Patent Abstract:
Herein disclosed are dual-mode electrosurgical devices designed to function in a first mode in which high-density RF energy is used to cut or vaporize tissue, and then a second mode in which lower-density RF energy desiccates tissue to produce hemostasis, as well as methods of performing electrosurgery using same. Devices formed in accordance with the principles of this invention may be used for any surgical procedure in which highly vascular tissue is cut electrosurgically in a dry or semi-dry field, examples of which include tonsillectomy, liver resection, and cosmetic procedures such as breast augmentation, breast reduction, breast mastopexy, and abdominoplasty.

Full Description:
PRIORITY 
     This application claims the benefit of U.S. Provisional Application Ser. No. 61/574,821 filed Aug. 10, 2011, the entire contents of which are incorporated by reference herein. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates generally to the field of medical instruments, and more particularly relates to surgical devices and methods that use radio frequency (RF) electrical energy for cutting and/or bulk removal by vaporization and coagulation with externally supplied liquid irrigants. 
     BACKGROUND OF THE INVENTION 
     Various types of electrosurgical devices are known and used in the medical field. Typically, such devices include a conductive tip that serves as an electrode in an electrical circuit which is completed either via a return electrode coupled to the patient or a return electrode mounted on the same device. Cutting and coagulation are essential operations of many electrosurgical devices. While the waveform of the supplied power to the electrode may affect the result, to a large extent the effect produced by a given device is determined by the density of the Radio Frequency (RF) current passing from the active electrode of the device to the tissue at the surgical site. High current density causes arcing to the tissue so as to produce cutting or bulk vaporization. Low current density causes tissue desiccation and hemostasis. 
     Bleeding is a common, yet undesired occurrence in medical surgical procedures because they may pose a threat to the patient, obscure the field of vision of the surgeon and interfere with the medical procedure. Stopping bleeding is time consuming and may be irritating to the physician. Various approaches to treat bleeding during surgery including medications, dressing and specialty devices are known 
     Another approach used in electrosurgical devices to switch from a cutting/evaporation mode to a coagulation mode is to change the power to the electrosurgical device, change the waveform, or both. For example, the medical staff may use a special interrupted waveform, like COAG, and a lower power level in order to treat bleeding. The problem with prior art electrosurgical devices has been that it is difficult to achieve both cutting/evaporation and coagulation in the same instrument even if a COAG waveform and a reduced power level are used either independently or jointly. 
     Muller et al. in U.S. Pat. No. 7,364,579 teaches an electrocautery device for achieving hemostasis, the device having an electrically conductive element, the element being either a freely rotating spherical element, or a “plug made of an electrically conductive porous material”. Also that “the conductive fluid emanating from the electrode/tip conducts the RF electrocautery energy away from the distal tip so that it is primarily the fluid, rather than the distal tip that actually accomplishes the cauterizing of tissue.” The devices taught by Mulier have geometry configured for cautery of surfaces and are used in conjunction with other cutting devices. The devices themselves are incapable of cutting tissue. In U.S. Pat. No. 7,794,460 Mulier et al. teaches a “fluid delivered out of a hollow electrocautery electrode/tip creates a virtual electrode which incises and cauterizes the tissue.” Although it is claimed that the fluid may “incise” the tissue, because the applied fluid spreads out freely over the tissue, it is incapable of “incising” or cutting the tissue. The device taught by Mulier is a cauterizing device only, both because of its electrode configuration (no cutting edges) and its continuous irrigant flow 
     In view of the foregoing problems it has been recognized as desirable to find an improved surgical device effective both for cutting/evaporation and also coagulation without the need to change either the power or the waveform. 
     SUMMARY OF THE INVENTION 
     In view of the foregoing considerations, the present invention is directed to an improved, dual-mode instrument. The present invention discloses devices having the ability to quickly change the current density at the electrode during use and thereby switch from the cutting/evaporation mode to the coagulation mode (dual-mode). In a first embodiment the current density is reduced by supplying an irrigant on command to the site only when desiccation is desired, the conductivity of the irrigant stream causing current to be dispersed where irrigant is in contact with the tissue. In a second embodiment the electrode device has a cutting edge with two adjacent regions, a first configured for high current density cutting and bulk vaporization, and a second configured for low current density for desiccation, again with irrigation supplied to the site selectively so as to control the current density. In a third embodiment the active electrode is an assembly having a first movable element and a second fixed element, the movable element in a first position contacting the tissue as a cutting element, and with the movable element in a second position the second fixed element contacting tissue so as to produce desiccation. In yet a fourth embodiment a “brush” of non-conductive fibers (bristles) spreads conductive irrigant over the site so as to reduce the current density and produce desiccation. In a fifth embodiment the nonconductive fibers are randomly oriented so as to form a wool or mat which is saturated with conductive irrigant which forms a conductive path for RF energy to tissue which contacts the nonconductive wool. 
