Patent Publication Number: US-2010125168-A1

Title: Methods and devices for endoscope control in a body cavity

Description:
FIELD 
     The present disclosure relates to devices and methods for controlling an endoscope in a body cavity. 
     BACKGROUND 
     Minimally invasive surgical techniques such as endoscopies and laparoscopies are often preferred over traditional open surgeries because the recovery time, pain, and surgery-related complications are typically less with minimally invasive surgical techniques. Rather than cut open large portions of the body in order to access inner cavities, such as the peritoneal cavity, surgeons either rely on natural orifices of the body or create one or more small orifices in which surgical instruments can be inserted to allow surgeons to visualize and operate at the surgical site. Surgeons can then perform a variety of diagnostic procedures, such as visual inspection or removal of a tissue sample for biopsy, or treatment procedures, such as removal of a polyp or tumor or restructuring tissue. 
     Because of the rise in popularity of minimally invasive surgeries, there has been significant development with respect to the instruments used in such procedures. These instruments need to be suitable for precise placement of a working end at a desired surgical site to allow the surgeon to see the site and perform the necessary actions at such site. Often times the instruments either themselves contain a device that allows the surgeon to see the site, or else the instruments are used in conjunction with an instrument that can provide visual assistance. At least one of these types of devices, an endoscope, is typically configured with both a lens to visualize the surgical site and one or more channels through which instruments can be delivered to the surgical site for subsequent use. The instruments themselves can be used to engage and or treat tissue and other portions within the body in a number of different ways to achieve a diagnostic or therapeutic effect. 
     Like most surgical procedures, minimally invasive procedures require stability and precision at the surgical site. This can be particularly difficult to achieve in body cavities because body cavities generally include a large amount of three-dimensional space, which in turn means that there is not much in the way of support within the cavity that the endoscope can rely upon for strength and stability. It is also challenging to remotely control a working end of an endoscope such that it can be directed to the desired location within the body cavity so that the desired procedures can be performed upon reaching the desired location. Further, the challenges of controlling an endoscope can also be experienced just trying to deliver the endoscope to the desired location. For example, organs or other materials in the body can get in the way of a desired path of the endoscope, in which case it is desirable to move the organs and materials out of the desired path without causing unwanted disruption to the organs and/or materials. 
     Accordingly, there remains a need for improved devices and methods for controlling endoscopes, and in particular the working end of endoscopes, to allow for more precision and accuracy during surgical procedures. 
     SUMMARY 
     Methods and devices are generally provided for controlling an endoscope in a body cavity. In one embodiment, an endoscopic surgical system includes an endoscope, an overtube configured to receive at least a portion of the endoscope, and a steering tether disposed external to the endoscope, coupled to at least a portion of the endoscope, and configured to be manipulatable to effect directional movement of a distal end of the endoscope. The steering tether can extend through the overtube from a proximal end thereof and can be coupled to a portion of the endoscope that is proximal to the distal end of the endoscope. The endoscope can include an accessory mount extending over at least a portion of a length of the endoscope and terminating proximal to the distal end of the endoscope. The steering tether can be disposed on the accessory mount. In one embodiment a portion of the steering tether extends beyond the accessory mount to form a loop and another portion of the steering tether extends back through the overtube to a proximal end of the endoscope. The loop can include a nominal arcuate diameter that is adjustable such that when the nominal arcuate diameter is adjusted, a range of access of the steering tether, and thereby a range of access of the endoscope, can be altered. Similarly, in embodiments that do not include an accessory mount, a portion of the steering tether can extend beyond the distal end of the endoscope to form a loop and another portion of the steering tether can extend back through the overtube to a proximal end of the endoscope. The loop can include an adjustable nominal arcuate diameter as already described. Regardless of whether the steering tether includes a loop or not, it can be configured to be pushed and pulled to effect directional movement of the distal end of the endoscope. The steering tether can also be manipulatable to displace objects to a surrounding area above or below a plane of the endoscope. The endoscopic surgical system can include a locking mechanism to set a position of the steering tether. In one embodiment the endoscopic surgical system includes a steering module that is configured to adjust a position of the steering tether. 
