US20100152726A1 - Electrosurgical system with selective control of active and return electrodes - Google Patents

Abstract

Electrosurgical system with selective control of active and return electrodes. At least some of the illustrative embodiments are systems comprising an electrosurgical wand and an electrosurgical controller. The wand comprises a non-conductive outer surface, at least three electrodes disposed on a distal end of the wand, and at least three electrical leads extending from a proximal end of the wand (one electrical lead electrically coupled to each electrode). The controller comprises a voltage generator and a control circuit coupled between the voltage generator and the electrodes of the wand. The control circuit is configured to: selectively electrically couple the active terminal singly and in combination to the electrodes of the wand; and selectively electrically couple the return terminal singly and in combination to electrodes of the wand.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS
• None.
BACKGROUND
• Electrosurgical systems are used by physicians to perform specific functions during surgical procedures. For example, in an ablation mode electrosurgical systems use high frequency electrical energy to remove soft tissue such as sinus tissue, adipose tissue, or meniscus, cartilage and/or sinovial tissue in a joint. In a coagulation mode, the electrosurgical device may aid the surgeon in reducing internal bleeding by assisting in the coagulation and/or sealing of vessels.
• However, while the mode of operation of an electrosurgical system is controlled to some extent by the voltage applied to the electrodes of an electrosurgical wand, the physical size and placement of electrodes on the electrosurgical wand also affect operation. For example, in an ablation mode, a relatively small active electrode conducting current to a proximally-located larger return electrode may be preferred to very precisely control the tissue ablated. By contrast, in a coagulation mode, relatively large active and return electrodes, perhaps along the side of an electrosurgical wand and yet still proximate to the distal end, may be preferred to ensure larger surface area for coagulation.
• In some situations, a surgeon may choose to change electrosurgical wands as between, for example, an ablation of tissue and a coagulation procedure. In other situations, an electrosurgical system may have the ability to change between an ablation and coagulation mode by controlling the active electrode on the electrosurgical wand and/or the voltage output of the controller. However, any advance that increases the functionality of an electrosurgical system provides competitive advantage.
BRIEF DESCRIPTION OF THE DRAWINGS
• For a detailed description of exemplary embodiments of the invention, reference will now be made to the accompanying drawings in which:
• FIG. 1 shows an electrosurgical system in accordance with at least some embodiments;
• FIG. 2 shows a perspective view a portion of a wand in accordance with at least some embodiments;
• FIG. 3 shows a cross-sectional view of a wand in accordance with at least some embodiments;
• FIG. 4 shows both an elevational end-view (left) and a cross-sectional view (right) of a wand connector in accordance with at least some embodiments;
• FIG. 5 shows both an elevational end-view (left) and a cross-sectional view (right) of a controller connector in accordance with at least some embodiments;
• FIG. 6 shows an electrical block diagram of an electrosurgical controller in accordance with at least some embodiments; and
• FIG. 7 shows a method in accordance with at least some embodiments.
NOTATION AND NOMENCLATURE
• Certain terms are used throughout the following description and claims to refer to particular system components. As one skilled in the art will appreciate, companies that design and manufacture electrosurgical systems may refer to a component by different names. This document does not intend to distinguish between components that differ in name but not function.
• In the following discussion and in the claims, the terms “including” and “comprising” are used in an open-ended fashion, and thus should be interpreted to mean “including, but not limited to . . . .” Also, the term “couple” or “couples” is intended to mean either an indirect or direct connection. Thus, if a first device couples to a second device, that connection may be through a direct connection or through an indirect electrical connection via other devices and connections.
• Reference to a singular item includes the possibility that there are plural of the same items present. More specifically, as used herein and in the appended claims, the singular forms “a,” “an,” “said” and “the” include plural references unless the context clearly dictates otherwise. It is further noted that the claims may be drafted to exclude any optional element. As such, this statement serves as antecedent basis for use of such exclusive terminology as “solely,” “only” and the like in connection with the recitation of claim elements, or use of a “negative” limitation. Lastly, it is to be appreciated that unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs.
• “Active electrode” shall mean an electrode of an electrosurgical wand which produces an electrically-induced tissue-altering effect when brought into contact with, or close proximity to, a tissue targeted for treatment, and/or an electrode having a voltage induced thereon by a voltage generator, power generator, or other suitable energy source.
• “Return electrode” shall mean an electrode of an electrosurgical wand which serves to provide a current flow path for electrons with respect to an active electrode, and/or an electrode of an electrical surgical wand which may not itself produce an electrically-induced tissue-altering effect on tissue targeted for treatment.
• “Proximate” shall mean, in relation to spacing of electrodes on a wand, within 5 centimeters, and in some cases less than 1 centimeter.
• Where a range of values is provided, it is understood that every intervening value, between the upper and lower limit of that range and any other stated or intervening value in that stated range is encompassed within the invention. Also, it is contemplated that any optional feature of the inventive variations described may be set forth and claimed independently, or in combination with any one or more of the features described herein.
• All existing subject matter mentioned herein (e.g., publications, patents, patent applications and hardware) is incorporated by reference herein in its entirety except insofar as the subject matter may conflict with that of the present invention (in which case what is present herein shall prevail). The referenced items are provided solely for their disclosure prior to the filing date of the present application. Nothing herein is to be construed as an admission that the present invention is not entitled to antedate such material by virtue of prior invention.
DETAILED DESCRIPTION
