Abstract:
Tissue may be cut and extracted from an interior location in a patient&#39;s body using a probe or tool which both effects cutting and causes vaporization of a liquid or other fluid to propel the cut tissue through an extraction lumen of the cutting device. The cutting may be achieved using an electrosurgical electrode assembly, including a first electrode on a cutting member and a second electrode within a cutting probe or tool. Thus, over a first cutting portion, radio frequency current may help cut the tissue and over a second or over transition region, the RF current may initiate vaporization of the fluid or other liquid to propel the tissue from the cutting device.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a continuation of U.S. patent application Ser. No. 14/249,032, filed Apr. 9, 2014; which is a continuation of U.S. patent application Ser. No. 13/910,873, filed Jun. 5, 2013, now U.S. Pat. No. 8,728,066; which is a divisional of U.S. patent application Ser. No. 13/277,913, filed Oct. 20, 2011, now U.S. Pat. No. 8,512,326; which claims the benefit of U.S. Provisional Application No. 61/501,106, filed on Jun. 24, 2011 and of U.S. Provisional Application No. 61/531,985, filed on Sep. 7, 2011, the full disclosures of which are incorporated herein by reference. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The present invention relates systems and methods for the cutting and extraction of uterine fibroid tissue, polyps and other abnormal uterine tissue. 
       BACKGROUND OF THE INVENTION 
       [0003]    Uterine fibroids are non-cancerous tumors that develop in the wall of uterus. Such fibroids occur in a large percentage of the female population, with some studies indicating that up to 40 percent of all women have fibroids. Uterine fibroids can grow over time to be several centimeters in diameter and symptoms can include menorrhagia, reproductive dysfunction, pelvic pressure and pain. 
         [0004]    One current treatment of fibroids is hysteroscopic resection or myomectomy which involves transcervical access to the uterus with a hysteroscope together with insertion of a cutting instrument through a working channel in the hysteroscope. The cutting instrument may be a mechanical tissue cutter or an electro surgical resection device such as a cutting loop. Mechanical cutting devices are disclosed in U.S. Pat. Nos. 7,226,459; 6,032,673 and 5,730,752 and U.S. Published Patent Appl. 2009/0270898. An electrosurgical cutting device is disclosed in U.S. Pat. No. 5,906,615. 
         [0005]    While hysteroscopic resection can be effective in removing uterine fibroids, many commercially available instrument are too large in diameter and thus require anesthesia in an operating room environment. Conventional resectoscopes require cervical dilation to about 9 mm. What is needed is a system that can effectively cut and remove fibroid tissue through a small diameter hysteroscope. 
       SUMMARY OF THE INVENTION 
       [0006]    The present invention provides methods for resecting and removing target tissue from a patient&#39;s body, such as fibroids from a uterus. The tissue is cut, captured in a probe, catheter, or other tissue-removal device, and expelled from the capture device by vaporizing a fluid, typically a liquid, adjacent to the captured tissue in order to propel the tissue from the device, typically through an extraction or other lumen present in a body or shaft of the device. Exemplary embodiments of the tissue removal device comprise a reciprocating blade, tubular cutter, or the like, where the blade may be advanced past a cutting window on the device in order to sever a tissue strip and capture the strip within an interior volume or receptacle on the device. The liquid or other expandable fluid is also present in the device, and energy is applied to the fluid in order to cause rapid expansion, e.g. vaporization, in order to propel the severed tissue strip through the extraction lumen. In this way, the dimensions of the extraction lumen can be reduced, particularly in the distal regions of the device where size is of critical importance. 
         [0007]    In a first method, according to the present invention, tissue is extracted from an interior of the patient&#39;s body by capturing a tissue volume in a distal portion of an interior passageway of an elongated probe. A fluid located distal to the captured tissue volume is expanded, which proximally propels the tissue volume from the device. The fluid typically comprises a liquid, and the expansion typically comprises a liquid-to-vapor phase transition. In other cases, the fluid might be a gas where the expansion results from very rapid heating. In preferred embodiments, the phase transition is achieved by applying electrical energy in an amount sufficient to vaporize the liquid, typically applying RF current between first and second polarity electrodes, where at least one of the electrodes is disposed on a distal side of the captured tissue volume. 
         [0008]    The liquid or other fluid may be provided to a working end of the probe in various ways. Often, the liquid or other fluid is provided from a fluid-filled space in the patient&#39;s body, for example from a distension fluid filled in the cavity to be treated, such as the uterus. Alternatively, the liquid or other fluid may be provided from a remote source through a passageway in the probe. The liquid volume to be vaporized is typically in the range from 0.004 mL to 0.080 mL. 
         [0009]    The tissue may be captured in a variety of ways. For example, the tissue may be resected with a blade number or alternatively with an RF electrode. In either case, the resected tissue may then be captured or sequestered within an interior passageway within the blade itself and/or within another portion of the probe. In addition to the propulsion force caused by the vaporizing fluid, the present invention might also rely on applying a negative pressure to a proximal end of the anterior passageway to assist in drawing the tissue in a proximal direction from the extraction lumen. 
         [0010]    In a further method according to the present invention, tissue is removed from the interior of a patient&#39;s body by engaging a tubular cutter against the targeted tissue. An RF electrode arrangement on the cutter is energized to electrosurgically cut the tissue, and the same or a different RF electrode is used to vaporize a liquid to apply a positive fluid pressure to a distal surface of the cut tissue. Usually, the same RF electrode arrangement is used to both electrosurgically cut the tissue and to vaporize the liquid. In such instances, the cutter carrying the RF electrode is usually first advanced to electrosurgically cut the tissue and thereafter advanced into the liquid to vaporize the liquid. The liquid is usually present in a chamber or other space having an active electrode at a distal end thereof, and the RF electrode arrangement on the cutter comprises a return electrode. In this way, with the smaller active electrode on the distal side of the tissue, the energy which vaporizes the liquid will be concentrated in the chamber on the distal side of the tissue, thus causing rapid vaporization of the liquid and propulsion of the tissue through the extraction lumen. 