     In another embodiment of an endoscopic surgical system, an endoscope and a steering tether are provided. The steering tether can be external to the endoscope and can be configured to couple to the endoscope. The steering tether can include a first portion that extends along side at least a portion of the endoscope and can be coupled to at least a portion of the endoscope, and a second portion that extends along side the first portion. A loop can be formed between the first and second portions. The loop can terminate proximal to a distal end of the endoscope and at least a portion of the loop can be coupled to the endoscope. The second portion of the steering tether can include a proximal portion that is configured to manipulate the loop to control movement of the endoscope. For example, the proximal portion can be configured to be pushed and pulled to control movement of the endoscope. The proximal portion can also be configured to be rotated about its longitudinal axis to displace objects to a surrounding area above or below a plane of the endoscope. The endoscopic surgical system can include a channel that has at least a portion of each of the endoscope and the steering tether disposed within it. In one embodiment the endoscope includes an accessory mount that extends over at least a portion of a length of the endoscope and terminates proximal to the distal end of the endoscope. At least part of the first portion of the steering tether can reside in the accessory mount. The loop can extend beyond the accessory mount. The loop can include a nominal arcuate diameter that is adjustable such that when the nominal arcuate diameter is adjusted, a range of access of the steering tether, and thereby a range of access of the endoscope, can be altered. In one embodiment the endoscopic surgical system includes a steering module that is configured to adjust a position of the steering tether. 
     In an embodiment of a surgical system, an elongate sheath having an accessory mount and a steering tether. The accessory mount of the elongate sheath can extend over at least a portion of a length of the accessory mount, and the accessory mount can terminate proximal to a distal end of the sheath. The steering tether can be disposed external to the elongate sheath, extend along at least a portion of the elongate sheath that is proximal to the distal end of the sheath, and can be manipulatable to effect directional movement of the distal end of the sheath. In one embodiment, at least a portion of the steering tether is disposed in the accessory mount. A portion of the steering tether can extend beyond the accessory mount to form a loop, while another portion of the steering tether can extend back through at least a portion of the accessory mount to a proximal end of the elongate sheath. An overtube can be coupled to the elongate sheath and at least a portion of each of the elongate sheath and the steering tether can be disposed therein. The system can also include an accessory channel coupled to the elongate sheath by way of a complimentary accessory mount that can be coupled to the accessory mount of the elongate sheath. 
     Methods for controlling movement of an endoscope in a body cavity are also provided. In one exemplary embodiment, an endoscope and a steering tether can be directed to a body cavity. Both the endoscope and the steering tether can be at least partially disposed within a channel and at least a portion of the steering tether can be coupled to the endoscope. The steering tether can include a proximal end and a looped distal end such that moving the proximal end of the steering tether can control the looped distal end, thereby controlling the directional movement of the endoscope. In one embodiment, moving the proximal end of the steering tether includes pushing and/or pulling it to move the looped distal end to a desired location. In another embodiment, moving the proximal end of the steering tether includes rotating it about a longitudinal axis of the steering tether to displace objects to a surrounding area above or below a plane of the endoscope. A nominal arcuate diameter of the looped distal end can be adjusted, and thus the method can include adjusting the nominal arcuate diameter of the looped distal end to adjust a range of access of the steering tether, and thereby the endoscope. In one embodiment, the method can also include directing a rail to a body cavity. The rail can be coupled to the endoscope, and thus, can be at least partially disposed in the channel. The rail can be configured to assist in moving the endoscope to a desired location. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
       This invention will be more fully understood from the following detailed description taken in conjunction with the accompanying drawings, in which: 
         FIG. 1  is a side perspective view of one exemplary embodiment of an endoscopic surgical system; 
         FIG. 2  is a further side perspective view of the endoscopic surgical system of  FIG. 1 ; 
         FIG. 3  is a perspective view of the proximal end of the endoscopic surgical system of  FIG. 1 ; 
         FIG. 4  is a perspective view of an exemplary embodiment of a surgical system that includes a sheath and an accessory channel; 
         FIG. 5  is a top perspective view of the endoscopic surgical system of  FIG. 1  illustrated with respect to a polar coordinate grid; 
         FIG. 6  is a top perspective view of the endoscopic surgical system of  FIG. 5  with an adjustable nominal arcuate diameter of a steering tether that is smaller than the nominal arcuate diameter of the system of  FIG. 5 ; 
         FIG. 7  is a top perspective view of the endoscopic surgical system of  FIG. 6  illustrating movement of a distal end of an endoscope of the system by way of the steering tether; 
         FIG. 8  is a distal end perspective view of the endoscopic surgical system of  FIG. 1  having an object at least partially disposed in a plane of the endoscope of the system; 
         FIG. 9  is a partially transparent distal end perspective view of the endoscopic surgical system of  FIG. 8  illustrating the system displacing the object from the plane of the endoscope of the system; and 
         FIGS. 10A-10F  illustrate a progression of a method for controlling movement of an endoscope. 