     Irrigant may be supplied to the device by gravity from a hung bag, by a manual pump activated by the surgeon, or by a mechanical pump. Irrigant may be supplied to the surgical site upon manual action, or electrical activation by the surgeon. 
     Devices formed in accordance with the principles of this invention may be used for any surgical procedure in which highly vascular tissue is cut electrosurgically in a dry or semi-dry field. Examples include but are not limited to tonsillectomy, liver resection, and cosmetic procedures such as breast augmentation, breast reduction or tummy tucks. 
     The above-noted objects and features of the invention will become more fully apparent when the following detailed description is read in conjunction with the accompanying figures and/or examples. However, it is to be understood that both the foregoing summary of the invention and the following detailed description are of a preferred embodiment and not restrictive of the invention or other alternate embodiments of the invention. In particular, while the invention is described herein with reference to a number of specific embodiments, it will be appreciated that the description is illustrative of the invention and is not constructed as limiting of the invention. Various modifications and applications may occur to those who are skilled in the art, without departing from the spirit and the scope of the invention, as described by the appended claims. Likewise, it will be understood by those skilled in the art that one or more aspects of this invention can meet certain of the above objectives, while one or more other aspects can meet certain other objectives. Each objective may not apply equally, in all its respects, to every aspect of this invention. As such, the objectives disclosed herein should be viewed in the alternative with respect to any one aspect of this invention. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
       Various aspects and applications of the present invention will become apparent to the skilled artisan upon consideration of the brief description of the figures and the detailed description of the present invention and its preferred embodiments that follows: 
         FIG. 1  depicts and electrosurgical system constructed in accordance with the principles of this invention. 
         FIG. 2  is a plan view of an active electrode for an electrosurgical device and system constructed in accordance with the principles of this invention. 
         FIG. 3  is a side elevational view of the objects of  FIG. 2 . 
         FIG. 4  is a perspective view of the objects of  FIG. 2 . 
         FIG. 5  is a distal axial view of the objects of  FIG. 2 . 
         FIG. 6  is a plan view of an electrosurgical device for use with the active electrode of  FIG. 2 . 
         FIG. 7  is a side elevational view of the objects of  FIG. 6 . 
         FIG. 8  perspective views of the objects of  FIG. 6 . 
         FIG. 9  is a distal axial view of the objects of  FIG. 6 . 
         FIG. 10  is an expanded view of the distal portion of  FIG. 6 . 
         FIG. 11  is a side elevational view of the objects of  FIG. 10 . 
         FIG. 12  is a perspective view of the objects of  FIG. 10 . 
         FIG. 13  is a distal axial view of the objects of  FIG. 10 . 
         FIG. 14  is a plan view of an electrode for use in another alternate embodiment. 
         FIG. 15  is a side elevational view of the objects of  FIG. 14 . 
         FIG. 16  is a perspective view of the objects of  FIG. 14 . 
         FIG. 17  is a distal axial view of the objects of  FIG. 14 . 
         FIG. 18  is a plan view of an irrigation collar for use with the electrode of  FIG. 14 . 
         FIG. 19  is a side elevational view of the objects of  FIG. 18 . 
         FIG. 20  is a side elevational sectional view of the objects of  FIG. 14  at location A-A of  FIG. 18 . 
         FIG. 21  is a perspective view of the objects of  FIG. 18 . 
         FIG. 22  is a distal axial view of the objects of  FIG. 18 . 
         FIG. 23  is a plan view of the electrode of  FIG. 14  assembled to the irrigation collar of  FIG. 18 . 
         FIG. 24  is a side elevational view of the objects of  FIG. 23 . 
         FIG. 25  is a side elevational sectional view of the objects of  FIG. 23  at location A-A of  FIG. 23 . 
         FIG. 26  is a perspective view of the objects of  FIG. 23 . 
         FIG. 27  is a distal axial view of the objects of  FIG. 23 . 
