Abstract:
A medical apparatus and method useful for resecting tissue from the gastrointestinal tract are disclosed. The apparatus can include an RF tissue cutting device disposed inward of a side opening in the device. A tissue stop can be used to control the depth of tissue resected, and the tissue stop can include holes for communicating vacuum for drawing tissue into the side opening. The tissue stop can be electrically grounded with respect to the RF tissue cutting device, and the tissue stop can provide one pole of an RF electrical circuit.

Description:
FIELD OF THE INVENTION 
   The present invention is related generally to endoscopy and more particularly to endoscopic mucosal resection. 
   BACKGROUND OF THE INVENTION 
   Cancerous or benign lesions of the GI tract often start in the mucosal layer of the stomach or intestines. With improved diagnostics and screening, such lesions are being identified prior to extension into the wall of the stomach or intestines. Unfortunately, definitive therapy has historically involved invasive surgical resection of the lesion and adjacent bowel. Treatment of such early lesions by local excision of the mucosal, with access via natural orifices, would represent a far less invasive approach. 
   Existing approaches to local mucosal resection have utilized a variety of endoscopic instruments. Current methods can be described as “suck and cut” or “lift and cut”. In the suck and cut method, a chamber attached to the end of the endoscope is placed near the lesion, suction is applied to draw the lesion into the chamber, an electrosurgical snare within the chamber is then activated to excise the entrapped tissue. This is done repeatedly to completely resect the affected tissue. In the lift and cut method, a two-channel endoscope is used. Through one channel of the endoscope a grasper is passed to lift the lesion. An electrosurgical snare, passed through the other endoscope channel is placed around the shaft of the grasper and advanced to encircle the lifted tissue. The snare is then activated to excise the tissue. Both approaches are commonly preceded by injecting saline or other solutions under the mucosal to raise the lesion away from the underlying muscle wall in an effort to limit perforation. This lesion, common in the art, is known as a “bleb”. 
   UK Patent Application GB 2365340A to Appleyard and Swain discloses a tissue resection device for removing tissue with a cavity of variable volume, which patent application is incorporated herein by reference. 
   Other devices and methods have been proposed for providing resection of tissue. Still, scientists and engineers continue to seek improved methods for the resection of tissue in the gastro-intestinal tract. 
   SUMMARY OF THE INVENTION 
   The present invention provides an apparatus which can employ suction to engage mucosal tissue for resection. In contrast to some existing devices which use suction for endoscopic mucosal resection, the suction chamber of the present device can open laterally, or on the side of apparatus corresponding to the long axis of the endoscope. Accordingly, the present invention can employ a suction opening which extends generally parallel to the long axis of the endoscope. Existing devices which employ an opening which is at the distal end of the device have the plane of the suction opening being substantially perpendicular to the long axis of the endoscope. 
   Once tissue is drawn into the resection chamber, an electrosurgical wire can be used for transection. In contrast to the flexible electrosurgical snares used in existing devices, the present invention can employ a relatively rigid wire positioned within the device to be drawn across or pushed across the chamber opeing to excise the entrapped tissue. The wire is only electrically active over the portion, which is exposed, non insulated, to the chamber opening. The present invention can also include a flexible, electrically conductive tissue stop, which can function to limit the depth of tissue that can enter the suction chamber for resection. Such a tissue stop can provide for greater safety of resection by reducing risk of alimentary canal perforation and reducing patient burns from monopolar ground pads. The tissue stop can also be perforated for communicating vacuum. 
   In one embodiment, the present invention provides a medical apparatus comprising a body with an outer surface having a side opening, the side opening for receiving tissue therethrough; a cutter adapted to receive energy for cutting tissue, the cutter disposed inward of the opening and adapted to traverse a length of the side opening for cutting tissue extending through the side opening; and a tissue stop disposed inward of the side opening and the cutter, the tissue stop having at least one opening therethrough for conveying vacuum to draw tissue through the side opening. The tissue stop can comprise a plurality of openings therethrough for conveying vacuum. 
   In another embodiment, the present invention provides a method comprising the steps of providing a source of vacuum; positioning a perforated tissue stop in the gastro-intestinal tract; drawing tissue against the perforated tissue stop in the gastro-intesinal tract; and cutting a tissue sample from the tissue drawn against the perforated tissue stop. 
   In another embodiment, the present invention provides a medical apparatus comprising: an overtube for receiving an endoscope therein, the overtube comprising a side opening for receiving tissue therethrough; and a tissue sample device disposed in the overtube, the tissue sample device comprising a tissue cutter adapted to traverse a length of the side opening for severing a tissue sample from tissue extending into the side opening. 
   In another embodiment, the present invention provides a method for obtaining a tissue sample comprising: providing an endoscope; providing an overtube having a side opening and a tissue cutter; inserting the overtube into a patient&#39;s body with the endoscope; receiving tissue into the side opening of the overtube; and cutting tissue extending into the side opening with the tissue cutter. 