     
    
    
     DETAILED DESCRIPTION 
     Certain exemplary embodiments will now be described to provide an overall understanding of the principles of the structure, function, manufacture, and use of the devices and methods disclosed herein. One or more examples of these embodiments are illustrated in the accompanying drawings. Those skilled in the art will understand that the devices and methods specifically described herein and illustrated in the accompanying drawings are non-limiting exemplary embodiments and that the scope of the present invention is defined solely by the claims. The features illustrated or described in connection with one exemplary embodiment may be combined with the features of other embodiments. Such modifications and variations are intended to be included within the scope of the present invention. 
     An endoscopic surgical system is generally provided that includes an endoscope having a distal end configured to be accurately controlled from a proximal end of the surgical system. Unlike many endoscopes steering and/or directional movement can be controlled even in the absence of the walls of a hollow organ within which an endoscope is often placed. Directional movement generally describes any number of directions or orientations that the endoscope, and in particular the distal end of the endoscope, can be directed to move by an operator. The system can include a steering tether that is external to the endoscope, extends along at least a portion of the endoscope, and that can be manipulated to effect directional movement of the endoscope&#39;s distal end. While the steering tether can come in a variety of forms and have a number of different configurations as discussed herein, in one exemplary embodiment the tether forms a loop near the distal end of the endoscope such that the steering tether extends back to a proximal end of the endoscope and/or a proximal end of the surgical system. The system can optionally include an overtube that is configured to receive at least a portion of the endoscope and the steering tether. When the steering tether forms a loop, the overtube can receive two portions of the steering tether—the portion extending from the proximal end of the system toward the distal end of the endoscope to form the loop and the portion extending from the loop and returning toward the proximal portion of the system. A person having ordinary skill in the art would recognize that while many embodiments are discussed with respect to a portion of an endoscope being manipulated by a steering tether, other surgical instruments or tools, or other devices configured to receive surgical instruments or tools, such as a sheath, can be associated with a steering tether in a similar fashion as the endoscopes discussed herein, and further, the steering tether can be operated in a similar manner as described herein. 
       FIGS. 1-3  illustrate one exemplary embodiment of an endoscopic surgical system  10  configured to allow for accurate movement of a distal end of an endoscope. The system  10  can include a number of different components, but in the illustrated embodiment it includes an endoscope  20  and a steering tether  30  at least portions of which are disposed in an overtube  40 . The overtube  40  can be configured to receive at least a portion of both the endoscope  20  and the steering tether  30 . The steering tether  30  can be external to the endoscope  20 , coupled to at least a portion of the endoscope  20 , and further, it can be manipulatable to effect directional movement of a distal end  20   d  of the endoscope  20 . 
     One skilled in the art will appreciate that endoscopes have many different configurations, and thus, an endoscope for use with the endoscopic surgical system  10  can have many different configurations. As shown in  FIG. 3 , the endoscope  20  can have a working channel  22  configured to receive one or more surgical instruments, or even the steering tether  30 , at a proximal end  20   p  of the endoscope  20 . In other embodiments, the endoscope  20  can include multiple working channels or have other configurations for use in surgical procedures. In still other embodiments of an endoscope that can be used in an endoscopic surgical system as discussed herein, the endoscope can include a mating element or accessory mount formed directly or indirectly on the endoscope and adapted to mate with another device, such as an elongate sheath or another endoscope. A mount formed indirectly on the endoscope may be, for example, a mount formed on a sheath within which an endoscope can be disposed. 
