Abstract:
A system for determining the shape of a surgical instrument includes an elongate instrument body having a selectively steerable distal tip, a pair of automatically controlled segments proximal to the selectively steerable distal tip, and a joint that couples the pair of adjacent automatically controlled segments together. An actuator changes an angle of the joint and a position encoder provides information associated with the joint angle. A controller receives the information associated with the angle of the joint and generates a three dimensional model of a shape of the instrument. A method for determining the three dimensional shape of an instrument includes providing axial position data to a controller, providing angular position data to the controller from a respective segment controller, and generating a three-dimensional model of a shape of said instrument using the axial position data and the angular position data.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     The present application is a continuation of U.S. patent application Ser. No. 12/950,921, now U.S. Pat. No. 8,845, 542 entitled “Steerable Segmented Endoscope and Method of Insertion” filed Nov. 19, 2010, which is a continuation of U.S. patent application Ser. No. 11/796,220 entitled “Steerable Segmented Endoscope and Method of Insertion” filed Apr. 27, 2007, now abandoned, which is a continuation of Ser. No. 10/622,801 entitled “Steerable Segmented Endoscope and Method of Insertion” filed Jul. 18, 2003, now abandoned, which is a continuation of U.S. patent application Ser. No. 09/969,927, now U.S. Pat. No. 6,610,007 entitled “Steerable Segmented Endoscope and Method of Insertion” filed Oct. 2, 2001, which is a continuation-in-part of U.S. patent application Ser. No. 09/790,204, now U.S. Pat. No. 6,468,203, entitled “Steerable Endoscope and Improved Method of Insertion” filed Feb. 20, 2001, which claims priority of U.S. Provisional Patent Application No. 60/194,140 filed Apr. 3, 2000, each of which is incorporated herein by reference in its entirety. 
    
