn off RF power and beep to indicate that fusion is complete. The unit then switches the electrodes to the cut configuration, sets the RF output for cut, and restarts the RF output. The cut operation is stopped by the clinician when the cut is completed. 
     Referring to  FIG.  40   , an overview of tool operations is provided. A tool connected to the electrosurgical generator is verified  601 . The endpoint is determined  602 . The tool applies energy  603 , e.g., RF energy, and continues until an endpoint is reached or an error condition is detected. Upon determination of an endpoint being reached or exceeded  604 , the tool is deactivated (e.g., application of energy is stopped) ending the process. 
     Based on the tool algorithm for the connected tool, the tool verification and determination of an end point can vary. In particular, a tool short is determined by measuring resistance at a tissue contacting surface of the tool. If the resistance is less than ten (10) Ohms, a tool short condition is recognized. In accordance with various embodiments, the product of measured tissue permittivity and conductivity or an initial phase shift is utilized to determine the end point for a connected tool. 
     In accordance with various embodiments, phase shift and/or a phase rate of change is measured throughout the process to determine if an endpoint is reached or exceeded. Also, timeout parameters, e.g., a timer or counter reaching or exceeding a set time limit, or a fault condition stops or interrupts the process even if the determined end point is not reached or exceeded. 
     Handheld Electrosurgical Tools 
     As described generally above and described in further detail below, various handheld electrosurgical tools can be used in the electrosurgical systems described herein. For example, electrosurgical graspers, scissors, tweezers, probes, needles, and other instruments incorporating one, some, or all of the aspects discussed herein can provide various advantages in an electrosurgical system. Various embodiments electrosurgical tool are discussed below. It is contemplated that one, some, or all of the features discussed generally below can be included in any of the embodiment of tool discussed below. For example, it can be desirable that each of the tools described below include a memory for interaction with a feedback circuit as described above. However, in other embodiments, the tools described below can be configured to interact with a standard bipolar power source without interaction of a tool memory. Furthermore, although it is contemplated that certain aspects of these embodiments can be combined with certain aspects of other electrosurgical tools within the scope of this application. Certain aspects of these electrosurgical tools are discussed generally herein, and in more detail with respect to various embodiments below. 
     As discussed above with respect to  FIGS.  1 A and  1 B , and electrosurgical tool can desirably include a memory. The memory can include an encryption module and a configuration device module. The configuration device module can store certain types of tool data. For example the configuration device module can store operational parameters for the tool, including software to be transferred to an electrosurgical unit upon successful electrical connection to the electrosurgical unit. These operational parameters can include data regarding various electrosurgical procedures to be performed by the tool and corresponding energy level ranges and durations for these operations, data regarding electrode configuration of a tool, and data regarding switching between electrodes to perform different electrosurgical procedures with the tool. Advantageously, unlike prior art electrosurgical systems, changes to tool profiles and periodic tool updates can be rapidly made without downtime to electrosurgical generators, as the software for tool operation can reside in electrosurgical tool itself, rather than the generator. Accordingly, updates can be made during tool production. 
     The configuration device module can further store a data log comprising, for example, a record of information of each previous tool use. For example, in some embodiments, the data log can contain timestamp data including an electrosurgical unit identifier, a log of electrosurgical procedures perform by the tool, and along of durations and energies applied to the tool. In some embodiments, it can be desirable that use of a particular tool is limited to a maximum usage period or number of procedures, especially where electrosurgical tool has not been configured for sterilization and reuse. Accordingly, in some embodiments, the configuration device module can be configured to prevent operation of a tool after a predetermined usage or number of procedures. In some embodiments, a tool can comprise a mechanical lockout in addition to or in place of the data log, such as a breakaway single-use connector to reduce the possibility of unintended reuse. 
     In some embodiments, it is desirable that the tool communicate with the electrosurgical unit through an encrypted protocol. Accordingly, the memory can further store an encryption module, or encryption key to facilitate this encrypted communication. 
     As discussed above with respect to  FIG.  18    and one be, it can be desirable that an electrosurgical tool for use in the electrosurgical system includes one or more audio and/or visual indicators. In some embodiments, the electrosurgical tool can include an array of LEDs, or a multi-color LED assembly such as a three-color LED assembly capable of generating many combined colors. The visual indicator can be configured to illuminate with a color corresponding to the type of electrosurgical procedure performed by the tool. Were a tool is configured to perform multiple different types of electrosurgical procedures, desirably the visual indicator updates to reflect the currently-selected electrosurgical procedure. Thus, advantageously, a user can tell, while watching the surgical field, what type of electrosurgical procedure the tool is configured to perform. 
     Electrosurgical Fusion Tool 
     With reference to  FIGS.  41 A- 41 B , one embodiment of a hand held laparoscopic sealer/divider or fusion tool  1100  is provided. In the illustrated embodiment, the sealer/divider comprises a handle assembly  1110 , an elongate shaft  1120  extending from the handle assembly  1110 , and a jaw assembly  1130  positioned on the elongate shaft  1120  opposite the handle assembly  1110 . The elongate shaft  1120  has a proximal end and a distal end defining a central longitudinal axis therebetween. In the illustrated embodiment, the handle assembly  1110  comprises a pistol-grip like handle. The elongate shaft  1120  and the jaw assembly  1130 , in one embodiment, are sized and shaped to fit through a 5 mm diameter trocar cannula or access port. In other embodiments, the elongate shaft and jaw assembly can be sized and configured to fit through trocar cannulae or access ports having other standard, or non-standard sizes. In  FIG.  41 A , the handle assembly  1110  is shown in a first or initial position in which the jaws are open. 
     With reference to  FIGS.  41 A- 42 B , the handle assembly  1110  comprises a stationary handle  1112  and an actuation handle  1114  movably coupled to the stationary handle. In the illustrated embodiment, the stationary handle  1112  comprises a housing formed of right  1112 R and left handle  1112 L frames. In other embodiments, the stationary handle  1112  can be a single component, or can be a housing formed of more than two pieces. In the illustrated embodiment, the actuation handle  1114  is slidably and pivotally coupled to the stationary housing, as discussed in further detail below. In operation, the actuation handle  1114  can be manipulated by a user, e.g., a surgeon to actuate the jaw assembly, for example, selectively opening and closing the jaws. 
     With continued reference to  FIGS.  42 A- 42 B , in the illustrated embodiment, the actuation handle  1114  is coupled to the stationary handle  1112  to form a force regulation mechanism  1200  coupling the handle assembly  1110  to the jaw assembly  1130 . Desirably, the force regulation mechanism  1200  can be configured such that in a closed configuration, the jaw assembly  1130  delivers a gripping force between the first jaw  1132  and the second jaw  1134  between a predetermined minimum force and a predetermined maximum force. 
     With continued reference to  FIGS.  42 A- 42 B , in the illustrated embodiment, the actuation handle  1114  is coupled to the stationary handle  1112  at two sliding pivot locations  1202 ,  1204  to form the force regulation mechanism  1200 . The actuation handle  1114  has a first end  1116  including a gripping surface formed thereon, and a second end  1118  opposite the first end  1116 . In the illustrated embodiment, the actuation handle  1114  is coupled to a pin  1206  adjacent the second end  1118 . In some embodiments, the actuation handle  1114  can be integrally formed with a protrusion extending therefrom defining a pin surface, while in other embodiments, a pin can be press-fit into an aperture in the actuation handle. The  1206  pin can be contained within slots in the stationary handle  1112 , such as corresponding slots formed in the right and left handle frames  1112 R,  1112 L of the stationary handle housing. These slots can allow the sliding pin  1206  to move over a predetermined range. In some embodiments, the slots can be configured to define a desired actuation handle path as the actuation handle is moved from the first position corresponding to open jaws to a second position corresponding to closed jaws. For example, the illustrated embodiment includes generally linear slots formed in the stationary handle  1112  at an angle from the central longitudinal axis of the elongate shaft  1120 . In other embodiments, the slots can be formed generally parallel to the central longitudinal axis. In some embodiments, the slots can be curvilinear. 
     In the illustrated embodiment, the force regulation mechanism  1200  includes a biasing member such as a trigger spring  1208  that biases the pin in a proximal direction towards the rear of the pin slots in the right and left handle frames (see, for example,  FIG.  42 B ). The trigger spring  1208  and the actuation handle  1114  can pivot freely or unhindered at their attachment point  1202 . The biasing member  1208  can be preloaded to a predetermined force. In operation, as a predetermined force is exerted on the actuation handle  1114 , a biasing force exerted by the trigger spring  1208  is overcome, and the second end  1118  of the actuation handle  1114  can translate generally distally, guided by the pin in the slots. 
     While the illustrated embodiment includes a pin-in-slot arrangement coupling one pivot point of the actuation handle to the stationary handle, in other embodiments, it is contemplated that other connections can be formed. For example, in some embodiments, a slot can be formed in the actuation handle and a mating projection can be formed in the stationary handle. Furthermore, while the illustrated embodiment includes a tension coil spring forming the biasing member, in other embodiments, other biasing members are contemplated. For example, the biasing member can comprise a compression spring, a torsion spring, an elastomeric band, a fluid-filled shock absorbing unit, or another suitable biasing device. 
     With continued reference to  FIGS.  42 A- 42 B , in the illustrated embodiment, the actuation handle  1114  is slidably and pivotably coupled to the stationary handle  1112  at a location between the first and second ends  1116 ,  1118  of the actuation handle. An actuation member such as a pull block  1250  can be coupled to the actuation handle. In the illustrated embodiment, an actuation path of the pull block  1250  is defined by rails formed in the right and left handle frames  1112 L,  1112 R. When the actuation handle  1114  is moved proximally, the pull block  1250  also moves, effectively closing the jaws thereby clamping any tissue between the jaws. In the illustrated embodiment, the rails guide the pull block  1250  to slide proximally and distally while limiting movement in other directions. In other embodiments, various other guide members such as a pin-in-slot arrangement can define the actuation path of the actuation member. 
     As illustrated, the pull block  1250  comprises a generally rectangular prismatic structure having a generally open top and bottom faces and a substantially closed proximal end. The actuation handle  1114  can extend through the top and bottom faces of the pull block  1250 . An edge of the actuation handle  1114  can bear on the proximal end of the pull block  1250  such that movement of the actuation handle  1114  relative to the stationary handle can move the pull block  1250  generally longitudinally along the actuation path defined by the rails. A distal end of the pull block  1250  can be coupled with an actuation shaft such as an actuation tube, bar, or rod, which can extend longitudinally along the elongate shaft of the sealer/divider. Thus, in operation, movement of the actuation handle  1114  from the first position to the second position translates the pull block  1250  longitudinally within the stationary housing, which correspondingly translates the actuation rod generally linearly along the longitudinal axis with respect to the elongate shaft. Movement of this actuation tube can control relative movement of the jaws in the jaw assembly. 
     With continued reference to  FIGS.  42 A and  42 B , in some embodiments, the sealer/divider can include a latch mechanism  1260  to maintain the actuation handle  1114  in the second position with respect to the stationary handle. In the illustrated embodiment, the actuation trigger comprises an extended latch arm  1262  which can engage a matching latch  1264  contained within actuation handle  1112  for holding the actuation trigger at a second or closed position. In other embodiments, it is contemplated that the one portion of the latch mechanism can be formed on a portion of the actuation handle  1114  adjacent the second end of the actuation handle  1114 , and a mating portion of the latch mechanism can be formed on the actuation handle  1112 . In still other embodiments, it is contemplated that a portion of the latch mechanism can be formed on the pull block  1250  and a mating portion of the latch mechanism can be formed on the stationary housing. 
     In some embodiments, the jaw assembly  1130  of the sealer/divider comprises an advanceable cutting blade  1400  ( FIG.  44 B ) that can be coupled to a blade actuator such as a blade trigger  1402  positioned on the handle assembly  1110 . A blade actuation mechanism  1404  can operatively couple the blade trigger to the cutting blade. In the illustrated embodiment, the blade trigger  1402  is positioned on a proximal surface of the handle assembly such that it can be easily operated in a pistol-grip fashion. As illustrated, the blade actuation mechanism  1404  comprises a pivoting blade advancement link that transfers and reverses the proximal motion of the blade trigger  1402  to a blade actuation shaft assembly coupled to the cutting blade. In other embodiments, the blade trigger  1402  can be positioned elsewhere on the actuation handle  1112  such as on a distal surface of the actuation handle  1112  such that distal movement of the blade trigger  1402  can advance the cutting blade distally without transfer of advancement directions via a linkage. In operation, a user can move the blade trigger  1402  proximally to advance the cutting blade  1400  from a retracted position to an extended position. The blade actuation mechanism  1404  can include a biasing member such as a blade return spring  1406  to biases the blade advancement lever distally within the actuator and thereby bias the cutting blade  1400  into the retracted position. 
