System for controlling an instrument using shape sensors

FIELD OF THE INVENTION

0001The present invention relates, generally, to articulating instruments or snake-like robots. More particularly, the present invention relates to sensing the shape of articulating instruments or snake-like robots.

BACKGROUND OF THE INVENTION

0002Endoscopes, colonoscopes and other controllable instruments have found widespread medical and industrial uses. As the complexity of the movement or use of such instruments increases, there is a need to more precisely control, locate within the body or identify the shape of the controllable instrument. A number of different types of shape sensing devices are available.

0003While shape sensing devices are available, challenges remain in the integration of shape sensing devices into controllable instruments. Challenges remain in systems capable of coordinated use of the shape information for control of operation of the controllable instrument or procedures that would benefit from shape information. Embodiments of the inventive systems and controllable instruments described herein address these and other challenges.

0004<patcit id="pcit0001" dnum="US4930494A"><text>US 4,930,494</text></patcit> discloses an apparatus in which the distal end of an insertion section of an endoscope is divided into a plurality of segments each including a pair of SMA coils which are arranged symmetrically with respect to an axis and memorize a close-winding shape. As the SMA coils recover their memorized shape, the distal end of the insertion section is bent. The SMA coils are restored to the memorized shape when they are conductively heated by means of a current supply circuit. The current supply circuit comprises an input unit for inputting a target value of the bend angle for a leading segment, a sensor for detecting the distance of insertion of the insertion section, a detector circuit for detecting the bend angle of each segment, and means for controlling the amount of current supply so that the bend angle of the SMA coils agrees with a target angle. The inputted angle is set as the target angle for the leading segment, and the detected bend angle of each segment is set as the target angle for each succeeding segment. The set value is renewed each time the insertion distance of the insertion section attains a predetermined distance.

0005<patcit id="pcit0002" dnum="WO2005084542A"><text>WO 2005/084542</text></patcit> discloses a medical apparatus comprising a catheter which is operable to be inserted into a human subject. Haptic sensors and deformation sensors are connected to the catheter and these are disposed at a plurality of locations along the length of the catheter. The haptic sensors measure 3D forces acting on the catheter at the disposed locations and these forces are provided to a haptic feedback device which provides haptic feedback to an interventional radiologist. The deformation sensors on the other hand, measure the deformation of the catheter at the disposed locations and this information determines the shape of the catheter which is represented on a display for viewing by the radiologist.

0006<patcit id="pcit0003" dnum="WO9933392A"><text>WO 99/33392</text></patcit> discloses a deformable probe which can be placed in cavities or mediums which cannot be observed. The probe comprises a plurality of deformation and distortion sensors which are distributed along the length of the probe. The supply lines are preferably guided outward in a multiplex circuit and are connected to a computer. A differential iterative computing method is used for calculating the deformation and position of the probe, and the position of the probe is displayed on a screen.

0007<patcit id="pcit0004" dnum="WO2006134881A"><text>WO 2006/134881</text></patcit> discloses an endoscope treating instrument comprising a long tube body provided with a flexible member to be inserted into a body cavity, a first curving unit provided at the tip end of the tube body to curve the tube body in the axial direction, a second curving unit continuously provided at the base end side of the first curving unit to curve the tube body in the axial direction, and a curving operating unit for independently curving the first and second curving units respectively.

0008<patcit id="pcit0005" dnum="US5728044A"><text>US 5,728,044</text></patcit> discloses a sensor device and system that projects a three-dimensional image of the position of the colonoscope within the gut onto a video screen next to the optical image from the end of the colonoscope. The sensor device comprises a plurality of strain gages mounted on a bendable rod at the head of the rod. As the head is pushed through the biopsy channel of the colonoscope, the head bends with the curvature of the colonoscope causing the deformation of the head to be captured by the strain gages. An encoder at the inlet to the biopsy channel records the velocity and distance of the head as the head is pushed in and through the channel. The combined electrical output from the strain gages and encoder enables an instantaneous generation of a three-dimensional image of the colonoscope on a view screen. The sensor device avoids the need for any equipment that is above or surrounds the abdomen of the patient.