    
     INCORPORATION BY REFERENCE 
     All publications and patent applications mentioned in this specification are herein incorporated by reference to the same extent as if each individual publication or patent application was specifically and individually indicated to be incorporated by reference. 
     FIELD OF THE INVENTION 
     The present invention relates generally to endoscopes and endoscopic medical procedures. More particularly, it relates to a method and apparatus to facilitate insertion of a flexible endoscope along a tortuous path, such as for colonoscopic examination and treatment. 
     BACKGROUND OF THE INVENTION 
     An endoscope is a medical instrument for visualizing the interior of a patient&#39;s body. Endoscopes can be used for a variety of different diagnostic and interventional procedures, including colonoscopy, bronchoscopy, thoracoscopy, laparoscopy and video endoscopy. 
     Colonoscopy is a medical procedure in which a flexible endoscope, or colonoscope, is inserted into a patient&#39;s colon for diagnostic examination and/or surgical treatment of the colon. A standard colonoscope is typically 135-185 cm in length and 12-19 mm in diameter, and includes a fiberoptic imaging bundle or a miniature camera located at the instrument&#39;s tip, illumination fibers, one or two instrument channels that may also be used for insufflation or irrigation, air and water channels, and vacuum channels. The colonoscope is inserted via the patient&#39;s anus and is advanced through the colon, allowing direct visual examination of the colon, the ileocecal valve and portions of the terminal ileum. Insertion of the colonoscope is complicated by the fact that the colon represents a tortuous and convoluted path. Considerable manipulation of the colonoscope is often necessary to advance the colonoscope through the colon, making the procedure more difficult and time consuming and adding to the potential for complications, such as intestinal perforation. Steerable colonoscopes have been devised to facilitate selection of the correct path though the curves of the colon. However, as the colonoscope is inserted farther and farther into the colon, it becomes more difficult to advance the colonoscope along the selected path. At each turn, the wall of the colon must maintain the curve in the colonoscope. The colonoscope rubs against the mucosal surface of the colon along the outside of each turn. Friction and slack in the colonoscope build up at each turn, making it more and more difficult to advance and withdraw the colonoscope. In addition, the force against the wall of the colon increases with the buildup of friction. In cases of extreme tortuosity, it may become impossible to advance the colonoscope all of the way through the colon. 
     Steerable endoscopes, catheters and insertion devices for medical examination or treatment of internal body structures are described in the following U.S. patents, the disclosures of which are hereby incorporated by reference in their entirety: U.S. Pat. Nos. 4,753,223; 5,337,732; 5,662,587; 4,543,090; 5,383,852; 5,487,757 and 5,337,733. 
     SUMMARY OF THE INVENTION 
     In keeping with the foregoing discussion, the present invention takes the form of a steerable endoscope for negotiating tortuous paths through a patient&#39;s body. The steerable endoscope can be used for a variety of different diagnostic and interventional procedures, including colonoscopy, upper endoscopy, bronchoscopy, thoracoscopy, laparoscopy and video endoscopy. The steerable endoscope is particularly well suited for negotiating the tortuous curves encountered when performing a colonoscopy procedure. 
     The steerable endoscope has an elongated body with a manually or selectively steerable distal portion and an automatically controlled proximal portion. The selectively steerable distal portion can be selectively steered or bent up to a full 180 degree bend in any direction. A fiberoptic imaging bundle and one or more illumination fibers extend through the body from the proximal end to the distal end. Alternatively, the endoscope can be configured as a video endoscope with a miniaturized video camera, such as a CCD camera, which transmits images to a video monitor by a transmission cable or by wireless transmission, or alternatively through the use of CMOS imaging technology. Optionally, the endoscope may include one or two instrument channels that may also be used for insufflation or irrigation, air and water channels, and vacuum channels. 
     A proximal handle attached to the elongate body includes an ocular for direct viewing and/or for connection to a video camera, a connection to an illumination source and one or more luer lock fittings that are connected to the instrument channels. The handle is connected to a steering control for selectively steering or bending the selectively steerable distal portion in the desired direction and to an electronic motion controller for controlling the automatically controlled proximal portion of the endoscope. An axial motion transducer is provided to measure the axial motion of the endoscope body as it is advanced and withdrawn. Optionally, the endoscope may include a motor or linear actuator for both automatically advancing and withdrawing the endoscope, or for automatically advancing and passively withdrawing the endoscope. 
     One preferable embodiment of the endoscope includes a segmented endoscopic embodiment having multiple independently controllable segments which may be individually motorized and interconnected by joints. Each of the individual adjacent segments may be pivotable about two independent axes to offer a range of motion during endoscope insertion into a patient. 
     This particular embodiment, as mentioned, may have individual motors, e.g., small brushed DC motors, to actuate each individual segment. Furthermore, each segment preferably has a backbone segment which defines a lumen therethrough to allow a continuous lumen to pass through the entire endoscopic instrument to provide an access channel through which wires, optical fibers, air and/or water channels, various endoscopic tools, or any variety of devices and wires may be routed. The entire assembly, i.e., motors, backbone, cables, etc., may be encased or covered in a biocompatible material, e.g., a polymer, which is also preferably lubricious to allow for minimal frictional resistance during endoscope insertion and advancement into a patient. This biocompatible cover may be removable from the endoscopic body to expose the motors and backbone assembly to allow for direct access to the components. This may also allow for the cover to be easily replaced and disposed after use in a patient. 
     The method of the present invention involves inserting the distal end of the endoscope body into a patient, either through a natural orifice or through an incision, and steering the selectively steerable distal portion to select a desired path. When the endoscope body is advanced or inserted further into the patient&#39;s body, the electronic motion controller operates the automatically controlled proximal portion of the body to assume the selected curve of the selectively steerable distal portion. This process is repeated by selecting another desired path with the selectively steerable distal portion and advancing the endoscope body again. As the endoscope body is further advanced, the selected curves propagate proximally along the endoscope body. Similarly, when the endoscope body is withdrawn proximally, the selected curves propagate distally along the endoscope body, either automatically or passively. This creates a sort of serpentine motion in the endoscope body that allows it to negotiate tortuous curves along a desired path through or around and between organs within the body. 
     The method can be used for performing colonoscopy or other endoscopic procedures, such as bronchoscopy, thoracoscopy, laparoscopy and video endoscopy. In addition, the apparatus and methods of the present invention can be used for inserting other types of instruments, such as surgical instruments, catheters or introducers, along a desired path within the body. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows a prior art colonoscope being employed for a colonoscopic examination of a patient&#39;s colon. 
         FIG. 2  shows a first embodiment of the steerable endoscope of the present invention. 
         FIG. 3  shows a second embodiment of the steerable endoscope of the present invention. 
         FIG. 4  shows a third embodiment of the steerable endoscope of the present invention. 
         FIG. 5  shows a fourth embodiment of the steerable endoscope of the present invention. 