• Before the various embodiments are described in detail, it is to be understood that this invention is not limited to particular variations set forth herein as various changes or modifications may be made, and equivalents may be substituted, without departing from the spirit and scope of the invention. As will be apparent to those of skill in the art upon reading this disclosure, each of the individual embodiments described and illustrated herein has discrete components and features which may be readily separated from or combined with the features of any of the other several embodiments without departing from the scope or spirit of the present invention. In addition, many modifications may be made to adapt a particular situation, material, composition of matter, process, process act(s) or step(s) to the objective(s), spirit or scope of the present invention. All such modifications are intended to be within the scope of the claims made herein.
• FIG. 1 illustrates anelectrosurgical system100 in accordance with at least some embodiments. In particular, the electrosurgical system comprises an electrosurgical instrument102 (hereinafter “wand”) coupled to an electrosurgical controller104 (hereinafter “controller”). Thewand102 comprises anelongate shaft106 that includesdistal end108 where at least some electrodes are disposed. In certain embodiments, theelongate shaft106 comprises a conductive material, but is covered with an insulating material. Theelongate shaft106 further defines a handle orproximal end110, where a user may grip thewand102 during a surgical procedure. Thewand102 further comprises a flexiblemulti-conductor cable112 housing a plurality of electrical leads (not specifically shown inFIG. 1), and the flexiblemulti-conductor cable112 terminates in awand connector114. Though not expressly shown in theFIG. 1, in someembodiments wand102 may include an internal passage or lumen fluidly coupled to a flexibletubular member116. The internal passage and flexibletubular member116 may be used as a conduit to supply conductive fluid, a non-conductive irrigant, or other desired fluid to be proximate to thedistal end108, or the internal passage and flexible tubular member may be used to aspirate the area proximate to thedistal end108 of thewand102.
• As shown inFIG. 1, thewand102 couples to thecontroller104, such as by acontroller connector120, on an outer surface122 (in the illustrative case ofFIG. 1 the front surface). A display device orinterface panel124 is visible through theouter surface122, and in some embodiments a user may select operational modes of thecontroller104 by way of theinterface device124 andrelated buttons126. The interaction of theinterface device124 andbuttons126 is discussed more thoroughly below with respect toFIG. 5.
• Still referring toFIG. 1, in some embodiments theelectrosurgical system100 may also comprise afoot pedal assembly130. Thefoot pedal assembly130 may comprise one ormore pedal devices132 and134, a flexiblemulti-conductor cable136 and apedal connector138. While only twopedal devices132,134 are shown, any number of pedal devices may be implemented. Theouter surface122 of thecontroller104 may comprise acorresponding connector140 that couples to theconnector138. A physician may use thefoot pedal assembly130 to control various aspects of thecontroller104, such as the operational mode. For example, a pedal device, such aspedal device132, may be used for on-off control of the application of radio frequency (RF) energy to thewand102, and more specifically for control of energy in an ablation mode. A second pedal device, such aspedal device134, may be used to control and/or set the operational mode of the electrosurgical system. For example, actuation ofpedal device134 may switch between ablation mode and a coagulation mode. Alternatively,pedal device134 may be used to control the application of RF energy towand102 in a coagulation mode. The pedal devices may also be used to change the voltage level delivered towand102. As another example, actuation of thepedal device134 may change the configuration of active and return electrodes on thewand102.
• Theelectrosurgical system100 of the various embodiments may have a variety of operational modes. One such mode employs Coblation® technology. In particular, the assignee of the present disclosure is the owner of Coblation® technology. Coblation® technology involves the application of a RF signal between one or more active electrodes and one or more return electrodes of thewand102 to develop high electric field intensities within conductive fluid in the vicinity of the target tissue sufficient to volumetrically dissociate or otherwise ablate tissue. The electric field intensities may be sufficient to vaporize an electrically conductive fluid over at least a portion of the one or more active electrodes in the region between the one or more active electrodes and the target tissue. The electrically conductive fluid may be inherently present in the body, such as blood, or in some cases extracelluar or intracellular fluid. In other embodiments, the electrically conductive fluid may be a liquid or gas, such as isotonic saline. In some embodiments the electrically conductive fluid is delivered in the vicinity of the active electrodes and/or to the target site by thewand102, such as by way of the internal passage and flexibletubular member116.
• When the electrically conductive fluid is heated to the point that the atoms of the fluid vaporize faster than the atoms recondense, a gas is formed. When sufficient energy is applied to the gas, the atoms collide with each other causing a release of electrons in the process, and an ionized gas or plasma is formed (the so-called “fourth state of matter”). Stated otherwise, plasmas may be formed by heating a gas and ionizing the gas by driving an electric current through the gas, or by directing electromagnetic waves into the gas. The methods of plasma formation give energy to free electrons in the plasma directly, electron-atom collisions liberate more electrons, and the process cascades until the desired degree of ionization is achieved. A more complete description of plasma can be found in Plasma Physics, by R. J. Goldston and P. H. Rutherford of the Plasma Physics Laboratory of Princeton University (1995), the complete disclosure of which is incorporated herein by reference.
• As the density of the plasma becomes sufficiently low (i.e., less than approximately 1020 atoms/cm³for aqueous solutions), the electron mean free path increases such that subsequently injected electrons cause impact ionization within the plasma. When the ionic particles in the plasma layer have sufficient energy (e.g., 3.5 electron-Volt (eV) to 5 eV), collisions of the ionic particles with molecules that make up the target tissue break molecular bonds of the target tissue, dissociating molecules into free radicals which then combine into gaseous or liquid species. Often, the electrons in the plasma carry the electrical current or absorb the electromagnetic waves and, therefore, are hotter than the ionic particles. Thus, the electrons, which are carried away from the target tissue toward the active or return electrodes, carry most of the plasma's heat, enabling the ionic particles to break apart the target tissue molecules in a substantially non-thermal manner.
• By means of the molecular dissociation (as opposed to thermal evaporation or carbonization), the target tissue is volumetrically removed through molecular dissociation of larger organic molecules into smaller molecules and/or atoms, such as hydrogen, oxygen, oxides of carbon, hydrocarbons and nitrogen compounds. The molecular dissociation completely removes the tissue structure, as opposed to dehydrating the tissue material by the removal of liquid within the cells of the tissue and extracellular fluids, as occurs in related art electrosurgical desiccation and vaporization. A more detailed description of the molecular dissociation can be found in commonly assigned U.S. Pat. No. 5,697,882 the complete disclosure of which is incorporated herein by reference.