   In another embodiment, the present invention provides a medical apparatus comprising: an outer surface having a side opening, the side opening for receiving tissue therethrough; a cutter adapted to receive RF energy for cutting tissue, the cutter supported inward of the side opening and adapted to traverse a length of the side opening for cutting tissue extending through the side opening; and a tissue stop disposed inward of the cutter; wherein the tissue stop comprises a pole of the RF circuit. 
   In another embodiment, the present invention provides a method of cutting tissue comprising the steps of: positioning an RF cutting device in the gastro-intestinal tract of a patient; positioning a tissue stop in the gastro-intestial tract; positioning a tissue mass against the tissue stop; energizing the RF cutting device; grounding the tissue stop; and cutting a tissue sample from the tissue mass. 

   
     BRIEF DESCRIPTION OF THE FIGURES 
       FIG. 1  is a perspective view of a cutting device, showing a cutter support attached to a distal end of an endoscope, and features internal to the cutter support. 
       FIG. 2  is a cross-sectioned end view of the cutter support of  FIG. 1 , taken along section line  16 — 16 , showing a circular embodiment of the cutter support and its internal features. 
       FIG. 3  is a plan view of an alternative cutting element. 
       FIG. 4  is a perspective view of an an alternative cutting device, showing a flexible overtube slidable along and rotatable about an endoscope. 
       FIG. 5  is a cross-sectioned end view of the flexible overtube of  FIG. 4 , taken along section line  18 — 18 , showing a circular embodiment of the cutter support and its internal features. 
       FIG. 6  is a cross-sectioned end view similar to  FIG. 5 , showing internal features in a different position by virtue of a tissue bleb sucked into an aperture in the overtube. 
       FIG. 7  is a cross-sectioned top plan view of the cutter support of  FIG. 1 , taken along section line  17 — 17  of  FIG. 2 , showing a cutting mechanism extended forward of an aperture in the cutter support. 
       FIG. 8  is a cross-sectioned side elevation view of the cutter support of  FIG. 1 , sectioned through the longitudinal axis thereof, showing a perpendicular view of the features of  FIG. 7 . 
       FIG. 9  is a cross-sectioned side elevation view similar to  FIG. 8 , showing a cutting mechanism retracted rearwardly of the aperture into a shear slot. 
       FIG. 10  is a cross-sectioned side elevation view similar to  FIG. 8 , with the addition of tissue shown adjacent the aperture, and a saline solution injection needle extended to enter the tissue to form a bleb. 
       FIG. 11  is a cross-sectioned side elevation view similar to  FIG. 10 , showing the tissue bleb sucked into the aperture and against a stop plate, and the injection needle retracted. 
       FIG. 12  is a cross-sectioned side elevation view similar to  FIG. 11 , showing a cutting element being retracted to cut through a first portion of a bleb, wherein mucosal and sub-mucosal tissue are cut from muscularis tissue. 
       FIG. 13  is a cross-sectioned side elevation view similar to  FIG. 12 , showing completion of cutting while vacuum holds the mucosal and sub-mucosal tissue to the underside of the stop plate. 
       FIG. 14  is a cross-sectioned side elevation view similar to  FIG. 13 , showing the removal of the cutter support from the muscularis tissue after the cut has been completed. 
       FIG. 15  is a schematic view showing a monopolar arrangement of the present invention. 
       FIG. 16  is a schematic view showing a bipolar arrangement of the present invention. 
       FIG. 17  is a schematic perspective illustration of a device of the present invention comprising a tissue stop having a foil conductor with rectangular openings thererin, and showing the tissue stop in an outwardly bowed, generally arcuate configuration. 
       FIG. 18  is a schematic perspective illustration of the device of  FIG. 17  showing the tissue stop deflected to a second configuration, such as by application of vacuum, to receive tissue and to permit passage of an endoscope thereby. 
       FIG. 19  is a schematic illustration an end view of one embodiment of the device of the present invention having an overtube that has a flattened or oval non circular cross-section, and depicting a tissue stop plate in first and second configurations, with the second configuration shown in phantom. 
       FIG. 20  is a schematic illustration of an embodiment of the device of the present invention including a transparent overtube, a transparent sleeve, and a perforated stop plate. 
       FIG. 21  is a schematic illustration of an embodiment of the device of the present invention including a tissue receiving aperture having serrated side edges. 
       FIGS. 22A–22F  illustrate various wire cutter configurations. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   With reference to  FIGS. 1 ,  2 ,  7  &amp;  8 , one embodiment of a cutting device  20  of the present invention is shown attached to a distal end  22  of a commercially available endoscope. Endoscope  24  may be made by Olympus Optical, having an outside diameter of about 0.2 to 0.7 inches. Cutting device  20  can have a rigid or semi-rigid cylindrical cutter support  26  which is attached to the endoscope perimeter by any suitable means, such as by shrink wrap, adhesive, snap fit, press fit, threaded engagement, or other suitable means known in the art for connecting one generally hollow member to another along parallel longitudinal axes. 