     With reference to  FIG.  42 C , the handle assembly also comprises a wire harness  1500 . The wire harness  1500 , in certain embodiments, comprises six insulated individual electrical wires or leads contained within a single sheath. As illustrated, the wire harness  1500  can exit the housing of the actuation handle  1112  at a lower surface thereof and can run generally upwards along the interior of the actuation handle  1112 . In other embodiments, other wire routings can be made. For example, in some embodiments, the wire harness  1500  can exit a lower portion of the proximal surface of the actuation handle  1112 . The wires within the harness can provide electrical communication between the sealer/divider and an electrosurgical generator and/or accessories thereof, as discussed above. 
     In certain embodiments of sealer/divider, inside the actuation handle  1112 , two of the leads are attached to rotational coupling clips  1502  configured to allow infinite rotation of the jaw assembly  1130 , as discussed in greater detail below, two of the other leads are attached to a visible indicator  1504 , such as a multi-colored LED, and the remaining two leads are attached to a switch  1506 . In some embodiments, the switch  1506  is connected to a user manipulated activation button and is activated when the activation button is depressed. In one aspect, once activated, the switch  1506  completes a circuit by electrically coupling the two leads together. As such, an electrical path is then established from an electrosurgical generator to the actuator to supply radio frequency power to one of the two leads attached to the rotational coupling clips  1502 . 
     Referring now to  FIG.  43   , the handle assembly is coupled to a rotational shaft assembly  1600 . In certain embodiments, coupling of the handle assembly to the rotational shaft assembly  1600  is configured to allow infinite 360 degree rotation of the jaw assembly  1130  with respect to the handle assembly. In the illustrated embodiment, the handle assembly  1110  connects to the shaft  1120  at five locations or connections providing a continuous 360 degree rotation of the entire shaft while simultaneously allowing complete actuation of the actuation handle  1114 , e.g., sealing and/or dividing of the vessel. As illustrated, the first two connections are rotational coupling clips  1502  which make contact with the rotational shaft assembly at the actuation tube and conductive sleeve. The next area of engagement or the third connection is a rotational hub assembly  1602  which is located between the two rotational coupling clips  1502 . 
     With continued reference to  FIG.  43   , the rotational shaft assembly  1600  is desirably contained within the right and left handle frames such that proximal and distal movement of the jaw assembly  1130  with respect to the handle assembly  1110  is prevented while allowing for rotational movement. For example, inwardly-extending flanges can be formed on the actuation handle  1112  that interfere with proximal and distal movement of the rotational hub assembly  1602 , rotational coupling clips  1502 , or other components of the rotational shaft assembly  1600 . The fourth connection is at a plurality of threaded nuts  1604  and the pull block  1250 . The fifth connection is between the blade lever  1608  and a rear blade shaft  1606 . The rotation shaft assembly  1600  can also comprises a rotation knob  1610  which is fixed to the outer cover tube. The rotation knob  1610  allows the surgeon to rotate the shaft of the device while gripping the handle. While the rotational shaft assembly  1600  is illustrated as having five connection locations with the actuation handle  1112 , in some embodiments, a rotational shaft assembly can have fewer connection locations, such as for example, 1, 2, 3, or 4 connection locations. In still other embodiments, it can be desirable that a rotational shaft assembly has more than 5 connection locations, such as, for example 6, 7, 8, or more than 8 connection locations. 
     Desirably, the rotational shaft assembly  1600  provides the vessel sealer/divider with continuous 360 degree rotation throughout operation of the electrosurgical instrument. By using rotational coupling clips  1502  for the electrical connections to the shaft, the shaft can operate, e.g., deliver RF energy, at any orientation or rotation of the jaw assembly  1130  relative to the handle assembly. Thus, advantageously, the surgeon is provided more surgical options for the placement and activation of the sealer/divider. Advantageously, with a rotational shaft assembly  1600 , the wires and electrical and mechanical connections, as such, do not interfere with continuous, infinite rotation of the shaft. To maintain a bipolar connection through the rotational shaft assembly  1600 , one of the electrical connections is electrically isolated from other conductive portions of the shaft. 
     As discussed in further detail below, in some embodiments, the sealer/divider can be configured to grasp with a gripping force within a predetermined range. In one embodiment, an overall tolerance stack-up over the length of the shaft can be controlled so that the force applied to the jaw assembly  1130  from the handle assembly can be maintained accurately within the predetermined range. The overall length of the shaft  1120  can be controlled by using threaded nuts  1604  and a threaded coupling. The threaded nuts  1604  can be adjusted to tightly control the length of the elongate shaft  1120 . The length is controlled by maintaining the location of the threaded nuts  1604  in relation to the hub portions of the shaft. In the illustrated embodiment, attached to the distal end of the actuation tube is a threaded coupling. Attached to the threaded coupling are two threaded nuts, which are configured to engage with the pull block  1250 . The pull block  1250  engages with the threaded nuts  1604  which are attached to the rear of the actuation tube, causing the actuation tube to move proximally. The described interaction can also be reversed so that the threaded nuts  1604  and coupling are attached to an outer cover tube rather than the actuation tube. In other embodiments, other length adjustment mechanisms can be used to control the overall tolerance stack-up such as a lock screw to selectively secure the position of the pull block  1250  at a desired location relative to the actuation tube or toothed ratchet interfaces defining set distance relationships between the pull bock and the actuation tube. In other embodiments, a length adjustment mechanism can be positioned at the distal end of the elongate shaft, e.g., where the elongate shaft interfaces with the jaw assembly  1130 . 
     Referring to  FIGS.  44 A- 44 D , the elongate shaft  1120  can comprise a plurality of actuation members extending therethrough. In the illustrated embodiment, the elongate shaft comprises an actuation tube  1122  coupling the jaw assembly  1130  with the handle assembly  1110  and a blade actuation shaft assembly  1124  coupling the blade trigger  1402  with the cutting blade. In some embodiments, the blade actuation shaft assembly  1124  comprises a two-piece shaft having a proximal portion and a distal portion. The proximal portion of the blade shaft assembly can terminate at a proximal end at an interface node  1126 . In the illustrated embodiment, the interface node  1126  comprises a generally spherical protrusion portion which is adapted to engage the blade advancing lever. In other embodiments, the interface node can comprise other geometries such as cubic or rectangular prismatic protrusions. In the illustrated embodiment, the proximal portion of the blade shaft is operatively coupled to the distal portion of the blade shaft assembly  1124 . The distal portion of the blade shaft can comprise a mount at its distal end for attachment of the cutting blade. In the illustrated embodiment, the mount comprises at least one heat stake post. In certain embodiments, both the proximal and distal portions of the blade shaft are at least partially positioned within a generally tubular section of the actuation tube  1122 . (see, e.g.,  FIG.  44 C ). 
     As discussed above with respect to length adjustment of the elongate shaft  1120 , in the illustrated embodiment attached to the distal end of the actuation tube  1122  is a threaded coupling  1150  ( FIG.  44 D ). As illustrated, attached to the threaded coupling  1150  are two thread nuts  1604 , which are configured to engage with the pull block  1250 . In the illustrated embodiment, the actuation tube  1122  is housed within an outer cover tube. While the actuation tube  1122  is illustrated as a generally tubular member that can be nested within the outer cover tube  1126 , and that can have a blade actuation shaft  1124  nested within it, in other embodiments, a non-tubular actuation member can be used, for example, a shaft, a rigid band, or a link, which, in certain embodiments can be positioned generally parallel to the blade actuation shaft within the outer cover tube. 
     With continued reference to  FIG.  44 A , in the illustrated embodiment, attached to the distal end of the outer cover tube  1126  is the rotational shaft assembly  1600 . The rotational shaft assembly  1600  comprises two mating hubs  1602  and a conductive sleeve  1610 . In the illustrated embodiment, the hubs  1602  snap together, engaging with the outer cover tube. In other embodiments, the hubs can be of a monolithic construction and configured to interface with mating features on the outer cover tube. The conductive sleeve  1610  can be attached to the proximal portion of the assembled hubs after they are attached to the outer cover tube. When the conductive sleeve  1610  is attached to the rear of the assembled hubs  1602 , the sleeve  1610  traps the exposed end of an isolated wire  1612  (see  FIG.  44 D ). In the illustrated embodiment, the isolated wire  1612  extends from its entrapment point under the conductive sleeve through a slot in the actuation tube  1122  and then inside a protective sleeve  1614 . The protective sleeve  1614  and isolated wire  1612  extend distally inside the actuation tube  1122 , towards the jaw assembly  1130 . In other embodiments, the isolated wire can be formed integrally with a protective sheath and no separate protective sleeve is present in the actuation tube. 
     With reference to  FIGS.  45 A- 45 C , attached to the distal end of the elongate shaft  1120  is the jaw assembly  1130 . In certain embodiments, the jaw assembly  1130  comprises a lower jaw  1134 , upper jaw  1132 , upper conductive assembly  1142 , lower nonconductive spacer  1144 , and jaw pivot pin  1146 . In the illustrated embodiments, the jaw pivot pin  1146  pivotally couples the upper and lower jaws  1132 ,  1134  and allows the upper jaw  1132  to pivot relative to the lower jaw  1134 . In other embodiments, other pivotal couplings are contemplated. As illustrated, the proximal portion of the upper jaw  1132  extends through the lower jaw  1134  and into a hole in the actuation tube  1122 . 
     In some embodiments, one jaw can be fixed with respect to the elongate shaft  1120  such that the opposing jaw pivots with respect to the fixed jaw between an open and a closed position. For example, in the illustrated embodiment, the proximal portion of the lower jaw  1134  extends inside the cover tube  1126  and is crimped in place, fixing the jaw assembly  1130  to the rotation shaft assembly  1600 . Thus, in the illustrated embodiment, the upper jaw  1132  is moveable with respect to a fixed lower jaw  1134 . In other embodiments, both jaws can be pivotally coupled to the elongate shaft such that both jaws can pivot with respect to each other. 
     Attached to the upper jaw  1132  is the upper conductive assembly  1142 , which comprises a nonconductive portion  1702  and a conductive pad  1704  (see  FIG.  45 B ). The nonconductive portion  1702  isolates the conductive pad  1704  from the upper jaw  1132 , likewise isolating it from the rest of the shaft assembly  1120 . The isolated wire  1612  can be routed to electrically couple the conductive pad  1704  on the upper jaw  1132  to the wiring harness  1500  in the handle assembly  1110 . In the illustrated embodiment, the isolated wire  1612  extends from the distal end of the protective sleeve which is housed at the proximal end of the lower jaw and extends into the upper jaw  1132 . The upper jaw  1132  can have a slot positioned to receive the isolated wire. The isolated wire  1612  then extends through a hole in the upper jaw  1132  and drops into a slot in the nonconductive portion. The isolated wire then extends to the distal end of the nonconductive portion and drops through to the conductive pad (see  FIG.  44 D ). 
     The jaw assembly  1130  can include one or more nonconductive space maintaining members such as spacers  1144  to reduce the risk that electrodes on the upper jaw  1132  and lower jaw  1134  can come into direct contact and create a short. In the illustrated embodiment, the lower nonconductive spacer  1144  is housed inside the u-groove portion of the lower jaw and contains space maintaining protrusions which prevent the conductive pad from contacting the lower jaw (see  FIG.  45 C ). 
     Turning now to some of the operational aspects of the electrosurgical instruments described herein, once a vessel  1030  or tissue bundle has been identified for sealing, the upper and lower jaws are placed around the tissue (see  FIG.  46 A ). The actuation handle  1114  is squeezed moving the actuation handle  1114  proximally with respect to the actuation handle  1112  (see  FIG.  46 B ). As the actuation handle  1114  moves proximally it pushes the pull block  1250  along the rails in the right and left handle frames. The pull block  1250  engages with the threaded nuts  1604  which are attached to the rear of the actuation tube  1122 , causing the actuation tube  1122  to move proximally. Proximal movement of the actuation tube pivots the upper jaw  1132 , coupled to the pull tube, towards the lower jaw, effectively clamping the tissue (see  FIG.  46 C ). The force applied to the tissue by the upper jaw is translated through the pull tube and pull block  1250  to the actuation handle  1114 . Once the preloaded force has been overcome, the actuation handle  1114  will begin to move the sliding pin  1206  distally (see  FIG.  46 D ). When the preload on the trigger spring has been overcome, the actuation handle  1114  pivot point shifts from the sliding pin  1206  to the rear portion of the pull block  1250  where it contacts the actuation trigger. The sliding pin  1206  can advance distally because the preloaded force on the trigger spring  1208  has been overcome. 