         FIG. 6  shows a wire frame model of a section of the body of the endoscope in a neutral or straight position. 
         FIG. 7  shows the wire frame model of the endoscope body shown in  FIG. 6  passing through a curve in a patient&#39;s colon. 
         FIG. 8  shows a representative portion of an alternative endoscopic body embodiment having multiple segments interconnected by joints. 
         FIG. 9  shows a partial schematic representation of the embodiment of  FIG. 8  showing two segments being pivotable about two independent axes. 
         FIG. 10  shows a preferable endoscope embodiment having motorized segmented joints. 
         FIGS. 11A-11B  show exploded isometric assembly views of two adjacent segments and an individual segment, respectively, from the embodiment shown in  FIG. 10 . 
         FIGS. 12-17  show the endoscope of the present invention being employed for a colonoscopic examination of a patient&#39;s colon. 
         FIGS. 18-20  show an endoscope being advanced through a patient&#39;s colon while a datum measures the distance advanced into the patient. 
         FIG. 21  shows a schematic representation of one embodiment of a control system which may be used to control and command the individual segments of a segmented endoscopic device of the type shown in  FIGS. 8-11B . 
         FIG. 22  shows a flow chart embodiment for the master controller algorithm which may be used to control the overall function during endoscope insertion into a patient. 
         FIG. 23  shows a flowchart embodiment of the segment controller algorithm. 
         FIGS. 24-26  shows a non-contact method of measurement and tracking of an endoscope using an external navigational system such as a global positioning system. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIG. 1  shows a prior art colonoscope  500  being employed for a colonoscopic examination of a patient&#39;s colon C. The colonoscope  500  has a proximal handle  506  and an elongate body  502  with a steerable distal portion  504 . The body  502  of the colonoscope  500  has been lubricated and inserted into the colon C via the patient&#39;s anus A. Utilizing the steerable distal portion  504  for guidance, the body  502  of the colonoscope  500  has been maneuvered through several turns in the patient&#39;s colon C to the ascending colon G. Typically, this involves a considerable amount of manipulation by pushing, pulling and rotating the colonoscope  500  from the proximal end to advance it through the turns of the colon C. After the steerable distal portion  504  has passed, the wall of the colon C maintains the curve in the flexible body  502  of the colonoscope  500  as it is advanced. Friction develops along the body  502  of the colonoscope  500  as it is inserted, particularly at each turn in the colon C. Because of the friction, when the user attempts to advance the colonoscope  500 , the body  502 ′ tends to move outward at each curve, pushing against the wall of the colon C, which exacerbates in the problem by increasing the friction and making it more difficult to advance the colonoscope  500 . On the other hand, when the colonoscope  500  is withdrawn, the body  502 ″ tends to move inward at each curve taking up the slack that developed when the colonoscope  500  was advanced. When the patient&#39;s colon C is extremely tortuous, the distal end of the body  502  becomes unresponsive to the user&#39;s manipulations, and eventually it may become impossible to advance the colonoscope  500  any farther. In addition to the difficulty that it presents to the user, tortuosity of the patient&#39;s colon also increases the risk of complications, such as intestinal perforation. 
       FIG. 2  shows a first embodiment of the steerable endoscope  100  of the present invention. The endoscope  100  has an elongate body  102  with a manually or selectively steerable distal portion  104  and an automatically controlled proximal portion  106 . The selectively steerable distal portion  104  can be selectively steered or bent up to a full 180 degree bend in any direction. A fiberoptic imaging bundle  112  and one or more illumination fibers  114  extend through the body  102  from the proximal end  110  to the distal end  108 . Alternatively, the endoscope  100  can be configured as a video endoscope with a miniaturized video camera, such as a CCD camera, positioned at the distal end  108  of the endoscope body  102 . The images from the video camera can be transmitted to a video monitor by a transmission cable or by wireless transmission where images may be viewed in real-time or recorded by a recording device onto analog recording medium, e.g., magnetic tape, or digital recording medium, e.g., compact disc, digital tape, etc. Optionally, the body  102  of the endoscope  100  may include one or two instrument channels  116 ,  118  that may also be used for insufflation or irrigation, air and water channels, and vacuum channels. The body  102  of the endoscope  100  is highly flexible so that it is able to bend around small diameter curves without buckling or kinking while maintaining the various channels intact. When configured for use as a colonoscope, the body  102  of the endoscope  100  is typically from 135 to 185 cm in length and approximately 12-13 mm in diameter. The endoscope  100  can be made in a variety of other sizes and configurations for other medical and industrial applications. 
     A proximal handle  120  is attached to the proximal end  110  of the elongate body  102 . The handle  120  includes an ocular  124  connected to the fiberoptic imaging bundle  112  for direct viewing and/or for connection to a video camera  126  or a recording device  127 . The handle  120  is connected to an illumination source  128  by an illumination cable  134  that is connected to or continuous with the illumination fibers  114 . A first luer lock fitting,  130  and a second luer lock fitting  132  on the handle  120  are connected to the instrument channels  116 ,  118 . 
     The handle  120  is connected to an electronic motion controller  140  by way of a controller cable  136 . A steering control  122  is connected to the electronic motion controller  140  by way of a second cable  13  M. The steering control  122  allows the user to selectively steer or bend the selectively steerable distal portion  104  of the body  102  in the desired direction. The steering control  122  may be a joystick controller as shown, or other known steering control mechanism. The electronic motion controller  140  controls the motion of the automatically controlled proximal portion  106  of the body  102 . The electronic motion controller  140  may be implemented using a motion control program running on a microcomputer or using an application-specific motion controller. Alternatively, the electronic motion controller  140  may be implemented using, a neural network controller. 
     An axial motion transducer  150  is provided to measure the axial motion of the endoscope body  102  as it is advanced and withdrawn. The axial motion transducer  150  can be made in many possible configurations. By way of example, the axial motion transducer  150  in  FIG. 2  is configured as a ring  152  that surrounds the body  102  of the endoscope  100 . The axial motion transducer  150  is attached to a fixed point of reference, such as the surgical table or the insertion point for the endoscope  100  on the patient&#39;s body. As the body  102  of the endoscope  100  slides through the axial motion transducer  150 , it produces a signal indicative of the axial position of the endoscope body  102  with respect to the fixed point of reference and sends a signal to the electronic motion controller  140  by telemetry or by a cable (not shown). The axial motion transducer  150  may use optical, electronic or mechanical means to measure the axial position of the endoscope body  102 . Other possible configurations for the axial motion transducer  150  are described below. 
       FIG. 3  shows a second embodiment of the endoscope  100  of the present invention. As in the embodiment of  FIG. 2 , the endoscope  100  has an elongate body  102  with a selectively steerable distal portion  104  and an automatically controlled proximal portion  106 . The steering control  122  is integrated into proximal handle  120  in the form or one or two dials for selectively steering, the selectively steerable distal portion  104  of the endoscope  100 . Optionally, the electronic motion controller  140  may be miniaturized and integrated into proximal handle  120 , as well. In this embodiment, the axial motion transducer  150  is configured with a base  154  that is attachable to a fixed point of reference, such as the surgical table. A first roller  156  and a second roller  158  contact the exterior of the endoscope body  102 . A multi-turn potentiometer  160  or other motion transducer is connected to the first roller  156  to measure the axial motion of the endoscope body  102  and to produce a signal indicative of the axial position. 