         [0011]    In a third method according to the present invention, tissue is cut and extracted from the interior of a patient&#39;s body by reciprocating a cutting member within a tubular cutter body to sever a tissue strip. The severed tissue strip is captured in an extraction lumen of the tubular cutter body, and a phase transition is caused in a fluid distal to the tissue strip to thereby apply a proximally directed expelling or propulsion force to the tissue strip. The phase transition may be caused by applying energy from any one of a variety of energy sources, including an ultrasound transducer, a high-intensity focused ultrasound (HIFU) energy source, a laser energy source, a light or optical energy source, a microwave energy source, a resistive heat source, or the like. Typically, the cutter will carry the energy source, and the energy source is also used to effect cutting of the tissue. In this way the cutter can also carry the energy source into the fluid after the tissue has been cut, and the cutting and vaporization steps can be performed sequentially as the cutter first moves through the tissue and then into the liquid or other fluid to be vaporized. 
         [0012]    In a still further method according to the present invention, tissue is cut and extracted by first cutting the tissue with a reciprocating cutting member over an extending stroke and a retracting stroke within a sleeve. The extending stroke cuts and captures tissue which has been drawn through a tissue-receiving window in the sleeve. Vaporization of a liquid distal to the captured tissue is caused by the cutting member while the cutting member is in a transition range between extension and retraction. The tissue is typically captured in the tissue extraction lumen formed at least partially in the cutter member. The cutter member typically carries a cutting electrode, and a second electrode is typically disposed at a distal end of the sleeve. Thus, RF current may be delivered to the cutting electrode and the second electrode in order to both effect cutting of the tissue over the extending stroke of the cutter and to also effect vaporization of the fluid while the cutter is in the transition range. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0013]      FIG. 1  is a plan view of an assembly including a hysteroscope and a tissue-cutting device corresponding to the invention that is inserted through a working channel of the hysteroscope. 
           [0014]      FIG. 2  is a schematic perspective view of a fluid management system used for distending the uterus and for assisting in electro surgical tissue cutting and extraction. 
           [0015]      FIG. 3  is a cross-sectional view of the shaft of the hysteroscope of  FIG. 1  showing various channels therein. 
           [0016]      FIG. 4  is a schematic side view of the working end of the electrosurgical tissue-cutting device of  FIG. 1  showing an outer sleeve and a reciprocating inner sleeve and an electrode arrangement. 
           [0017]      FIG. 5  is a schematic perspective view of the working end of the inner sleeve of  FIG. 4  showing its electrode edge. 
           [0018]      FIG. 6A  is a schematic cut-away view of a portion of outer sleeve, inner RF cutting sleeve and a tissue-receiving window of the outer sleeve. 
           [0019]      FIG. 6B  is a schematic view of a distal end portion another embodiment of inner RF cutting sleeve. 
           [0020]      FIG. 7A  is a cross sectional view of the inner RF cutting sleeve of  FIG. 6B  taken along line  7 A- 7 A of  FIG. 6B . 
           [0021]      FIG. 7B  is another cross sectional view of the inner RF cutting sleeve of  FIG. 6B  taken along line  7 B- 7 B of  FIG. 6B . 
           [0022]      FIG. 8  is a schematic view of a distal end portion of another embodiment of inner RF cutting sleeve. 
           [0023]      FIG. 9A  is a cross sectional view of the RF cutting sleeve of  FIG. 8  taken along line  9 A- 9 A of  FIG. 8 . 
           [0024]      FIG. 9B  is a cross sectional view of the RF cutting sleeve of  FIG. 8  taken along line  9 B- 9 B of  FIG. 8 . 
           [0025]      FIG. 10A  is a perspective view of the working end of the tissue-cutting device of  FIG. 1  with the reciprocating RF cutting sleeve in a non-extended position. 
           [0026]      FIG. 10B  is a perspective view of the tissue-cutting device of  FIG. 1  with the reciprocating RF cutting sleeve in a partially extended position. 
           [0027]      FIG. 10C  is a perspective view of the tissue-cutting device of  FIG. 1  with the reciprocating RF cutting sleeve in a fully extended position across the tissue-receiving window. 
           [0028]      FIG. 11A  is a sectional view of the working end of the tissue-cutting device of  FIG. 10A  with the reciprocating RF cutting sleeve in a non-extended position. 
           [0029]      FIG. 1  IB is a sectional view of the working end of  FIG. 10B  with the reciprocating RF cutting sleeve in a partially extended position. 
           [0030]      FIG. 11C  is a sectional view of the working end of  FIG. 10C  with the reciprocating RF cutting sleeve in a fully extended position. 
           [0031]      FIG. 12A  is an enlarged sectional view of the working end of tissue-cutting device of  FIG. 1  IB with the reciprocating RF cutting sleeve in a partially extended position showing the RF field in a first RF mode and plasma cutting of tissue. 
           [0032]      FIG. 12B  is an enlarged sectional view of the working end of  FIG. 11C  with the reciprocating RF cutting sleeve almost fully extended and showing the RF fields switching to a second RF mode from a first RF mode shown in  FIG. 12A . 
           [0033]      FIG. 12C  is an enlarged sectional view of the working end of  FIG. 11C  with the reciprocating RF cutting sleeve again almost fully extended and showing the explosive vaporization of a captured liquid volume to expel cut tissue in the proximal direction. 
           [0034]      FIG. 13  is an enlarged perspective view of a portion of the working end of  FIG. 12C  showing an interior chamber and a fluted projecting element. 
           [0035]      FIG. 14  is a sectional view of the working end of  FIG. 12C  showing an interior chamber and a variation of a projecting element. 
           [0036]      FIG. 15  is a sectional view of the working end of  FIG. 12C  showing an interior chamber and a variation of a projecting element configured to explosively vaporize the captured liquid volume. 
           [0037]      FIG. 16A  is a perspective view of an alternative working end with a rotational cutter in a window open position. 
           [0038]      FIG. 16B  is a perspective view of the working end of  FIG. 16A  with the rotating cutting element in a second position. 
           [0039]      FIG. 16C  is a view of the working end of  FIGS. 16A-16B  with the rotating cutting element in a third position. 
           [0040]      FIG. 17  is an exploded view of the outer sleeve of the working end of  FIGS. 16A-16C  showing the mating components comprising a ceramic body and a metal tube. 
           [0041]      FIG. 18  is a view of the inner sleeve of the working end of  FIGS. 16A-16C  de-mated from the outer sleeve. 
           [0042]      FIG. 19  is an exploded view of the inner sleeve of  FIG. 18  showing the mating components comprising a ceramic body and a metal tube. 
           [0043]      FIG. 20A  is a cross sectional view of the working end of  FIGS. 16A-16C  with the rotating inner sleeve in a first position cutting tissue in a first RF mode. 