0009<patcit id="pcit0006" dnum="US2008097159A"><text>US 2008/097159</text></patcit> discloses an endoscopic treatment instrument including: a long tube body to be inserted into a body cavity, including a flexible member; a first bending portion provided to a distal end part of the tube body, for bending the tube body with respect to an axial direction; a second bending portion provided in a linked manner to a proximal end side of the first bending portion, for bending the tube body in the axial direction; and a bending operation portion for independently bending the first and second bending portions.

SUMMARY OF THE INVENTION

0010The invention provides a system and method for controlling an instrument as set out in the appended claims.

0011Disclosed is an instrument having an elongate body, comprising a steerable distal portion and a plurality of articulating segments. The instrument can be modified to incorporate a shape sensor to indicate the shape of at least a portion of the instrument. In one embodiment, the shape sensor is an optical shape sensor. In other embodiments, the shape sensor can be a resistance changing flexible band, a bend sensor, a potentiometer, or a magnetic sensor, for example.

0012An aspect of the invention provides a system that closes the control loop between the control signals used to direct the movement of an instrument and the shape indicating signal for the shape of all or a portion of the instrument. The system can comprise a user input device, a controller, an instrument having articulating segments, and a shape sensor, for example. The controller is configured to direct the movement of the instrument in response to a control signal from the user input device and a shape signal from the shape sensor.

BRIEF DESCRIPTION OF THE DRAWINGS

0013The novel features of the invention are set forth with particularity in the appended claims. A better understanding of the features and advantages of the present invention will be obtained by reference to the following detailed description that sets forth illustrative embodiments, in which the principles of the invention are utilized, and the accompanying drawings of which: <ul id="ul0001" list-style="none" compact="compact"><li><figref idref="f0001"><b>FIG. 1</b></figref> illustrates a steerable endoscope in accordance with one embodiment of the present invention.</li><li><figref idref="f0002"><b>FIGS. 2A-2C</b></figref> depict embodiments of vertebrae-type links in accordance with an embodiment of the present invention.</li><li><figref idref="f0003"><b>FIG. 3</b></figref> illustrates a system that closes the control loop between control signals used to direct the movement of a controllable instrument and a shape indicating signal for the shape of all or a portion of the controllable instrument in accordance with an embodiment of the present invention.</li><li><figref idref="f0004"><b>FIG. 4</b></figref> illustrates an articulating segment having an optical shape sensing fiber along its length in accordance with an embodiment of the present invention.</li><li><figref idref="f0005"><b>FIG. 5</b></figref> illustrates an articulating segment utilizing a resistance changing flex sensor to sense the shape of the articulating segment in accordance with an embodiment of the present invention.</li><li><figref idref="f0006"><b>FIG. 6</b></figref> illustrates an articulating segment utilizing a bend sensor to sense the shape of the articulating segment in accordance with an embodiment of the present invention.</li><li><figref idref="f0007"><b>FIG. 7</b></figref> illustrates a flowchart illustrating steps taken to control an instrument having an elongate body in accordance with an embodiment of the present invention.</li></ul>