     The continued manipulation of the actuation handle  1114  pivots the actuation handle  1114  to a location where the actuation handle  1114  engages with the latch mechanism  1260  in the right and left handle frames that maintains the trigger in the engaged position and prevents the trigger from returning to an opened position. When the engaged position is reached and nothing is present between the upper and lower jaws  1132 ,  1134 , the trigger spring is extended to a distance that ensures that the force applied to the electrodes of the jaw assembly  1130  is near the lower end of the force range required for optimal vessel sealing. When a large, e.g., maximum, amount of tissue is placed in the jaws, the actuation handle  1114  extends the trigger spring  1208  a greater distance. However, the trigger spring  1208  ensures that the maximum amount of force applied does not exceed the maximum end of the force range used for optimal vessel sealing. From the engaged position, sealing radio frequency energy is applied to the tissue by depressing the power activation button. Once the tissue has been sealed, the actuation trigger can be reopened by continuing proximal advancement to a position that allows the actuation trigger&#39;s finger portion to disengage from the latch portions of the left and right handle frames. (See  FIGS.  46 A- 46 F )) 
     The floating dual pivoting mechanism including a sliding pin  1206  and a pull block  1250  described above desirably provides a minimum force, optimal for sealing vessels and tissue, is maintained regardless of the amount of substance contained between the upper and lower jaws. This mechanism also reduces the risk that an extremely large amount of force is applied to the tissue. If too much force is applied to a vessel or tissue bundle, potential damage could occur. Thus, if a very small vessel or thin tissue bundle is clamped within the jaw, the instrument applies the minimum amount of force required to obtain a good tissue weld. The same is true with a very large vessel or tissue bundle. Since the travel of the jaw can vary greatly depending on tissue thickness, the force applied by the jaw is adjustable. It is desired that the instrument be self-adjusting and automatic (no action from the user). The floating dual pivot mechanism described below provides the self-adjustment, applying a specific range of force along the length of the electrode. 
     Once the actuation handle  1114  has been depressed to a predetermined force range for optimal vessel sealing, it will engage the matching latch of the right and left handle frames, locking the actuation trigger from moving further distally (See  FIG.  46 E ). At this point the user can depress the activation button, applying the appropriate energy to the tissue for proper sealing. 
     Once the tissue has been sealed, the user can actuate the blade trigger  1402 . When the blade trigger  1402  is moved proximally, the blade lever pivots, forcing the front and rear blade shafts and cutting blade  1400  to move distally. The cutting blade advances forward and divides the sealed portion of the tissue (see  FIG.  46 F ). When the user releases the blade trigger  1402 , the blade spring resets the cutting blade to its original position. When the blade trigger  1402  has been returned to its original or initial position the user can continue to squeeze the actuation handle  1114  to open the upper jaw. Continued proximal movement of the actuation handle  1114  will disengage the actuation handle  1114  from the latch mechanism  1260  of the right and left handle frames by biasing the extended arm portion  1262  of the actuation trigger upwards, over the end of the latch, to a position where the trigger can be released (see  FIG.  46 G ). 
     The electrosurgical instrument is connectable to an electrosurgical generator specifically configured to apply the proper amount of energy to the tissue when the activation button is depressed, such as the electrosurgical generator described above. With reference to  FIG.  47   , the instrument is also connectable to an intermediate control unit  1800  in conjunction with an electrosurgical generator. The intermediate control unit  1800  can monitor the tissue sealing and ensure that the proper amount of sealing energy is applied to the tissue. The control unit  1800  in one aspect can have a set of cables configured to plug into most typical electrosurgical generators. The control unit also has a port for connecting the wiring harness  1500  plug from the instrument (see  FIG.  47   ). 
     With continued reference to  FIG.  47   , in certain embodiments, the non-sterile power controller interfaces with the sterile vessel sealer/divider through a cord extending from the sealer/divider beyond the sterile field and plugged into the controller. In one aspect, the controller regulates and/or distributes power from a non-sterile reusable power supply to which the controller is attached or integrated. In some embodiments, the controller can be configured for a single use to maintain sterility of the surgical environment. In order to prevent reuse of the non-reusable controller, the cord of the electrosurgical tool, once plugged into the non-sterile controller cannot be removed. This connection permanently couples the sterile and non-sterile portions, preventing the user from being able to disconnect the controller for reuse in unintended surgical procedures or purposes. (see  FIG.  47   ) 
     In grasping jaw assemblies such as the jaw assembly  1130  of the electrosurgical tool, the gripping force generated between the jaws can vary along the length of the jaws from a relative maximum Fmax near the proximal end to a relative minimum Fmin near the distal end. In some embodiments, the electrosurgical tool can be configured such that the forces are optimized along the length of the active electrode portions of the jaws, a predetermined force range for vessel sealing is maintained. A predetermined maximum amount of force utilized to obtain a proper vessel seal is desirably not exceeded at the proximal end of the active electrodes (closest to the pivot). In addition a gripping force at the distal most ends of the active electrodes is desirably greater than a predetermined minimum amount of force for optimal vessel sealing. Desirably, the gripping force generated at every point along the jaw assembly  1130  is within the range defined by the predetermined maximum force and the predetermined minimum force to achieve optimal sealing. (See  FIG.  48 A ). 
     In some embodiments, the electrode width to form vessel seals is between about 0.25 mm and about 1.5 mm. In other embodiments, the electrode width is desirably between about 0.4 mm and about 1 mm. In other embodiments, the electrode width is preferably between about 0.6 mm and 0.8 mm. In some embodiments, the electrode width is approximately 0.75 mm. With an electrode of 0.75 mm, and the sufficient pressure for this type of electrode to achieve a vessel seal is approximately 3 pounds (see  FIGS.  48 B and  48 C ). However it can bee seen from  FIG.  48 C  that a force range of approximately 0.4 pound to 2.3 kg on a 0.75 mm electrode can maintain burst pressures greater than 15 psi. In some embodiments, the jaw and electrode arrangement desirably can maintain a pressure of between 3 and 39 kg/cm{circumflex over ( )}2, more desirably 10-30 kg/cm{circumflex over ( )}2, and preferably approximately 23 kg/cm{circumflex over ( )}2. Embodiments having different electrode widths can have different force ranges. In order to maximize sealing surface area while still maintaining the electrode configuration described above, in some embodiments, multiple rows of 0.75 mm electrodes may be provided (see  FIG.  48 D ). 
     In some embodiments, electrode geometry on the conductive pads of the jaw assembly  1130  ensures that the sealing area completely encloses the distal portion of the blade cutting path. Single linear electrodes could cause vessel leakage when only a portion of a vessel is sealed. In one embodiment, the electrodes positioned on the jaw assembly  1130  comprise a single u-shaped electrode  1902  surface on each of the upper and lower jaws. Each u-shaped electrode can comprise generally parallel linear legs  1910  extending from a proximal end of the conductive pad of the jaw towards the distal end and a curved connector  1912  at the distal end extending from one leg to the opposite leg. Desirably, the u-shaped electrodes can completely encompass the distal end of the blade cutting path. In other embodiments, to provide a greater sealing area, two or more spaced u-shaped electrode surfaces on both the upper and lower jaws can be provided (see  FIG.  49   ). In some embodiments, the electrodes  1904  can be connected at the distal ends to create a completely enclosed seal (see  FIG.  49   ). In certain embodiments one or multiple bridge members  1908  between the u-shaped electrode  1906  surfaces can further ensure that the sealing area completely encloses the distal portion of the blade cutting path. 
     In some embodiments, for some surgical procedures the outer shape of the jaws  1130 ′ can be curved such that the distal ends of the jaws are offset with respect to the longitudinal axis from the proximal ends of the jaws to improve visibility for a user such as a surgeon. In embodiments with curved jaws, the u-shaped electrodes can also be provided in a curved fashion while still maintaining proper electrode width and spacing (see  FIG.  50   ). 
     With reference to  FIG.  51   , in certain embodiments, the electrosurgical device can include a tissue dissector formed on the jaw assembly  1130 ″. Advantageously, this integrated tissue dissector can facilitate dissection of non-vascular tissue either bluntly or electro-surgically, without having to exchange the vessel sealer/divider with another instrument. Thus, this multiple tool functionality can advantageously facilitate quicker surgical procedures. The reduced number of tool exchanges can be especially advantageous in laparoscopic procedures or procedures with relatively limited access as tool exchanges can be time consuming in these surgical environments. 
     With continued reference to  FIG.  51   , in some embodiments, one of the jaws of the jaw assembly  1130 ″ can have an extended distal end distally beyond the distal end of the other jaw (see  FIG.  51   ). In the illustrated embodiment, the lower jaw  1134 ″ can have an extended distal end. Advantageously, in embodiments where the lower jaw  1134 ″ is pivotally fixed to the elongate shaft, this extended arrangement can facilitate stability of the lower jaw during dissection. In other embodiments, the upper jaw  1132  can have an extended distal end, allowing the tissue dissector to be pivoted during the dissection operation by movement of the actuation handle  1114 . In some embodiments, the extended distal end can be tapered in shape such that the distal end is relatively short and narrow compared to relatively more proximal portions of the jaw. Advantageously, this tapered shape allows the distal end to access tissue positioned in relatively confined environments while reducing the risk that adjacent tissue is contacted. 
     With reference to  FIGS.  52 A,  52 B , In some embodiments, both jaws of the jaw assembly  1130 ′″ are tapered laterally and/or in height along the length of the jaw&#39;s electrode portions, or at least part of the electrode portions. In these embodiments, the jaw assembly  1130 ′″ has a low-profile distal end which can be used for tissue dissection. Advantageously, the low-profile distal end can also enhance access of the jaw assembly  1130 ′″ to relatively confined surgical environments. 
     With reference to  FIGS.  53 A,  53 B , in certain embodiments, a cutting/coagulating electrode can be disposed on an exterior surface of the jaw assembly  1130  to provide tissue dissection. In some embodiments, the cut/coagulation electrode is located on the jaw at, for example, the distal end on the outer surface of either the upper or lower jaw (see  FIG.  53 A ). Desirably, the electrode  1920  can be electrically isolated or insulated from other components of the jaw assembly  1130 , providing an active electrode for the bi-polar instrument. As such, an isolated wire can extend from the cut/coagulation electrode  1920  to the proximal end of the elongate shaft  1120  (similar to the isolated wire extending from the conductive pad on the upper jaw) to electrically couple the cut/coagulation electrode to the wiring harness  1500  of the electrosurgical tool in the handle assembly. In some embodiments, the isolated wire can extend within a protective sleeve within the outer cover tube of the elongate shaft. In other embodiments, the isolated wire can be integrally formed with a protective sheath. The isolated wire also in one aspect is coupled to a rotational connection, e.g., a rotational clip, similar to the isolated wire extending for the conductive pad. 
     With reference to  FIG.  53 B , the cut/coagulation electrode in one aspect can be selectively activated by at least one actuation button  1922 ,  1924  or switch on the handle assembly  1110 . In some embodiments, the handle assembly can comprise a cut button  1922  to actuate the electrode with a tissue cutting electrosurgical signal and a coagulation button  1924  to actuate the electrode with a tissue coagulating electrosurgical signal. For example, in  FIG.  53 B , separate cut and coagulation buttons are illustrated on the actuator adjacent a tissue sealing button to actuate the electrodes on inner surfaces of the jaws. In other embodiments, a single, multifunction switch or button can actuate the cut/coagulation electrode in the desired configuration. In still other embodiments, the cut/coagulation electrode can be configured to receive only a cutting or only a coagulation electrosurgical signal, and a single corresponding actuation button or switch can be used to selectively actuate the electrode. 