           [0044]      FIG. 20B  is a cross sectional view of the working end of  FIG. 20A  with the rotating inner sleeve in a second window-closed position with a second RF mode vaporizing saline captured in the interior extraction channel. 
           [0045]      FIG. 21  is a longitudinal sectional view corresponding to the view of  FIG. 20B  with the rotating inner sleeve in a window-closed position and with the second RF mode vaporizing saline captured in the interior extraction channel to expel tissue proximally. 
           [0046]      FIG. 22  is a view of an alternative embodiment of a metal tube component of an inner sleeve. 
           [0047]      FIG. 23  is a view of an alternative embodiment of a metal tube component of an inner sleeve. 
           [0048]      FIG. 24  is a perspective view of an alternative probe that is configured to stop the inner rotating sleeve in a particular position. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0049]      FIG. 1  illustrates an assembly that comprises an endoscope  50  used for hysteroscopy together with a tissue-extraction device  100  extending through a working channel  102  of the endoscope. The endoscope or hysteroscope  50  has a handle  104  coupled to an elongated shaft  105  having a diameter of 5 mm to 7 mm. The working channel  102  therein may be round, D-shaped or any other suitable shape. The endoscope shaft  105  is further configured with an optics channel  106  and one or more fluid inflow/outflow channels  108   a ,  108   b  ( FIG. 3 ) that communicate with valve-connectors  110   a ,  110   b  configured for coupling to a fluid inflow source  120  thereto, or optionally a negative pressure source  125  ( FIGS. 1-2 ). The fluid inflow source  120  is a component of a fluid management system  126  as is known in the art ( FIG. 2 ) which comprises a fluid container  128  and pump mechanism  130  which pumps fluid through the hysteroscope  50  into the uterine cavity. As can be seen in  FIG. 2 , the fluid management system  126  further includes the negative pressure source  125  (which can comprise an operating room wall suction source) coupled to the tissue-cutting device  100 . The handle  104  of the endoscope includes the angled extension portion  132  with optics to which a videoscopic camera  135  can be operatively coupled. A light source  136  also is coupled to light coupling  138  on the handle of the hysteroscope  50 . The working channel  102  of the hysteroscope is configured for insertion and manipulation of the tissue-cutting and extracting device  100 , for example to treat and remove fibroid tissue. In one embodiment, the hysteroscope shaft  105  has an axial length of 21 cm, and can comprise a 0° scope, or 15° to 30° scope. 
         [0050]    Still referring to  FIG. 1 , the tissue-cutting device  100  has a highly elongated shaft assembly  140  configured to extend through the working channel  102  in the hysteroscope. A handle  142  of the tissue-cutting device  100  is adapted for manipulating the electro surgical working end  145  of the device. In use, the handle  142  can be manipulated both rotationally and axially, for example, to orient the working end  145  to cut targeted fibroid tissue. The tissue-cutting device  100  has subsystems coupled to its handle  142  to enable electrosurgical cutting of targeted tissue. A radiofrequency generator or RF source  150  and controller  155  are coupled to at least one RF electrode carried by the working end  145  as will be described in detail below. In one embodiment shown in  FIG. 1 , an electrical cable  156  and negative pressure source  125  are operatively coupled to a connector  158  in handle  142 . The electrical cable couples the RF source  150  to the electrosurgical working end  145 . The negative pressure source  125  communicates with a tissue-extraction channel  160  in the shaft assembly  140  of the tissue extraction device  100  ( FIG. 4 ). 
         [0051]      FIG. 1  further illustrates a seal housing  162  that carries a flexible seal  164  carried by the hysteroscope handle  104  for sealing the shaft  140  of the tissue-cutting device  100  in the working channel  102  to prevent distending fluid from escaping from a uterine cavity. 
         [0052]    In one embodiment as shown in  FIG. 1 , the handle  142  of tissue-cutting device  100  includes a motor drive  165  for reciprocating or otherwise moving a cutting component of the electrosurgical working end  145  as will be described below. The handle  142  optionally includes one or more actuator buttons  166  for actuating the device. In another embodiment, a footswitch can be used to operate the device. In one embodiment, the system includes a switch or control mechanism to provide a plurality of reciprocation speeds, for example 1 Hz, 2 Hz, 3 Hz, 4 Hz and up to 8 Hz. Further, the system can include a mechanism for moving and locking the reciprocating cutting sleeve in a non-extended position and in an extended position. Further, the system can include a mechanism for actuating a single reciprocating stroke. 
         [0053]    Referring to  FIGS. 1 and 4 , an electrosurgical tissue-cutting device has an elongate shaft assembly  140  extending about longitudinal axis  168  comprising an exterior or first outer sleeve  170  with passageway or lumen  172  therein that accommodates a second or inner sleeve 
         [0000]      175  that can reciprocate (and optionally rotate or oscillate) in lumen  172  to cut tissue as is known in that art of such tubular cutters. In one embodiment, the tissue-receiving window  176  in the outer sleeve  170  has an axial length ranging between 10 mm and 30 mm and extends in a radial angle about outer sleeve  170  from about 45° to 210° relative to axis  168  of the sleeve. The outer and inner sleeves  170  and  175  can comprise a thin-wall stainless steel material and function as opposing polarity electrodes as will be described in detail below.  FIGS. 6A-8  illustrate insulative layers carried by the outer and inner sleeves  170  and  175  to limit, control and/or prevent unwanted electrical current flows between certain portions of the sleeve. In one embodiment, a stainless steel outer sleeve  170  has an O.D. of 0.143″ with an I.D. of 0.133″ and with an inner insulative layer (described below) the sleeve has a nominal I.D. of 0.125″. In this embodiment, the stainless steel inner sleeve  175  has an O.D. of 0.120″ with an I.D. of 0.112″. The inner sleeve  175  with an outer insulative layer has a nominal O.D. of about 0.123″ to 0.124″ to reciprocate in lumen  172 . In other embodiments, outer and or inner sleeves can be fabricated of metal, plastic, ceramic of a combination thereof. The cross-section of the sleeves can be round, oval or any other suitable shape. 
         [0054]    As can be seen in  FIG. 4 , the distal end  177  of inner sleeve  175  comprises a first polarity electrode with distal cutting electrode edge  180  about which plasma can be generated. The electrode edge  180  also can be described as an active electrode during tissue cutting since the electrode edge  180  then has a substantially smaller surface area than the opposing polarity or return electrode. In one embodiment in  FIG. 4 , the exposed surfaces of outer sleeve  170  comprises the second polarity electrode  185 , which thus can be described as the return electrode since during use such an electrode surface has a substantially larger surface area compared to the functionally exposed surface area of the active electrode edge  180 . 