   Distal end  22  of endoscope  24  can be located at one end of cutter support  26 . A flexible conical member  28  can be attached to the opposite, distal end of cutter support  26 . Conical member  28  can be employed to provide for a smooth entry of cutting device  20  into the alimentary canal of a patient. Conical member  28  can have an open distal end  30  of about 0.3 inches in diameter through which tooling, not shown, from a working channel  32  of endoscope  24  may extend, and through which unobstructed camera vision of the inside of the patient&#39;s alimentary canal is obtained. Conical member  28  can have an open distal end  30  which permits passage of the distal end of the endoscope  24  therethrough. 
   Conical member  28  can be made of a flexible polymer, such as polyvinylchloride (PVC), polyethylene terephthalate (PET), or other suitable flexible materials. Conical member  28  can be attached to cutter support  26  by threading it thereon, polymer welding, press fit, snap-fit, or other means well known in the art. Conical member  28  can be coaxial with cutter support  26 , whereas a longitudinal axis of endoscope  24  can be offset from a longitudinal axis of cutter support  26 . 
   Cutter support  26  can be generally cylindrical in shape, and can have an outer diameter of between about 0.50 and 0.75 inch, and an axial length of between about 1.0 and about 1.50 inch. In one embodiment, cutter support  26  can have an outer diameter of about 0.60 inches and an axial length of about 1.25 inches. Cutter support  26  can be formed of a transparent polymer, such as polycarbonate or PVC. 
   Cutter Support  26  also can employ a lateral tissue receiving aperture  34 . Aperture  34  can have any suitable shape, and in the embodiment shown is generally rectangular when viewed straight on, and is positioned along one side of the cutter support  26 . The lateral tissue receiving aperture  34  can be about 0.60 to 1.00 inches long (as measured parallel to the axial length of the cutter support  26 ), and about 0.30 to 0.50 inches wide (as measured around the circumference of the outside surface of the cutter support  26 ). 
   A perforated tissue stop plate  36  can be disposed radially inward from tissue receiving aperture  34 , to be positioned inward of tissue receiving aperture  34 . Tissue stop plate  36  can be injection molded to the inner wall of cutter support  26 , or alternatively, made separately and otherwise fixedly attached to the inner wall of cutter support  26 . Stop plate  36  can be semi-rigid, and can be deformable. In one embodiment, stop plate  36  can be formed and attached to cutter support  26  so that stop plate  36  can take on a first configuration (such as an outwardly bowed, generally arcuate configuration), and a second configuration at least a portion of the tissue stop plate is drawn or otherwise deformed or deflected inward (such as by vacuum) to receive tissue through the aperture  34 . Stop plate  36  can be, in whole or in part, transparent, and can be made of or comprise a conductive material. For instance, stop plate  36  can be formed of a polymer or biocompatible metal which is conductive, or a polymer having a conductive ink applied thereto, or can include a generally transparent base layer with a conductive outer layer having openings therethrough, such as in the form of a grid pattern. 
   In  FIG. 1 , stop plate  36  is shown having a plurality of perforations therethrough. Perforations in stop plate  36  can be employed to provide openings through the thickness of the stop plate  36 , and to communicate vacuum from a source of vacuum to draw tissue into the tissue receiving aperture  34 . In one embodiment, the perforations in the stop plate  36  can be about 0.03 to 0.10 inches in diameter and spaced about 0.10 to 0.30 inches apart. While circular perforations are shown, other suitable shapes, including rectangular, square, elliptical, or oval shapes can be employed. 
   Cutter support  26  can have a support  38  molded therein, which contains rectangular wire guide slots  40  ( FIG. 2 ) which can be located parallel to the long edges of aperture  34  on opposite sides of aperture  34 . Guide slots  40  can be disposed outward of stop plate  36 , and inward of aperture  34 . Wire guide slots  40  are sized for wire insulating sleeves  42  to slide longitudinally therein. Insulating sleeves  42  surround two wires that extend from a heating source to distal ends of slots  40  near conical member  28 , where they are attached to a heatable (such as by RF energy) cutting element  44 . Cutting element  44  extends from the sleeves  42  across aperture  34 . As the wires and sleeves  42  are moved parallel to the longitudinal axis of cutter support  26  within slots  40 , cutting element  44  passes across aperture  34  and cuts tissue drawn into aperture  34 . 
   Cutting element  44  can be in the form of a straight wire filament about 0.01 to about 0.04 inches diameter, a flat blade about 0.01 inches thick and 0.03 inches deep, a braided wire about 0.01 to about 0.04 inches in diameter, or other suitable tissue cutting devices. Such cutting element configurations can be about 0.50 inches wide to in order to span aperture  34 , and can be made of a material capable of being heated, such as by radio frequency (RF) energy. Suitable materials from which cutting element  44  can be formed when used with RF energy include electrically conductive materials including without limitation, steel, steel alloys, titanium, or titanium alloys. 