• In addition to the Coblation® mode, theelectrosurgical system100 ofFIG. 1 is also useful for sealing larger arterial vessels (e.g., on the order of about 1 mm in diameter), when used in what is known as a coagulation mode. Thus, the system ofFIG. 1 may have an ablation mode where RF energy at a first voltage is applied to one or more active electrodes sufficient to effect molecular dissociation or disintegration of the tissue, and the system ofFIG. 1 has a coagulation mode where RF energy at a second, lower voltage is applied to one or more active electrodes (either the same or different electrode(s) as the ablation mode) sufficient to heat, shrink, seal, fuse, and/or achieve homeostasis of severed vessels within the tissue.
• The energy density produced byelectrosurgical system100 at thedistal end108 of thewand102 may be varied by adjusting a variety of factors, such as: the number of active electrodes; electrode size and spacing; electrode surface area; asperities and/or sharp edges on the electrode surfaces; electrode materials; applied voltage; current limiting of one or more electrodes (e.g., by placing an inductor in series with an electrode); electrical conductivity of the fluid in contact with the electrodes; density of the conductive fluid; and other factors. Accordingly, these factors can be manipulated to control the energy level of the excited electrons. Since different tissue structures have different molecular bonds, theelectrosurgical system100 may be configured to produce energy sufficient to break the molecular bonds of certain tissue but insufficient to break the molecular bonds of other tissue. For example, fatty tissue (e.g., adipose) has double bonds that require an energy level higher than 4 eV to 5 eV (i.e., on the order of about 8 eV) to break. Accordingly, the Coblation® technology in some operational modes does not ablate such fatty tissue; however, the Coblation® technology at the lower energy levels may be used to effectively ablate cells to release the inner fat content in a liquid form. Other modes may have increased energy such that the double bonds can also be broken in a similar fashion as the single bonds (e.g., increasing voltage or changing the electrode configuration to increase the current density at the electrodes).
• A more complete description of the various phenomena can be found in commonly assigned U.S. Pat. Nos. 6,355,032, 6,149,120 and 6,296,136, the complete disclosures of which are incorporated herein by reference.
• FIG. 2 illustrates thedistal end108 ofwand102. In some embodiments,distal end108 ofwand102 compriseselectrode support member105 that may be constructed of an inorganic insulating (i.e., non-conductive) material. Thedistal end108 further comprises a plurality of electrodes. For example, in the illustrative case ofFIG. 2, sevenelectrodes202,204,206,208,210,212 and214 are shown; however, any suitable configuration of three or more electrodes may be equivalently used. As illustrated inFIG. 2, the electrodes may take many forms.Electrodes202,204 and206 are illustrative of wire-type electrodes that protrude slightly from theend216 ofelectrode support member105. The wire-type electrodes202,204 and206 may be used, for example, singly or in combination to be the active electrodes to which the RF energy is applied in the ablation mode.Electrodes208,210 are disposed on a radial orside surface218 of thedistal end108, and theelectrodes208,210 span a certain circumferential distance.Electrodes212,214 are similar toelectrodes208,210, but span a smaller circumferential distance. Theelectrodes208,210,212 and214 may be used in some modes as return electrodes for ablation, and in other modes may be the active and/or return electrodes in the coagulation mode. Other electrode types, such as button electrodes (i.e., round electrodes), arrays of button electrodes, or screen electrodes, may be equivalently used. Alternatively, the disposition of electrodes may also be changed such that smaller electrodes are disposed on a side surface and not on an end ofwand102.
• Still referring toFIG. 2, in some embodiments thewand102 includes aninternal lumen250 that fluidly couples to the flexible tubular member116 (FIG. 1). In some modes of operation, theinternal lumen250 may preferably be used to supply conductive fluid to the target area. In other modes of operation, theinternal lumen250 may be used to aspirate the area near thedistal end108 of thewand102, such as when sufficient conductive fluid is already present at the target location and ablation is taking place, or to remove byproducts of the ablation process including fluid, gas bubbles, or particles of tissue.
• In accordance with the various embodiments, while awand102 may be designed to have a multitude of electrode types and arrangements, in at least some embodiments the electrodes are in a fixed relationship for any one design. For example, the center-to-center distance “D” ofillustrative electrodes212 and214 is set by the design of theparticular wand102, and remains constant as between use and non-use. Similar fixed relationships exist between all the illustrative electrodes ofwand102. Furthermore, while awand102 may be designed to have a multitude of exposed electrode surface areas, in at least some embodiments at least one electrode has a surface area less than three-quarters the surface area of another electrode. In the illustrative case ofFIG. 2, for example,electrode212 as shown has a surface area less than three-quarters of eitherelectrode208 or210. Thus, in accordance with the various embodiments, one is able not only to select particular electrodes to control the relationship of the electrodes from a distance perspective, but is also able to select electrodes to control the relative cumulative proportion of surface area between the active electrodes and the return electrodes. For example, in a first mode, a user may select an active electrode and a return electrode having the same surface area (e.g.,electrodes208 and210); however, in a second mode the user may select an active electrode and a return electrode having different sizes (e.g.,electrode212 as an active electrodes andelectrode210 as a return electrodes).
• In at least some embodiments, in ablation modes (using, for example, Coblation® technology as discussed herein) the one or more return electrodes are spaced proximally from the one or more active electrodes a suitable distance to avoid electrical shorting between the electrodes when in the presence of electrically conductive fluid. In many cases, the distal edge of the exposed surface of the closest return electrode is about between about 0.5 milli-meters (mm) to about 25 mm from the proximal edge of the exposed surface of the closest active electrode, and in some embodiments between about 1.0 mm to 5.0 mm. For example,electrode208 may be selected to be a return electrode andelectrode210 may be selected to be an active electrode, and the axial distance betweenelectrode208 and210 may be in the range of 0.5 mm to 25 mm. As yet another example using the Coblation® technology, one, two or all the wire-type electrodes202,204 and206 may be active, and electrode210 (which was the active electrode in the previous example) may be the return electrode. In the second example, the axial distance between the active electrode(s) and thereturn electrode210 may be 0.5 mm to 25 mm. As yet another example,electrodes202 and206 may be return electrodes, with any of theelectrodes204,208, or210 being active. The distances may vary with different voltage ranges, conductive fluids, and proximity of tissue structures to available active and return electrodes. In some embodiments, return electrode may have an exposed length in the range of about 1 mm to 20 mm.