         [0055]    In one aspect of the invention, the inner sleeve or cutting sleeve  175  has an interior tissue extraction lumen  160  with first and second interior diameters that are adapted to electrosurgically cut tissue volumes rapidly—and thereafter consistently extract the cut tissue strips through the highly elongated lumen  160  without clogging. Now referring to  FIGS. 5 and 6A , it can be seen that the inner sleeve  175  has a first diameter portion  190 A that extends from the handle  142  ( FIG. 1 ) to a distal region  192  of the sleeve  175  wherein the tissue extraction lumen transitions to a smaller second diameter lumen  190 B with a reduced diameter indicated at B which is defined by the electrode sleeve element  195  that provides cutting electrode edge  180 . The axial length C of the reduced cross-section lumen  190 B can range from about 2 mm to 20 mm. In one embodiment, the first diameter A is 0.112″ and the second reduced diameter B is 0.100″. As shown in  FIG. 5 , the inner sleeve  175  can be an electrically conductive stainless steel and the reduced diameter electrode portion also can comprise a stainless steel electrode sleeve element  195  that is welded in place by weld  196  ( FIG. 6A ). In another alternative embodiment, the electrode and reduced diameter electrode sleeve element  195  comprises a tungsten tube that can be press fit into the distal end  198  of inner sleeve  175 .  FIGS. 5 and 6A  further illustrates the interfacing insulation layers  202  and  204  carried by the first and second sleeves  170 ,  175 , respectively. In  FIG. 6A , the outer sleeve  170  is lined with a thin-wall insulative material  200 , such as PFA, or another material described below. Similarly, the inner sleeve  175  has an exterior insulative layer  202 . These coating materials can be lubricious as well as electrically insulative to reduce friction during reciprocation of the inner sleeve  175 . 
         [0056]    The insulative layers  200  and  202  described above can comprise a lubricious, hydrophobic or hydrophilic polymeric material. For example, the material can comprise a bio-compatible material such as PFA, TEFLON®, polytetrafluroethylene (PTFE), FEP (Fluorinated ethylenepropylene), polyethylene, polyamide, ECTFE (Ethylenechlorotrifluoro-ethylene), ETFE, PVDF, polyvinyl chloride or silicone. 
         [0057]    Now turning to  FIG. 6B , another variation of inner sleeve  175  is illustrated in a schematic view together with a tissue volume being resected with the plasma electrode edge  180 . In this embodiment, as in other embodiments in this disclosure, the RF source operates at selected operational parameters to create a plasma around the electrode edge  180  of electrode sleeve  195  as is known in the art. Thus, the plasma generated at electrode edge  180  can cut and ablate a path P in the tissue  220 , and is suited for cutting fibroid tissue and other abnormal uterine tissue. In  FIG. 6B , the distal portion of the cutting sleeve  175  includes a ceramic collar  222  which is adjacent the distal edge  180  of the electrode sleeve  195 . The ceramic  222  collar functions to confine plasma formation about the distal electrode edge  180  and functions further to prevent plasma from contacting and damaging the polymer insulative layer  202  on the cutting sleeve  175  during operation. In one aspect of the invention, the path P cut in the tissue  220  with the plasma at electrode edge  180  provides a path P having an ablated width indicated at W, wherein such path width W is substantially wide due to tissue vaporization. This removal and vaporization of tissue in path P is substantially different than the effect of cutting similar tissue with a sharp blade edge, as in various prior art devices. A sharp blade edge can divide tissue (without cauterization) but applies mechanical force to the tissue and may prevent a large cross section slug of tissue from being cut. In contrast, the plasma at the electrode edge  180  can vaporize a path P in tissue without applying any substantial force on the tissue to thus cut larger cross sections of slugs or strips of tissue. Further, the plasma cutting effect reduces the cross section of tissue strip  225  received in the reduced cross-section region  190 B of tissue-extraction lumen  160 .  FIG. 6B  depicts a tissue strip  225  entering the reduced cross-section region  190 B, wherein the tissue strip  225  has a smaller cross-section than the lumen due to the vaporization of tissue. Further, the cross section of tissue  225  as it enters the larger cross-section lumen  190 A results in even greater free space  196  around the tissue strip  225 . Thus, the resection of tissue with the plasma electrode edge  180 , together with the lumen transition from the smaller cross-section ( 190 B) to the larger cross-section ( 190 A) of the tissue-extraction lumen  160  can significantly reduce or eliminate the potential for successive resected tissue strips  225  to clog the lumen. Prior art resection devices with such small diameter tissue-extraction lumen typically have problems with tissue clogging. 
         [0058]    In another aspect of the invention, the negative pressure source  225  coupled to the proximal end of tissue-extraction lumen  160  (see  FIGS. 1 and 4 ) also assists in aspirating and moving tissue strips  225  in the proximal direction to a collection reservoir (not shown) outside the handle  142  of the device. 
         [0059]      FIGS. 7A-7B  illustrate the change in lumen diameter of cutting sleeve  175  of  FIG. 6B .  FIG. 8  illustrates the distal end of a variation of cutting sleeve  175 ′ which is configured with an electrode cutting element  195 ′ that is partially tubular in contrast to the previously described tubular electrode element  195  ( FIGS. 5 and 6A ).  FIGS. 9A-9B  again illustrate the change in cross-section of the tissue-extraction lumen between reduced cross-section region  190 B′ and the increased cross-section region  190 A′ of the cutting sleeve  175 ′ of  FIG. 8 . Thus, the functionality remains the same whether the cutting electrode element  195 ′ is tubular or partly tubular. In  FIG. 8A , the ceramic collar  222 ′ is shown, in one variation, as extending only partially around sleeve  175 ′ to cooperate with the radial angle of cutting electrode element  195 ′. Further, the variation of  FIG. 8  illustrates that the ceramic collar  222 ′ has a larger outside diameter than insulative layer  202 . Thus, friction may be reduced since the short axial length of the ceramic collar  222 ′ interfaces and slides against the interfacing insulative layer  200  about the inner surface of lumen  172  of outer sleeve  170 . 