   Cutting element  44  may be heated by a number of heating means including conduction and RF heating, which are commonly known in the endoscopic cutting art. Wire sleeves  42  can be formed of electrical insulating material such as teflon and can be about 0.03 inches in diameter. Electrically conducting wires and their sleeves  42  can extend along the outside of endoscope  24  to an insulated slide block  46 . Block  46  can be is slidably attached to a handle located alongsidean endoscope operating handle. Sleeves  42  can be slidably attached at multiple places to endoscope  24  along its length. Slide block  46  can be supported to move longitudinally according to arrow  47  in  FIG. 1 , to extend and retract sleeves  42  along endoscope  24  and through wire guide slots  40  so that cutting element  44  may be moved past the entire length of aperture  34 . Moving block  46  in a distal direction moves cutting element  44  across the length of aperture  34  in a distal direction, while moving block  46  in a proximal direction moves cutting element across the length of aperture  34  in a proximal direction. 
   For RF heating embodiments, an RF generator can be connected to the wires attached to the cutting element via a switching mechanism to deliver a wattage range of from about 10 to about 150 watts at a suitable frequency, such as a frequency of between about 300 kiloHertz to 3 megaHertz, thereby rapidly heating cutting element  44  to a temperature from about 60° C. to about 120° C. whenever heating is desired. In one embodiment, an Erbe 300 brand generator can be used with the following settings in monopolar or bipolar mode: pure cut, 40 Watts. 
   In an RF heating embodiment an RF grounding plate or pad is typically located outside a patient&#39;s body. However, in the present invention an RF grounding plate may be located within cutting device  20 , for example, by forming tissue stop plate  36  of a conducting material, or disposing a conductor on using tissue stop plate  36  as a metal or metallized electrical grounding plane.  FIG. 2  shows an attachment of a ground wire  48  to the edge of stop plate  36 . Ground wire  48  extends along side endoscope  24  to a ground, not shown, attached to the RF generator. Accordingly, the cutting device  20  can provide an electrical configuration which cutting element  44  provides one pole, and the tissue stop plate  36  provides the other pole. 
   Support  38  for wire slots  40  can also include at one or both ends of the wire slots a cutting element shear slot  50 , into which cutting element  44  moves at the end of a cutting stroke in order to strip tissue from the cutting element. With shear slots  50  located at both ends of aperture  34  (as illustrated in  FIG. 7 ), cutting may occur in either direction, pushing or pulling cutting element  44  through tissue. The sizes of shear slot  50  and cutting element  44  can be selected such that any removed tissue will not be allowed to adhere to the cutting element  44  due to the wiping action of the elements. For example, a cutting element  44  having a diameter of about 0.020 inch and fitting within a shear slot  50  with a clearance spacing of about 0.005 inch is suitable. 
     FIG. 3  shows one of many possible configurations of an alternative cutting element  52 , which includes a pointed portion  54 . One or more points may be employed to “bite into” or initiate contact with tissue and begin cutting without deflecting the tissue out of the path of the cutting element. Also, an angled or pointed cutting element allows for slicing tissue parallel to aperture  34  in a progressive fashion to reduce resistance of cutting. Cutting element  44  may also have a modified surface to be roughened or otherwise textured such as by being sand blasted, bead blasted, and/or machined roughened, which roughened profile can be useful to improve cutting efficiency by biting into the tissue to be resected. 
     FIGS. 22A–22F  show various wire cutter configurations.  FIG. 22A  illustrates a rectangular wire for providing intial cutting across the full width of the wire.  FIG. 22B  illustrates an angled cutting wire for initiating cutting at one corner of the wire, and for progressively engaging more tissue as the cutting wire is advanced along the length of the aperture  34 .  FIG. 22C  illustrates a multiple point wire for providing multiple points of contact with tissue.  FIG. 22D  illustrates a single point or notch for providing single point contact upon initial tissue engagement.  FIG. 22E  illustrates a relatively sharp single point cutter for relatively high initial current density and mechanical penetration.  FIG. 22F  illustrates a wire cutter having a flattened (as opposed to circular cross-section) blade which can have a sharpened edge and points for cutting tissue with or without RF energy. 
   Serrated edges can provided along the perimeter of a tissue receiving aperture. The textured surface provided by serrated aperture edges can provide for better gripping of the tissue during cutting.  FIG. 21  illustrates a tissue receiving aperture having serrated edges. 
   In order to cut a mucosal layer of tissue from the alimentary canal of a patient for external study, the mucosal layer and sub-mucosal layers are typically separated somewhat from a muscularis layer of tissue by injecting a saline solution between them. This is commonly done by extending an injection needle through working channel  32  of endoscope  24  to contact and penetrate the target tissue. 