     The endoscope  100  may be manually advanced or withdrawn by the user by grasping the body  102  distal to the axial motion transducer  150 . Alternatively, the first roller  156  and/or second roller  158  may be connected to at least one motor, e.g., motor  162 , for automatically advancing and withdrawing the body  102  of the endoscope  100 . 
       FIG. 4  shows a third embodiment of the endoscope  100  of the present invention, which utilizes an elongated housing  170  to organize and contain the endoscope  100 . The housing  170  has a base  172  with a linear track  174  to guide the body  102  of the endoscope  100 . The housing  170  may have an axial motion transducer  150 ′ that is configured as a linear motion transducer integrated into the linear track  174 . Alternatively, the housing,  170  may have an axial motion transducer  150 ″ configured similarly to the axial motion transducer  150  in  FIG. 2 or 3 . The endoscope  100  may be manually advanced or withdrawn by the user by grasping the body  102  distal to the housing  170 . Alternatively, the housing  170  may include a motor  176  or other linear motion actuator for automatically advancing and withdrawing the body  102  of the endoscope  100 . In another alternative configuration, a motor with friction wheels, similar to that described above in connection with  FIG. 3 , may be integrated into the axial motion transducer  150 ″. 
       FIG. 5  shows a fourth embodiment of the endoscope  100  of the present invention, which utilizes a rotary housing  180  to organize and contain the endoscope  100 . The housing  180  has a base  182  with a rotating drum  184  to guide the body  102  of the endoscope  100 . The housing  180  may have an axial motion transducer  150 ′″ that is configured as a potentiometer connected to the pivot axis  186  of the rotating drum  184 . Alternatively, the housing  180  may have an axial motion transducer  150 ″ configured similarly to the axial motion transducer  150  in  FIG. 2 or 3 . The endoscope  100  may be manually advanced or withdrawn by the user by grasping the body  102  distal to the housing  180 . Alternatively, the housing  180  may include a motor  188  connected to the rotating drum  184  for automatically advancing and withdrawing the body  102  of the endoscope  100 . In another alternative configuration, a motor with friction wheels, similar to that described above in connection with  FIG. 3 , may be integrated into the axial motion transducer  150 ″. 
       FIG. 6  shows a wire frame model of a section of the body  102  of the endoscope  100  in a neutral or straight position. Most of the internal structure of the endoscope body  102  has been eliminated in this drawing for the sake of clarity. The endoscope body  102  is divided up into sections  1 ,  2 ,  3  . . .  10 , etc. The geometry of each section is defined by four length measurements along the a, b, c and d axes. For example, the geometry of section  1  is defined by the four length measurements l 1a , l 1b , l 1c , l 1d , and the geometry of section  2  is defined by the four length measurements l 2a , l 2b , l 2c , l 2d , etc. Preferably, each of the length measurements is individually controlled by a linear actuator (not shown). The linear actuators may utilize one of several different operating principles. For example, each of the linear actuators may be a self-heating NiTi alloy linear actuator or an electrorheological plastic actuator, or other known mechanical, pneumatic, hydraulic or electromechanical actuator. The geometry of each section may be altered using the linear actuators to change the four length measurements along the a, b, c and d axes. Preferably, the length measurements are changed in complementary pairs to selectively bend the endoscope body  102  in a desired direction. For example, to bend the endoscope body  102  in the direction of the a axis, the measurements l 1a , l 2a , l 3a  . . . l 10a  would be shortened and the measurements l 1b , l 2b , l 3b  . . . l 10b  would be lengthened an equal amount. The amount by which these measurements are changed determines the radius of the resultant curve. 
     In the selectively steerable distal portion  104  of the endoscope body  102 , the linear actuators that control the a, b, c and d axis measurements of each section are selectively controlled by the user through the steering control  122 . Thus, by appropriate control of the a, b, c and d axis measurements, the selectively steerable distal portion  104  of the endoscope body  102  can be selectively steered or bent up to a full 180 degrees in any direction. 
     In the automatically controlled proximal portion  106 , however, the a, b, c and d direction measurements of each section are automatically controlled by the electronic motion controller  140 , which uses a curve propagation method to control the shape of the endoscope body  102 . To explain how the curve propagation method operates,  FIG. 7  shows the wire frame model of a part of the automatically controlled proximal portion  106  of the endoscope body  102  shown in  FIG. 6  passing, through a curve in a patient&#39;s colon C. For simplicity, an example of a two-dimensional curve is shown and only the a and b axes will be considered. In a three-dimensional curve all four of the a, b, c and d axes would be brought into play. 
     In  FIG. 7 , the endoscope body  102  has been maneuvered through the curve in the colon C with the benefit of the selectively steerable distal portion  104  (this part of the procedure is explained in more detail below) and now the automatically controlled proximal portion  106  resides in the curve. Sections  1  and  2  are in a relatively straight part of the colon C, therefore l 1a =l 1b  and l 2a =l 2b . However, because sections  3 - 7  are in the S-shaped curved section, l 3a &lt;l 3b , l 4a &lt;l 4b  and l 5a &lt;l 5b , but l 6a &gt;l 6b , l 7a &lt;l 7b  and l 8a &gt;l 8b . When the endoscope body  102  is advanced distally by one unit, section  1  moves into the position marked  1 ′, section  2  moves into the position previously occupied by section  1 , section  3  moves into the position previously occupied by section  2 , etc. The axial motion transducer  150  produces a signal indicative of the axial position of the endoscope body  102  with respect to a fixed point of reference and sends the signal to the electronic motion controller  140 , under control of the electronic motion controller  140 , each time the endoscope body  102  advances one unit, each section in the automatically controlled proximal portion  106  is signaled to assume the shape of the section that previously occupied the space that it is now in. Therefore, when the endoscope body  102  is advanced to the position marked  1 ′, l 1a =l 1b , l 2a =l 2b , l 3a =l 3b , l 4a &lt;l 4b , l 5a &lt;l 5b , l 6a &lt;l 6b , l 7a &gt;l 7b  and l 8a &gt;l 8b , and l 9a &gt;l 9b , when the endoscope body  102  is advanced to the position marked  1 ″, l 1a =l 1b , l 2a =l 2 , l 3a =l 3b , l 4a =l 4b , l 5a &lt;l 5b , l 6a &lt;l 6b , l 7a &lt;l 7b , l 8a &gt;l 8b , l 9a &gt;l 9b , and l 10a &gt;l 10b . Thus, the S-shaped curve propagates proximally along the length of the automatically controlled proximal portion  106  of the endoscope body  102 . The S-shaped curve appears to be fixed in space, as the endoscope body  102  advances distally. 
     Similarly, when the endoscope body  102  is withdrawn proximally, each time the endoscope body  102  is moved proximally by one unit, each section in the automatically controlled proximal portion  106  is signaled to assume the shape of the section that previously occupied the space that it is now in. The S-shaped curve propagates distally along the length of the automatically controlled proximal portion  106  of the endoscope body  102 , and the S-shaped curve appears to be fixed in space, as the endoscope body  102  withdraws proximally. 
     Whenever the endoscope body  102  is advanced or withdrawn, the axial motion transducer  150  detects the change in position and the electronic motion controller  140  propagates the selected curves proximally or distally along the automatically controlled proximal portion  106  of the endoscope body  102  to maintain the curves in a spatially fixed position. This allows the endoscope body  102  to move through tortuous curves without putting unnecessary force on the wall of the colon C. 