         FIG. 28  is a plan view of another alternate embodiment having an extendable active electrode element and constructed in accordance with the principles of this invention, the active electrode being in a first extended position. 
         FIG. 29  is a side elevational view of the objects of  FIG. 28 . 
         FIG. 30  is a plan view of the distal portion of the objects of  FIG. 28 . 
         FIG. 31  is a side elevational sectional view of the objects of  FIG. 30  at location A-A of  FIG. 30 . 
         FIG. 32  is a perspective view of the objects of  FIG. 28 . 
         FIG. 33  is a distal axial view of the objects of  FIG. 28 . 
         FIG. 34  is an expanded perspective view of the distal portion of the objects of  FIG. 32 . 
         FIG. 35  is a plan view of the alternate embodiment of  FIG. 28  with the extendable active electrode element in the second retracted position. 
         FIG. 36  is a side elevational view of the objects of  FIG. 35 . 
         FIG. 37  is a perspective view of the objects of  FIG. 35 . 
         FIG. 38  is an expanded perspective view of the distal portion of the objects of  FIG. 37 . 
         FIG. 39  is an expanded plan view of the objects of  FIG. 37 . 
         FIG. 40  is a side elevational sectional view of the objects of  FIG. 39  at location A-A of  FIG. 39 . 
         FIG. 41  is an expanded plan view of the distal portion of another alternate embodiment constructed in accordance with the principles of this invention, the embodiment being like the embodiment of  FIGS. 28 through 40  but with nonconductive fibers affixed to the distal end of the fixed electrode element to form an electrode brush. 
         FIG. 42  is a side elevational sectional view of the objects of  FIG. 41 . 
         FIG. 43  is a plan view of the objects of  FIG. 41  but with the movable electrode element being in the retracted position rather than the extended position of  FIGS. 41 and 42 . 
         FIG. 44  is a side elevational sectional view of the objects of  FIG. 43  at location A-A of  FIG. 43 . 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     A unifying concept of the embodiments of this invention is the ability of the devices herein disclosed to function in a first mode in which high-density RF energy is used to cut or vaporize tissue, and a second mode in which lower-density RF energy desiccates tissue to produce hemostasis. Although any methods and materials similar or equivalent to those described herein can be used in the practice or testing of embodiments of the present invention, the preferred methods, devices, and materials are now described. However, before the present materials and methods are described, it is to be understood that this invention is not limited to the particular compositions, methodologies or protocols herein described, as these may vary in accordance with routine experimentation and optimization. It is also to be understood that the terminology used in the description is for the purpose of describing the particular versions or embodiments only, and is not intended to limit the scope of the present invention which will be limited only by the appended claims. 
     DEFINITIONS 
     In the context of the present invention, the following definitions apply: 
     The words “a”, “an”, and “the” as used herein mean “at least one” unless otherwise specifically indicated. 
     In common terminology and as used herein, the term “electrode” may refer to one or more components of an electrosurgical device (such as an active electrode or a return electrode) or to the entire device, as in an “ablator electrode” or “cutting electrode”. Such electrosurgical devices are often interchangeably referred to herein as electrosurgical “probes” or “instruments”. 
     The present invention makes reference to an “active electrode” or “active element”. As used herein, the term “active electrode” refers to one or more conductive elements formed from any suitable metallic material, such as stainless steel, nickel, titanium, tungsten, and the like, connected, for example via cabling disposed within the elongated proximal portion of the instrument, to a power supply, for example, an externally disposed electrosurgical generator, and capable of generating an electric field. 
     In certain embodiments, the present invention makes reference to a “return electrode”. As used herein, the term “return electrode” refers to one or more powered conductive elements to which current flows after passing from the active electrode(s) back to the electrical RF generator. This return electrode may be located on the ablator device or in close proximity thereto and may be formed from any suitable electrically conductive material, for example a metallic material such as stainless steel, nickel, titanium, tungsten, aluminum and the like. Alternatively, one or more return electrodes, referred to in the art as “dispersive pads” or “return pads”, may be positioned at a remote site on the patient&#39;s body. 
     In certain embodiments, the present invention makes reference to “fluid(s)”. As used herein, the term “fluid(s)” refers to liquid(s), either electrically conductive or non-conductive, and to gaseous material, or a combination of liquid(s) and gas(as). 