   In one embodiment, the present invention can provide an improved device and method for injecting saline solution. In the embodiments shown in  FIGS. 1 ,  2 , and  7 – 14 , support  38  has secured therein a flexible sheath  56  for an injection needle  58 . Sheath  56  can extend along side endoscope  24  to a handle, not shown, which is operated to deliver saline solution thru a hollow cable connected to injection needle  58 . The hollow cable can be slidable within sheath  56  so that needle  58  may be extended beyond the fixed end of sheath  56  to engage mucosal tissue adjacent aperture  34 . Sheath  56 , which can be fixedly attached to cutter support  26 , serves as a needle guide that is supported on the cutter support  26 . Sheath  56  can enable the operator of the injection needle to control its position more accurately (in order to avoid penetrating the muscularis tissue) than when a needle and a sheath are operated through an endoscope&#39;s working channel. 
   Injection needle  58  can be used to deliver saline solution  60 , as shown in  FIGS. 10–13 , through mucosal tissue  62  and sub-mucosal tissue  64  only. These softer tissues separate from stiffer muscularis tissue  66  when saline solution  60  is introduced. After injection, the needle is withdrawn from the tissue. Needle  58  and sheath  56  are shown in  FIG. 2  in a retracted position extending through support  38  and angled toward aperture  34 , in a plane which generally bisects aperture  34  and is centered between wire slots  40 . 
   Tissue is drawn into aperture  34  by means of vacuum from a vacuum source, not shown, external to the patient&#39;s body. A suitable vacuum source can provide a vacuum of about 50 to 250 mm hg. Vacuum can be drawn through working channel  32  in endoscope  24 . Air is drawn from the patient&#39;s alimentary canal, causing the canal to close down around cutter support  26  and bring tissue layer  62  in contact with the side of cutter support  26  where the tissue engages aperture  34 . Vacuum communicated through the working channel  32  of the endoscope  24  and then through the openings in the stop plate  36  draws tissue layer  62  against stop plate  36  as air flows through the openings in the stop plate  36  to the opposite side of stop plate  36  where the distal end  22  of endoscope  24  can be positioned. 
   Although  FIG. 2  shows a circular cross-section for cutter support  26 , a flattened oval or other shape may enable an aperture to be wider for cutting a larger sample of tissue. Similarly, while aperture  34  is shown as a generally rectangular shaped opening on a cylindrical surface, other aperture shapes can be employed, including without limitation oval, circular, and polygonal. 
     FIGS. 4–6  illustrates an alternative embodiment of a cutting device  80  of the present invention. In  FIGS. 4–6 , an endoscope is not fixedly attached to a cutting device  80 . Instead, the cutting device  80  can comprise an overtube  86 . The overtube can slide along an endoscope and rotate about the endoscope. Such an embodiment can permit closer access by the distal end of the endoscope to target tissue for examination and/or manipulation before or after mucosal tissue cutting. Alternatively, the cutting device and overtube can employ integral vacuum lines and visualization means (e.g. ccd camera) so that the cutting device and overtube can be used independently of an endoscope. 
   In  FIG. 4 , cutting device  80  is shown having a distal end  82  of a commercially available endoscope  84  extended therethrough. Endoscope  24  may be made by Olympus Optical, having an outside diameter of about 0.2 to 0.7 inches. Cutting device  80  has a flexible cylindrical overtube  86  slidably disposed along the length of the endoscope perimeter along parallel longitudinal axes. Overtube  86  can be relatively short and rigid, or can be flexible enough to conform to the articulations of flexible endoscope  84 . Overtube  86  can have has at a distal end a flexible conical member  88 , which provides for a smooth entry of cutting device  80  into the alimentary canal of a patient. Conical member  88  can be made of a flexible polymer such as PVC, PET, etc., and it has an open outer end  90  about 0.3 inches in diameter. The opening in the outer end can expand or be enlarged upon application of force so that endoscope  84  may extend therethrough. Conical member  88  can also be made of flexible polymer, and can be integral with overtube  86 , or attached to overtube  86 , such as by threading it onto overtube  86 , by polymer welding, by snap-fit, or by other means. Conical member  88  cab be coaxial with overtube  86 , whereas a longitudinal axis of endoscope  84  may be offset from a longitudinal axis of overtube  86 , as shown in  FIG. 2 . The flexibility of the conical member  88  allows distal advancement of the endoscope to deflect the open end so that the endoscope is able to pass through the open end of member  88 . 
   Overtube  86  can have a smooth outer diameter of about 0.40 to about 0.80 inches and a length of about 0.7 to 2.0 inches. The overtube  86  can be disposed at the distal end of a elongated, flexible tube or sleeve. In  FIG. 4 , the proximal end of the overtube  86  is molded or otherwise connected a flexible sleeve for receiving an endoscopic therethrough, which sleeve can be in the form of an elongated, corrugated tubular portion  92 . Alternatively, the tubular portion  92  can be generally smooth. Tubular portion  92  can have an internal diameter sized to receive an endoscope therethrough, and tubular portion  92  can have a length at least about the length of the portion of the endoscope which is inserted into the patient. Corrugated portion  92  can have generally the same outside diameter as overtube  86 . It may be connected to the overtube similar to the conical member, and shrink wrap material may be added at the connection to seal the corrugated portion to the overtube. In one embodiment, the flexible, elongated corrugated portion  92  can have a length of between about 2.7 feet and about 4.0 feet. In one embodiment, the internal diameter of the tubular portion  92  can be greater than 0.15 inch and less than about 0.85 inch, and more particularly between about 0.30 to about 0.75 inch. 