DETAILED DESCRIPTION OF THE INVENTION

0014<figref idref="f0001"><b>FIG. 1</b></figref> depicts an instrument <b>10,</b> in accordance with an embodiment of the present invention. Instrument <b>10</b> has elongate body <b>12</b> with steerable distal portion <b>14,</b> automatically controlled proximal portion <b>16,</b> and flexible and passively manipulated proximal portion <b>18.</b> Automatically controlled proximal portion <b>16</b> may also be flexible and passively manipulated, although it is preferred to provide automatically controlled proximal portion <b>16.</b> Elongate body <b>12</b> can have only steerable distal portion <b>14</b> and automatically controlled portion <b>16.</b> As described below and as schematically illustrated in <figref idref="f0003"><b>FIG. 3</b></figref><b>,</b> the instrument 10 and the associated control system or controller may be modified to incorporate a shape sensor and control the instrument based at least in part on a shape indicating signal provided by one or more shape sensors on or associated with the instrument 10. Fiber optic imaging bundle <b>20</b> and illumination fiber(s) <b>22</b> may extend through elongate body <b>12</b> to steerable distal portion <b>14,</b> or video camera <b>24</b> (<i>e.g.,</i> CCD or CMOS camera) may be positioned at the distal end of steerable distal portion <b>14.</b> A user views live or delayed video feed from video camera <b>24</b> via a video cable (<i>e.g.</i>, wire or optical fiber, not shown) or through wireless transmission of the video signal. Typically, instrument <b>10</b> will also include one or more access lumens, working channels, light channels, air and water channels, vacuum channels, and a host of other well known complements useful for both medical and industrial endoscopy. These channels and other amenities are shown generically as working channel <b>26.</b> In particular these amenities may include multiple tool channels in order to provide access for tools to a surgical site by passing the instrument through a natural orifice proximate to a surgical target site, as in natural orifice transluminal (or transgastric) endoscopic surgery (NOTES). Various details of the use of a controllable instrument and methods for using a controllable instrument in a transluminal or NOTES procedure are further described in <patcit id="pcit0007" dnum="US52230506A" dnum-type="L"><text>U.S. Pat. Appln. Ser. No. 11/522,305</text></patcit> titled "Methods and Apparatus for Performing Transluminal and Other Procedures," filed on September 14, 2006 and commonly assigned to the assignee of the present application. The systems, instruments and devices described in "Methods and Apparatus for Performing Transluminal and Other Procedures" may be modified as described herein to provide shape sensing capabilities and/or control to the systems, instruments and methods described therein.

0015Preferably, automatically controlled proximal portion <b>16</b> comprises a plurality of articulating segments <b>28,</b> which are controlled via computer and/or electronic controller <b>30.</b> Such an automatically controlled endoscope is described in further detail in commonly assigned <patcit id="pcit0008" dnum="US229577A" dnum-type="L"><text>U.S. Pat. Appln. Ser. No. 10/229,577</text></patcit>, now <patcit id="pcit0009" dnum="US6858005B"><text>U.S. Pat. No. 6,858,005</text></patcit>, titled "Tendon-Driven Endoscope and Methods of Insertion," filed on August 27, 2002, and <patcit id="pcit0010" dnum="US75098807A" dnum-type="L"><text>U.S. Pat. Appln. Ser. No. 11/750,988</text></patcit> titled "Methods and Apparatus for Displaying Three-Dimensional Orientation of a Steerable Distal Tip of an Endoscope," filed on May 18, 2007, both commonly assigned to the assignee of the present application. Preferably, the distal end of a tendon is mechanically connected to each articulating segment <b>28</b> or steerable distal portion <b>14,</b> with the proximal end of the tendon mechanically connected to actuators to move articulating segments <b>28</b> or steerable distal portion <b>14.</b> The actuators driving the tendons may include a variety of different types of mechanisms capable of applying a force to a tendon, <i>e.g.</i>, electromechanical motors, pneumatic and hydraulic cylinders, pneumatic and hydraulic motors, solenoids, shape memory alloy wires, electronic rotary actuators or other devices or methods as known in the art. If shape memory alloy wires are used, they can be configured into several wire bundles attached at a proximal end of each of the tendons within the actuator. The actuators driving the tendons may be positioned inside instrument 10, or, alternatively, the actuators may be positioned outside instrument <b>10.</b>