         [0060]    In general, one aspect of the invention comprises a tissue cutting and extracting device ( FIGS. 10A-11C ) that includes first and second concentric sleeves having an axis and wherein the second (inner) sleeve  175  has an axially-extending tissue-extraction lumen therein, and wherein the second sleeve  175  is moveable between axially non-extended and extended positions relative to a tissue-receiving window  176  in first sleeve  170  to resect tissue, and wherein the tissue extraction lumen  160  has first and second cross-sections. The second sleeve  175  has a distal end configured as a plasma electrode edge  180  to resect tissue disposed in tissue-receiving window  176  of the first sleeve  170 . Further, the distal end of the second sleeve, and more particularly, the electrode edge  180  is configured for plasma ablation of a substantially wide path in the tissue. In general, the tissue-extraction device is configured with a tissue extraction lumen  160  having a distal end portion with a reduced cross-section that is smaller than a cross-section of medial and proximal portions of the lumen  160 . 
         [0061]    In one aspect of the invention, referring to  FIGS. 7A-7B and 9A-9B , the tissue-extraction lumen  160  has a reduced cross-sectional area in lumen region  190 B proximate the plasma cutting tip or electrode edge  180  wherein said reduced cross section is less than 95%, 90%, 85% or 80% of the cross sectional area of medial and proximal portions  190 A of the tissue-extraction lumen, and wherein the axial length of the tissue-extraction lumen is at least 10 cm, 20 cm, 30 cm or 40 cm. In one embodiment of tissue-cutting device  100  for hysteroscopic fibroid cutting and extraction ( FIG. 1 ), the shaft assembly  140  of the tissue-cutting device is 35 cm in length. 
         [0062]      FIGS. 10A-10C  illustrate the working end  145  of the tissue-cutting device  100  with the reciprocating cutting sleeve or inner sleeve  175  in three different axial positions relative to the tissue receiving window  176  in outer sleeve  170 . In  FIG. 10  A, the cutting sleeve  175  is shown in a retracted or non-extended position in which the sleeve  175  is at it proximal limit of motion and is prepared to advance distally to an extended position to thereby electrosurgically cut tissue positioned in and/or suctioned into window  176 .  FIG. 10B  shows the cutting sleeve  175  moved and advanced distally to a partially advanced or medial position relative to tissue cutting window  176 .  FIG. 10C  illustrates the cutting sleeve  175  fully advanced and extended to the distal limit of its motion wherein the plasma cutting electrode  180  has extended past the distal end  226  of tissue-receiving window  176  at which moment the resected tissue strip  225  in excised from tissue volume  220  and captured in reduced cross-sectional lumen region  190 B. 
         [0063]    Now referring to  FIGS. 10A-10C ,  FIGS. 11A-11C  and  FIGS. 12A-12C , another aspect of the invention comprises “tissue displacement” mechanisms provided by multiple elements and processes to “displace” and move tissue strips  225  ( FIG. 12A ) in the proximal direction in lumen  160  of cutting sleeve  175  to thus ensure that tissue does not clog the lumen of the inner sleeve  175 . As can be seen in  FIG. 10A  and the enlarged views of  FIGS. 11A-11C , one tissue displacement mechanism comprises a projecting element  230  that extends proximally from distal tip  232  which is fixedly attached to outer sleeve  170 . The projecting element  230  extends proximally along central axis  168  in a distal chamber  240  defined by outer sleeve  170  and distal tip  232 . In one embodiment depicted in  FIG. 11  A, the shaft-like projecting element  230 , in a first functional aspect, comprises a mechanical pusher that functions to push a captured tissue strip  225  proximally from the small cross-section lumen  190 B of cutting sleeve  175  ( FIG. 12A ) as the cutting sleeve  175  moves to its fully advanced or extended position. 
         [0064]    In a second functional aspect, the chamber  240  in the distal end of sleeve  170  is configured to capture a volume of saline distending fluid  244  ( FIG. 12A ) from the working space, and wherein the existing RF electrodes of the working end  145  are further configured to explosively vaporize the captured fluid  244  to generate proximally-directed forces on tissue strips  225  resected and disposed in lumen  160  of the cutting sleeve  175  ( FIGS. 12B and 12C ). Both of these functional elements and processes (tissue displacement mechanisms) can apply a substantial mechanical force on the captured tissue strips  225  by means of the explosive vaporization of liquid in chamber  240  and can function to move tissue strips  225  in the proximal direction in the tissue-extraction lumen  160 . It has been found that using the combination of multiple functional elements and processes can virtually eliminate the potential for tissue clogging the tissue extraction lumen  160 . 
         [0065]    More particularly,  FIGS. 12A-12C  illustrate the functional aspects of the tissue displacement mechanisms and the subsequent explosive vaporization of fluid captured in chamber  240 . In  FIG. 12A , the reciprocating cutting sleeve  175  is shown in a medial position advancing distally wherein plasma at the cutting electrode edge  180  is cutting a tissue strip  225  that is disposed within lumen  160  of the cutting sleeve  175 . In  FIG. 12A-12C , it can be seen that the system operates in first and second electrosurgical modes corresponding to the reciprocation and axial range of motion of cutting sleeve  175  relative to the tissue-receiving window  176 . As used herein, the term “electrosurgical mode” refers to which electrode of the two opposing polarity electrodes functions as an “active electrode” and which electrode functions as a “return electrode”. The terms “active electrode” and “return electrode” are used in accordance with convention in the art—wherein an active electrode has a smaller surface area than the return electrode which thus focuses RF energy density about such an active electrode. In the working end  145  of  FIGS. 10A-11C , the cutting electrode element  195  and its cutting electrode edge  180  must comprise the active electrode to focus energy about the electrode to generate the plasma for tissue cutting. Such a high-intensity, energetic plasma at the electrode edge  180  is needed throughout stroke X indicated in  FIG. 12A-12B  to cut tissue. The first mode occurs over an axial length of travel of inner cutting sleeve  175  as it crosses the tissue-receiving window  176 , at which time the entire exterior surface of outer sleeve  170  comprises the return electrode indicated at  185 . The electrical fields EF of the first RF mode are indicated generally in  FIG. 12A . 