   Overtube  86  has a rectangular tissue receiving aperture  94  along one side, which is about 0.80 inches long and about 0.40 inches wide. A flexible stop plate  96  can be disposed just inside aperture  94 . Stop plate  96  can be fastened to the inner wall of overtube  86  or otherwise disposed in aperture  94  such that stop plate  96  is able to toggle between (or otherwise assume) two different configurations. Two opposite edges of the stop plate  96  can be joined directly or indirectly along their lengths to the overtube  86 , while the two opposite end edges of the stop plate can remain free and unconnected to other portions of the device to facilitate movement of the stop plate from one configuration to another. In one embodiment Stop plate  96  can have a width greater than a chord length across the overtube where stop plate  96  is mounted so that stop plate  96  is bowed (or otherwise deflected or deformed) in a generally arcuate fashion toward aperture  94  or away from aperture  94 . In one embodiment, the flexible stop plate  96  is biased to bow toward aperture  94  to enable endoscope  84  to pass over it on an opposite side. In such an embodiment, stop plate  96  can be formed of a thin flexible material, such as PVC, PET or other flexible polymer. Stop plate  96  can have a thickness of less than about 0.05 inches, and can extend longitudinally beyond both ends of aperture  94 . 
   The outwardly facing surface of stop plate  96  can include a portion which is conductive and which can serve as a ground or other pole of a electrical cutting circuit. In one embodiment, stop plate  96  has a conductive ink applied to one surface (e.g. the outwardly facing surface) so that it may serve as a grounding plate for RF heating of a cutting element as described for cutting device  20 . Alternatively, an electrically conductive surface may be co-extruded on the stop plate  96 , or the stop plate may be made of thin bio-compatible metal. 
   Overtube  86  can have a support  98  molded therein, which contains rectangular wire guide slots  100  between stop plate  96  and aperture  94 . Wire guide slots  100  are sized for insulating sleeves  102  to slide longitudinally therein, just outside the width of aperture  94 . Insulating sleeves  102  surround two wires that extend from an RF heating source (not shown) to distal ends of slots  100  near conical member  88 , where they are attached to a heatable cutting element  104 . Cutting element  104  extends from the sleeves  102  across aperture  94 . As wires and sleeves  102  are slid parallel to the longitudinal axis of overtube  86  within slots  100 , cutting element  104  passes across aperture  94  in order to cut tissue of a patient drawn into aperture  94 , similar to the operation of cutting device  20 . Cutting element  104  can be the same as that described for cutting element  44  or cutting element  52  above. 
   Cutting element  104  may be heated by a number of heating means including conduction and RF heating, which are commonly known in the endoscopic cutting art. Wire sleeves  102  are made of electrical insulating material such as Teflon, similar to insulating sleeves  42 , and they extend along the outside of endoscope  84  to an insulated slide block, not shown. The slide block, similar to slide block  46 , can be slidably attached to a handle located alongside an endoscope operating handle, such that the slide block is moved longitudinally to extend and retract sleeves  102  along endoscope  84  and through wire guide slots  100  so that cutting element  104  may be moved past the entire length of aperture  94  in overtube  86 . 
   The heating of cutting element  104  may be the same as or similar to cutting element  44 . In an RF heating embodiment, an RF grounding surface may be located within cutting device  80 , for example by using a conductive tissue stop plate  96 . Alternatively, a grounding plate separate from the stop plate  96  can be employed, but outside of the path of endoscope  84 , so that the endoscope may freely pass through the overtube. A ground wire can be attached to the separate ground plate or to the stop plate, and the ground wire extends to a grounded location outside of the patient. 
   Supports  98  can also include, at each end of the wire slots  100 , cutting element shear slots  110 . The cutting element  104  can move into the shear slots  110  at the end of a cutting stroke in order to strip tissue from the cutting element. Such shear slots  110  can be the same as or similar to slots  50  of cutting device  20 , and cutting may occur in two directions, either by pushing cutting element distally, or by pulling cutting element  104  proximally, through tissue. 
     FIGS. 4–6  show that overtube  86  has secured in support  98  a flexible sheath  116  for an injection needle  118 . Sheath  116  extends along side endoscope  84  inside corrugated portion  92  to deliver saline solution thru a hollow cable connected to injection needle  58 , in a similar manner to sheath  56  and needle  58 , to engage mucosal tissue adjacent aperture  94 . Needle  118  and sheath  116  are shown in  FIGS. 4 and 5  in a retracted position extending through support  98  and angled toward aperture  94 , in a plane centered within aperture  94 , and between wire slots  100  and the aperture. 