• As alluded to by the examples of preceding paragraph, in accordance with at least some embodiments, any single electrode or combination of multiple electrodes may be selected as the active electrode for a particular mode of operation. Likewise in accordance with at least some embodiments, any single electrode or combination of multiple electrodes may be selected as the return electrode for a particular mode of operation. However, in any scenario discussed above, at least one electrode shall be selected as an active electrode and at least one electrode shall be selected as a return electrode. It follows that, in accordance with various embodiments, most if not all electrodes ofwand102 are preferably electrically isolated from each other, and thus have individual electrical leads that run from each electrode to thewand connector114.
• FIG. 3 shows a cross-sectional view ofwand102 in accordance with at least some embodiments. In particular,FIG. 2 illustrates theelongate shaft106 comprisingdistal end108 andproximal end110.Distal end108 comprises a plurality ofelectrodes300, and while theelectrodes300 are similar to the electrodes ofFIG. 2,electrodes300 are not necessarily the same as those ofFIG. 2. In accordance with the various embodiments where anyelectrode300 may be selected singly or in combination with other electrodes to be active electrode(s), and likewise anyelectrode300 may be selected singly or in combination withother electrodes300 to be the return electrode(s), eachelectrode300 has an electrical lead associated therewith that runs through theelongate shaft106 to the flexiblemulti-conductor cable112. In particular,electrode300A has dedicatedelectrical lead302A which runs within the elongate shaft to the become part ofcable112. Similarly,electrode300B has dedicatedelectrical lead302B which runs within theelongate shaft106 to become part ofcable112.Illustrative electrodes300C and300D likewise have dedicatedelectrical leads302C and302D which run within theelongate shaft106 to become part ofcable112. In some embodiments, theelongate shaft106 has dedicated internal passages (in addition to internal lumen250) through which theelectrical leads302 run. In other embodiments, theelectrical leads302 may be cast within the material that makes up the elongate shaft.
• FIG. 3 also illustratesinternal lumen250 having anaperture304 fluidly coupled to the flexibletubular member116 on theproximal end110. In other embodiments, the fluid coupling of theinternal lumen250 to the flexibletubular member116 may be between thedistal end108 andproximal end110. Theinternal lumen250 is used in some embodiments to supply conductive fluid through theaperture302 to the target area, and in other embodiments theinternal lumen250 is used for aspiration of ablated tissue fragments and/or molecules. In some embodiments, anelectrode300D may be disposed within theinternal lumen250 proximate to theaperture304. Anelectrode300D within theinternal lumen250 may, for example, be selected as either an active or return electrode in an ablation mode, and may aid in disassociation of tissue pieces into smaller pieces during ablation and aspiration procedures.
• The power provided to thewand102 may be current limited or otherwise controlled so that undesired heating of the target tissue or surrounding (non-target) tissue does not occur. In some embodiments, current limiting inductors are placed in series with some or all the electrodes, where the inductance of each inductor is in the range of 10 micro-Henries (pH) to 50,000 pH, depending on the electrical properties of the target tissue, the desired tissue heating rate and the operating frequency. Alternatively, inductor-capacitor (LC) circuit structures may be employed, as described in U.S. Pat. No. 5,697,909, the complete disclosure of which is incorporated herein by reference. Additionally, current-limiting resistors may be selected. The current-limiting resistors will have a large positive temperature coefficient of resistance so that, as the current level begins to rise for any individual active electrode in contact with a low resistance medium (e.g., saline or blood), the resistance of the current limiting resistor increases significantly, thereby reducing the power delivery from the active electrode into the low resistance medium. In some embodiments, the current limited devices may reside within theelongate shaft106, or may reside within theflexible cable112.
• As illustrated inFIG. 1, flexible multi-conductor cable112 (and more particularly its constituent electrical leads302) couple to thewand connector114.Wand connector114 couples to thecontroller104, and more particularly thecontroller connector120.FIG. 4 shows both a cross-sectional view (right) and an end elevation view (left) ofwand connector114 in accordance with at least some embodiments. In particular,wand connector114 comprises atab400.Tab400 works in conjunction with a slot on controller connector120 (shown inFIG. 5) to ensure that thewand connector114 andcontroller connector120 only couple in one relative orientation. Theillustrative wand connector114 further comprises a plurality ofelectrical pins402 protruding fromwand connector114. Theelectrical pins402 are coupled one each to a singleelectrical lead302. Stated otherwise, eachelectrical pin402 couples to a singleelectrical lead302, and thus each illustrativeelectrical pin402 couples to a single electrode300 (FIG. 3). WhileFIG. 4 shows only four illustrative electrical pins, in some embodiments up to 26 or more electrical pins may be present in thewand connector114.
• FIG. 5 shows both a cross-sectional view (right) and an end elevation view (left) ofcontroller connector120 in accordance with at least some embodiments. In particular,controller connector120 comprises aslot500. Slot500 works in conjunction with atab400 on wand connector114 (shown inFIG. 4) to ensure that thewand connector114 andcontroller connector120 only couple in one orientation. Theillustrative controller connector120 further comprises a plurality ofelectrical pins502 residing with respective holes ofcontroller connector120. Theelectrical pins502 are each individually coupled to a relay within the controller104 (discussed more thoroughly below). Whenwand connector114 andcontroller connector120 are coupled, eachelectrical pin502 couples to a singleelectrical pin402, and thus each illustrativeelectrical pin502 couples to a single electrode300 (FIG. 3). WhileFIG. 5 shows only four illustrative electrical pins, in some embodiments as many as 26 or more electrical pins may be present in thewand connector120.
• Whileillustrative wand connector114 is shown to have thetab400 and maleelectrical pins402, andcontroller connector120 is shown to have theslot500 and femaleelectrical pins502, in alternative embodiments the wand connector has the female electrical pins and slot, and thecontroller connector120 has the tab and male electrical pins. In other embodiments, the arrangement of the pins within the connectors may enable only a single orientation for connection of the connectors, and thus the tab and slot arrangement may be omitted. In yet still other embodiments, other suitable mechanical arrangements to ensure the wand connector and controller connector couple in only one orientation may be equivalently used.