       FIG. 8  shows a representative portion of an alternative endoscopic body embodiment  190  which has multiple segments  192  interconnected by joints  194 . In this embodiment, adjacent segments  192  can be moved or angled relative to one another by a joint  194  having at least one degree-of-freedom, and preferably having multiple degrees-of-freedom, preferably about two axes as shown here. As seen further in  FIG. 9 , a partial schematic representation  196  of the embodiment  190  is shown where two segments  192  may be rotated about joint  194  about the two independent axes. The range of motion may be described in relation to spherical axes  198  by angles α and β. 
     As mentioned above, such a segmented body may be actuated by a variety of methods. A preferable method involves the use of electromechanical motors individually mounted on each individual segment to move the segments relative to one another.  FIG. 10  shows a preferable embodiment  200  having motorized segmented joints. Each segment  192  is preferably comprised of a backbone segment  202 , which also preferably defines at least one lumen running through it to provide an access channel through which wires, optical fibers, air and/or water channels, various endoscopic tools, or any variety of devices and wires may be routed through. The backbone segment may be made of a variety of materials which are preferably biocompatible and which provide sufficient strength to support the various tools and other components, e.g., stainless steel. Although much of the description is to an individual segment  192 , each of the segments  192  are preferably identical, except for the segment (or first few segments) located at the distal tip, and the following description readily applies to at least a majority of the segments  192 . 
     A single motor, or multiple motors depending upon the desired result and application, may be attached to at least a majority of the segments. An embodiment having a single motor on a segment is illustrated in  FIG. 10  where an individual motor  204  is preferably attached to backbone  202  and is sufficiently small and compact enough so as to present a relatively small diameter which is comfortable and small enough for insertion into a patient without trauma. Motor  204 , which is shown here as being a small brushed DC motor, may be used for actuating adjacent segments  192  and may be controlled independently from other motors. Various motors, aside from small brushed DC motors, may also be used such as AC motors, linear motors, etc. Each motor  204  also preferably contains within the housing not only the electromechanical motor assembly EM itself, but also a gear reduction stage GR, and a position encoder PE. A gear reduction stage GR attached to the motor assembly EM will allow for the use of the motor  204  in its optimal speed and torque range by changing high-speed, low-torque operating conditions into a more useful low-speed, high-torque output. The position encoder PE may be a conventional encoder to allow the controlling computer to read the position of the segment&#39;s joint  194  by keeping track of the angular rotational movement of the output shaft of the motor  204 . 
     Each motor  204  has a rotatable shaft which extends from an end of the motor  204  to provide for the transmission of power to actuate the segments  192 . Upon this shaft, a spool  206  may be rotatingly attached with a first end of the cable  208  further wound about the spool  206 . The cable  208  may then be routed from spool  206  through a channel  212  which is defined in the cable guide  210  and out through opening  214  (as seen in greater detail in  FIGS. 11A-11B ) to cable anchor  216 , to which the second end of the cable  208  is preferably attached, e.g., by crimping and/or soldering. The cable guide  210  serves to capture the cable  208  that is wound about the spool  206 . The cable anchor  216  is attached across a universal joint pivot  220  to an adjacent segment  192  via a pin  218  and may be shaped like a conventional electronic ring connector having a round section defining a hole therethrough for mounting to the segment  192  and an extension protruding from the anchor  216  for attaching the second end of the cable  208 . Cable  208  may comprise a wide variety of filaments, strands, wires, chains, braids, etc. any of which may be made of a wide variety of biocompatible materials, e.g., metals such as stainless steel, polymers such as plastics and Nylon, etc. 
     In operation, when the motor  204  is operated to spin the shaft in a first direction, e.g., clockwise, the spool  206  rotates accordingly and the cable  208  pulls in a corresponding direction on the adjacent segment  192  and transmits the torque to subsequently actuate it along a first axis. When the motor  204  is operated to spin the shaft in a second direction opposite to the first, e.g., counter-clockwise, the spool  206  again rotates accordingly and the cable  208  would then pull in the corresponding opposing direction on the adjacent segment  192  to subsequently transmit the torque and actuate it in the opposite direction. 
       FIGS. 11A and 11B  show exploded isometric assembly views of two adjacent segments and an individual segment, respectively, from the embodiment shown in  FIG. 10 . As seen in  FIG. 11A , backbone  202  is seen with the lumen  221 , which may be used to provide a working channel, as described above. Also seen are channel  212  defined in cable guide  210  as well as opening  214  for the cable  208  to run through. In interconnecting adjacent segments and to provide the requisite degree-of-freedom between segments, a preferable method of joining involves using the universal joint pivot  220 . However, other embodiments, rather than using a universal joint pivot  220 , may use a variety of joining methods, e.g., a flexible tube used to join two segments at their respective centers, a series of single degree-of-freedom joints that may be closely spaced, etc. This particular embodiment describes the use of the universal joint pivot  220 . At the ends of backbone  202  adjacent to other segments, a pair of universal yoke members  224  may be formed with a pair of corresponding pin openings  226 . As the universal joint pivot  220  is connected to a first pair of yoke members  224  on one segment, a corresponding pair of yoke members  224  from the adjacent segment may also be attached to the joint pivot  220 . 
     As seen further in  FIG. 11B , the universal joint pivot  220  is shown in this embodiment as a cylindrical ring having two sets of opposing receiving holes  228  for pivotally receiving corresponding yoke members  224 . The receiving holes  228  are shown as being spaced apart at 90° intervals, however, in other variations, receiving holes may be spaced apart at other angles depending upon the desired degree-of-freedom and application. Also seen is an exploded assembly of spool  206  removed from motor  204  exposing drive shaft  205 . With motor  204  displaced from backbone  202 , the groove  230  is revealed as formed in the backbone  202 . This groove  230  may be depressed in backbone  202  to preferably match the radius of the motor  204  housing not only to help locate the motor  204  adjacent to backbone  202 , but also to help in reducing the overall diameter of the assembled segment. The motor  204  may be attached to the backbone  202  by various methods, e.g., adhesives, clamps, bands, mechanical fasteners, etc. A notched portion  232  may also be formed in the cable guide  210  as shown to help in further reducing segment diameter. 
     Prior to insertion into a patient, the endoscope  200  may be wound onto the rotating drum  184  within the rotary housing  180  of  FIG. 5  for storage and during use, where it may optionally be configured to have a diagnostic check performed automatically. When the endoscope  200  is wound onto the drum  184 , adjacent segments  192  will have a predetermined angle relative to one another, as determined initially by the diameter of the drum  184  and the initial configuration of the storage unit in which the endoscope  200  may be positioned. During a diagnostic check before insertion, a computer may be configured to automatically sense or measure the angles between each adjacent segments  192 . If any of the adjacent segments  192  indicate a relative measured angle out of a predetermined acceptable range of angles, this may indicate a segment  192  being out of position and may indicate a potential point of problems during endoscope  200  use. Accordingly, the computer may subsequently sound an audible or visual alarm and may also place each of the segments  192  into a neutral position to automatically prevent further use or to prevent any trauma to the patient. 