0016Segment articulation may be accomplished by applying energy, <i>e.g.,</i> electrical current, electrical voltage, heat, etc., to each of the bundles to actuate a linear motion in the wire bundles which in turn actuate the tendon movement. The linear translation of the actuators within the controller may be configured to move over a relatively short distance to accomplish effective articulation depending upon the desired degree of segment movement and articulation. In one embodiment, knobs attached to rack and pinion gearing can be used to actuate the tendons attached to steerable distal portion <b>14.</b> An axial motion transducer <b>32</b> (also called a depth referencing device or datum) may be provided for measuring the axial motion, <i>i.e.,</i> the depth change, of elongate body <b>12</b> as it is advanced and withdrawn. As elongate body <b>12</b> of instrument <b>10</b> slides through axial motion transducer <b>32,</b> it indicates the axial position of the elongate body <b>12</b> with respect to a fixed point of reference. Axial motion transducer <b>32</b> is more fully described in <patcit id="pcit0011" dnum="US52230506A" dnum-type="L"><text>U.S. Pat. Appln. Ser. No. 11/522,305</text></patcit> titled "Methods and Apparatus for Performing Transluminal and Other Procedures," filed on September 14, 2006. Additionally, an optical sensor may be used to determine the axial position of the instrument, either alone or in combination with an optical shape sensor as more fully described below. In either case, the depth information combined with the shape information can be used to construct a three-dimensional image of the elongate body as it is inserted or withdrawn. Additionally, information from such a system may be used to provide, the shape of the pathway followed by the sensor from a reference point (i.e., the datum). Additionally, information from such a system may be used as input to a control system to: (i) Drive the instrument to a location under the control of a user; (ii) Provide recommended steering commands to a user to manipulate the instrument to a desired location or orientation (iii) Automatically control the instrument to conform to inputs from a user, a predetermined pathway (surgical planning) or inputs from an imaging system or display.

0017In the embodiment depicted in <figref idref="f0001"><b>FIG. 1</b></figref><b>,</b> handle <b>34</b> is connected to illumination source <b>36</b> by illumination cable <b>38</b> that is connected to or continuous with illumination fibers <b>22.</b> Handle <b>34</b> is connected to electronic controller <b>30</b> by way of controller cable <b>40.</b> User input device <b>42</b> (<i>e.g</i>., a joy stick) is connected to electronic controller <b>30</b> by way of second cable <b>44</b> or directly to handle <b>34.</b> Controller <b>30</b> controls the movement of the segmented automatically controlled proximal portion <b>16.</b>

0018In one embodiment, articulating segments <b>28</b> of instrument <b>10</b> can be constructed from a plurality of links <b>200</b> as shown in <figref idref="f0002"><b>FIGS. 2A-2C. FIG. 2A</b></figref> shows an end view of a single link <b>200.</b> Each link <b>200</b> can define a central aperture or working channel <b>202</b> that can collectively form the internal lumen as previously described. As shown in <figref idref="f0002"><b>FIG. 2B</b></figref><b>,</b> the links <b>200</b> may have two pairs of hinges <b>204</b> and <b>206.</b> The first pair of hinges <b>204</b> can project perpendicularly from a first face of link <b>200</b> and a second pair of hinges <b>206</b> located 90 degrees around the circumference from the first pair, projecting perpendicularly away from the face of link <b>200</b> on a second face of the vertebra opposite to the first face. In the embodiment shown in <figref idref="f0002"><b>FIG. 2C</b></figref><b>,</b> each articulating segment <b>28</b> can comprise four links <b>200,</b> although any number of links may be used including just one link. The ultimate number of links <b>200</b> used is primarily defined by the purpose for which articulating segments <b>28</b> or instrument <b>10</b> will be used. Each link <b>200,</b> in this embodiment, can move with one degree of freedom relative to an adjacent link. Multiple links provide a segment <b>28</b> with two degrees of freedom. Further details of the articulating segments can be found in <patcit id="pcit0012" dnum="US87110407A" dnum-type="L"><text>U.S. Pat. Appln. Ser. No. 11/871,104</text></patcit> titled "System for Managing Bowden Cables in Articulating Instruments," filed on October 11, 2007 and commonly assigned to the assignee of the present application.