     The vessel sealer/divider can use thin metallic tubes and small diameter machined rods for the internal elongated components used to actuate jaws such as the actuation tube and the blade actuation shaft. However, such components can be costly and in some embodiments, manufacturing and materials costs can be desirably reduced through the use of elongate injection molded plastic components. As discussed above with respect to the blade actuation shaft  1124 , in some embodiments, costs and manufacturing difficulties can be reduced further through the use of an elongated shaft formed of two mating polymer shaft sections  124   a ,  1124   b  such as a proximal or rear shaft portion and a distal or front shaft portion. In some embodiments, the two shaft portions  1124   a ,  1124   b  can be connected by interlocks  1960 , e.g., projections on one shaft section or component mating with corresponding slots on the other shaft section, to maintain concentricity and prevent unnecessary movement in their axial direction (see  FIG.  54 A-C ). In other embodiments, other mating structures can be formed on the two mating shaft portions. For example, one of the shaft portions can be formed with one or more barbs thereon and the other shaft portion can be formed with a recess configured to receive and retain the barbs. In still other embodiments, the two mating shaft portions can be adhered with a chemical adhesive or epoxy, either in addition to, or in place of interlocks formed on the shaft portions. 
     With reference to  FIGS.  55 A and  55 B , in certain embodiments, the elongate shaft  1120  of the electrosurgical tool can be configured such that the outer surface thereof does not translate proximally and distally during actuation of the jaw assembly  1130  by the actuation handle  1114 . In other embodiments, moving the outer shaft component can be used to open and close the jaws and provide a proper clamping force without manipulating the handle assembly. However, moving the outer shaft component can also cause the vessel sealer/divider to move in relation to a trocar seal and thus potentially complicating a gas seal between the sealer/divider and the insufflated body cavity. As such, it can be desirable that the outer most shaft components remaining stationary throughout a surgical procedure. As such, in certain embodiments, the elongate shaft maintains the moving components (e.g., the pull tube and the blade actuation shaft) on the inside of a stationary outer cover tube (which may also con a dielectric coating or insulating sleeve). With continued reference to  FIGS.  55 A and  55 B , as illustrated, the stationary outer cover tube is connected to the stationary portion of the jaws, while the pull tube is connected to the moving portion of the jaws (e.g., the upper jaw). Thus, as the jaw assembly  1130  is actuated from an open position ( FIG.  55 A ) to a closed position ( FIG.  55 B ), the pull tube translates longitudinally proximally while the outer cover sleeve remains stationary. 
     As discussed above with respect to the electrosurgical system, in certain embodiments the electrosurgical tool can comprise a memory such as a tool ID chip mounted on a small PCB. In some embodiments, the PCB can be disposed on or in the actuation handle  1112 . In other embodiments, the PCB and chip can be integrated in the plug of the wiring harness. The PCB and chip can be molded with a tool-specific pattern. The tool ID chip and PCB can be electrically connected into the wiring harness and plug of the electrosurgical tool. A “spacer” between the plug and the tool ID chip, can allow the use of the same connector for all tools. In some embodiments, the spacer can have the same shape for all tools on the plug side, and a tool-specific pattern on the chip side such that during assembly there is a reduced risk that a PCB for one type of electrosurgical tool can be assembled into a different type of electrosurgical tool. 
     As discussed above with respect to the electrosurgical system, when the plug is inserted into the generator, the encrypted tool information stored in the memory is verified. General information (serial number of tool and generator) are exchanged, and the tool-specific software is uploaded into the generator. With completion of each tool use, tool-specific information (connections to generator, individual tool uses, errors, etc.) can be communicated, if needed, and stored in memory of the generator, the tool chip or both. In exemplary embodiment, the generator&#39;s memory is sized to hold data for about two months while the tool chip&#39;s memory can hold data for one surgical procedure. 
     As discussed above with respect to the electrosurgical system, in some embodiments, the electrosurgical fusion tool can be used in a system which monitors various operational parameters and determines a radiofrequency endpoint based on phase angle. 
     Although the present invention has been described in certain specific aspects, many additional modifications and variations would be apparent to those skilled in the art. It is therefore to be understood that the present invention may be practiced otherwise than specifically described, including various changes in the size, shape and materials, without departing from the scope and spirit of the present invention. Thus, embodiments of the present invention should be considered in all respects as illustrative and not restrictive. 
     Electrosurgical Dissection Tool 
     Laparoscopic surgical procedures typically require the dissection of connective or vascular tissue. Depending on factors such as tissue type, size, location and condition of the specific tissue, different tools and techniques can be used to perform a specific procedure. The choice of an individual tool can be based on functionality combined with a desire that the selected tool provide relatively little traumatic damage to the surrounding tissue. As an example, the dissection of connective tissue is usually performed by mechanical or electrosurgical cutting, whereas the dissection of vascular tissue typically relies on ligating techniques employing clips or staplers followed by a mechanical cut. Consequently, a typical laparoscopic procedure including dissection of both connective tissue and vascular tissue calls for multiple tools being consecutively exchanged through trocar access ports to the surgical site. This tool exchange increases both the cost and time of the surgical procedure. It is hence desirable to provide multi-functional tools that can greatly reduce the number of tool exchanges during laparoscopic procedures. 
     Referring now to  FIG.  56   , in the illustrated embodiment, a bloodless tissue-dissecting tool  2101  comprises a proximal hand-piece  2102  that connects through a shaft  2103  to a distal end-piece  2104 . Activation of the trigger  2105  on the hand-piece  2102  allows closing and opening of the jaw elements  2106 ,  2107  on the distal end-piece  2104  so that tissue can be clamped between the upper  2106  and lower  2107  jaw elements. 
     With continued reference to  FIG.  56   , in some embodiments, the tool  2101  can be configured to be electrically coupled to an electrosurgical generator. For example, in some embodiments, the tool  2101  can include an integrated power cord, or a socket or other connector adapted to receive a power cord. At least a portion of the tool can be selectively energized through actuation of a control or switch on the electrosurgical generator. For example, in some embodiments, the tool can be energized with a handswitch or a footswitch on or coupled to the electrosurgical generator. 
     With reference to  FIG.  57   , an exemplary prior art electrosurgical device is illustrated. Electrosurgical tissue sealing devices that include a mechanical cutter can be used to first electrosurgically coagulate and then mechanically cut through a variety of tissue types. Certain harmonic tissue dividers can also be used to coagulate and/or to dissect a variety of tissue, ranging from connective to highly vascular tissue, such as organs. 
     As schematically depicted in  FIG.  57   , prior-art electrosurgical tissue dissectors include a lower jaw forming a first electrode  2201  and an upper jaw forming a second electrode  2202 . In the prior art devices, the two jaw elements—or electrodes  2201 ,  2202 —supply a relatively large amount of pressure to the tissue. High pressure with simultaneous application of electrical energy to the compressed tissue can be used to permanently occlude very large blood vessels by electrosurgical vessel fusion. After the electrical fusion process has been completed, the tissue can be separated by advancing a mechanical blade  2203 . 
     In contrast to the prior art electrosurgical devices, with reference to  FIG.  58   a   , one embodiment of an electrosurgical tool that can be configured in either an electrosurgical coagulation state or an electrosurgical cutting state is shown. In the illustrated embodiment, a lower jaw element  2301  comprises a first coagulating electrode  2302 , a second coagulating electrode  2303 , and an electrosurgical cutting electrode  2304 . Each of the electrodes can be electrically isolated from each other by insulating members  2305 . The upper jaw  2306  is not energized in this embodiment, but is merely used to press tissue against the lower jaw element  2301 . 
     With the electrode arrangement illustrated in  FIG.  58   a   , tissue that is in contact with the lower jaw element  2301  can be coagulated by electrically coupling each of the two coagulation electrodes  2302 ,  2303  with the corresponding outlet of a bipolar electrosurgical unit. Here, the two coagulation electrodes  2302  and  2303  can be supplied with electrical energy having opposite polarities. In some embodiments, it can be desirable that the supplied electrical energy has a potential difference of no more than 200V to reduce the risk of arcing and that electrode  2302  and  2303  have the same contact area with the tissue. The latter ensures the same electrosurgical effect for both electrodes. 
     With continued reference to  FIG.  58   a   , after the two coagulation electrodes  2302 ,  2303  have achieved substantial hemostasis within the coagulated tissue volume, the tissue can be electrosurgically cut by applying energy to an electrosurgical cutting electrode  2304 . During the electrosurgical cutting operation, the two coagulation electrodes  2302 ,  2303  can be electrically coupled to a corresponding outlet or outlets of a bipolar electrosurgical unit to function as return electrodes. Here, the potential difference between the cutting electrode  2304  and the two return electrodes  2302  and  2303  can desirably be between approximately 300-500V, while the two return electrodes can desirably be substantially equipotential. 
     With continued reference to  FIG.  58   a   , in some embodiments, it can be desirable that the relative contact area of the electrodes with the tissue is much smaller for the cutting electrode  2304  than for the return electrodes  2302 ,  2303 . For example, in some embodiments, desirably the cutting electrode can have a contact area that is between approximately 1% and 20% as large as a contact area of one of the return electrodes  2302 ,  2303 . More desirably, the cutting electrode can have a contact area that is between about 5% and 10% as large as a contact area of one of the return electrodes  2302 ,  2303 . In one embodiment, the cutting electrode can have a contact area that is approximately 10% as large as a contact area of one of the return electrodes  2302 ,  2303 . This relative proportion between cutting area sizes lead to a relatively high current density (and hence high power density) in tissue close to the cutting electrode, which facilitates localized vaporization, or electrosurgical cutting of the tissue. 
     With continued reference to  FIG.  58   a   , an additional aspect of the illustrated electrode arrangement is that the lower jaw  2301  can be used for both coagulation and cutting, regardless of whether the jaws are in an opened or closed position. This multiple functionality is advantageous when using the tool to spot-coagulate tissue, or to dissect tissue by configuring the tool in a cutting state and brushing the tool against the tissue. 
     Another embodiment of electrode arrangement for a surgical tool is illustrated in  FIG.  58   b   . In the illustrated embodiment, the upper jaw  2306 ′ is not only used to press tissue against the lower jaw element  2301 , but it also includes an upper electrode  2307  disposed thereon which can be supplied with electrical energy. Tissue can be coagulated by supplying the two lower coagulation electrodes  2302 ,  2303  with a first electrical polarity, and the upper electrode  2307  with a second, opposing polarity from a bipolar electrosurgical unit. Again, it is desirable that when configured for coagulation, the potential difference between the upper electrode  2307  and the two lower electrodes  2302 ,  2303  does not exceed 200V to reduce the risk of arcing to the tissue and that electrode  2307  has the same contact area with the tissue as the combined surface area of electrodes  2302  and  2303 . The latter ensures the same electrosurgical effect for both electrode sides. 
     With continued reference to  FIG.  58   b   , after hemostasis of the tissue between the upper electrode  2306 ′ and the two lower electrodes  2302 ,  2303  has been substantially achieved, the tissue can be electrosurgically cut by supplying the electrosurgical cutting electrode  2304  with electrical energy. The upper coagulation electrode  2307  on the upper jaw  2306 ′ can be configured as a return electrode by electrically coupling it with the corresponding outlet of a bipolar electrosurgical unit. 
     With continued reference to  FIG.  58   b   , when the surgical tool is configured as a electrosurgical cutting device, desirably the potential difference between the cutting electrode  2304  and the return electrode  2307  is between approximately 300-500V. In some embodiments, it can be desirable that the contact area of the electrodes with the tissue is much smaller for the cutting electrode  2304  than with the return electrode  2307  on the upper jaw  2306 ′. For example, in some embodiments, desirably the cutting electrode can have a contact area that is between approximately 1% and 20% as large as a contact area of the return electrode  2307 . More desirably, the cutting electrode can have a contact area that is between about 5% and 10% as large as a contact area of the return electrode  2307 . In one embodiment, the cutting electrode can have a contact area that is approximately 10% as large as a contact area of the return electrode  2307 . This relative sizing can lead to relatively high current density (and hence high power density) in the tissue close to the cutting electrode  2304 , which facilitates localized vaporization, or electrosurgical cutting of the tissue. With the surgical tool distal end of  FIG.  58   b    having electrodes  2302 ,  2303 ,  2304 ,  2307  as described above, only tissue between the two jaw elements can be coagulated and/or cut. Thus, unlike the embodiment of  FIG.  58   a   , the tool illustrated in  FIG.  58   b    is not configured to be used by employing the lower electrode only. 