     The term “proximal” refers to that end or portion which is situated closest to the user; in other words, the proximal end of an electrosurgical instrument of the instant invention will typically include the handle portion. 
     The term “distal” refers to that end or portion situated farthest away from the user; in other words, the distal end of an electrosurgical instrument of the instant invention will typically include the active electrode portion. 
     In certain embodiments, present invention makes reference to the vaporization of tissue. As used herein, the term “tissue” refers to biological tissues, generally defined as a collection of interconnected cells that perform a similar function within an organism. Four basic types of tissue are found in the bodies of all animals, including the human body and lower multicellular organisms such as insects, including epithelium, connective tissue, muscle tissue, and nervous tissue. These tissues make up all the organs, structures and other body contents. The present invention is not limited in terms of the tissue to be treated but rather has broad application to the vaporization any target tissue with particular applicability to the ablation, destruction and removal of problematic joint tissues. 
     The instant invention has both human medical and veterinary applications. Accordingly, the terms “subject” and “patient” are used interchangeably herein to refer to the person or animal being treated or examined. Exemplary animals include house pets, farm animals, and zoo animals. In a preferred embodiment, the subject is a mammal. 
     Unless otherwise defined, 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. In case of conflict, the present specification, including definitions, will control. 
     EXAMPLES 
     Hereinafter, the present invention is described in more detail by reference to the exemplary embodiments. However, the following examples only illustrate aspects of the invention and in no way are intended to limit the scope of the present invention. As such, embodiments similar or equivalent to those described herein can be used in the practice or testing of the present invention. 
       FIG. 1  depicts an electrosurgical system constructed in accordance with the principles of this invention. Electrosurgical device  100  constructed in accordance with the principles of this invention is connected by cord  20  to electrosurgical generator  22 , and by tubular element  24  to flow control element  26 , and therethrough by tubular member  28  to irrigant source  30 . In the preferred embodiment depicted, control element  26  is a foot control; in others control element  26  is a valve controlled by electrosurgical device  100 . The foot control  26  depicted has a fluid control means  32  which may be a valve which allows irrigant from source  30  to flow to device  100  when the foot control  26  is depressed. In another embodiment, foot control  26  fluid control means  32  is a deformable vessel having valves such that depressing the foot pedal causes a volume of irrigant to be expelled from the vessel and supplied to device  100  via tube  20 . When the volume is expelled, the foot pedal is allowed to return to its first position and the vessel refills with irrigant from source  30  via tube  28 . 
     It will be understood that foot control  26  may be replaced with another control means without departing from the principles of this invention. For instance, the control means may be part of the handle with an activation means such as a button or deformable vessel, or may be combined with the button for activating the electrosurgical generator such that activating the generator in a coagulate mode causes saline to flow to the surgical site. 
     In one embodiment tubular element  28 , fluid control means  32  and tubular member  24  are a tubing set having at the proximal end of element  28  a conventional spike for connection to an irrigant bag, and having at the distal end of element  24  a connector for attachment to device  100 . In another embodiment the tubing set is attached to and packaged with device  100 . In other embodiments elements are  24 ,  28  and  32  are discrete elements. 
       FIGS. 2 through 5  depict an active electrode  120  constructed in accordance with the principles of this invention. Electrode  120  is formed from a suitable metal tubing of diameter  128 , the distal portion  124  of length  134  being coined to a thickness  130  and width  132  and the proximal portion  122  retaining its original shape. Distal-most end  138  may be trimmed to a predetermined desired shape such as, for instance, flat, arcuate, or having serrations or other irregularities to enhance cutting performance. Irrigation ports  136  at distal end  140  of proximal portion  122  are in communication with the lumen of proximal portion  122 . In a preferred embodiment, there are ports on the top and bottom side of electrode  120 . In other embodiments there is a port on the top only or on the bottom only. 
     As seen in  FIGS. 6 through 13 , handle  101  of electrosurgical device  100  has a proximal end  102  from which pass cable  20  and tubular member  24 , and a distal end  104  to which is mounted proximal end  126  of electrode  120 . Means within handle  101  allow communication between the lumen of proximal portion  122  of electrode  120  and tubular member  24  such that irrigant from source  30  flows to irrigation ports  136  and therethrough to the surgical site when flow control  26  is activated. Handle  101  has a top surface  106  positioned on which are first button  108  and second button  110 , buttons  108  and  110  providing means for controlling electrosurgical generator  22  such that when button  108  is depressed RF current of a first waveform and first power level are supplied via means within device  100  to electrode  120 . When second button  110  is depressed, RF current of a second waveform and second power level are supplied to electrode  120 . 