0019<figref idref="f0003"><b>FIG. 3</b></figref> illustrates an exemplary system <b>300</b> and method that closes the control loop between the control signals used to direct the movement of the instrument and a shape indicating signal for the shape of all or a portion of a controllable instrument. The following description of system <b>300</b> includes references to instrument <b>10</b> of <figref idref="f0001"><b>FIG. 1</b></figref><b>,</b> since the system <b>300</b> is implemented utilizing an instrument such as instrument <b>10.</b> In order to determine the shape of elongate body <b>12,</b> instrument <b>10</b> can further include shape sensor <b>302</b> in contact with elongate body <b>12.</b> For example, the shape sensor can be an optical sensing fiber or fiber bundle extending along the length of the elongate body. Embodiments of the present invention build upon the concept of measuring the shape of the optical fiber and using those measurements to determine curvature and/or relative position of an instrument to which the optical fiber is associated. In some embodiments, shape sensing is accomplished by creating a linear array of high spatial resolution fiber optic bend sensors. In general, by assuming each element is sufficiently small, by knowing the curvature of the structure at each individual element the overall shape is reconstructed through an integration process. Additional types of shape sensors and their orientation on or within instrument <b>10</b> will be discussed below in more detail.

0020In addition to shape sensor <b>302,</b> system <b>300</b> of <figref idref="f0003"><b>FIG. 3</b></figref> also includes user input device <b>42,</b> controller <b>30,</b> actuator <b>304,</b> and articulating segments <b>28.</b> As previously described, user input device <b>42</b> is in communication with controller <b>30</b> and is configured to provide a control signal to change the shape of at least one of the articulating segments <b>28.</b> Controller <b>30</b> is in communication with actuator <b>304</b> to direct the movement of articulating segments <b>28</b> and, thus, control the shape of elongate body <b>12.</b> In particular, a user inputs a control signal into user input device <b>42</b> (i.e., such as a joystick or a computer) which then transmits the control signal to the controller <b>30.</b> The user may control the instrument <b>10</b> or indicate desired motions in several exemplary ways. In one embodiment, the user steers the steerable distal portion <b>14</b> with user input device <b>42</b> and identifies the direction instrument <b>10</b> needs to proceed. Instrument <b>10</b> is then advanced and the segments following steerable distal portion <b>14</b> take on the shape of the segment before it. This follow-the-leader shape determination, in general, works by proximately adjacent segments taking on the shape of an adjacent distal segment as instrument <b>10</b> is advanced distally. The determination as to the degree a segment has conformed to the shape of another segment and the determination of the shape of one or more segments are determined at least in part by a shape sensor. The follow-the-leader shape determination works the same whether advancing distally or withdrawing proximally. Alternatively, in another embodiment, the user can enter any desired shape of the elongate body (i.e., such as into a computer, interacting with a visual display or graphical user interface), irrespective of the steerable distal portion and even without advancement or withdrawal of elongate body <b>12.</b> In other words, the controller, with or without input from a user, can manipulate the elongate body <b>12</b> into any desired shape. The determination as to whether or to what degree the elongate body <b>12</b> has moved into the desired shape depends at least in part on a shape indicating signal produced by a shape sensor in communication with the elongate body <b>12</b> and the controller <b>30.</b>

0021As the shape of instrument <b>10</b> changes in response to the control signal from user input device <b>42,</b> shape sensor <b>302</b> provides a shape signal corresponding to the shape of at least one of articulating segments <b>28.</b> For example, if shape sensor <b>302</b> runs along the entire length of elongate body <b>12,</b> then the shape signal can correspond to the shape of the entire length of elongate body <b>12.</b> However, for applications where instrument <b>10</b> is inserted into a patient, it can be understood that shape sensor <b>302</b> need not run along the entire length of elongate body <b>12,</b> but rather, only be sufficiently long to indicate the shape of the portion of elongate body <b>12</b> inserted into a patient (i.e., the portion of elongate body <b>12</b> out of sight from the user).