         [0066]      FIG. 12  B illustrates the moment in time at which the distal advancement or extension of inner cutting sleeve  175  entirely crosses the tissue-receiving window  176  ( FIG. 12A ). At this time, the electrode sleeve  195  and its electrode edge  180  are confined within the mostly insulated-wall chamber  240  defined by the outer sleeve  170  and distal tip  232 . At this moment, the system is configured to switch to the second RF mode in which the electric fields EF switch from those described previously in the first RF mode. As can be seen in  FIG. 12B , in this second mode, the limited interior surface area  250  ( FIG. 12C ) of distal tip  232  that interfaces chamber  240  functions as an active electrode and the distal end portion of cutting sleeve  175  exposed to chamber  240  acts as a return electrode. In this mode, very high energy densities occur about surface  250  and such a contained electric field EF can explosively and instantly vaporize the fluid  244  captured in chamber  240 . The expansion of water vapor can be dramatic and can thus apply tremendous mechanical forces and fluid pressure on the tissue strip  225  to move the tissue strip in the proximal direction in the tissue extraction lumen  160 .  FIG. 12C  illustrates such explosive or expansive vaporization of the distention fluid  244  captured in chamber  240  and further shows the tissue strip  225  being expelled in the proximal direction the lumen  160  of inner cutting sleeve  175 . 
         [0067]      FIG. 14  shows the relative surface areas of the active and return electrodes at the extended range of motion of the cutting sleeve  175 , again illustrating that the surface area of the non-insulated distal end surface  250  is small compared to surface  255  of electrode sleeve which comprises the return electrode. 
         [0068]    Still referring to  FIGS. 12A-12C , it has been found that a single power setting on the RF source  150  and controller  155  can be configured both (i) to create plasma at the electrode cutting edge  180  of electrode sleeve  195  to cut tissue in the first mode, and (ii) to explosively vaporize the captured distention fluid  244  in the second mode. Further, it has been found that the system can function with RF mode-switching automatically at suitable reciprocation rates ranging from 0.5 cycles per second to 8 or 10 cycles per second. In bench testing, it has been found that the tissue-cutting device described above can cut and extract tissue at the rate of from 4 grams/min to 8 grams/min without any potential for tissue strips  225  clogging the tissue-extraction lumen  160 . In these embodiments, the negative pressure source  125  also is coupled to the tissue-extraction lumen  160  to assist in applying forces for tissue extraction. 
         [0069]    Of particular interest, the fluid-capture chamber  240  defined by sleeve  170  and distal tip  232  can be designed to have a selected volume, exposed electrode surface area, length and geometry to optimize the application of expelling forces to resected tissue strips  225 . In one embodiment, the diameter of the chamber is 3.175 mm and the length is 5.0 mm which taking into account the projecting element  230 , provided a captured fluid volume of approximately 0.040 mL. In other variations, the captured fluid volume can range from 0.004 mL to 0.080 mL. 
         [0070]    In one example, a chamber  240  with a captured liquid volume of 0.040 mL together with 100% conversion efficiency in and instantaneous vaporization would require 103 Joules to heat the liquid from room temperature to water vapor. In operation, since a Joule is a W*s, and the system reciprocate at 3 Hz, the power required would be on the order of 311 W for full, instantaneous conversion to water vapor. A corresponding theoretical expansion of 1700× would occur in the phase transition, which would results in up to 25,000 psi instantaneously (14.7 psi×1700), although due to losses in efficiency and non-instantaneous expansion, the actual pressures would be much less. In any event, the pressures are substantial and can apply significant expelling forces to the captured tissue strips  225 . 
         [0071]    Referring to  FIG. 12A , the interior chamber  240  can have an axial length from about 0.5 mm to 10 mm to capture a liquid volume ranging from about 0.004 mL 0.01 mL. It can be understood in  FIG. 12A , that the interior wall of chamber  240  has an insulator layer  200  which thus limits the electrode surface area  250  exposed to chamber  240 . In one embodiment, the distal tip  232  is stainless steel and is welded to outer sleeve  170 . The post element  248  is welded to tip  232  or machined as a feature thereof. The projecting element  230  in this embodiment is a non-conductive ceramic. 
         [0072]      FIG. 13  shows the cross-section of the ceramic projecting element  230  which may be fluted, and which in one embodiment has three flute elements  260  and three corresponding axial grooves  262  in its surface. Any number of flutes, channels or the like is possible, for example from two to about 20. The fluted design increases the available cross-sectional area at the proximal end of the projecting element  230  to push the tissue strip  225 , while at the same time the three grooves  262  permit the proximally-directed jetting of water vapor to impact the tissue exposed to the grooves  262 . In one embodiment, the axial length D ( FIG. 12A ) of the projecting element  230  is configured to push tissue entirely out of the reduced cross-sectional region  190 B of the electrode sleeve element  195 . In another embodiment, the volume of the chamber  240  is configured to capture liquid that when explosively vaporized provides a gas (water vapor) volume sufficient to expand into and occupy at least the volume defined by a 10% of the total length of extraction channel  160  in the device, usually at least 20% of the extraction channel  160 , often at least 40% of the extraction channel  160 , sometimes at least 60% of the extraction channel  160 , other times at least 80% of the extraction channel  160 , and sometimes at least 100% of the extraction channel  160 . 
         [0073]    As can be understood from  FIGS. 12A to 12C , the distending fluid  244  in the working space replenishes the captured fluid in chamber  240  as the cutting sleeve  175  moves in the proximal direction or towards its non-extended position. Thus, when the cutting sleeve  175  again moves in the distal direction to cut tissue, the interior chamber  240  is filled with fluid  244  which is then again contained and is then available for explosive vaporization as described above when the cutting sleeve  175  closes the tissue-receiving window  176 . In another embodiment, a one-way valve can be provided in the distal tip  232  to draw fluid directly into interior chamber  240  without the need for fluid to migrate through window  176 . 
         [0074]      FIG. 15  illustrates another variation in which the active electrode surface area  250 ′ in the second mode comprises a projecting element  230  with conductive regions and non-conductive regions  260  which can have the effect of distributing the focused RF energy delivery over a plurality of discrete regions each in contact with the captured fluid  244 . This configuration can more efficiently vaporize the captured fluid volume in chamber  240 . In one embodiment, the conductive regions  250 ′ can comprise metal discs or washers on post  248 . In other variation (not shown) the conductive regions  250 ′ can comprise holes, ports or pores in a ceramic material  260  fixed over an electrically conductive post  248 . 
         [0075]    In another embodiment, the RF source  150  and controller  155  can be programmed to modulate energy delivery parameters during stroke X and stroke Y in  FIGS. 12A-12C  to provide the optimal energy (i) for plasma cutting with electrode edge  180 , and (ii) for explosively vaporizing the captured fluid in chamber  240 . 