• FIG. 6 illustrates acontroller104 in accordance with at least some embodiments. In particular, thecontroller104 in accordance with at least some embodiments comprises aprocessor600. Theprocessor600 may be a microcontroller, and therefore the microcontroller may be integral with read-only memory (ROM)602, random access memory (RAM)604, digital-to-analog converter (D/A)606, digital outputs (D/O) and digital inputs (D/I)610. Theprocessor600 may further provide one or more externally available peripheral busses, such as a serial bus (e.g., I²C), parallel bus, or other bus and corresponding communication mode. Theprocessor600 may further be integral with acommunication logic612 to enable theprocessor600 to communicate with external devices, as well as internal devices, such asdisplay device124. Although in some embodiments thecontroller104 may implement a microcontroller, in yet other embodiments theprocessor600 may be implemented as a standalone central processing unit in combination with individual RAM, ROM, communication, D/A, D/O and D/I devices, as well as communication port hardware for communication to peripheral components.
• ROM602 stores instructions executable by theprocessor600. In particular, theROM602 may comprise a software code that implements the various embodiments of selectively coupling the electrodes of the wand to thevoltage generator616, as well as interfacing with the user by way of the display device614 and/or the foot pedal assembly130 (FIG. 1) and/or a speaker assembly (not specifically shown). TheRAM604 may be the working memory for theprocessor600, where data may be temporarily stored and from which instructions may be executed.Processor600 couples to other devices within thecontroller104 by way of the D/A converter606 (i.e., the voltage generator616), digital outputs608 (i.e., electrically controlled switches620), digital inputs610 (i.e., push button switches126, and the foot pedal assembly130 (FIG.1)), communication device612 (i.e., display device124), and other peripheral devices. The other peripheral devices may comprise electrode relays and/or switches, devices to set desiredvoltage generator616 output voltage, and other secondary devices internal to the generator.
• Voltage generator616 generates selectable alternating current (AC) voltages that are applied to the electrodes of thewand102. In some embodiments, the voltage generator defines anactive terminal624 and areturn terminal626. Theactive terminal624 is the terminal upon which the voltages and electrical currents are induced by thevoltage generator616, and thereturn terminal626 provides a return path for electrical currents. In some embodiments, thereturn terminal626 may provide a common or ground being the same as the common or ground within the balance of the controller104 (e.g., the common628 used on push-buttons622), but in other embodiments thevoltage generator616 may be electrically “floated” from the balance of the supply power in thecontroller104, and thus thereturn terminal626, when measured with respect to the common (e.g., common628) within thecontroller104, may show a voltage difference; however, an electrically floatedvoltage generator616 and thus the potential for voltage readings on thereturn terminal626 does not negate the return terminal status of the terminal626 relative to theactive terminal624.
• The voltage generated and applied between theactive terminal624 and return terminal626 by thevoltage generator616 is a RF signal that, in some embodiments, has a frequency of between about 5 kilo-Hertz (kHz) and 20 Mega-Hertz (MHz), in some cases being between about 30 kHz and 2.5 MHz, preferably being between about 50 kHz and 500 kHz, often less than 350 kHz, and often between about 100 kHz and 200 kHz. In some applications, a frequency of about 100 kHz is useful because target tissue impedance is much greater at 100 kHz. In other applications, such as procedures in or around the heart or head and neck, higher frequencies may be desirable (e.g., 400-600 kHz) to reduce low frequency current flow into the heart or the nerves of the head and neck.
• The RMS (root mean square) voltage generated by thevoltage generator616 may be in the range from about 5 Volts (V) to 1000 V, preferably being in the range from about 10 V to 500 V, often between about 10 V to 400 V depending on the active electrode size, the operating frequency and the operation mode of the particular procedure or desired effect on the tissue (i.e., contraction, coagulation, cutting or ablation). The peak-to-peak voltage generated by thevoltage generator616 for ablation or cutting in some embodiments is a square wave form in the range of 10 V to 2000 V and in some cases in the range of 100 V to 1800 V and in other cases in the range of about 28 V to 1200 V, often in the range of about 100 V to 320V peak-to-peak (again, depending on the electrode size, number of electrodes the operating frequency and the operation mode). Lower peak-to-peak voltage is used for tissue coagulation, thermal heating of tissue, or collagen contraction and may be in the range from 50 V to 1500V, preferably 100 V to 1000 V and more preferably 60 V to 130 V peak-to-peak (again, these values are computed using a square wave form).
• The voltage and current generated by thevoltage generator616 may be delivered in a series of voltage pulses or AC voltage with a sufficiently high frequency (e.g., on the order of 5 kHz to 20 MHz) such that the voltage is effectively applied continuously (as compared with, e.g., lasers claiming small depths of necrosis, which are pulsed about 10 Hz to 20 Hz). In addition, the duty cycle (i.e., cumulative time in any one-second interval that energy is applied) of the square wave voltage produced by thevoltage generator616 is on the order of about 50% for some embodiments as compared with pulsed lasers which may have a duty cycle of about 0.0001%. Although square waves are generated and provided in some embodiments, the various embodiments may be equivalently implemented with many applied voltage waveforms (e.g., sinusoidal, triangular).
• Still referring to thevoltage generator616, thevoltage generator616 delivers average power levels ranging from several milliwatts to hundreds of watts per electrode, depending on the voltage applied to the target electrode for the target tissue being treated, and/or the maximum allowed temperature selected for thewand102. Thevoltage generator616 is configured to enable a user to select the voltage level according to the specific requirements of a particular neurosurgery procedure, cardiac surgery, arthroscopic surgery, dermatological procedure, ophthalmic procedures, open surgery or other endoscopic surgery procedure. For cardiac procedures and potentially for neurosurgery, thevoltage generator616 may have a filter that filters leakage voltages at frequencies below 100 kHz, particularly voltages around 60 kHz. Alternatively, avoltage generator616 configured for higher operating frequencies (e.g., 300 kHz to 600 kHz) may be used in certain procedures in which stray low frequency currents may be problematic. A description of onesuitable voltage generator616 can be found in commonly assigned U.S. Pat. Nos. 6,142,992 and 6,235,020, the complete disclosure of both patents are incorporated herein by reference for all purposes.