     Another embodiment of electrode arrangement for a surgical tool is illustrated in  FIG.  58   c   . In the illustrated embodiment, the upper jaw  2306 ″ includes an upper electrode  2307 ′, but also shows two cutting electrodes  2304  and  2309  that are sandwiched between two coagulation electrodes  2302  and  2303 . In difference to the embodiment shown in  FIG.  58   b   , both coagulation and cutting is distinguished for cases where the hand tool (and hence the jaw members) are fully opened or not fully opened. With a fully opened tool, tissue can be coagulated by applying the two lower coagulation electrodes  2302  and  2303  with opposing polarities, and will be cut by applying cutting electrode  2304  with the first and both electrodes  2302  and  2303  to the second polarity. In difference, a not fully opened tool will coagulate tissue by applying both lower coagulation electrodes  2302  and  2303  with one polarity and electrode  2307 ′ to the opposing one, while cutting occurs between electrode  2309  and return electrode  2307 ′. Again, it is desirable that when configured for coagulation, the potential difference between the two lower electrodes  2302  and  2303  (tool fully open) or the upper electrode  2307 ′ and the two lower electrodes  2302 ,  2303  (tool not fully open) does not exceed 200V to reduce the risk of arcing to the tissue. 
     The separation of cutting electrodes  2304  and  2309  facilitates cutting of tissue that is positioned within the upper and lower jaw elements (not fully opened), or cutting of tissue in contact with the bottom side of the tool. The separation prevents inadvertent cutting of tissue. 
     Another embodiment of electrode arrangement for a surgical tool is illustrated in  FIG.  58   d    where the upper jaw  2306 ′″ includes two separate electrodes  2307 ″ and  2308 . In this configuration, the upper jaw element  2306 ′″ can be used to press tissue against the lower jaw element  2301 , but can also supply electrical energy. 
     With continued reference to  FIG.  58   d   , the electrodes  2302 ,  2303 ,  2307 ″,  2308  can be selectively configured to a coagulation state. By supplying the coagulation electrodes  2302 ,  2303  on the lower jaw  2301  and the two coagulation electrodes  2307 ′,  2308  on the upper jaw  2306 ′″ with alternating polarities, tissue within the jaws can be coagulated. For example, in one possible coagulation state configuration, one coagulation electrode  2302  on the lower jaw  2301 , and one coagulation electrode  2308  on the upper jaw  2306 ′″ can be electrically coupled to a source of electrical energy having a first polarity. The other coagulation electrode  2303  on the lower jaw  2301 , and the other coagulation electrode  2307 ″ on the upper jaw  2306 ′″ can be electrically coupled to a source of electrical energy having a second polarity generally opposite the first polarity. While this is an illustrative example, it is contemplated that other combinations of connections of the electrodes  2302 ,  2303 ,  2307 ″,  2308  with electrical energy sources are possible to configure the tool in a coagulation state. It can be desirable that the contact area of the opposing coagulation electrode(s) are the same to provide the same electrosurgical effect for both electrode sides. 
     With continued reference to  FIG.  58   d   , after homeostasis of the tissue between the upper electrodes  2307 ″,  2308  and the two lower electrodes  2302 ,  2303  by application of electrical energy with the electrodes in the coagulation state, the tissue can be electrosurgically cut. The distal end of the surgical tool can be configured into a cutting state by supplying the electrosurgical cutting electrode  2304  with electrical energy. In various embodiments, one, some, or all of the other electrodes  2302 ,  2303 ,  2307 ″,  2308  can be configured to function as return electrodes when the tool is in a cutting state by electrically coupling them with the corresponding outlet of a bipolar electrosurgical unit. 
     With continued reference to  FIG.  58   d   , when the tool is configured in a cutting state, the potential difference between the cutting electrode and the return electrode is desirably between approximately 300-500V. Further, it can be desirable that the relative contact area of the electrodes with the tissue is much smaller for the cutting electrode  2304  than for any of the return electrodes  2302 ,  2303 ,  2307 ″,  2308  or combinations thereof. For example, in some embodiments, desirably the cutting electrode  2304  can have a contact area that is between approximately 1% and 20% as large as a contact area of one of the return electrodes. More desirably, the cutting electrode can have a contact area that is between about 5% and 10% as large as a contact area of one of the return electrodes. In one embodiment, the cutting electrode can have a contact area that is approximately 10% as large as a contact area of one of the return electrodes. Just as with the embodiment illustrated and described with respect to  FIG.  58   a   , the electrode arrangement illustrated in the embodiment of  FIG.  58   d    can be used to spot-coagulate tissue, or to dissect the tissue when “brushing” the tool against it in a cutting mode. 
     The practicality of the tool configurations of  FIGS.  58   a  through  58   d    can be further enhanced by selective activation and/or deactivation of the selected electrodes. In some embodiments, this selective activation and deactivation can be performed by operator-depressed electrical switches such as wired or wireless hand or foot operated switches, or switches positioned on the hand-piece. The electrosurgical unit will then address specific electrodes, depending on how far the jaws are opened and closed. 
       FIG.  59   a    illustrates a schematic circuit diagram for an electrode arrangement as given in  FIG.  58   a   . Here, activation of a single-pole electrical switch  401  connects the outer coagulating electrodes  2302 ,  2303  to opposing polarities, while the center “cutting” electrode  2304  remains disengaged. This setting configures the electrodes in a coagulation state. Alternately, activation of a double-pole electrical switch  402  supplies the center “cutting” electrode  2304  with electrical energy having a first polarity, and the outer return electrodes  2302 ,  2303  with electrical energy having a second polarity generally opposing the first polarity. This setting configures the electrodes in a cutting state. As a result, the tool can be used for electrosurgical coagulation and/or cutting, and hence can perform the bloodless dissection of tissue. 
       FIG.  59   b    illustrates a schematic power supply circuit that can be used for the electrode arrangement shown in  FIG.  58   b   . In the illustrated embodiment, activation of a double-pole electrical switch  2403  connects the two outer coagulating electrodes  2302 ,  2303  on the lower jaw to a supply of electrical energy of a first polarity, and the coagulating electrode  2307  on the upper jaw to a supply of electrical energy of a second polarity substantially opposite the first polarity. With the switch  2403  in this position, the cutting electrode  2304  remains disengaged. This setting configures the electrodes of the surgical tool in a coagulation state. Alternately, activation of a single-pole electrical switch  2404  allows the lower jaw electrodes  2302 ,  2303  to be used for coagulation. The electrode on the upper jaw  2307  and the cutting electrode  2304  remain disengaged in this alternate coagulation configuration. To dissect tissue after it has been coagulated, a separate electrode outlet  2405  on an electrosurgical generator is used to address the cutting electrode  2304 . Desirably, the cutting electrode is supplied with voltages of 300-500V with respect to the two return electrodes  2302 ,  2303  on the lower jaw. 
       FIG.  59   c    illustrates a schematic power supply circuit that can be used to address the electrode arrangement of  FIG.  58   d   . In the illustrated embodiment, activation of a double-pole electrical switch  2406  connects the two coagulating electrodes  2302 ,  2303 ,  2307 ″,  2308  on both the lower and upper jaw to sources of electrical energy having opposing polarities. The cutting electrode  2304  remains disengaged. This setting can be used to configure the electrodes of a surgical tool in a coagulation state to coagulate tissue that is clamped between the upper and lower jaw element. Alternately, in other embodiments, a second coagulation double-pole switch  2407  can be implemented to separate the activation of the upper and lower jaws such that one or both jaws can be selectively actuated during a coagulation state. To utilize the lower jaw of the tool for electrosurgical cutting of coagulated tissue, activation of the cutting double-pole switch  2408  connects the cutting electrode  2304  to a source of electrical energy having a first polarity and the two return electrodes  2302 ,  2303  to a source of electrical energy having a second polarity substantially opposite the first polarity. The voltage supplied by the generator for this setting is desirably between approximately 300-500V to facilitate electrosurgical cutting. In the illustrated embodiment, the electrodes  2307 ″,  2308  on the upper jaw element remain unaddressed during electrosurgical cutting. 
     As discussed in more detail above, the activation (or deactivation) of specific electrodes can configure the tool in a coagulation state or a cutting state. In certain embodiments, the selective activation and deactivation of specific electrodes can be facilitated by push-buttons, switches, or other electrical switching devices mounted on the hand-piece of the laparoscopic tool, or wired or wireless switches. In other embodiments, the selective activation and deactivation of specific electrodes can be facilitated by switches or other electrical switching devices that are incorporated into the handle mechanism of the hand-piece to switch at various positions of the jaw elements. 
     Regarding the circuit shown in  FIG.  59   a   , referring to the tool shown in  FIG.  58   a   , switching devices mounted on the hand-piece can be used to allow a user to selectively configure the electrodes on the tool. Switch  2401  can be a hand-activated switching device mounted on the hand-piece that can be selectively activated to configure the electrodes of the tool in a coagulation state. Switch  2402  can be a hand-activated switching device mounted on the hand-piece that can be selectively activated to configure the electrodes of the tool in a cutting state. In another embodiment, switches  2401 ,  2402  can be incorporated into the handle mechanism to such that the tool is automatically switched from a coagulation state to a cutting state at a predetermined position of the clamping members. 
     One benefit of switching the electrodes from a coagulation state to a cutting state at different positions of the jaw elements (e.g., open and nearly closed jaws) can be seen with respect to the embodiment of  FIG.  59   b   . In certain embodiments, switches  2403  and  2404  can be incorporated within the handle of the surgical tool for self-switching based on the position of the trigger mechanism, rather than on the outside of the hand tool for hand-activation. In one embodiment, switch  2403  can be disengaged and switch  2404  engaged in a fully open jaw element position. Thus, with the jaw elements fully opened, the switches  2403 ,  2404  can be configured such that only the lower jaw element can be used for spot coagulation. In this embodiment when the trigger of the hand-piece is actuated to move the jaw elements closed from the fully opened jaw position, switch  2404  is disengaged and  2403  simultaneously engaged. Thus, with the jaw elements moved into a partially-closed configuration, the tool can be used to coagulate or cut tissue that is clamped between the upper and lower jaw element. 
     In the described embodiment, the electrode switches are automatically actuated as the jaw elements are closed. Although the described embodiment includes a switch point between a coagulation state and a cutting state upon commencement of closure from the jaws fully opened position, other embodiments can have different switching positions. For example, with this automatic switching, the switches  2403 ,  2404  can be configured such that the electrodes are activated and deactivated at any position in an opening or closing cycle. In other embodiments, a surgical tool can include the electrode configuration of  FIG.  58   b    and the switching circuit of  FIG.  59   b    with the switches  2403 ,  2404  configured for manual actuation, such as by positioning on the tool hand-piece. 
     Similarly, in certain embodiments, a surgical tool having the electrode configuration of  FIG.  58   d    with the switching circuit of  FIG.  59   c    can have the switches  2406 ,  2408  incorporated into the trigger mechanism for automatic switching between a coagulation state and a cutting state at certain jaw element positions. In certain embodiments, it can also be desirable to incorporate the second coagulation switch  2407  into the trigger mechanism of the hand-piece, disengaging the electrodes on the upper jaw element in predetermined jaw position such as a fully opened jaw position. This switching arrangement of the second coagulation switch  2407  allows for example to spot-coagulate tissue using the lower jaw element without inadvertently touching tissue with the electrodes on the upper jaw element. In other embodiments, it can be desirable for the second coagulation switch  2407  to be positioned on the hand-piece to be manually actuated by a user, allowing a user to selectively engage and disengage the electrodes on the upper jaw element. In other embodiments, all of the switches  2406 ,  2407 ,  2408  of the switching circuit of  FIG.  59   c    can be positioned on the hand-piece of the surgical tool to be manually actuated by the user. 
     With reference to  FIG.  60   , one configuration of tool switching is illustrated. In the illustrated embodiment, electrical contacts are incorporated both into the hand-piece  2501  and the trigger  2502 . For example, as illustrated, the hand-piece  2501  includes a first electrical contact  2504 , a second electrical contact  2506 , and a third electrical contact  2507  positioned therein. In the illustrated embodiment, the trigger  2502  includes a first electrical contact  2503  and a second electrical contact  2505 . All of the electrical contacts  2503 ,  2504 ,  2505 ,  2506 ,  2507  are positioned to engage and disengage one another at predetermined relative positions of the trigger  2502  and the hand-piece  2501 . 