         [0076]      FIGS. 16A-16C  illustrate another embodiment RF cutting probe  700  with working end  702  comprising a tubular cutter adapted for electrosurgical cutting and extracting targeted tissue from the interior of a patient&#39;s body. However, in this embodiment, the inner cutting sleeve is configured to rotate instead of reciprocate as in the previously-described embodiments. 
         [0077]    Referring to  FIG. 16A , the outer sleeve  705  comprises a metal tubular member  708  that extends from a handle (not shown) to a working end  702  that again carries a distal dielectric body  710  defining a window  712  therein. The inner second sleeve or cutting sleeve  715  comprises a metal tubular member  718  that carries a distal dielectric body  720  with a windowed side  724  that is adapted to cooperate with window  712  in the outer sleeve  705 . 
         [0078]      FIGS. 16B-16C  show the working end  702  of probe  700  with the rotating cutting sleeve  715  and RF electrode edge  725  in two different rotational positions with respect to outer sleeve  705  and window  712 . In  FIG. 16B , the inner sleeve  715  is rotated approximately 90° relative to the outer sleeve  705 . In  FIG. 16C , the inner sleeve  715  is rotated 180° to a position relative to inner sleeve  715  to effectively close the window  712  defined by the outer sleeve  705 . It can easily be understood how rotation of electrode edge  725  thus can cut tissue during rotation and capture the tissue in the window-closed position within the tissue-receiving lumen  730  of the probe. 
         [0079]    In this embodiment of  FIGS. 16A-16C , the RF electrode edge  725  of the inner sleeve  715  comprises a first polarity electrode. The exterior surface  732  of the outer sleeve  705  comprises a second polarity electrode as described in previous embodiments. As can be understood from  FIGS. 16A-16C , it is critical that the first and second polarity electrode surfaces ( 725  and  732 ) are spaced apart by a predetermined dimension throughout the rotation of inner sleeve  715  relative to outer sleeve  705 . In one aspect the invention, the distal ends of the inner and outer sleeves comprise ceramic bodies  710  and  720  with an interface  740  therebetween. In other words, the ceramic bodies  710  and  720  rotate about interface  740  and the bodies provide exact electrode spacing ES between the first and second polarity electrodes  725  and  732 . 
         [0080]    Now referring to  FIG. 17 , it can be seen how the outer sleeve  705  comprises as an assembly between the tubular metal sleeve  708  and the dielectric body  710 , which in this variation can be a ceramic such as zirconium. In  FIG. 17 , it can be seen that the ceramic body  710  has a thin wall  742  which can range in thickness from about 0.003″ and 0.010″ wherein the ceramic extends 360° around window  712 . Ceramic body  710  can thus be slidably inserted into and bonded to bore  728  in metal sleeve  708 . 
         [0081]    Now turning to  FIG. 18 , the distal end of inner sleeve  715  is shown de-mated from the outer sleeve assembly  705  (see  FIG. 16A ). The tubular metal sleeve  718  of  FIG. 18  is fabricated to allow insertion of the ceramic body  720  which supports the electrode edge  725  and provides a rotational bearing surface about the interface  740  (see  FIG. 16A ).  FIG. 19  shows an exploded view of the inner sleeve assembly of  FIG. 18 . In  FIG. 19 , it can be seen that ceramic body  720  has a hemispherical cross-sectional shape and includes an elongated slots  744  for receiving and supporting an electrode edge  725 .  FIG. 19  further shows metal sleeve  718  without ceramic body  720  wherein the electrode edge  725  is cut from a rounded end sleeve  718 . It can be understood that the slot  744  can receive ceramic body  720  and thus the electrode edge  725  extends in a loop and under rotation will have a leading edge  745  and a trailing edge  745 ′ depending on the direction of rotation. As used herein, the term ‘leading edge’ refers to the electrode edge  725  extending around the distal end of the sleeve  715  to its centerline on its rotational axis. 
         [0082]    In one aspect of the invention, the tissue cutting probe  700  comprises an outer sleeve  705  and an inner sleeve  715  that is rotatable to provide window-open and window-closed positions and wherein the distal ends of the first and second sleeves  705 ,  715  include ceramic bodies  710 ,  720  that provide surfaces on either side of a rotational interface  740 . Further, the first and second sleeves provide ceramic bodies  710 ,  720  that contact one another on either side of the rotational interface  740  and thus provide a predetermined electrode spacing ES ( FIG. 16A ). In one variation, the wall thickness of the ceramic body  710  is from 0.003″ to 0.004″. Likewise, the wall thickness of ceramic body  720  can be from 0.003″ to 0.004″. Thus, the radial dimension between the first and second polarity electrodes at a minimum in this variation is 0.006″. In another variation in which the inner sleeve  715  carries an outer polymeric dielectric layer which can be 0.001″ in thickness to thus provide an electrode spacing dimension ES of 0.004″. In other variations having a larger diameter, the dimension between the first and second polarity electrodes can range up to 0.030″. In general, the scope of the invention includes providing a rotational tubular cutter with bi-polar electrodes spaced apart between 0.004″ inches and 0.030″ inches wherein the cutting sleeve  715  rotates about an interface  740  having dielectric materials on either side thereof. 
         [0083]    In the embodiment shown in  FIGS. 16A-16C , the length of the window can range from about 5 mm to 30 mm. The diameter of the probe working end can range from about 3 mm to 6 mm or more. The rotational speed of the inner sleeve can range from 100 rpm to 5,000 rpm. In one embodiment, a rotation ranging from about 200 rpm to 500 rpm cut tissue efficiently and allowed for effective tissue extraction as described below. 
         [0084]    In another aspect of the invention, referring to  FIGS. 17, 20A and 20B , it can be seen that an opening  748  is provided in ceramic body  710  which provides exposure through the ceramic body  710  to metal sleeve  708  which comprises the first polarity electrode when assembled. Thus, the metal sleeve provides an interior electrode surface  750  that is exposed to interior chamber  730 . It can be understood that in this variation, the working end  702  can function in two RF modes as described in the previous reciprocating probe embodiments (see  FIGS. 12A-12C ). In the first RF mode, the exterior surface  732  of outer sleeve  705  functions as a first polarity electrode in the interval when the inner sleeve  715  and its second polarity electrode edge  725  rotates from the window-open position of  FIG. 16A  toward the window-closed position of  FIG. 16B .  FIG. 20A  depicts this interval of rotation, wherein it can be seen that the first RF mode operates for approximately 180° of rotation of the inner cutting sleeve  715 . In this position depicted in  FIG. 20A , the leading edge  745  and trailing edge  745 ′ of electrode edge  725  are exposed to the open window  712  and electric fields EF extend to the first polarity electrode surface  732  about the exterior of the probe and plasma is formed at leading edge  745  to cut tissue. 