   As shown in  FIG. 6 , when cutting device  80  is slid along endoscope  84  to a position where endoscope  84  no longer interferes with the toggling of stop plate  96 , tissue may be drawn into aperture  94  by means of vacuum from a vacuum source, not shown, external to the patient&#39;s body. Vacuum is drawn through working channel  112  in endoscope  84 . Air is drawn from the patient&#39;s alimentary canal, causing the canal to close down around overtube  86  and bring tissue  114  in contact with the side of overtube  86  where the tissue engages aperture  94 . Vacuum draws tissue  114  against stop plate  96  and causes stop plate  96  to toggle away from, or otherwise deflect or deform away from, the aperture  94 . 
   Although  FIGS. 5 and 6  show a circular cross-section for overtube  86 , a flattened oval or other shape may be used to permit an aperture to be wider for cutting a larger sample of tissue. 
   Cutting devices  20  and  80  are operated in a similar manner to remove a tissue sample.  FIGS. 10–14  describe one method of using cutting device  20 .  FIG. 10  shows typical alimentary canal tissue, with mucosal layer  62  atop sub-mucosal layer  64  atop muscularis layer  66  brought into contact with aperture  34 , by placement of the cutting device against the tissue or by a low level of vacuum from the endoscope working channel to close the alimentary canal wall against cutter support  26 . In this position, needle  58  is extended from sheath  56  by pushing a hollow cable through the sheath, as described hereinbefore. Saline solution  60  is then injected into the tissue through the needle, preferably at a depth where sub-mucosal tissue and muscularis are separable, as is commonly understood in the endoscopic mucosal tissue cutting art. An amount of solution  60  is injected which separates the layers sufficient for cutting layers  62  and  64  without cutting layer  66 . 
     FIG. 11  shows needle  58  withdrawn from the tissue and a higher level of vacuum sucking the tissue into aperture  34  and against stop plate  36 . Cutting element  44  in this particular method, is shown extended to shear slot  50 . RF energy is now delivered via wires surrounded by insulating sleeves  42  to cutting element  44 , using conductive stop plate  36  as a ground for the RF energy path. Wire  48  connects stop plate  36  to an external ground, not shown. Cutting is ready to begin as cutting element  44  is rapidly heated to the desired temperature by controlling the level of RF energy. 
     FIG. 12  shows slide block  46  being moved along arrow  120  to pull cutting element  44  into tissue layers  62  and  64  and solution  60 . Solution  60  can be drawn out by the vacuum, which vacuum can also be employed to secure the cut portion of tissue layers  62  and  64  against stop plate  36 . 
     FIG. 13  shows slide block  46  being moved further along arrow  120  to complete the cut and shear tissue off cutting element  44  by pulling the cutting element into shear slot  50 . Severed layers of tissue  62  and  64  continue to be held against perforated stop plate  36  by vacuum from endoscope  24  located on the opposite side of the stop plate. RF power can then be switched off. In  FIGS. 12 and 13 , stop plate  36  is not shown as being deformable. However, it will be understood that stop plate  36  can be made to be deformable as described above. 
     FIG. 14  shows cutting device lifted away from the remaining layers of tissue so that the cutting device may be withdrawn from the patient to examine the cut sample of tissue. A relatively lower level of vacuum can be employed to hold the cut tissue against the stop plate. The endoscope and cutting device may be rotated to a position such that the tissue sample is held against the stop plate by gravity when the vacuum is turned off. Alternatively, the cutting element (with not RF power applied) can be moved forward to a position similar to that of  FIG. 12  to hold the cut tissue against the stop plate when the endoscope and tissue support  26  are manipulated to withdraw them from the patient. In another alternative, the cut tissue can be released from the stop plate and allowed to exit the aperture. Then the endoscope and cutting device can be partially withdrawn to where a gripper may be extended from a working channel of the endoscope through open distal end  30  to grasp the cut sample of tissue. 
     FIG. 15  shows a monopolar arrangement of one embodiment of the present invention. The electrocautery generator  200  supplies the RF energy via a ground connected to the ground pad  203  at the patient&#39;s skin. The RF energy path  205  is connected to the RF cutting element  44 / 104 . The vacuum pump  201  communicates with the cutter support  26 /overtube  86  via a vacuum channel  204  which can be integral to the endoscope  84   
     FIG. 16  shows a bipolar arrangement of another embodiment of the present invention. The electrocautery generator  200  supplies the RF energy via energy paths  205 . One polarity of the RF energy path  205  is connected to the RF cutting element  44 / 104  and the other polarity is connected to the stop plate  36 / 96 . The vacuum pump  201  is connected to the support  26 /overtube  86  via a vacuum channel  204  which can be integral to the endoscope  84 . 