       FIGS. 12-17  show the endoscope  100  of the present invention being employed for a colonoscopic examination of a patient&#39;s colon. In  FIG. 12 , the endoscope body  102  has been lubricated and inserted into the patient&#39;s colon C through the anus A. The distal end  108  of the endoscope body  102  is advanced through the rectum R until the first turn in the colon C is reached, as observed through the ocular  124  or on a video monitor. To negotiate the turn, the selectively steerable distal portion  104  of the endoscope body  102  is manually steered toward the sigmoid colon S by the user through the steering control  122 . The control signals from the steering control  122  to the selectively steerable distal portion  104  are monitored by the electronic motion controller  140 . When the correct curve of the selectively steerable distal portion  104  for advancing the distal end  108  of the endoscope body  102  into the sigmoid colon S has been selected, the curve is logged into the memory of the electronic motion controller  140  as a reference. This step can be performed in a manual mode, in which the user gives a command to the electronic motion controller  140  to record the selected curve, using keyboard commands or voice commands. Alternatively, this step can be performed in an automatic mode, in which the user signals to the electronic motion controller  140  that the desired curve has been selected by advancing the endoscope body  102  distally. In this way, a three dimensional map of the colon or path may be generated and maintained for future applications. 
     Whether operated in manual mode or automatic mode, once the desired curve has been selected with the selectively steerable distal portion  104 , the endoscope body  102  is advanced distally and the selected curve is propagated proximally along the automatically controlled proximal portion  106  of the endoscope body  102  by the electronic motion controller  140 , as described above. The curve remains fixed in space while the endoscope body  102  is advanced distally through the sigmoid colon S. In a particularly tortuous colon, the selectively steerable distal portion  104  may have to be steered through multiple curves to traverse the sigmoid colon S. 
     As illustrated in  FIG. 13 , the user may stop the endoscope  100  at any point for examination or treatment of the mucosal surface or any other features within the colon C. The selectively steerable distal portion  104  may be steered in any direction to examine the inside of the colon C. When the user has completed the examination of the sigmoid colon S, the selectively steerable distal portion  104  is steered in a superior direction toward the descending colon D. Once the desired curve has been selected with the selectively steerable distal portion  104 , the endoscope body  102  is advanced distally into the descending colon D, and the second curve as well as the first curve are propagated proximally along the automatically controlled proximal portion  106  of the endoscope body  102 , as shown in  FIG. 14 . 
     If, at any time, the user decides that the path taken by the endoscope body  102  needs to be revised or corrected, the endoscope  100  may be withdrawn proximally and the electronic motion controller  140  commanded to erase the previously selected curve. This can be done manually using keyboard commands or voice commands or automatically by programming the electronic motion controller  140  to go into a revise mode when the endoscope body  102  is withdrawn a certain distance. The revised or corrected curve is selected using the selectively steerable distal portion  104 , and the endoscope body  102  is advanced as described before. 
     The endoscope body  102  is advanced through the descending colon D until it reaches the left (splenic) flexure F 1  of the colon. Here, in many cases, the endoscope body  102  must negotiate an almost 180 degree hairpin turn. As before, the desired curve is selected using the selectively steerable distal portion  104 , and the endoscope body  102  is advanced distally through the transverse colon T, as shown in  FIG. 15 . Each of the previously selected curves is propagated proximally along the automatically controlled proximal portion  106  of the endoscope body  102 . The same procedure is followed at the right (hepatic) flexure Fr of the colon and the distal end  108  of the endoscope body  102  is advanced through the ascending colon G to the cecum E, as shown in  FIG. 16 . The cecum E, the ileocecal valve V and the terminal portion of the ileum I can be examined from this point using, the selectively steerable distal portion  104  of the endoscope body  102 . 
       FIG. 17  shows the endoscope  100  being withdrawn through the colon C. As the endoscope  100  is withdrawn, the endoscope body  102  follows the previously selected curves by propagating the curves distally along the automatically controlled proximal portion  106 , as described above. At any point, the user may stop the endoscope  100  for examination or treatment of the mucosal surface or any other features within the colon C using the selectively steerable distal portion  104  of the endoscope body  102 . At any given time, the endoscope  100  may be withdrawn or back-driven by a desired distance. 
     In one preferred method according to the present invention, the electronic motion controller  140  includes an electronic memory in which is created a three-dimensional mathematical model of the patient&#39;s colon or other anatomy through which the endoscope body  102  is maneuvered. The three-dimensional model can be annotated by the operator to record the location of anatomical landmarks, lesions, polyps, biopsy samples and other features of interest. The three-dimensional model of the patient&#39;s anatomy can be used to facilitate reinsertion of the endoscope body  102  in subsequent procedures. In addition, the annotations can be used to quickly find the location of the features of interest. For example, the three-dimensional model can be annotated with the location where a biopsy sample was taken during an exploratory endoscopy. The site of the biopsy sample can be reliably located again in follow-up procedures to track the progress of a potential disease process and/or to perform a therapeutic procedure at the site. 
     In one particularly preferred variation of this method, the electronic motion controller  140  can be programmed, based on the three-dimensional model in the electronic memory, so that the endoscope body  102  will automatically assume the proper shape to follow the desired path as it is advanced through the patient&#39;s anatomy. In embodiments of the steerable endoscope  100  that are configured for automatically advancing and withdrawing the endoscope body  102 , as described above in connection with  FIGS. 3, 4 and 5 , the endoscope body  102  can be commanded to advance automatically though the patient&#39;s anatomy to the site of a previously noted lesion or other point of interest based on the three-dimensional model in the electronic memory. 
     Imaging software would allow the three-dimensional model of the patient&#39;s anatomy obtained using the steerable endoscope  100  to be viewed on a computer monitor or the like. This would facilitate comparisons between the three-dimensional model and images obtained with other imaging modalities, for example fluoroscopy, radiography, ultrasonography, magnetic resonance imaging (MRI), computed tomography (CT scan), electron beam tomography or virtual colonoscopy. Conversely, images from these other imaging modalities can be used to map out an approximate path or trajectory to facilitate insertion of the endoscope body  102 . In addition, images from other imaging modalities can be used to facilitate locating suspected lesions with the steerable endoscope  100 . For example, images obtained using a barium-contrast radiograph of the colon can be used to map out an approximate path to facilitate insertion of the endoscope body  102  into the patient&#39;s colon. The location and depth of any suspected lesions seen on the radiograph can be noted so that the endoscope body  102  can be quickly and reliably guided to the vicinity of the lesion. 