     In use distal portion of  124  of electrode  120  is used to cut tissue. Irrigant is not supplied to the site, any fluid present being blood or other body fluids. Because the site is relatively dry, RF energy flows only from portions of portion  124  which contact or are in close proximity to tissue. If bleeding is encountered, footpedal  26  is depressed causing irrigant from supply  30  to flow to the surgical site. With conductive irrigant present, current flows from all portions of the electrode which are in contact with the irrigant to all portions of the tissue which are in contact with the irrigant. Because the area of tissue to which current flows is much greater than when operating in a dry environment without conductive irrigant, the energy density is much lower. The low density RF energy desiccates tissue in contact with the saline puddle so as to stop bleeding. When hemostasis has been achieved, the saline flow is terminated. When irrigant has been drained or removed from the region, cutting resumes. 
       FIGS. 14 through 17  depict an electrode  200  for an alternate embodiment formed in accordance with the principles of this invention. Electrode  200  has a proximal portion  202  of diameter  210  and length  212  suitable for mounting in a standard electrosurgical pencil. Middle portion  204  of diameter  220  larger than diameter  210  and length  230  has formed therein axial channel  222  having a bottom surface  224  coplanar with first surface  226  of distal portion  206  and terminating at its proximal end in proximal surface  242 . Distal to planar surface  226  first distal end surface  228  has formed therein grooves  232 . Second distal surface  234  terminates in distal radius  236 . Distal radius  236  of second surface  234  and first distal end surface  228  together form distal edge  240 . 
       FIGS. 18 through 22  depict an irrigation collar  250  for use with electrode  200  and constructed in accordance with the principles of this invention. Collar  250  has a tubular axial portion  252  having a lumen  254  of diameter  256 , diameter  256  of lumen  254  being slightly small than diameter  220  of middle portion  204  of electrode  200 , and a tapered tubular lateral portion  260  having a lumen  262 , lumens  262  and  254  being in communication. Lumen  254  has formed therein alignment key  266 . 
       FIGS. 23 through 27  depict an alternate embodiment device constructed in accordance with the principles of this invention. Device  300  is constructed by inserting electrode  200  into irrigation collar  250 , the angular alignment and relative axial position being established by channel  222  and key  266 . Because lumen  254  is slightly smaller than diameter  220  of middle portion  204  of electrode  200 , friction between the mating surfaces prevents unintended disassembly. Lumen  262  is in communication channel  222  such that when tubular member  24  ( FIG. 1 ) is attached to tapered lateral portion  260  of irrigation collar  250  a path is established for irrigant such that when flow control  26  is activated, irrigant from source  30  is supplied to the surgical site via channel  222 . In use, proximal end  202  of electrode  200  is inserted into a standard electrosurgical pencil. Tapered lateral portion  260  of collar  200  is connected to tubular element  24  ( FIG. 1 ), and therethrough to irrigant supply  30  with which it communicates. In a first mode of operation, irrigant is not supplied to the surgical site and any fluids present are blood or other body fluids. Current flows only from portions of the electrode in contact with, or in close proximity to tissue. Accordingly, the surgeon uses edge  240  to cut tissue and distal end surface  228  to vaporize regions of tissue, both regions being configured so as to produce high current densities. When bleeding occurs, irrigant from irrigant source  30  may be supplied to the site by activating footswitch  26  such that saline from tubular element  260  flows via lumen  262  to channel  222  and thereby to the distal end of distal region  206 . The supplied saline diffuses the RF energy in the same manner as the previous embodiment. Alternatively, the energy may be diffused over a large by “painting” the bleeding tissue with distal radius  236  of second surface  234 , the surface having no features to increase current density. If desired, irrigant may be supplied to the site as the surface is painted thereby increasing the area over which power is dissipated so as to achieve lower current density and improved tissue desiccation. 
     In yet another alternate embodiment constructed in accordance with the principles of this invention the device has two modes of operation based on the position of an active electrode having two elements, one fixed and one axially movable between a first position and a second position. In the first position the movable electrode element contacts tissue and functions as a cutting device. In the second position the movable electrode element is retracted within the fixed element of the electrode so as to create an irrigation port. Irrigant is supplied to the surgical site and the fixed portion of the electrode contacts tissue so as to desiccate tissue in contact with the fixed element or the supplied irrigant or both. 