     While the mating element or accessory mount can have a variety of configurations, including for example interlocking elements, engaging elements, complementary shapes, sliding members, magnetic elements, spring-loaded retaining members, and elastic members, in the embodiment of a surgical system  110  illustrated in  FIG. 4  the mating element is a T-shaped track  124  formed along at least a portion of an external length of an elongate sheath  121 , which can house an endoscope (not shown). In some embodiments, the sheath is an endoscope. The sheath  121  can have characteristics and features that are similar to the endoscope  20  of the endoscopic surgical system  10 . In the illustrated embodiment, the track  124  extends across the entire length of the sheath  121 , terminating at a distal end  121   d  of the sheath  121 , although in other embodiments the track  124  can terminate proximal to the distal end  121   d  of the sheath  121  or be positioned along any portion thereof. The track  124  is configured to be slidably mated to a complimentary rail  424  of a second device, such as accessory channel  420 . The track  124  can have virtually any length, but in one exemplary embodiment the length compliments the length of the sheath  121  so that a second device can be securely mated thereto. Allowing a second device or channel to be disposed next to the sheath  121  can allow other tools to be delivered adjacent to the distal end  121   d  of the sheath  121 . By way of non-limiting example, the independent articulating accessory channel discussed in U.S. Patent Application Publication No. 2008/0132758 of Stefanchik et al., filed on Dec. 5, 2006, and entitled “Independent Articulating Accessory Channel,” which is incorporated by reference in its entirety, is one type of configuration in which the teachings of a steering tether like steering tethers  30  and  130 , both of which are discussed in greater detail below, can be incorporated. Likewise, mechanisms for controlling any portion of the sheath  121  can then be disposed along any length of the sheath  121 . For example, devices that assist in stiffening the sheath  121 , or instruments disposed therein, either entirely or portions thereof, can be disposed along a length of the sheath  121  by way of the mating element. By way of non-limiting example, stiffening elements such as those discussed in U.S. patent application Ser. No. 11/952,475 of Stefanchik et al., filed on Dec. 7, 2007, and entitled “Selective Stiffening Devices and Methods,” which is hereby incorporated by reference in its entirety, can be used in association with the surgical systems disclosed herein. By further way of non-limiting example, other embodiments of endoscopes that can be used in the surgical systems disclosed herein are discussed in U.S. Patent Application Publication No. 2008/0183035 of Vakharia et al., filed on Jan. 26, 2007, and entitled “Endoscopic Accessory Control Mechanism,” and in U.S. patent application Ser. No. 11/971,410 of Stefanchik et al., filed on Jan. 9, 2008, and entitled “Articulating Surgical Device and Method of Use,” each of which is hereby incorporated by reference in its entirety. While in the illustrated embodiment the track  124  is disposed along an external length of the sheath  121  and is configured to be slidably mated to the complimentary rail  424  of the accessory channel  420 , in alternative embodiments the sheath  121  can include a rail while a complimentary track, like the track  124 , can be disposed on a second device. Still further, mating elements or accessory mounts of the sheath  121  can be configured to mate with portions of a steering tether  130  or an overtube (not shown). 
     Referring again to  FIGS. 1-3 , the steering tether  30  is an elongate member that is configured to control the distal end  20   d  of the endoscope  20 , for example by being external to the endoscope  20  and/or being coupled to at least a portion of the endoscope  20 . In one embodiment, the steering tether is coupled to a portion of the endoscope  20  that is proximal to the distal end  20   d  of the endoscope  20 . As shown, the steering tether  30  is coupled to the proximal end  20   p  of the endoscope  20  and remains coupled to the endoscope  20  along the length of the endoscope  20  up to a portion that is proximal of the distal end  20   d  of the endoscope  20 . The steering tether  30  can thus dovetail with a length of the endoscope  20 . In alternative embodiments, select portions of the steering tether  30  are coupled to select portions of the endoscope  20 , which can allow for varying degrees of control of the endoscope  20 . Still further, although in the illustrated embodiment the steering tether  30  is external to the endoscope  20 , in other embodiments portions of the steering tether  30  can be disposed in the endoscope  20  such that a portion or segment of the steering tether  30  is internal to the endoscope  20  while a second portion or segment of the steering tether  30  is external to the endoscope  20 . 
     One skilled in the art will appreciate that different configurations of associating the steering tether  30  with the endoscope  20  can allow a variety of directional movement of the distal end  20   d  of the endoscope  20  to be effected. As the steering tether  30  is manipulated, by techniques discussed in further detail below including, for example, pushing and pulling the tether  30 , the distal end  20   d  of the endoscope  20  is controlled. In the illustrated embodiment, the steering tether  30  is configured such that a loop  34  is formed at a distal end  30   d  thereof. The loop  34  can be manipulated at a proximal end  30   p  of the steering tether  30 . In one embodiment, the loop  34  can be formed between a first portion  31  of the steering tether  30  that is coupled to at least a portion of the endoscope  20  and a second portion  32  of the steering tether  30  that can extend along side the first portion  31  and can include a proximal portion  32   p  that is configured to manipulate the loop  34 . Manipulation of the loop  34  can control directional movement of the endoscope  20 . The proximal portion  32   p  can be controlled in a variety of ways, such as by manipulating a portion of the proximal end  30   p  of the steering tether  30 , or alternatively, the system  10  can include a steering module  50  ( FIG. 1 ). The steering module  50  can be adapted to control movement of the proximal portion  32   p  of the steering tether  30 , thereby controlling directional movement of the distal end  20   d  of the endoscope  20 . In one embodiment the steering module  50  is operated by an operator during the course of a procedure. In another embodiment the steering module  50  is programmed to operate autonomously, e.g., programmed to make one or more desired movements. Ideally the system  10  is operable from a proximal end  10   p  thereof. 