     Imaging modalities that provide three-dimensional information, such as biplanar fluoroscopy, CT or MRI, can be used to program the electronic motion controller  140  so that the endoscope body  102  will automatically assume the proper shape to follow the desired path as it is advanced through the patient&#39;s anatomy. In embodiments of the steerable endoscope  100  that are configured for automatically advancing and withdrawing the endoscope body  102 , the endoscope body  102  can be commanded to advance automatically though the patient&#39;s anatomy along the desired path as determined by the three-dimensional imaging information. Similarly, the endoscope body  102  can be commanded to advance automatically to the site of a suspected lesion or other point of interest noted on the images. 
     As described above, the axial motion transducer  150  can be made in many possible configurations, e.g., shown in  FIG. 2  as a ring  152 . It functions partially as a fixed point of reference or datum to produce a signal indicative of the axial position of the endoscope body  102  with respect to the fixed point of reference. The axial motion transducer  150  may use optical, electronic or mechanical methods to measure the axial position of the endoscope body  102 . One preferable embodiment of the datum  234  is shown schematically in  FIGS. 18-20  as an instrumented speculum which may be placed partially into the rectum of the patient or at least adjacent to the anus A of a patient. Prior to the segmented endoscopic body  238  being inserted into the anus A, it is preferably first passed through the datum channel  236  of datum  234 . The datum  234  may house the electronics and mechanical assemblies necessary to measure the depth of insertion, as discussed below, and it may also provide a fixed, solid base to aid in co-locating the endoscopic body  238  adjacent to the anus A or body orifice as well as provide a base to stabilize and insert the endoscope body  238  into the orifice. The instrumented speculum may be constructed of a biocompatible material, such as injection-molded plastic, and house inexpensive electronics, as the speculum may preferably be disposable. 
     As the endoscopic body  238  passes through the datum channel  236 , one preferable optical method of measuring the depth of insertion and axial position may involve measurement through the use of reflective infra-red sensors mounted on the datum  234 . The outer surface of the endoscopic body  238  may have hatch marks or some other indicative or reflective marking placed at known intervals along the body  238 . As the endoscopic body  238  is advanced or withdrawn through the anus A and the datum channel  236 , an optical sensor can read or sense the hatch marks and increment or decrement the distance traveled by the endoscopic body accordingly. Thus, a sensor reading such marks may have an output that registers as a logic-level “1” or “ON” when a mark is sensed and a logic-level “0” or “OFF” when no mark is sensed. By counting or tracking the number of 1-to-0 transitions on a sensor output, the depth may be measured accordingly. Thus resolution of the depth measurement may be determined in part in this embodiment by the spacing between the hatch marks. 
     A simplified representation of how the distance may be used to advance the device may be seen in  FIG. 18 . The endoscopic body  238  is advanced until the distal tip reaches a depth of L 1 , as measured from the midpoint of the datum speculum  234 . At this depth, it is necessary for the user to selectively steer the tip to follow the sigmoid colon S such that the body forms a radius of curvature R 1 . Once the position and depth of this feature has been defined by the distal tip, any proximal segment that reaches this depth of L 1  can be commanded to configure itself in the same manner as the distal tip segment until it has achieved the correct combination of bends to negotiate the turn. As the body  238  is further advanced, as seen in  FIG. 19 , it will eventually reach the second major bend at a depth of L 1 +L 2 . Accordingly, as for L 1 , any segment that is advanced and reaches a depth of L 1 +L 2  will likewise be commanded to execute a turn as defined by the distal tip being selectively steered when it first passed the second bend into the descending colon D. Again as the body  238  is further advanced, as shown in  FIG. 20 , any subsequent segment that is advanced to reach a depth of L 1 +L 2 +L 3  will be commanded to execute and negotiate the turn to follow the transverse colon T, again where the original curve has been defined by the selectively steerable distal tip. 
       FIG. 21  shows a schematic of one embodiment of a control system which may be used to control and command the individual segments of a segmented endoscopic device of the type shown in  FIGS. 8-11B . As seen, a master controller  248 , which preferably resides at a location away from the segmented endoscope  242 , may be used to control and oversee the depth measurement as the endoscope  242  is inserted  256  into a patient. The master controller  248  may also be used to manage and communicate the actuation efforts of each of the joints and segments  242   1  to  242   n  by remaining in electrical communication through communications channels  252 , which may include electrical wires, optical fibers, wireless transmission, etc. As also shown in this embodiment, the master controller  248  may also be in communication with datum  244  via datum communication channel  254  to measure and track the depth of insertion of the endoscope  242  as it passes through datum channel  246 , as described above. 
     The segmented embodiment  242  may be comprised of a number of individual segments  242   1  to  242   n  (only segments  242 , to  2425  are shown for clarity). Each segment  242   1  to  242   n  preferably has its own separate controller  250   1  to  250   n , respectively, contained within each segment. Types of controllers used may include microcontrollers. The controllers  250   1  to  250   n  may serve to perform several functions, e.g., measuring the angle of each segment joint in each of the two axes α and β, as described above, activating the motors contained within the segments  242   1  to  242   n  to actuate endoscope  242  movement, and receiving and handling commands issued from the master controller  248 . Having individual controllers  250   1  to  250   n  in each respective segment  242   1  to  242   n  enables each segment to manage the requirements for a given configuration locally at the controller level without oversight from the master controller  248  after a command has been issued. 
     Accordingly, a flow chart embodiment for the master controller algorithm  260 , as shown in  FIG. 22 , may be used to control the overall function during insertion into a patient. During an initial step  262 , the overall system (such as that shown in  FIG. 21 ) may be initialized where all position sensors are zeroed. The master controller  248  then enters a waiting state where it continually monitors the depth measurement gathered by the datum  244  located proximally of body opening, as shown in step  264 . Once movement, i.e., depth measurement, is detected by the datum  244  in step  264 , the master controller  248  then determines whether the direction of motion of the endoscopic body  242  is being advanced, i.e., inserted, or withdrawn. As shown in step  266 , if the endoscopic body  242  is being inserted and the depth is increasing, the current depth is incremented, as in step  268 ; otherwise, the current depth is decremented, as in step  270 . Once the depth has been determined, the master controller  248  communicates to each segment  242   1  to  242   n  individually and commands each to actuate to adjust or correct its position relative to the adjacent segments for the current depth, as shown in step  272 . Afterwards, the master controller  248  continues to monitor any changes in depth and the process is repeated as shown. 
     To maintain the orientation of each axis α and β and the positioning and the depth of each segment  242   1  to  242   n , a data array, or similar data structure, may be used by the master controller  248  to organize the information, as shown in the following Table 1. Depth index D 1  to D n  is used here to denote the individual hatch marks, as seen in  FIG. 21 , and the distance between the hatch marks is a known value. Thus, the resolution with which the endoscope  242  can maintain its shape may depend at least in part upon the spacing between the depth indices D 1  to D n . Moreover, the number and spacing of the indices D 1  to D n  may be determined and set according to the specific application and necessary requirements. Additional smoothing algorithms may be used and implemented to further create gradual transitions between segments  242   1  to  242   n  or between discrete depth measurement indices D 1  to D n . 
     