     With continued reference to  FIG.  60   , as shown, the first contact  2503  on the trigger  2502  engages the first contact  2504  on the hand-piece  2501  when the jaws are in a fully opened position, but the first contacts  2503 ,  2504  are disconnected when the trigger  2502  is moved from the open position to close the jaws. In the illustrated embodiment, with the jaws in the fully opened position, the second contact  2505  on the trigger  2502  engages the second contact  2506  on the hand-piece  2501 . But, the second contacts  2505 ,  2506  are disconnected when the trigger  2502  is moved from the open position to close the jaws. As the jaws are closed further, the second contact  2505  on the trigger  2502  becomes engaged with the third contact  2507  on the hand-piece  2501 , and the first contact  2503  on the trigger engages the second contact  2506  on the hand-piece  2501 . This engagement allows switching of the polarity of the contacts  2507  as the hand-piece is closed further. As a result, and with reference to  FIG.  58   b   , the switching mechanism in  FIG.  60    allows for activation of the upper electrode  2307  and a lower coagulating electrode  2303  with opposing polarities in a fully open jaw position. With progressive tissue desiccation, the jaws start to close, and the upper electrode  2307  becomes electrically disengaged (by disconnecting contact  2503  and  2504  in  FIG.  60   ), whereas the lower electrode  2303  is switched to the same polarity as the second electrode  2302  (by connecting contact  2505  from  2506  to contact  2507  in  FIG.  60   ). In a separate step, the desiccated tissue between the upper and lower jaw elements can now be electrosurgically dissected. 
     With reference to  FIG.  61   , another embodiment of a switching mechanism is illustrated with the jaw members in a fully opened position. In the illustrated embodiment, concentric contact strips are disposed on the hand-piece and opposing contact pins are mounted on the trigger. In other embodiments, contact pins can be mounted on the hand-piece and contact strips positioned on the trigger. In the illustrated embodiment, trigger movement allows the pin contacts (which are connected to specific electrodes) to be supplied with electrical energy at certain tool positions. In some embodiments, the polarity of a single pin (i.e., the same electrode) might change as the jaws are opened or closed. 
     One contact strip and pin arrangement is illustrated in  FIG.  61    for an electrode configuration of  FIG.  3   b   . In the illustrated embodiment, pin  2601  is electrically coupled to the electrode  2307  ( FIG.  58   b   ) on the upper jaw member and is disengaged. As illustrated, pin  2602  is electrically coupled to one of the coagulating electrodes  2302 ,  2303  ( FIG.  58   b   ) on the lower jaw. As illustrated, pin  2602  is engaged as the trigger is moved from the “fully-open” position to a partially closed position. With further advancement of trigger, pin  2602  changes to the same polarity as the second coagulating electrode so that both can be used as return electrodes for cutting. 
     While both  FIG.  60    and  FIG.  61    show active switching mechanisms in the hand tool (where active electrodes can be switched), which allows the tools to be used with “conventional” electrosurgical generators,  FIG.  62    shows a configuration for passive switching. Here, a momentary switch  2701  is mounted in the handle and is closed by a trigger  2702  when lever  2703  is brought into the “fully open” position. 
     Similarly,  FIG.  63    shows the incorporation of two momentary switches  2801  and  2802  that are closed by trigger  2803  and  2804  in the “tool fully open” and “tool fully closed” position, respectively. The closing of the momentary switches as shown in  FIGS.  62  and  63    is then used for logic switching of multi-electrode generators, as described in the following. 
       FIG.  64    shows a schematic of a multi-electrode switching power supply for directly connecting individual tool electrodes (such as all individual electrodes in  FIGS.  58   a  through  58   d   ) to an internal RF power source. Instead of switching two polarities of an external electrosurgical unit to different electrodes with active switches in the hand tools, this arrangement facilitates population of individually-connected electrodes with different polarities by switching within the power supply. Depending on the tool position, as determined by tool position switches shown in  FIGS.  62  and  63   , the electrodes can be populated differently as determined by pre-determined logic. As such, the five electrode connection points  2901  through  2905  are connected to a relay bank  2906  to a bus bar  2907 . Through selected switching of all relays in the relay bank  2906 , each outlet point  2901  through  2905  can be independently and/or concurrently connected to the plant connection points  2908  and  2909 , respectively. The plant connection points  2908  and  2909  themselves can be connected through the relay bank  2910  to the two outlets of a tissue measurement circuit  2911 , or a RF plant  2912 . 
     With reference to  FIG.  65   , in certain embodiments, methods of using an electrosurgical tool for substantially bloodless tissue dissection are schematically illustrated. The illustrated method includes a positioning step  2952 , a tissue assessment step  2954 , an applying-electrical-energy-to-coagulate step  2956 , a tissue measurement step  2958 , a switching step  2960 , and an applying-electrical-energy-to-cut step  2962 . In the positioning step  2952  an electrosurgical tool having a plurality of electrodes being configurable in one of a coagulation configuration and a cutting configuration is positioned adjacent to tissue to be dissected. In certain embodiments, the electrosurgical tool comprises aspects of the electrosurgical tools discussed herein and illustrated in  FIGS.  56  and  58 - 63   . 
     In the tissue assessment step  2954 , a measurement signal is applied to the tissue by the coagulation electrodes to determine a future trigger level to switch from coagulation to cutting. This determination can be achieved by measuring the product of conductivity and permittivity of the tissue, pointing to the desired electrical phase shift switching level for the respective tissue. For example, in some embodiments, desirable cutting switching levels occur at 10 degrees to 40 degrees. More desirably, the preferred switching level for blood vessels is between 10 to 30 degrees phase shift, while for highly vascular tissue (such as organs) it is rather between 20 to 40 degrees. 
     In the applying-electrical-energy-to-coagulate step  2956 , electrical energy is applied to the electrosurgical tool in a coagulation configuration to achieve hemostasis in the tissue. In various embodiments discussed herein, electrode configurations for coagulation are provided. For example, applying electrical energy to the electrosurgical tool in the coagulation configuration can comprise supplying one of a plurality of electrodes with electrical energy having a first polarity and supplying another of the plurality of electrodes with electrical energy having a second polarity generally opposite the first polarity. Desirably, a potential difference between the electrode having the first polarity and the electrode having the second polarity is no more than approximately 200 V. 
     During the coagulation process of the tissue the phase shift between applied voltage and incurred current is measured concurrently in step  2958  to provide feedback of the coagulation status. Once the pre-determined switching level is reached, the process will proceed to the switching step  2960 . 
     In the switching step  2960 , as discussed above, some embodiments of electrosurgical tool can comprise a handle assembly including a switching mechanism. This switching mechanism can selectively configure the electrosurgical tool in either the coagulation configuration or the cutting configuration depending on a position of a trigger of the handle assembly. As discussed above, in some embodiments the switching mechanism can be configured such that with the electrosurgical tool in an open position, the electrodes are configured in the coagulation configuration. The switching mechanism can further be configured such that when the electrosurgical tool is moved towards a closed position, the electrodes are configured in the cutting configuration. In other embodiments, switching of the configuration of electrodes from the coagulation configuration to the cutting configuration can occur at different predetermined positions of the trigger of the handle assembly. In yet another embodiment, the switching can occur within a multi-electrode power supply as shown in  FIG.  64   . 
     In the applying-electrical-energy-to-cut step  2962 , electrical energy is applied to the electrosurgical tool in a cutting configuration to dissect the tissue. In various embodiments discussed herein, electrode configurations for cutting are provided. For example, applying electrical energy to the electrosurgical tool in the cutting configuration can comprise supplying one of a plurality of electrodes with electrical energy and configuring another of the plurality of electrodes as a return electrode. Desirably, a potential difference between the cutting electrode and the return electrode is between approximately 300 V and approximately 500 V. 
     Electrosurgical Tissue Stapler 
     Historically, connecting or reconnecting living tissue has involved the use of suture, clips or staples. More recently, the use of electricity or heat has come to be used to complete the connection of living tissue or seal connected tissue against leakage or bleeding. 
     However, there remains a need to secure or connect portions of living tissue, especially conduits, without the use of staples, suture or clips. 
     An apparatus and method for permanently attaching or connecting living tissue comprising an electro-surgically generated electrical current that is delivered to tissue by a clamping jaw having features that increase current density at preferred locations are provided. 
     Referring to  FIGS.  66 - 72    a surgical tissue fusing or welding instrument  3200  having an elongate body  3210 , a proximal end  3230  comprising an operable handle  3235 , and a distal end  3220  comprising a jaw assembly is provided. In some embodiments the jaw assembly can include fixed jaw  3280  and an operable jaw  3260  pivotable with respect to the fixed jaw  3280 . In other embodiments, the jaw assembly can include two operable jaws. As discussed in further detail below, the tissue fusing or welding instrument  3200  can be configured to perform a stapling-like procedure, which can desirably be applied, for example in bariatric surgical procedures, or other procedures where staple-like closure of tissues is desirable. 
     With reference to  FIGS.  66 - 68   , in certain embodiments, the elongate body  3210  can be sized and configured to be used through a surgical access port such as a trocar cannula for use in a laparoscopic procedure. For example, the elongate body can have an outer diameter corresponding to one of several standard sizes of trocar cannulae, or the elongate body can be sized for a non-standard application-specific access port. In other embodiments, the elongate body  3210  can be sized and configured for use in a portless surgical incision. 
     With continued reference to  FIGS.  66 - 68   , the proximal handle  3235  can be sized and configured to be usable by one hand of a user. The proximal handle  3235  can provide connecting features such as an electrical plug for connection to an electrosurgical surgical generator such as the electrosurgical generator discussed above with respect to the electrosurgical system. In some embodiments, the proximal handle  3235  can include an operating switch  3240 . The operating switch  3240  can allow the user to electrically energize an active portion of the device  3200  selectively. The proximal handle can also include a movable lever  3236  operatively coupled to the jaw assembly to allow the user to grasp, hold and compress selected tissue between the distal jaw portions  3260 ,  3280 .  FIG.  66    illustrates the electrosurgical tool  3200  in a closed state with surfaces  3261 ,  3281  of the distal jaw portions  3260 ,  3280  proximate one another.  FIGS.  67 - 68    illustrate the electrosurgical tool  3200  in an open state with surfaces  3261 ,  3281  of the distal jaw portions  3260 ,  3280  spaced apart from one another such that tissue can be received in a gap  3295  formed therebetween. 
     With reference to  FIGS.  69 - 72   , the jaw assembly  3250  of the electrosurgical tool  3200  can include a plurality of electrodes positioned thereon to simulate stapling action during application. In the illustrated embodiment, a plurality of electrodes  3320  is arranged in pairs in spaced rows within correspondingly spaced recesses  3300  in the first, fixed jaw  3280 . The electrodes extend in four generally parallel columns extending longitudinally from a proximal end of the jaw assembly to a distal end of the jaw assembly. In other embodiments, it is contemplated that the number and arrangement of electrodes can be different from the illustrated embodiment. For example, in some embodiments, the first jaw  3280  can include spaced single electrodes, in other embodiments, the first jaw  3280  can include spaced rows of 3, 4, 5, 6, 7, or more than 7 electrodes. In still other embodiments, the first jaw  3280  can include geometric arrangements of electrodes such as, for example, electrodes in angled, curvilinear, or shaped rows, or electrodes can be randomly distributed in corresponding randomly distributed recesses in the first jaw  3280 . For use in bipolar surgical procedures, it can be desirable that the electrodes are configured to be applied in pairs such that one pair member can be electrically coupled to an electrical energy source having a first polarity and the second member of each pair can be electrically coupled to an electrical energy source having a second polarity opposite the first polarity. In the illustrated embodiment, the electrodes  3320  are sized and configured to selectively extend and recede into the recesses  3300  to contact tissue positioned in the jaw assembly as further discussed below. 
     With continued reference to  FIGS.  69 - 72   , In the illustrated embodiment, the second jaw  3260  is pivotably coupled to the first jaw  3280 . As illustrated, the movable second jaw  3260  is hingedly coupled to the first jaw  3280  at a proximal pivot point  3290 . The second jaw  3260  can be operatively coupled to the movable lever  3236  such that the jaw assembly can be opened and closed by force supplied to the movable lever  3236 . 
     With continued reference to  FIGS.  69 - 72   , the jaw assembly can further comprise a cutting element  3371  such as a slidable or movable cutting blade. In the illustrated embodiment, the first jaw  3280  comprises a linear slot  3370  that is sized and configured to hold the cutting element  3371 . In operation, the cutting element is advanceable along the slot  3370  from a proximal position within the first jaw  3280  to a distal position within the first jaw  3280 . In other embodiments, other cutting elements  3371  can be used in the electrosurgical tool. For example, some embodiments can have reciprocating mechanical cutting blades or radially advanceable cutting elements. Other embodiments of electrosurgical tool can include electrical cutting elements such as cutting electrodes. 
     With reference also to  FIGS.  73 - 80    in certain embodiments, the electrodes  3320  can be urged upward or selectively extended by a distally moving actuation member such as a sled  3380  comprising a substantially flat elongate body  3381  and at least one cam or peak  3385  arranged to contact the electrodes  3320  at desired intervals. In some embodiments, the electrodes  3320  can be arranged in a staggered pattern. In other embodiments, the cams or peaks  3385  on the actuation member may be arranged in a staggered pattern to accomplish a sequential extension of the electrodes  3320 . In still other embodiments, all of the plurality of electrodes  3320  can be selectively extended substantially concurrently, such as by movement of a plurality of cams or peaks on an actuation member. 