     While in the described embodiment the proximal portion  32   p  of the second portion  32   p  of the steering tether  30  is configured to manipulate the loop  34 , in other embodiments a proximal portion  31   p  of the first portion  31  of the steering tether  30  can be configured to manipulate the loop  34  or both of the proximal portions  31   p ,  32   p  can be configured to manipulate the loop  34  independently, cooperatively, or simultaneously. The proximal portion  31   p  can be controlled in the same ways in which the proximal portion  32   p  can be controlled, including, by way of non-limiting example, via the steering module  50 . 
     While one exemplary configuration of the steering tether  30  includes a loop, in other configurations a loop need not be used. One skilled in the art will appreciate other configurations that would also be effective to cause directional movement in the distal end  20   d  of the endoscope  20  by manipulating the steering tether  30 . By way of non-limiting example, the steering tether  30  cab be a string coupled at or near the distal end  20   d  of the endoscope  20 . The string can be pushed and pulled to control the movement of the distal end  20   d  of the endoscope  20 . In one embodiment, the string is tensioned. Still other configurations could also be used, which are contemplated and able to be adapted to effect directional movement of the distal end  20   d  of the endoscope  20  from the proximal end  10   p  of the system  10 . 
     It is important to note that while the steering tether  30  is configured to control the distal end  20   d  of the endoscope  20 , it can perform its functions in lieu of, in conjunction with, and/or in addition to traditional mechanisms and means used to control endoscope movement. The steering tether  30  provides a mechanical advantage outside of the endoscope to enable desired control of the distal end  20   d  of the endoscope  20 , while traditional mechanisms, such as steering wires disposed within the endoscope  20 , can provide some means of control as well. As discussed herein, however, traditional mechanisms are constrained by the fact that they generally do not operate well in large cavities in which the endoscope is unable to rely on walls of lumens to control movement thereof. 
     As illustrated, the endoscopic surgical system  10  can optionally include a channel or overtube  40  that is configured to receive at least a portion of the endoscope  20  and/or one or more portions of the steering tether  30 . In one embodiment each of the first and second portions  31 ,  32  of the steering tether  30  extend through the overtube  40 . As shown, the loop  34  is formed distal of the overtube  40 , directly after the steering tether  30  exits a distal end  40   d  of the overtube  40 , although the loop  34  can be formed from any portion of the steering tether  30  and in any location with respect to the overtube  40 , such as, for example, within the overtube  40  or at a location distal of a location directly past the distal end  40   d  of the overtube  40 . The overtube  40  can be coupled to the endoscope  20  to provide a rigid and stable location through which the steering tether  30  can pass. It can be desirable to slidably mate the overtube  40  with the endoscope  20  such that the rigid and stable location through which the steering tether  30  can pass can be adjusted as desired. Further, changing the location of the overtube  40  can be effective to change a nominal arcuate diameter of the loop  34 , the effect of which will be discussed in further detail below. In some embodiments, only one portion  31 ,  32  of the steering tether  30  is disposed in the overtube  40 , and still in other embodiments the overtube  40  does not house the steering tether  30  at all, either because it has other instruments disposed therein or because it is not included in the system  10 . Generally the overtube  40  is rigid and stiff, and it can be made of a variety of materials, such as polymers. In one exemplary embodiment the overtube  40  is made of Teflon Polyethylene Nylon. 
     As shown in  FIG. 4 , in embodiments that include an accessory mount, such as the track  124 , the steering tether  130  can be disposed in the accessory mount. Alternatively, the steering tether  130  can be disposed on the accessory mount. The steering tether  130  can have characteristics and features that are similar to the steering tether  30  of the endoscopic surgical system  10 . Accordingly, similar to coupling the steering tether  30  with the endoscope  20 , the steering tether  130  can be coupled to any portion of the track  124 , including the entire portion, or alternatively, select portions of the steering tether  130  can be coupled to select portions of the track  124 . In the illustrated embodiment a portion of the steering tether  130  extends beyond the track  124  in forming a loop  134 , while another portion of the steering tether  130  extends through the track  124  and back toward a proximal end  121   p  of the sheath  121 . Although not illustrated, in other embodiments, an overtube, similar to the overtube  40  as described above, can be mounted to the sheath  121 . Similar to the overtube  40  of the endoscope  20 , the overtube in embodiments that include an accessory mount can optionally be part of the surgical system  110  and can have characteristics and features that are similar to the overtube  40  of the surgical system  10 . The overtube can be located along any portion of the sheath  121 , including at a location proximal to the distal end  121   d  approximately where the loop  134  terminates, it can be slidable to assist in changing the capabilities and range of access of the steering tether  130 , and it can allow at least a portion of a second device, like the accessory channel  420 , to be disposed therein. While an overtube can be mounted to the sheath  121 , it can also be mounted to the accessory mount, such as track  124 . A person having ordinary skill in the art could apply the teachings related to the overtube  40  to an embodiment including an accessory mount, like the surgical system  110 , without difficulty. 