         [0085]    The second RF mode is shown in  FIG. 20B , wherein the inner sleeve  715  rotates to the window-closed position and the probe switches instantly to such a second RF mode since the electrode edge  725  is exposed only to the tissue-receiving lumen  730 . It can be understood that the second RF mode operates only when the window  712  is closed as in  FIGS. 16C and 20B  which causes the instant explosive vaporization of captured saline in the lumen  730 . In  FIG. 20B , it can be seen that the electrode edge  725  is exposed only to the interior of lumen  730  and electric fields EF extend between the leading and trailing electrode edges ( 745  and  745 ′) to the exposed electrode surface  750  to thus cause the explosive vaporization of captured saline. The vaporization occurs instantly within limited degrees of rotation of the inner sleeve, e.g., 5° to 20° of rotation, upon closing the window  712  to thereby expel the resected tissue in the proximal direction as described previously. It has been found that saline captured in the interior channel  730  can be distal to the resected tissue or adjacent to the resected tissue in the lumen and the fluid expansion in the liquid-to-vapor transition will instantly expel the resected tissue outwardly or proximally in lumen  730 . 
         [0086]      FIG. 21  is a longitudinal sectional view of the working end  702  corresponding to  FIG. 20B  wherein the electrical fields EF are confined within the interior lumen  730  to thus cause the explosive vaporization of captured saline. Thus, the second RF mode and the vaporization of captured saline  754  as depicted in  FIG. 20B  will expel the resected tissue  755  proximally within the tissue extraction channel  730  that extends proximally through the probe to a collection reservoir as described in previous embodiments. In general, a method of the invention includes capturing a tissue volume in a closed distal portion of an interior passageway of an elongate probe and causing a phase transition in a fluid proximate to the captured tissue volume to expand the fluid to apply a proximally directed expelling force to the tissue volume. The time interval for providing a closed window to capture the tissue and for causing the explosive vaporization can range from about 0.01 second to 2 seconds. A negative pressure source also can be coupled to the proximal end of the extraction lumen as described previously. 
         [0087]    Now turning to  FIG. 22 , another variation of inner sleeve  715 ′ is shown. In this embodiment, the leading edge  745  and the trailing edge  745 ′ of electrode edge  725  are provided with different electrical characteristics. In one variation, the leading edge  745  is a highly conductive material suited for plasma ignition as described previously. In this same variation shown in  FIG. 22 , the trailing edge  745 ′ comprises a different material which is less suited for plasma formation, or entirely not suited for plasma formation. In one example, the trailing edge  745 ′ comprises a resistive material (e.g., a resistive surface coating) wherein RF current ignites plasma about the leading edge  745  but only resistively heats the trailing  745 ′ edge to thus provide enhanced coagulation functionality. Thus, the leading edge  745  cuts and the trailing edge  745 ′ is adapted to coagulate the just-cut tissue. In another variation, the trailing edge  745 ′ can be configured with a capacitive coating which again can be used for enhancing tissue coagulation. In yet another embodiment, the trailing edge  745 ′ can comprise a positive temperature coefficient of resistance (PTCR) material for coagulation functionality and further for preventing tissue sticking. In another variation, the trailing edge  745 ′ can have a dielectric coating that prevents heating altogether so that the leading edge  745  cut tissues and the trailing edge  745 ′ has no electrosurgical functionality. 
         [0088]      FIG. 23  illustrates another embodiment of inner sleeve component  718 ′ in which the electrode edge  725  has a leading edge  745  with edge features for causing a variable plasma effect. In this embodiment, the projecting edges  760  of the leading edge  745  electrode will create higher energy density plasma than the scalloped or recessed portions  762  which can result in more efficient tissue cutting. In another embodiment, the electrode surface area of the leading edge  745  and trailing edge  745 ′ can differ, again for optimizing the leading edge  745  for plasma cutting and the trailing edge  745 ′ for coagulation. In another embodiment, the trailing edge  745 ′ can be configured for volumetric removal of tissue by plasma abrasion of the just-cut surface since it wiped across the tissue surface. It has been found that a substantial amount of tissue (by weight) can be removed by this method wherein the tissue is disintegrated and vaporized. In general, the leading edge  745  and trailing edge  745 ′ can be dissimilar with each edge optimized for a different effect on tissue. 
         [0089]      FIG. 24  illustrates another aspect of the invention that can be adapted for selective cutting or coagulating of targeted tissue. In this variation, a rotation control mechanism is provided to which can move the inner sleeve  715  to provide the leading edge  745  in an exposed position and further lock the leading edge  745  in such an exposed position. In this locked (non-rotating) position, the physician can activate the RF source and controller to ignite plasma along the exposed leading edge  745  and thereafter the physician can use the working end as a plasma knife to cut tissue. In another variation, the physician can activate the RF source and controller to provide different RF parameters configured to coagulate tissue rather than to cut tissue. In one embodiment, a hand switch or foot switch can upon actuation move and lock the inner sleeve in the position shown in  FIG. 24  and thereafter actuate the RF source to deliver energy to tissue. 
         [0090]    It should be appreciated that while an RF source is suitable for causing explosive vaporization of the captured fluid volume, any other energy source can be used and falls within the scope of the invention, such as an ultrasound transducer, HIFU, a laser or light energy source, a microwave or a resistive heat source. 
         [0091]    In another embodiment, the probe can be configured with a lumen in communication with a remote liquid source to deliver fluid to the interior chamber  240 . 
         [0092]    Although particular embodiments of the present invention have been described above in detail, it will be understood that this description is merely for purposes of illustration and the above description of the invention is not exhaustive. Specific features of the invention are shown in some drawings and not in others, and this is for convenience only and any feature may be combined with another in accordance with the invention. A number of variations and alternatives will be apparent to one having ordinary skills in the art. Such alternatives and variations are intended to be included within the scope of the claims. Particular features that are presented in dependent claims can be combined and fall within the scope of the invention. The invention also encompasses embodiments as if dependent claims were alternatively written in a multiple dependent claim format with reference to other independent claims.