     With continued reference to  FIGS.  73 - 80   , in some embodiments, the electrosurgical tool is configured such that a sequential extension pattern includes a number of electrodes  3320  extended at any given moment or with any given force to desirably maximize the force supplied to the proximal lever  3236  and maximize the current density between the electrodes  3320  and the compressed tissue  3030 . Advantageously, sequential extension and energizing of the electrodes  3320  can prevent excessive thermal damage to compressed tissue  3030  as would be the case if all electrodes  3320  were to be energized at the same time. In embodiments of electrosurgical tool including concurrent extension of the plurality of electrodes  3320 , the electrodes can be sequentially energized to reduce the risk of thermal damage to tissue. 
     With reference to  FIG.  75   , in certain embodiments, the electrodes  3320  can be electrically coupled to the electrosurgical tool through contacts disposed on the actuation member or sled  3380 . In other embodiments, the electrodes can be electrically coupled to the electrosurgical tool through one or more wires extending longitudinally within the jaw assembly, a contact strip disposed on or in one of the jaws, or another electrical coupling. In the illustrated embodiment, electrical contact between the actuation member peaks  3385  and electrosurgical tool, which can be coupled to an electrical power source such as a generator can be provided by contact strips  3390 ,  3391 ,  3392 ,  3393  associated with the elongate flat portion  3381  of the movable actuator sled  3380 . The sled  3380  can be configured to move and energize the electrodes in a sequence or rhythm. In various embodiments, the sled  3380  can be automatically or manually controlled. 
     As discussed further below, in some embodiments, the contact strips  3390 ,  3391 ,  3392 ,  3393  can be electrically energized such that the electrosurgical tool operates as a bipolar surgical tool. In the illustrated embodiment, which includes four longitudinally extending columns of electrodes  3320  (see, e.g.,  FIG.  71   ), one of the contact strips  3390 ,  3391 ,  3392 ,  3393  can electrically couple with one or more electrodes  3320  in a corresponding longitudinal column of electrodes. In other embodiments, other electrical contact arrangements are contemplated including more or fewer than four contact strips on the actuation member. For example, two contact strips can be relatively wide to each couple with two columns of electrodes in a four electrode column electrosurgical tool such as that illustrated in  FIG.  71   . In other embodiments, the electrosurgical tool can have more or fewer than four longitudinal columns of electrodes and can have a correspondingly more or fewer than four contact strips. 
     With reference to  FIG.  76   , the electrodes  3320  can be configured to be extended and retracted by the sliding actuation member peaks. In the illustrated embodiment, the electrodes  3320  comprise a flat body portion  3324  that is sized and configured to nest within recesses  3300  of the first jaw portion  3280  and maintain the electrode  3320  in a particular position depending on the relative position of the actuation member peak  3385 . The flattened body  3324  can include a contacting surface  323  that is configured to elevate the electrode  3320  in response to the motion of an associated cam or contactor peak  3385 . The flattened structural portion  3321  of the electrode  3320  transitions into a pair of pointed penetrating elements  3325 ,  3327  that extend through holes in the recesses  3300  of the first jaw  3280 . 
     In operation, as the sled  3380  is advanced distally, the contacting surfaces  3323 ,  3322  of the electrodes  3320  and the cam surfaces  389  of the contactor peaks  3385  engage and extend the individual pairs of electrodes  3320  beyond the contacting face  3281  of the first jaw  3280 . As the sled  3380  is advanced distally past a pair of electrodes  3320 , the pair retracts into the first jaw  3280 . Desirably, the electrodes  3320  are configured to be maintained within the jaw assembly after extension of the electrodes rather than be deposited in tissue once the electrosurgical tool is removed from a tissue site. As illustrated, the electrode pairs  3320  do not extend completely out of the first jaw  3280  as a contact surface  330  on the upper surface of the flattened structural portion  3321  interferes with the contacting face  3281  of the first jaw. While the illustrated embodiment illustrates paired electrodes  3320  with a connecting flattened structural portion  3321 , in other embodiments, single electrodes  3320  can be maintained within the first jaw by a flared lower portion or flanged extensions that interfere with the contacting face  3281  of the first jaw. 
     With reference to  FIGS.  77 - 80   , in certain embodiments, the movable lever  3236  is configured to actuate both the jaw assembly and moveable electrodes in a multi-step actuation process. In some embodiments, the movable lever  3236  can be operatively coupled to the jaw assembly such that a first action associated with a user grasping the movable proximal lever  3236  is that of the jaw assembly grasping selected tissue positioned therein, such as a body conduit or vessel  3030  ( FIG.  77   ). Upon further movement of the movable lever  3236  by the user, the jaw assembly begins to compress the selected, grasped tissue  3030  ( FIG.  78   ) as the movable jaw  3260  continues to pivot from the open state ( FIG.  67   ) towards the closed state ( FIG.  66   ). In the illustrated embodiments, the movable lever  3236  is operatively coupled to the plurality of electrodes  3320  in the jaw assembly such that upon advancement of the movable lever  3236 , the plurality of paired-electrodes  3320  are sequentially advanced by the sled  3380  up from within the first jaw  3280  and toward the opposing face  261  of the movable, second jaw  3260  ( FIGS.  79 - 80   ). 
     With reference to  FIGS.  79  and  80   , as the electrodes  3320  are sequentially advanced through the tissue  3030  compressed between the first jaw  3280  and the second jaw  3260 , the electrodes  3320  are energized sequentially as they are extended by electrical coupling to the contacts  3390 ,  3391 ,  3392 ,  3393  on the sled  3380  ( FIG.  75   ). This sequential energizing can create an exaggerated current density as the electrodes  3320  extend into the compressed tissue  3030 . Once the electrodes  3320  have been extended and energized, they are sequentially disconnected from electrical contact with the corresponding electrical contacts on the sled  3380 . The disconnected electrodes  3320  can then cool down in contact with the treated tissue  3030 . In the illustrated embodiment, only the electrodes  3320  in direct contact with the sliding peaks  3385  of the actuation sled  3380  are energized. Once the contactor peaks  3385  have fully extended the electrodes  3320  and moved beyond any particular electrode or electrode pair, there is no longer a connection of the previous electrodes  3320  to a power supply to which the electrosurgical tool  3200  is coupled. In other embodiments, substantially all of the electrodes  3320  can be energized substantially concurrently by arrangement of electrical coupling to selectively provide energy to the electrodes  3320 . 
     Referring now to  FIGS.  81 - 83   , exemplary illustrations of a body conduit  3030  that may be closed, occluded, or sealed and subsequently separated are shown in accordance with certain embodiments of a jaw assembly of an electrosurgical tool  3200 . In  FIG.  81   , the conduit  3030  is first selected and grasped. In  FIGS.  82 - 83   , the grasped tissue  3030  is fully compressed between distal jaws  3260 ,  3280 . The movable lever  3236  associated with the proximal handle  3235  can be further actuated and the electrodes  3320  are sequentially energized and elevated into the compressed tissue  3030  (see, e.g.,  FIGS.  77 - 80   ). When the tissue  3030  is fully fused or welded in response to the energy supplied by the electrodes, a cutting element  3371  may be selectively advanced, as further discussed below with respect to  FIGS.  98 - 100   . The cutting element  3371  is sized and configured to cut the conduit or tissue  3030  between rows of electrode fusion leaving a plurality of fusion rows on each side of the cut. The electrodes  3320  are subsequently withdrawn from the selected tissue  3030  as the jaws  3260 ,  3280  are separated (see, e.g.,  FIGS.  77 - 80   ). 
     With reference to  FIGS.  84 - 85   , certain aspects of a bipolar electrosurgical tissue fusion operation are illustrated. In previous bipolar surgical tools, electrical energy of a first polarity (+) can be provided to surface contact electrode pins  3405  on a first paddle  3400 , and electrical energy of a second polarity (−) can be provided to electrode pins  3425  on a second paddle  3420 . The paddles can be compressed over tissue such as a vessel having two portions  3030 ,  3030 ′ such that the first paddle  3400  compresses an outer wall  3036  of the first portion  3030 , and the second paddle  3420  compresses an outer wall  3037  of the second portion  3030 ′. In order for the two portions of tissue to be welded or fused together, the electrical energy must travel a relatively long distance between the pins  3405 ,  3425  to the interface between inner walls  3033 ,  3034  of the tissue portions  3030 ,  3030 ′. As the distance between pins increases in a bipolar electrosurgical instrument, the current density tends to decrease. Therefore, using such a device, it can be necessary to apply electrical energy over a fairly long duration, which can undesirably damage tissue  3030 ,  3030 ′. 
     With reference to  FIGS.  86 - 91   , advantageously, with an electrosurgical tool  3200 , high current density of a short duration can produce effective seals/welds and with minimal or substantially no radiant thermal effects. Unlike conventional surface contact electrodes, an exemplary inserted electrode  3325  in the electrosurgical tool  3200  can provide a dense current path resulting in elevated thermal activity within the compressed tissue  3030 . The margin of thermal damage concomitant to electrosurgical surface radiation is potentially noteworthy and as such the minimization or elimination of the margin of radiant thermal damage by inserting the electrodes  3325  such as, for example with sharpened or tapered tips  3326  to allow the electrodes  3325  to penetrate tissue to be fused. In other embodiments, the electrode  3325  can be otherwise configured to direct the current path in a manner that concentrates or focuses the energy at a particular location. 
     A section view of the activity associated with the electrodes  3325  may be seen in  FIGS.  86 - 91    where a penetrating electrode element  3325  is inserted through or into a portion of compressed tissue  3030  through action of the tapered tip  3326  to create an interface surface  3470  within the tissue  3030 . Energy from an energy source is supplied to the electrode  3325  and subsequently radiated into the adjacent tissue radially from the interface surface  3470 . As the tissue is energized, it heats to a particular temperature at which it loses fluid content. The tissue  3030  then fuses at the cellular level in a manner that resembles cross-linking. The cross-linked collagen forms a continuous structure  3465  of denatured cells. When the electrode  3325  is removed, the denatured structure  3465  remains. As illustrated in  FIGS.  89 - 91   , the denatured structure  3465  may serve as a connecting structure  3475  between two portions of tissue  3030 ,  3030 ′ such as two opposing walls  3033 ,  3034  of a compressed conduit  3030  that have been compressed to form a closure or occlusion. When fused with an electrosurgical tool  3200  described herein, the denatured structure  3475  generally extends through all tissue that has been compressed between the jaws  3260 ,  3280  of the electrosurgical tool  3200  and energized by the movable electrodes  3320 . The denatured structure  3475  can resemble an “hourglass” shape where there is a wide first, insertion portion, a narrow mid portion and a wide exit portion. 
     Electro-surgery involves managing the timing and temperature of the procedure. Too little generated heat within the tissue prevents the tissue from properly fusing or welding and too much heat within the tissue may destroy it and result in complications. As such, the electrosurgical tool can be less sensitive to the variables within living tissue. The instrument may be coupled to feedback systems that measure or respond to conditions that develop within treated tissue. For instance, the electrosurgical tool may desiccate tissue during the heating phase so that resistance to electrical current develops. In some embodiments, that resistance may be measured or otherwise used to control the delivery of electrosurgical energy to the electrodes. In some embodiments, the phase changes between the initiation of the electrosurgical energy and any subsequent point during the delivery of the electrosurgical energy may be used to control the delivery. In other embodiments, a measurement of the temperature of the treated tissue can also be used to control the delivery. 
     A comparison between various methods of conduit occlusion may be appreciated in  FIGS.  92 - 95   .  FIG.  92    illustrates a sutured conduit  3030 . The sutured conduit  3030  comprises a plurality of individual or running sutures  3480  terminating in at least one knot  3481 . The suturing process can require expertise, be time consuming, and may not always result in optimum occlusion. As a result the conduit  3030  may leak or ooze. 