     In embodiments in which the steering tether of an endoscopic surgical system is a loop, a size of the loop can be adjusted to affect directional movement and/or a range of access of the endoscope. A range of access generally describes a finite number of locations that can be reached via directional movements. As a range of access is adjusted, a new finite number of locations can be achieved via directional movements. The finite number of locations between various ranges of access can overlap. With specific references to the loop  34 , as the loop  34  is made bigger and smaller, the locations within the body that the distal end  20   d  of the endoscope  20  can reach changes, as does the directional movements that can be made by the distal end  20   d  of the endoscope  20 . As illustrated in  FIGS. 5 and 6 , the loop  34  of the steering tether  30  includes a nominal arcuate diameter  36  that can be adjusted. One skilled in the art will appreciate that although the loop  34  is discussed with respect to having a nominal arcuate diameter, to the extent that it has any non-circular shape, an equivalent to the nominal arcuate diameter can easily be determined. One skilled in the art will also appreciate that the nominal arcuate diameter  36  can be adjusted in a variety of ways, such as, by way of non-limiting example, adjusting a location of the overtube  40 , but in one exemplary embodiment at least one of the first and second portions  31 ,  32  can be moved with respect to each other to adjust the nominal arcuate diameter  36 . Similar to manipulating the loop  34 , proximal portions  31   p ,  32   p  of the first and second portions  31 ,  32  can be configured to operate independently, cooperatively, or simultaneously to adjust the nominal arcuate diameter  36  of the loop  34 . Adjusting the nominal arcuate diameter  36  adjusts a range of access of the steering tether  30 , which in turn adjust a range of access of the endoscope  20  because the tether  30  is manipulatable to effect directional movement of the distal end  20   d  of the endoscope  20 . 
       FIG. 5  illustrates the system  10  with respect to a polar grid in which the nominal arcuate diameter  36  is relatively large and is approximately circular in shape. More particularly, the nominal arcuate diameter  36  is approximately the same size as the diameter of the largest circle E of the polar grid, although as illustrated a portion of the endoscope  20  proximal to the distal end  20   d  sits inside the circle E and a portion of the loop  34  that is opposite of this portion of the endoscope  20  sits outside of the circle E.  FIG. 6  also illustrates the system  10  with respect to the polar grid, but the nominal arcuate diameter  36  of the steering tether  30  is smaller than in  FIG. 5  and is approximately in the shape of a tear-drop. More particularly, the nominal arcuate diameter  36  is approximately the same size as the diameter of circle B of the polar grid. Of course, the nominal arcuate diameter  36  can be any number of sizes, and in fact the loop  34  can take on a number of different shapes as the nominal arcuate diameter  36  is adjusted. For example, the nominal arcuate diameter  36  can be adjusted to cover a range of access between 180 and 360 degrees. Further, the nominal arcuate diameter  36  can be adjusted prior to disposing the steering tether  30  at a surgical site, while the steering tether  30  is being delivered to the surgical site, or after it has been delivered to the surgical site. 
     Once a nominal arcuate diameter  36  of a desired size is achieved, it can be locked in place using a locking mechanism (not shown). One skilled in the art will appreciate that many different locking mechanisms can be suitable for locking the adjustable nominal arcuate diameter  36 , such as by way of non-limiting example a knob that can move between unlocked and locked positions. The choice of locking mechanism can be based at least in part on how the nominal arcuate diameter  36  is configured to adjust. In one embodiment the locking mechanism holds the first and second portions  31 ,  32  approximately stationary with respect to each other. Further, the locking mechanism can be located at any portion of the tether  30 , for example at the proximal end  10   p  of the system  10 , at a portion distal of the overtube  40 , or as part of the steering module  50 . 
     A locking mechanism can also be used to hold the location of the tether  30  and/or the endoscope  20  once it reaches a desired location, methods of which are discussed in further detail below. The locking mechanism for holding a location of one or more components of the system  10  such as the tether  30  and the endoscope  20  can be similar to the locking mechanism for holding the nominal arcuate diameter  36  of the loop  34  and such teachings can be easily adapted for use with a locking mechanism for holding the location of components of the system  10 . In one embodiment, both the locking mechanism for holding the nominal arcuate diameter  36  of the loop  34  and the locking mechanism for holding the location of the tether  30  and/or the endoscope  20  can be one in the same. Each of the two described locking mechanisms can be adapted to cooperate with each other. 