• In accordance with at least some embodiments, thevoltage generator616 is configured to limit or interrupt current flow when low resistivity material (e.g., blood, saline or electrically conductive gel) causes a lower impedance path between the return electrode(s) and the active electrode(s). Further still, in some embodiments thevoltage generator616 is configured by the user to be a constant current source (i.e., the output voltage changes as function of the impedance encountered at the wand102).
• In some embodiments, the various operational modes of thevoltage generator616 may be controlled by way of digital-to-analog converter606. That is, for example, theprocessor600 may control the output voltage by providing a variable voltage to thevoltage generator616, where the voltage provided is proportional to the voltage generated by thevoltage generator616. In other embodiments, theprocessor600 may communicate with the voltage generator by way of one or more digital output signals from thedigital output608 device, or by way of packet based communications using thecommunication612 device (the alternative embodiments not specifically shown so as not to unduly complicateFIG. 6).
• In addition to controlling the output of thevoltage generator616, in accordance with the various embodiments thecontroller104 is also configured to selectively electrically couple theactive terminal624 singly or in combination to the electrodes of the wand (by way of the electrical pins of the controller connector120). Likewise, in the various embodiments, thecontroller104 is also configured to selectively electrically couple thereturn terminal626 singly or in combination to the electrodes of the wand (again by way of the electrical pins of the controller connector120). In order to perform the selective coupling, thecontroller104 implements a control circuit630, shown in dashed lines inFIG. 6. For convenience of the figure the control circuit has two parts,630A and630B, but the two parts nevertheless comprise the control circuit630. In particular, the control circuit630 comprises theprocessor600, voltage controlledswitches620 and mechanic relays R1-R6. The coils of relays R1-R6 are shown withinportion630A, while the contacts for each mechanical relay are shown withinportion630B. The correlation between the coils for mechanical relays R5 and R6 and the contacts for mechanical relays R5 and R6 are shown by dashed arrow-headedlines650 and652 respectively. The correlation between the remaining coils and contacts is not specifically shown with arrow-headed lines so as not to unduly complicate the figure; however, the correlation is noted by way of corresponding references.
• In accordance with at least some embodiments, at least three electrodes of thewand102 are separately electrically coupled to thecontroller104. Thus, the description ofFIG. 6 is based on three separately electrically coupled electrodes, but it will be understood that three or more separately electrically coupled electrodes may be used. The electrical pin of thecontroller connector120 for each electrode is configured to be selectively coupled to either theactive terminal624 or thereturn terminal626. For example, the electrical lead configured to coupleillustrative electrode1 ofFIG. 6 couples to the normally open contact terminals for the mechanical relays R1 and R2. The other side of the normally open contact for mechanical relay R1 couples to theactive terminal624, while the other side of the normally open contact for the mechanical relay R2 couples to thereturn terminal626. Thus, by selectively activating mechanical relay R1 or mechanical relay R2,electrode1 can be either an active or return electrode in the surgical procedure. Alternatively, both relays can remain inactivated, and thuselectrode1 may remain unconnected.
• Similarly, the electrical lead configured to coupleillustrative electrode2 couples to the normally open contact terminals for the mechanical relays R3 and R4. The other side of the normally open contact for mechanical relay R3 couples to theactive terminal624, while the other side of the normally open contact for the mechanical relay R4 couples to thereturn terminal626. Thus, by selectively activating mechanical relay R3 or mechanical relay R4,electrode2 can be either an active or return electrode in the surgical procedure. Alternatively, both relays R3 and R4 can remain inactivated, and thuselectrode2 may remain unconnected. Finally with respect to theillustrative electrode3, the electrical lead configured to couple toillustrative electrode3 couples to the normally open contact terminals for the mechanical relays R5 and R6. The other side of the normally open contact for mechanical relay R5 couples to theactive terminal624, while the opposite side of the normally open contact for the mechanical relay R6 couples to thereturn terminal626. Thus, by selectively activating mechanical relay R5 or mechanical relay R6,electrode3 can be either an active or return electrode in the surgical procedure. Alternatively, both relays can remain inactivated, and thuselectrode3 may remain unconnected.
• In accordance with at least some embodiments, mechanical relays R1-R6 are selectively activated (by way of their respective coils634) by voltage controlled switches620. For example, when the control circuit630 desires to couple the active terminal toelectrode1, the voltage controlled switch620A is activated, which allows current to flow through thecoil634A of mechanical relay R1. Current flow through thecoil634 activates the relay, thus closing (making conductive) the normally open contacts. Similarly, the control circuit630 may selectively activate any of the voltage controlledswitches620, which in turn activate respective mechanical relays R1-R6. In accordance with at least some embodiments, each mechanical relay is a part number JW1FSN-DC 12V relay available from Panasonic Corporation of Secaucus, N.J.; however, other mechanical relays may be equivalently used. Moreover, whileFIG. 6 illustrates the use of field effect transistors as the voltage controlledswitches620 to control the current flow through coils of the mechanical relays, other devices (e.g., transistors, or if coils use AC driving current, triacs) may be equivalently used. Further still, in embodiments where thedigital outputs608 have sufficient current carrying capability, the voltage controlled switches may be omitted.
• The selection of which electrode(s) of thewand102 be active electrodes, and which electrode(s) to be return electrodes, may be determined in any of several forms. For example, a user may observe options for electrode selection by way of thedisplay device124, and may select particular options by interaction with thecontroller104 by way ofpush buttons126. In other embodiments, selection of particular electrodes as active or return may be made way of footpedal assembly102. In the embodiments illustrated inFIG. 6, selection of particular electrodes as active or return is conveyed to theillustrative processor600 by way of thedigit inputs610; however,FIG. 6 is merely illustrative of a control circuit630 implemented using a processor. In other embodiments, the processor may be omitted and the logic implemented by way of discrete logic devices.
• In order to illustrate the flexibility of the electrosurgical system in accordance with the various embodiments, the table below shows the possible status of each electrode in a system having an illustrative three electrodes:

• 	TABLE (1)
  	Electrode 1	Electrode 2	Electrode 3
  	Isolated	Isolated	Isolated
  	Return	Active	Active
  	Return	Return	Active
  	Active	Return	Return
  	Active	Active	Return
  	Active	Isolated	Return
  	Return	Isolated	Active
  	Isolated	Active	Return
  	Isolated	Return	Active
  	Active	Return	Isolated
  	Return	Active	Isolated

  
  Where “Isolated” indicates that a particular electrode is connected to neither the active terminal nor the return terminal of the voltage generator, “Active” means that the electrode is connected to the active terminal of the voltage generator, and “Return” means that the electrode is coupled to the return terminal of the voltage generator. It should be noted that in certain configurations an “isolated” electrode may still attract current and may heat up, acting essentially as an antennae. In this scenario, the isolated state may be referred to as “floating.” Table (1) illustrates that, in accordance with at least some embodiments, an electrode of the wand can be an active electrode or a return electrode, and that depending on the mode of operation, multiple electrodes may be the active electrode at any one time. Likewise, multiple electrodes may be a return electrode at any one time.
• FIG. 7 illustrates a method in accordance with at least some embodiments. In particular, the method starts (block700) and proceeds to treating a first portion of a target tissue with an electrosurgical wand electrically coupled to a controller by a connector by generating a current path between a first electrode of the wand as an active electrode, and a second electrode of the wand as a return electrode (block704), for example, during a molecular disassociation. Then, and without de-coupling the connector from the controller, the method proceeds to electrically isolating both the first and second electrodes (block708), activating a third electrode of the electrosurgical wand as an as an active electrode with the third electrode different than the first and second electrodes (block712), and activating a fourth electrode of the electrosurgical wand as a return electrode with the fourth electrode different than the first and second electrodes (block716). Thereafter, the method comprises treating a second portion of the target tissue with the electrosurgical wand (block720), and the method ends (block724). Treating the second portion of the target tissue may comprise, for example, generating a current path between the third and fourth electrodes during a molecular disassociation
• The above discussion is meant to be illustrative of the principles and various embodiments of the present invention. Numerous variations and modifications possible. For example, while three or more electrodes may have the ability to be either active, return or isolated, other electrodes may be present without departing from the scope and spirit of the invention. Moreover, two electrodes may be electrically coupled within thewand102, such that the coupled electrodes act as single electrode from the perspective of the controller, with the ability to be active, return or isolated. Further still, the system may provide audible feedback to the user as to the selected electrode configuration and/or voltage output level. For example, inFIG. 6 the audible feedback may be provided by way ofspeaker670 coupled to the digital-to-analog converter606. It is intended that the following claims be interpreted to embrace all such variations and modifications.
• While preferred embodiments of this disclosure have been shown and described, modifications thereof can be made by one skilled in the art without departing from the scope or teaching herein. The embodiments described herein are exemplary only and are not limiting. Because many varying and different embodiments may be made within the scope of the present inventive concept, including equivalent structures, materials, or methods hereafter though of, and because many modifications may be made in the embodiments herein detailed in accordance with the descriptive requirements of the law, it is to be understood that the details herein are to be interpreted as illustrative and not in a limiting sense.