       FIG.  93    illustrates a stapled conduit  3030  in which a plurality of staples  3490  have been driven into the conduit  3030 . The staples  3490  have folds  3491  to retain them in the conduit  3030  and apply occlusive forces to the conduit. Stapling using a surgical stapler, results in a more secure closure than suturing in many cases. However, even with stapling, suturing may be used to complete the closure since staples  3490  may not accommodate the wide variations in tissue thickness or texture. Several surgical procedures make use of stapling. In these cases, most of the staples  3490  remain within the surgical site. Generally, the staples  3490  are made from metal, such as titanium. It may be appreciated that a great deal of force is applied to the jaw portions of a stapling device to accomplish all the actions required to occlude the subject tissue  3030  and subsequently insert the staples  3490  and fold  3491  them appropriately. It should also be noted that the cartridges holding the staples  3490  are complex and expensive devices and hold only a single load of staples  3490 . Therefore, there are generally several exchanges of stapling instruments during a typical surgical procedure. For example, during a surgical procedure involving the intestines, it is not uncommon to use, between three and ten cartridges of staples with each cartridge holding, up to thirty-six or more staples. The residual metal mass left behind is therefore significant. Moreover, if removal is desired, staples are not easily cut and, in addition, some of them may be dislodged during a cutting procedure. This may result in residual pieces of metal within a body cavity. In addition, electro-cautery is often used to completely seal a vessel or conduit  3030  that has been stapled. 
     With reference to  FIG.  94   , compressive, external electrosurgical fusion such as applied by surface contact electrodes described above with respect to  FIGS.  84  and  85    can be adequate for small vessels or conduits. However, as discussed above, there may be excessive radiant thermal damage associated with the use of these modalities, especially in larger conduits  3030 . Thermal damage that eliminates the regeneration of residual tissue or prevents vascular re-perfusion or regeneration is undesirable in most cases. Accordingly, compressive, external electrosurgical fusion can be undesirable in relatively larger vessels or conduits where thermal damage can occur. Additionally, in some instances, compressive electrosurgical fusion can fail to provide sufficient compressive forces, resulting in non-occluded areas  3032  adjacent the conduit wall  3031 . Both suturing and stapling accommodate regeneration when done properly in most cases. However, surgical stapling can often be responsible for necrosis of residual tissue since the delivery devices do not compensate well for variations in tissue thickness or texture. 
     As is apparent from the above discussion and  FIG.  94   , the electrosurgical tool  3200  described herein can fuse or weld in a manner that emulates the placement of a plurality of staples. The portions of tissue that have been treated resemble a connection made by staples. Moreover, with the electrosurgical tool  3200  described herein, unlike a stapler, the second, closing jaw does not have to be of sufficient strength to provide an anvil for the folding or bending of staple legs. Thus, the electrosurgical tool  3200  can be particularly advantageous in applications where the device may have to be operated through a small tubular access port. 
     With reference to  FIG.  95   , compressing selected tissue and subsequently creating a plurality of denatured connecting structures  3475  for example with an electrosurgical tool  3200  as described herein provides a combination of occlusive security and minimal thermal radiation damage. Adequate vascular regeneration and minimization of necrosis of residual tissue are also provided. Accordingly, use of the electrosurgical tools  3200  described herein for conduit occlusion can desirably provide advantages of tissue suturing or stapling with reduction of the drawbacks of external contact electrosurgical fusion. Advantageously, sealing a conduit with an electrosurgical tool  3200  as described herein can also be accomplished relatively quickly and easily by a surgeon. 
     With reference to  FIG.  96   , experimental data for sealing strength of various embodiments of electrosurgical tools is presented graphically. Various experiments were performed on porcine small intestinal tissue to demonstrate the strength of sealing of an electrosurgical tool  3200  as described herein. Using tools having trenchwidth (that is, spacing between adjacent electrodes) of between 0 and 0.055 inches, porcine intestinal tissue was sealed using the electrosurgical tool  3200  described herein and its burst pressure measured. As a control, it was initially established that a conventionally stapled section of intestinal tissue can withstand a burst pressure of 0.5+−0.1 pounds per square inch. Multiple tests were conducted at various trenchwidths, and a statistical range of the results was plotted in  FIG.  96   , with mean data for each trenchwidth appearing at a point designated in the range. As is apparent from  FIG.  96   , for relatively small trenchwidths, the electrosurgical tool  3200  can create an intenstinal tissue seal burst strength that outperforms conventional stapling. For relatively large trenchwidths, the electrosurgical tool  3200  can create an intenstinal tissue seal burst strength that performs similarly to, or marginally less than conventional stapling. Accordingly, the electrosurgical tools  3200  described herein offer similar or increased burst strength performance while being faster and easier to use and having other advantages discussed above. 
     Referring to  FIGS.  97 - 100   , as discussed above, in some embodiments, the jaw assembly of the electrosurgical tool  3200  can include a cutting element  3371  such as a selectively operable cutting component. The cutting component can be selectively moved between a proximal location and a distal location to cut tissue compressed between the jaws of the jaw assembly. In various embodiments, the cutting element  3371  can be a sharp blade, hook, knife, or other cutting element that is sized and configured to cut between denatured structures  3475  in compressed tissue. As illustrated in  FIG.  99   , in some embodiments, the cutting element  3371  includes a sharpened edge  3372  on one of the proximal edge or the distal edge to allow cutting of tissue when the cutting element  3371  is moved in one direction towards the sharpened edge  3372 . As illustrated in  FIG.  100   , in some embodiments, the cutting element  3371  includes a first sharpened edge  3372  and a second sharpened edge  373  on each of the proximal edge and the distal edge of the cutting element  3371  to allow cutting of tissue when the cutting element  3371  is moved either proximally or distally along the slot  3370  in the fixed jaw  3280 . 
     While in illustrated embodiments, the cutting element is illustrated as a mechanical element, in other embodiments, the cutting element  3371  can comprise an energizable element or wire that can be selectively energized by a generator or power source. An electrosurgical cutting element  3371  can easily separate the compressed and fused tissue portion and can additionally provide fluid stasis or additional sealing of the lumen  3032  associated with the treated tissue  3030 . 
       FIGS.  101 - 106    illustrate various configurations of current intensifying elements  3500 ,  3510 ,  3520 ,  3522 ,  3524 ,  3526 ,  3530 ,  3540 ,  3545 ,  3550  for use in an electrosurgical tool such as the electrosurgical tool  3200  described herein. The elements can be configured to focus or direct energy on or into a position within compressed tissue  3030 . Thus, in various embodiments an electrosurgical tool can include a plurality of current intensifying elements in place of or in addition to a plurality of extendable electrodes as discussed above. Each of the various current intensifying elements can be desirable for certain surgical environments depending, among other considerations, on the depth of tissue penetration desired and the degree of energy intensification desired. In some embodiments, an electrosurgical tool can include a plurality of extendable electrodes as described above on one jaw of a jaw assembly and a plurality of current intensifying elements on the other jaw of the jaw assembly. In other embodiments, an electrosurgical tool can include a first plurality of current intensifying elements on one jaw of the jaw assembly and a second plurality of current intensifying elements on the other jaw of the jaw assembly. 
     In some embodiments, the elements can comprise holes  3500  that function as energy horns, as shown in  FIG.  101   . In other embodiments, the elements can additionally comprise rods  3510  or spikes that are stationary or movable, as depicted in  FIG.  102   . As an alternative, some applications may use a less intrusive configuration such as a plurality of subtle arcs or mounds  3520  ( FIG.  103   a   ). Some applications may favor a slightly more aggressive configuration comprising a plurality of raised squares  3522  ( FIG.  103   b   ), rods  3524  ( FIG.  103   c   ), “ball-and-cup”-like configurations  3526  ( FIG.  103   d   ), or rectangles  3530  ( FIG.  104   ) where energy can be focused or concentrated at edges and corners. In other embodiments, the elements can comprise a plurality of elongate rows  3540  ( FIG.  105   a   ) or socket-and-spickets  3545  ( FIG.  105   b   ). In other embodiments, the elements can comprise a plurality of pyramids or cones  3550  ( FIG.  106   ) or the like that are sized and configured to penetrate into the surface of tissue. 
       FIG.  107    illustrates a cross-sectional view of tissue that has been compressed and fused with an electrosurgical tool. As illustrated, the tissue  3030  is compressed within a square-patterned embodiment of the upper  3260  and lower jaw  3280  elements, and subjected to electrical RF current or thermal energy. This energy application can be accomplished by connecting both upper and lower jaw elements to a bipolar electrosurgical unit, or by encapsulating electrical (ohmic) heaters within each jaw element. Even though there can be some compression between “uncompressed” tissue areas, as well as some energy overspill into the “uncompressed” tissue area, the directly compressed and energized tissue areas will be the first areas to fuse together and can be the only ones to seal. 
     With reference to  FIG.  108   a   , an example of the visual appearance of the obtained results on a fused and separated blood vessel  3030  is illustrated. As can be seen, each of the two sections of a sealed and cut vessel may include a pattern corresponding to the pattern of electrodes or current intensifying elements. For example, as shown in  FIGS.  103   a - b   , the divided portions of the vessel are each sealed in a fluid tight manner by the respective double-rows of fused squares. The tissue between the fused squares, on the other hand, does not have to be fused, or even connected. For example, with reference to  FIG.  108   b   , a cross-section along line  8 - 8  in  FIG.  108   a    illustrates the fused and non-fused areas in the cut vessel. In this example, the fused and denatured (square) tissue elements are separated by tissue areas that have not been connected to opposing tissue areas. 
       FIG.  109   a    illustrates an exemplary sealed and cut tissue segment  3030 , obtained by welding the tissue in two double-rows of round areas, and cutting the tissue between the two double rows. The divided portions of the tissue are each sealed in a fluid tight manner by the respective double-rows of fused circles. The tissue between the fused circles, on the other hand, does not have to be fused, or even connected. This is shown, for example, in  FIG.  109   b   , which depicts a cross-section along line  9 - 9  in  FIG.  109   a   . In this example, the fused and denatured (circular) tissue elements are separated by tissue areas that have not been connected (to opposing tissue areas). 
     With reference to  FIG.  110   , tissue  3030  within a jaw assembly  3250  of an electrosurgical tool having square patterned recesses is illustrated in cross-section. As illustrated, the tissue  3030  is compressed within the square pattern of the upper and lower jaw elements. In some embodiments of electrosurgical tool, energy can be supplied to the tissue by applying the upper electrode with ultrasonic energy, which can cause friction of the tissue with both upper and lower jaw element. The movement of the upper jaw element in  FIG.  110    is indicated for illustrative purposes as parallel to the drawing plane, although the movement can also be provided in the transversal direction. Even though there will be some compression between “uncompressed” tissue areas into the “uncompressed” tissue area, also through heat conduction by the tissue, the directly compressed and energized tissue areas can be initially fused and can be the only areas to seal. 
     Referring to  FIG.  111   , tissue  3030  within a jaw assembly  3250  of an electrosurgical tool having square patterned recesses is illustrated in cross-section. Energy is then supplied to the tissue by irradiating it with UV and/or IR radiation, provided for example through fiber-optical cables within the square-patterned areas. Even though there will be some compression between “uncompressed” tissue areas, as well as some UV/IR energy overspill into the “uncompressed” tissue area, also through scattering, the directly compressed and energized tissue areas will be the first ones and can be the only ones to seal. 
     It is believed that UV (200 to 400 nanometers) is absorbed by proteins (and hemoglobin), leading to cleavage of chemical bonds within the proteins, while IR (&gt;1 micrometer) is strongly absorbed by water, causing heating of the tissue. It has been demonstrated that the fusion of clamped arteries using incoherent UV within the spectral range of 300 to 500 nanometers, without substantial heating of the artery can be accomplished. The irradiation of the pressurized tissue with UV can cause collagens to bind each other through photochemical reactions, without desiccation or thermally-induced collagen degeneration. 
     In one aspect, the tissue is fused or welded in a manner that emulates the placement of a plurality of staples. The portions of tissue that have been treated resemble a connection made by staples. However, using the electrosurgical tool, a single grasping procedure can simulate the release of tens of staples, thus resulting in significant time savings over a similar procedure with a surgical stapler. When compared with a surgical stapler, advantageously, the second, closing jaw of the electrosurgical tool does not need to be of sufficient strength to provide an anvil for the folding or bending of staple legs. It may therefore favor laparoscopic applications where the device may have to be operated through a small tubular access port. 
     Although this application discloses certain preferred embodiments and examples, it will be understood by those skilled in the art that the present inventions extend beyond the specifically disclosed embodiments to other alternative embodiments and/or uses of the invention and obvious modifications and equivalents thereof. Further, the various features of these inventions can be used alone, or in combination with other features of these inventions other than as expressly described above. Thus, it is intended that the scope of the present inventions herein disclosed should not be limited by the particular disclosed embodiments described above, but should be determined only by a fair reading of the following claims.