     The steering tether  30  can be made from a variety of materials and have a variety of sizes. Preferably the steering tether  30  is semi-rigid, semi-flexible, or flexible. Many polymers can be used to provide the desired flexibility. In one embodiment of a semi-flexible tether  30 , polyethylene is used to form the tether  30 . In another embodiment of a semi-flexible tether  30 , polytetrafluoroethylene, e.g., Teflon, is used to form the tether  30 . The tether  30  can likewise have any length and thickness, but in one embodiment the length can be approximately in the range of 100 to 300 cm, and more particularly can be approximately 200 cm, while a thickness in one embodiment can be approximately in the range of about 1 to 10 mm, and more particularly can be approximately 6 mm. 
     In use, the endoscopic surgical system  10  is designed so that the distal end  20   d  of the endoscope  20  can be moved to a number of different locations by manipulating the steering tether  30 . This is at least partially because while the endoscope  20  is generally good in torsion, it does not generally curl, and thus the steering tether  30  can use the existing torque stiffness to help maneuver the endoscope  20 . The steering tether  30  can provide a mechanical advantage or leverage to assist in controlling the endoscope  20 . The steering tether can be manipulated in a number of different ways, which are based at least in part on the configuration of the steering tether and its association with the endoscope. In one embodiment the proximal portion  32   p  of the second portion  32  of the steering tether  30  can be manipulated to effect the desired directional movement of the distal end  20   d  of the endoscope  20 . In other embodiments, the proximal portion  31   p  of the first portion  31  of the steering tether  30  can be manipulated to effect the desired directional movement of the distal end  20   d  of the endoscope. The proximal portions  31   p ,  32   p  can be operated individually, cooperatively, and/or simultaneously as desired. 
     As illustrated by  FIGS. 6 and 7 , two ways of manipulating the steering tether  30  are by pushing and pulling it. As shown, pulling on the proximal portion  32   p  of the steering tether  30  in a direction P can move the distal end  20   d  of the endoscope  20  from a first position, illustrated by  FIG. 6 , in which the distal end  20   d  is located at a position d 1  on a circle D of the polar grid, toward the proximal portion  10   p  of the system  10  to a second position, illustrated by  FIG. 7 , in which the distal end  20   d  is located at a position d 2  on the circle D of the polar grid. Likewise, pushing on the proximal portion  32   p  of the steering tether  30  in a direction F can move the distal end  20   d  of the endoscope  20  from the second position to the first position. One skilled in the art will appreciate that the illustrated positions are just examples of locations to which the steering tether  30  can move the distal end  20   d , and that any number of positions can be achieved by manipulating the steering tether  30 , as discussed in more detail above. Further, the positions that the distal end  20   d  can reach can be affected, at least in part, by adjusting a range of access of the steering tether  30 , as also discussed in more detail above, such as, for example, by adjusting the nominal arcuate diameter  36  of the loop  34  of the steering tether  30 . 
     The steering tether can also be manipulated to allow the endoscopic surgical system to displace objects to a surrounding area above or below a plane of an endoscope. As illustrated in  FIGS. 8 and 9 , the steering tether can be twisted or rotated about its longitudinal axis  1 , which in turn can lift objects out of a desired pathway. In  FIG. 8 , an object  60 , representative of an organ or other component of a body, is disposed in a desired pathway of an endoscopic surgical system  10 ″, which is similar to the endoscopic surgical system  10 . More particularly, at least a portion of the object  60  is disposed in a plane Q. As illustrated in  FIG. 8 , the plane Q is substantially aligned with a surface of an endoscope  20 ″, and the desired pathway extends through and past the portion of the object  60  that is disposed in the plane Q. In order to move the object  60  from the desired pathway, the endoscopic surgical system  10 ″ can be brought into the vicinity of the object  60  such that manipulation can place the endoscope  20 ″ in contact with the object  60 . In the illustrated embodiment the endoscope  20 ″ is moved directly into contact with the object  60 , but in other embodiments, the endoscope  20 ″ can be manipulated, such as by twisting, and/or rotating a steering tether  30 ″, to move the endoscope  20 ″ into contact with the object  60  once the endoscope  20 ″ is in the vicinity of the object  60 . As shown in  FIG. 9 , once the endoscope  20 ″ is in contact with the object  60 , it can be rotated in a direction R″ out of the plane Q, thereby displacing the object  60  from the plane Q. After displacing the object  60 , the endoscope  20 ″ and the steering tether  30 ″ can be returned approximately to the plane Q and/or the desired pathway as appropriate, or a second device, such as a second endoscopic surgical system, can be directed to the desired pathway as desired by the operator. 