Claims (26)

1. A system comprising:

a wand comprising a non-conductive outer surface, at least three electrodes disposed on a distal end of the wand, and at least three electrical leads extending from a proximal end of the wand, one electrical lead electrically coupled to each electrode; and

a controller comprising:

a controller connector coupled to the electrical leads;

a voltage generator configured to generate voltage of varying amplitude, the voltage generator has an active terminal and a return terminal; and

a control circuit coupled between the controller connector and the voltage generator;

the control circuit configured to selectively electrically couple the active terminal singly and in combination to the electrodes of the wand; and

the control circuit configured to selectively electrically couple the return terminal singly and in combination to electrodes of the wand.

2. The system ofclaim 1 wherein the controller further comprises an operator interface device, and wherein the control circuit is configured to selectively electrically couple the active and return terminals to the electrical leads based on commands received through the operator interface.

3. The system ofclaim 1 further comprising a foot pedal assembly operationally coupled to the controller, and wherein the control circuit is configured to selectively electrically couple the active and return terminals based on actuation of the foot pedal.

4. The system ofclaim 1 wherein the wand further comprises an internal passage, and wherein at least one electrode resides within the internal passage proximate to the distal end of the wand.

5. The system ofclaim 1 further comprising:

a wand connector coupled to the electrical leads, the wand connector comprising at least three electrical pins, one pin electrically coupled to each electrical lead;

wherein the controller connector and wand connector are configured to couple in only one orientation.

6. The system ofclaim 5 wherein the wand connector and controller connector further comprise a tab and slot arrangement where the tab and slot are configured to allow the connectors to couple in the only one orientation.

7. The system ofclaim 6 wherein the tab and slot arrangement is at least one selected from the group consisting of: the tab on the wand connector and the slot on the controller connector; and the tab on the controller connector and the slot on the wand connector.

8. The system ofclaim 1 wherein each electrode of the defines a surface area, and at least one electrode has a surface area less than three-quarters the surface area of another electrode.

9. The system ofclaim 1 wherein distances between centers of each electrode are constant during deployment and use.

10. An electrosurgical wand comprising:

an elongate shaft that defines a proximal end and a distal end, at least a portion of the exterior surface comprising non-conductive material;

a connector comprising a plurality of pins;

a first electrode disposed on the distal end of the elongate shaft, and a first electrical lead electrically coupled to the first electrode and a first pin of the connector;

a second electrode disposed on the distal end of the elongate shaft, and a second electrical lead electrically coupled to the second electrode and a second pin of the connector; and

a third electrode disposed on the distal end of the elongate shaft, and a third electrical lead electrically coupled to the third electrode and a third pin of the connector;

each electrode defines a center, and distances between centers are fixed; and

wherein each electrode is configured to be selectively coupled to a high frequency voltage generator as an active electrode and as a return electrode.

11. The electrosurgical wand ofclaim 10 further comprising an internal passage at least partially through the elongate shaft and having an aperture at the distal end of the elongate shaft.

12. The electrosurgical wand ofclaim 11 further comprising the first electrode disposed within the internal passage.

13. The electrosurgical wand ofclaim 10 wherein the connector is further configured to couple to a connector of a controller in only one orientation.

14. The electrosurgical wand ofclaim 13 wherein the connector comprises at least one selected from the group consisting of: a tab configured to mechanically couple to a slot of the connector of the controller; and a slot configured to mechanically couple to a tab of the connector of the controller.

15. The electrosurgical wand ofclaim 10 wherein each electrode of the wand defines a surface area, and at least one electrode has a surface area less than three-quarters the surface area of another electrode.

16. An electrosurgical controller comprising:

a first connector disposed on an outer surface of the electrosurgical controller, the first connector configured to couple to a connector of an electrosurgical wand, and the first connector comprising at least three electrical pins;

a voltage generator configured to generate a selectable alternating current (AC) output voltage, the voltage generator has a active terminal and a return terminal;

a control circuit coupled between the first connector and the voltage generator, the control circuit configured to selectively electrically couple the active terminal singly or in combination to the electrical pins of the first connector; and

the control circuit configured to selectively electrically couple the return terminal singly or in combination to the electrical pins of the first connector.

17. The electrosurgical controller ofclaim 16 wherein the connector is further configured to couple to the connector of an electrosurgical wand in only one orientation.

18. The electrosurgical controller ofclaim 17 wherein the connector comprises at least one selected from the group consisting of: a tab configured to mechanically couple to a slot of the connector of the electrosurgical wand; and a slot configured to mechanically couple to a tab of the connector of the electrosurgical wand.

19. The electrosurgical controller ofclaim 16 further comprising:

a second connector disposed on the outer surface of the electrosurgical controller, the second connector configured to couple to a pedal device;

the control circuit is configured to select a configuration of electrically coupling the active and return terminals to the electrical pins based on the actuation of the pedal.

20. The electrosurgical controller ofclaim 16 further comprising:

an interface panel visible on the outer surface of the electrosurgical controller, and the interface panel electrically coupled to the control circuit;

the control circuit is configured to select a configuration of electrically coupling the active and return terminals to the electrical pins based on a user's interaction with the interface panel.

21. A method comprising:

treating a first portion of a target tissue with an electrosurgical wand electrically coupled to a controller by a connector, wherein treating the first portion comprises generating a current path between a first electrode of the wand as an active electrode, and a second electrode and a third electrode of the wand as return electrodes; and without de-coupling the connector from the controller;

electrically isolating the first, second, and third electrodes;

activating the third electrode of the electrosurgical wand as an active electrode;

activating a fourth electrode of the electrosurgical wand and at least one of the first and second electrodes as return electrodes, the fourth electrode different than the first and second electrodes; and then treating a second portion of the target tissue with the electrosurgical wand, wherein treating the second portion comprises generating a current path between the third and fourth electrodes and the at least one of the first and second electrodes.

22. The method ofclaim 21 wherein electrically isolating and activating further comprises interacting with an operator interface device on a controller.

23. The method ofclaim 21 wherein electrically isolating and activating further comprises interacting with a foot pedal device.

24. The method ofclaim 21 further comprising, concurrently with activating the third electrode as an active electrode, activating a fifth electrode of the electrosurgical wand as an active electrode, the fifth electrode different than the first and second electrode.

25. An electrosurgical wand comprising:

an elongate shaft that defines a proximal end and a distal end;

a connector comprising a plurality of pins;

at least two first electrodes disposed on the distal end of the elongate shaft;

at least two second electrodes disposed on the distal end of the elongate shaft;

wherein each of the electrodes is electrically coupled to one of the plurality of pins via an electrical lead;

wherein each of the at least two first electrodes have a surface area less than three-quarters the surface area of each of the at least two second electrodes; and

wherein in a first mode the at least two first electrodes are coupled to a high frequency voltage generator as active electrodes and the at least two second electrodes are coupled to the voltage generator as return electrodes.

26. The electrosurgical wand ofclaim 25 wherein in a second mode at least one of the first electrodes is electrically isolated from the voltage generator.

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