     Referring now to  FIGS. 28 through 34  depicting the device  400  with the movable element of the active electrode in its first extended position. Handle  401  is identical to handle  101  in all aspects except as noted. Handle  401  has a distal end  404  to which are mounted an active electrode assembly having a closed-distal-end tubular fixed element  406  with a distal end  420 , inner lumen  412 , and distal end wall  416  in which is formed opening  414 , and a movable blade element  408  having a distal end  418 . Handle  401  also has a lever  410  for controlling the position of movable active blade element  408 , lever  410  having a first position (shown) in which blade element  408  is extended and a second position in which blade element  408  is refracted. Through means within handle  401 , lumen  412  is in communication with tube  24  and therethrough with irrigant supply  30  such that lumen  412  if filled with irrigant. Because movable element  408  is positioned within opening  414 , irrigant cannot flow distally from lumen  412  therethrough. 
       FIGS. 35 through 40  depict device  400  with handle  410  in its second position and with the movable blade element  408  in the retracted position, distal end  418  being withdrawn into lumen  412  of fixed element  406  so as to allowing opening  414  in distal end wall  416  of fixed element  406  to function as an irrigation port. As best seen in  FIG. 40 , irrigant  430  flows through lumen  412  to opening  414  and therethrough to tissue in contact with or close proximity to distal end  420  of fixed element  406  so as to disperse RF energy of an area sufficient to cause desiccation of tissue. 
     In yet another alternate embodiment of this invention, the dispersal of irrigant and therefore RF energy over an area is aided by nonconductive fibers (bristles) affixed to the distal end of the device so as to form a type of brush that provides pathways for the irrigant. In the illustrative depiction of such a device  500  shown in  FIGS. 41 through 44 , the handle is identical to handle  401  of the embodiment of  FIGS. 28 through 40 . Referring to  FIGS. 41 through 44 , movable active electrode element  508  is identical to element  408  of embodiment  400 . Fixed electrode element  506  is like element  406  in that it has a distal end  520 , inner lumen  512 , and distal end wall  516  in which is formed opening  514 . Additionally, nonconductive fibers  540  are affixed to distal end  520  of fixed element  506  surrounding opening  514  in distal end wall  516 . As depicted in  FIG. 44 , in which movable blade element  508  in the retracted position, distal end  518  being withdrawn into lumen  512  of fixed element  506  so as to allowing opening  514  in distal end wall  516  of fixed element  506  to function as an irrigation port. Irrigant  530  flows through lumen  512  to opening  514  and therethrough to nonconductive fibers  540 , fibers  540  directing and dispersing irrigant  530  to a region approximating the region of contact between the fibers and adjacent tissue. RF energy flowing through the irrigant is dispersed over the area defined by this region so as to decrease the current density to a level, which causes desiccation of tissue with resulting hemostasis. 
     In embodiment  500  the fibers are aligned like the bristles of a brush. In other embodiments the nonconductive fibers are randomly oriented to for a non-conductive wool, a mass of which is affixed to the fixed element of the active electrode. In these embodiments the conductive irrigant saturates the fibers such that any portion of the mass that contacts tissue will conduct low-density RF energy to the tissue so as to achieve hemostasis. 
     While embodiments with nonconductive fibers for enhancing and controlling the irrigant dispersal are depicted as modifications to device with movable active electrode elements, it will be recognized that other configurations using such fibers are possible and limited only by the desired medical application and the operational and engineering objectives of the designer. 
     All patents and publications mentioned herein are incorporated by reference in their entirety. Nothing herein is to be construed as an admission that the invention is not entitled to antedate such disclosure by virtue of prior invention. 
     While the invention has been described in detail and with reference to specific embodiments thereof, it is to be understood that the foregoing description is exemplary and explanatory in nature and is intended to illustrate the invention and its preferred embodiments. Through routine experimentation, one skilled in the art will readily recognize that various changes and modifications can be made therein without departing from the spirit and scope of the invention. 
     Other advantages and features will become apparent from the claims filed hereafter, with the scope of such claims to be determined by their reasonable equivalents, as would be understood by those skilled in the art. Thus, the invention is intended to be defined not by the above description, but by the following claims and their equivalents.

Technology Classification (CPC): 0