       
         
               
             
               
               
               
               
               
             
           
               
                 TABLE 1 
               
             
             
               
                   
               
               
                 Data array of individual segments. 
               
             
          
           
               
                   
                 Segment 1 
                 Segment 2 
                   
                 Segment N 
               
               
                 Depth Index 
                 α/β 
                 α/β 
                 . . . 
                 α/β 
               
               
                   
               
               
                 D 1   
                 α D1 /β D1   
                 α D1 /β D1   
                 . . . 
                 α D1 /β D1   
               
               
                 D 2   
                 α D2 /β D2   
                 α D2 /β D2   
                 . . . 
                 α D2 /β D2   
               
               
                 D 3   
                 α D3 /β D3   
                 α D3 /β D3   
                 . . . 
                 α D3 /β D3   
               
               
                 . . . 
                 . . . 
                 . . . 
                 . . . 
                 . . . 
               
               
                 D n   
                 α Dn /β Dn   
                 α Dn /β Dn   
                 . . . 
                 α Dn /β Dn   
               
               
                   
               
             
          
         
       
     
       FIG. 23  shows a flowchart embodiment of the segment controller algorithm  280 . While the master controller  248  manages the measurement of the overall depth of insertion of the endoscope  242  and determines the overall shape, it may also communicate with the individual controllers  250   1  to  250   n  in each segment  242   1  to  242   n , respectively, so that the computation task of managing the motion of the entire system is preferably distributed. 
     As discussed above, the individual controllers  250   1  to  250   n  may serve a variety of functions, including accepting commands from the master controller  248 , managing communications with other controllers as necessary, measuring and controlling the position of individual segments  242   1  to  242   n , and performing diagnostics, error checking, etc., among other things. The algorithm to control each segment  242   1  to  242   n  is preferably similar for each segment; although the lead segment  242   1  or first few segments are under the guidance of the physician to selectively control and steer so that the desired curve is set for an appropriate path to be followed 
     The initial step  282  for the system preferably first occurs where all communications, actuator (or motor), position sensors, and orientation are initialized. The controllers  250   1  to  250   n  may then wait to receive any communications from the master controller  248  in step  284 . If no communications are received, the controllers  250   1  to  250   n  preferably enter into a main loop while awaiting commands. When a command is received, each of the controllers  250   1  to  250   n  may request diagnostic data, as in step  286 . If diagnostic data is requested, the appropriate diagnostics are performed in step  288  and the results are sent back to the master controller  248 , as in step  290 . If no diagnostic data is requested in step  286 , each of the controllers  250   1  to  250   n  in step  292  may then determine whether actuation or motion has been requested by the master controller  248 . If no actuation or motion has been requested, the relevant segment may continue to receive a command; otherwise, the relevant segment determines whether a command has been issued affecting the segment axis α, as in step  294 , or segment axis β, as in step  300 . If the segment axis α is to be altered, the command is sent to the α axis PID controller (or to a superior control scheme) in step  296 , and the appropriate actuator is subsequently activated effecting the actuation of the segment in the α axis, as in step  298 . Likewise, if the segment axis β is to be altered, either alone or in conjunction with the α axis, the command is sent to the β axis PID controller (or to a superior control scheme) in step  302 , and the appropriate actuator is subsequently activated effecting the actuation of the segment in the β axis, as shown in step  304 . Once the appropriate commands have been effectuated, the controllers  250   1  to  250   n  again enter the main loop to await any further commands. 
     Although the endoscope of the present invention has been described for use as a colonoscope, the endoscope can be configured for a number of other medical and industrial applications. In addition, the present invention can also be configured as a catheter, cannula, surgical instrument or introducer sheath that uses the principles of the invention for navigating through tortuous body channels. 
     In a variation of the method that is particularly applicable to laparoscopy or thoracoscopy procedures, the steerable endoscope  100  can be selectively maneuvered along a desired path around and between organs in a patient&#39;s body cavity. The distal end  108  of the endoscope  100  is inserted into the patient&#39;s body cavity through a natural opening, through a surgical incision or through a surgical cannula, introducer, or trocar. The selectively steerable distal portion  104  can be used to explore and examine the patient&#39;s body cavity and to select a path around and between the patient&#39;s organs. The electronic motion controller  140  can be used to control the automatically controlled proximal portion  106  of the endoscope body  102  to follow the selected path and, if necessary, to return to a desired location using the three-dimensional model in the electronic memory of the electronic motion controller  140 . 
     A further variation which involves a non-contact method of measurement and tracking of the steerable endoscope is seen in  FIGS. 24 to 26 . This variation may be used in conjunction with sensor-based systems or transponders, e.g., coils or magnetic sensors, for tracking of the endoscope via magnetic detection technology or a navigational system or device external to the patient employing a scheme similar to that used in global positioning systems (GPS). Magnetic sensors may be used, but coils are preferable because of their ability to resonate at distinct frequencies as well as their ability to have a unique “signature”, which may allow for the use of several different coils to be used simultaneously. Seen in  FIG. 24 , the endoscopic body  238  may be inserted into a patient via the anus A. Located on the endoscope body  238  are transponders  310  to  318  which may be placed at predetermined positions such as the selectively steerable distal tip. 
     As the endoscope  238  is advanced through the descending D and transverse colon T, the transponders may be detected by an external navigational unit  320  which may have a display  322  showing the position of the endoscope  238  within the patient. As the endoscope  238  is further advanced within the patient, as seen in  FIG. 26 , the navigational unit  320  may accordingly show the corresponding movement. The use of a navigational unit  320  presents a non-contact method of navigating a device such as the endoscope  238  and may be used to measure and locate different positions within the patient relative to anatomical landmarks, such as the anus A or ileocecal valve. Furthermore, such an embodiment may be used either alone or in conjunction with the datum speculum  234  instrumentation as described above. 
     Use of the navigational unit  320  may also be particularly applicable to laparoscopy or thoracoscopy procedures, as described above, in spaces within the body other than the colon. For example, the endoscope  238  may also be selectively maneuvered along a desired path around and between organs in a patient&#39;s body cavity through any of the openings into the body discussed above. While being maneuvered through the body cavity, the endoscope  238  may be guided and tracked by the externally located navigational unit  320  while the endoscope&#39;s  238  location may be electronically marked and noted relative to a predetermined reference point, such as the datum, or relative to anatomical landmarks, as described above. 
     While the present invention has been described herein with respect to the exemplary embodiments and the best mode for practicing the invention, it will be apparent to one of ordinary skill in the art that many modifications, improvements and subcombinations of the various embodiments, adaptations and variations can be made to the invention without departing from the spirit and scope thereof.