     Still further, as discussed with respect to  FIGS. 5 and 6  above, the nominal arcuate diameter  36  of the loop  34  can be adjusted as desired. Adjusting the nominal arcuate diameter  36  can be done on its own or it can be done in conjunction and/or simultaneously with some of the other manipulations of the steering tether  30 ,  30 ″ discussed above. More particularly, it can be desirable to use any combination of pushing, pulling, twisting, and rotating of the steering tether  30 , and adjusting the nominal arcuate diameter  36  of the loop  34  of the steering tether  30 , in any sequence and in any combination, including performing more than one of the manipulations at the same time. 
       FIGS. 10A-10F  illustrate one example of a progression of an endoscopic surgical system  10 ′ in use. The components of the surgical system  10 ′ are similar to the components discussed with respect to the endoscopic surgical systems  10  and  10 ″. The progression shows how a steering tether  30 ′ can be used to guide a distal end  20   d ′ of an endoscope  20 ′ around a desired location L. As shown in  FIG. 10A , the endoscope  20 ′ and the steering tether  30 ′ are at least partially disposed in an overtube  40 ′. A first portion  31 ′ of the steering tether  30 ′ is coupled to the endoscope  20 ′ along a length thereof and a second portion  32 ′ of the steering tether  32 ′ extends along side the first portion  31 ′ within the overtube  40 ′. A loop  34 ′ is formed between the first and second portions  31 ′,  32 ′. The loop  34 ′ extends beyond the endoscope  20 ′ and terminates proximal to the distal end  20   d ′ of the endoscope  20 ′, more particularly approximately at a distal end  40   d ′ of the overtube  40 ′. Pushing a proximal portion (not illustrated) of the second portion  32 ′ of the steering tether  30 ′ in a direction F′ and rotating the same in a direction R′ about its longitudinal axis l′ allows the distal end  20   d ′ of the endoscope  20 ′ to be moved to the location illustrated in  FIG. 10B . As shown, the distal end  20   d ′ is now distal of the location L and the loop  34 ′ encircles the location L to allow the distal end  20   d ′ to begin to wrap around the desired location L. The steering tether  30 ′ can be pushed further in the direction F′, as shown in FIG.  10 C, to allow more of the endoscope  20 ′ to be distal of the desired location L, thereby allowing more of the endoscope  20 ′ to eventually be wrapped around the location L. As shown in  FIG. 10D , the proximal portion (not illustrated) of the second portion  32 ′ of the steering tether  30 ′ can be pulled in the direction P′ to begin moving the distal end  20   d ′ of the endoscope  20 ′ toward the desired location L. In the illustrated embodiment the distal end  20   d ′ is no longer distal of the desired location L, but rather, is approximately in line with the desired location L. This action also allows the endoscope  20 ′ as a whole to encircle the desired location L more fully. Further pulling in the direction P′ can move the distal end  20   d ′ proximal of the desired location L, as shown in  FIG. 10E . In the embodiment illustrated in  FIG. 10E , a portion of the endoscope  20 ′ that is proximal of the distal end  20   d ′ is pulled closer to the desired location L and a nominal arcuate diameter  36 ′ of the loop  34 ′ is decreased, thus allowing the endoscope  20 ′ to almost fully encircle the desired location L. As shown in  FIG. 10F , the distal end  20   d ′ can be bent further by pulling the proximal portion (not illustrated) of the second portion  32 ′ in the direction P′ and adjusting the nominal arcuate diameter  36 ′ of the loop  34 ′. More particularly, a distance W′ between the distal end  20   d ′ of the endoscope  20 ′ and a portion proximal of the distal end  20   d ′ of the endoscope  20 ′ in  FIG. 10E  is greater than the distance W′ in  FIG. 10F . 
     One skilled in the art will appreciate that the progression described with respect to  FIGS. 10A-10F  is only one of a myriad of ways in which methods can be performed that use the devices described herein. Any combination of manipulation steps can be used to control movement of an endoscope in a body cavity. Various amounts of pushing, pulling, twisting, and rotating any portion of a steering tether, and in embodiments in which the steering tether includes a loop, adjusting a nominal arcuate diameter of the loop, can be used to effect the desired directional movement of a distal end of an endoscope. Further, making minor changes to the design of the endoscopic surgical system can also cause the methods performed to be adjusted, and one skilled in the art, relying on the disclosures herein, would be able to apply various manipulation techniques to such endoscopic surgical systems. 
     One skilled in the art will appreciate further features and advantages of the invention based on the above-described embodiments. Accordingly, the invention is not to be limited by what has been particularly shown and described, except as indicated by the appended claims. All publications and references cited herein are expressly incorporated herein by reference in their entirety.