     FIGS. 17 and 18  illustrate an emobidment of the present invention wherein the overtube  86  and elongated portion  92  can be transparent, and wherein the tissue stop plate  96  can be formed of a thin, transparent flexible polymeric material with a conductive grid  97  disposed on a surface of the tissue stop  96  facing the tissue recieiving aperture  94 . Grid  97  can define grid openings  99 , which are generally rectangular in  FIGS. 17 and 18 . One or more openings  99  can be perforated for communicating vacuum therethrough if desired. Grid  97  can be formed of a suitable conductive material, such as a conductive metallic foil, or be painted or printed on with a conductive ink or coating. The conductive surface of the grid  97  can be between about 2 and about 10 times the conductive surface area of the cutter  104 , and in one embodiment the conductive surface area of grid  97  can be about 4 times the conductive surface area of cutter  104 . 
   The tissue stop  96  in  FIGS. 17 and 18  can take on a first configuration in  FIG. 17  (which permits passage of an endoscope thereby), and a second configuration shown in  FIG. 18  when vacuum is applied (such as through endoscope  84 ) for limiting the amount of tissue drawn into aperture  94 . The longitudinally extending sides  95  of tissue stop  96  can be fixed, such as by being joined to overtube  86 . The proximal and distal ends of the tissue stop  96  can be unsupported and free to deform. The first and second configurations can be bowed, generally arcuate shapes, as shown in  FIGS. 17 and 18 . In one embodiment, the tissue stop  96  does not stretch or elongate in taking on the first and second configurations, but instead “toggles” or “snaps-through” from one configuration to the other. 
   A suitable tissue stop  96  can be formed from a section of a clear PET angioplasty balloon. The tissue stop  96  can be an arcuate segment cut from a generally cylindrical angioplasty balloon formed of PET. The arcuate segment can be cut from an angioplasty balloon cylinder having a diameter between about 10 and about 16 mm and a wall thickness of about 0.001 to about 0.002 inch. One suitable angioplasty balloon from which tissue stop  96  can be formed is a 10 mm diameter angioplasty balloon having a wall thickness of 0.002 inch (0.05 mm) available from Advanced Polymers of Salem, N.H. An arcuate segment can be cut from the angioplasty balloon to form the clear tissue stop  96 . A thin metallic foil having a thickness of about 0.005 inch or less, such as a steel foil having a thickness of about 0.001 inch can then be applied to the surface of the stop  96  facing tissue receiving aperture  94 , such as with an adhesive. Prior to attaching the foil to the stop  96 , the foil can be cut to form a series of openings therethrough to provide the grid  97  shown in  FIGS. 17 and 18 . 
     FIG. 19  illustrates a cross-sectional view of an overtube  86  having a noncircular cross-section, with a generally flattened outer surface portion in which tissue receiving aperture  94  is formed. An endoscope  84  is shown positioned in the overtube  86 . The generally flattened outer surface portion is located on a bottom half of the overtube  86  as viewed in  FIG. 19 . Providing the tissue receiving aperture  94  in such a generally flattened surface portion can be useful in positioning the aperture  94  relative to tissue to be resected.  FIG. 19  also shows first and second configurations of tissue stop  96 , with the second configuration shown in phantom. In one embodiment, the overtube  86  can be formed in two shell-like halves, such as a generally semi-circular upper half and a non-circular lower half. The tissue stop  96  can be formed from a nonplanar, arcuate section of thin polymeric film material (such as a section of an angioplasty balloon described above), and the side edges of the arcuate tissue stop can be captured between the upper and lower halves of the overtube as the upper and lower halves are joined together, such as by adhesive or other suitable means. The proximal and distal ends of the tissue stop  96  can remain free and unsupported so that the tissue stop can snap through, toggle, or other wise deflect from the first configuration to the second configuration. 
     FIG. 20  illustrates an embodiment of the present invention having a transparent overtube  86  and transparent elongated sleeve portion  92 . The tissue stop  96  is generally planar, with generally circular shaped vacuum openings therethrough.  FIG. 21  illustrates an embodiment of the present invention wherein the overtube  86  has a tissue receiving aperture having serrated side edges  93  for assisting in grasping and cutting tissue with the cutting element  104 . Tissue stop  96  is omitted from  FIG. 21  for purposes of clarity in illustrating the side edges of aperture  94 . 
   While the present invention has been illustrated by description of several embodiments, it is not the intention of the applicant to restrict or limit the spirit and scope of the appended claims to such detail. For instance, but without limitation, RF energy has been described as the tissue cutting method in the illustrated embodiments, but it will be understood that other tissue cutting modes, such as ultrasonic energy modes, mechanical cutting, and other methods could be employed in various embodiments of the present invention. Numerous other variations, changes, and substitutions will occur to those skilled in the art without departing from the scope of the invention. Moreover, the structure of each element associated with the present invention can be alternatively described as a means for providing the function performed by the element. Accordingly, it is intended that the invention be limited only by the spirit and scope of the appended claims.