0022Shape sensor <b>302</b> is configured to provide a shape signal corresponding to the shape of at least one of the articulating segments <b>28.</b> Controller <b>30,</b> being in communication with both user input device <b>42</b> and shape sensor <b>302,</b> can direct the movement of at least one of the articulating segments <b>28</b> in response to the control signal from user input device <b>42</b> and the shape signal from shape sensor <b>302.</b> It can be appreciated that an articulating instrument or snake-like robot as described above may not always achieve the shape intended by the user. For example, an actuator may fail, or the tendons responsible for moving articulating segments <b>28</b> may bind, stretch, slip, or break, causing articulating segments <b>28</b> to fail to achieve the shape intended by the user. As such, controller <b>30</b> can direct the movement of instrument <b>10</b> in response to the shape signal from shape sensor <b>302</b> to compensate for any errors within instrument <b>10</b> so that instrument <b>10</b> can automatically achieve the shape intended by the user.

0023In one embodiment, a user may guide or steer instrument <b>10</b> with user input device <b>42</b> while monitoring the actual shape of elongate body <b>12,</b> as sensed by shape sensor <b>302.</b> For example, system <b>300</b> can further include a video display (not shown in <figref idref="f0003"><b>FIG. 3</b></figref>) configured to receive the shape signal from shape sensor <b>302</b> and display an output representing the shape of a portion of elongate body <b>12.</b> Thus, the user can guide, steer or direct movement or alteration of the shape of the instrument <b>10</b> by monitoring the shape of elongate body <b>12</b> as it is displayed on the video display. Since controller <b>30</b> directs the movement of elongate body <b>12</b> in response to the control signal from user input device <b>42</b> and the shape signal from shape sensor <b>302,</b> system <b>300</b> provides a closed-loop feedback control system for controlling instrument <b>10</b> in response to the actual shape of the elongate body <b>12.</b>

0024In yet another embodiment of system <b>300,</b> the user can input a desired shape onto an interactive display such as a graphical user interface display or the like and controller <b>30</b> can direct instrument <b>10</b> to automatically achieve the desired shape. This is accomplished in a similar fashion as described above, as controller <b>30</b> directs the movement of elongate body <b>12</b> in response to the shape signal from shape sensor <b>302</b> until the shape of elongate body <b>12</b> matches the desired shape from the user.

0025System <b>300</b> can be implemented in a variety of surgical procedures. For example, a surgical opening can be created in a patient into which instrument <b>10</b> can be inserted and controlled using the system as described above. The surgical opening can also be a natural body orifice, or an opening created after first passing at least a portion of the elongate body through a natural or created opening in the body. In a NOTES procedure, for example, elongate body <b>12</b> can be inserted into a patient's stomach through the nose or mouth and then through the esophagus. In this example, once elongate body <b>12</b> is within the stomach, a surgical opening can be incised in the stomach wall to provide entry for elongate body <b>12</b> into the peritoneal or abdominal cavity. Thus, the system <b>300</b> can accurately sense, measure, determined and/or control the shape of elongate body <b>12</b> when it is inside a patient, including all or a portion of elongate body <b>12</b> beyond the surgical opening, beyond a natural body orifice or both.

0026As known in the art, an optical sensing fiber can comprise high-density linear arrays of fiber Bragg gratings (FBGs) in the cores of a multicore fiber, as described in "<nplcit id="ncit0001" npl-type="s"><text>Sensing Shape", SPIE's OEMagazine, pp. 18-21 September 2005</text></nplcit>. There are multiple ways to measure the shape of a fiber, and, thereby, the shape of the instrument with which it is aligned. One method comprises shining a swept wave length laser down the fiber bundle and measuring the reflected light from the fiber bundle. Bends in the fiber bundle change the reflection properties of the FBGs, thereby the FBGs act as local strain gauges. The challenge comes in accurately reading the many FBG arrays to determine the shape of the fiber bundle.

0027One technique of reading the FBG arrays is the energy leakage technique that strips the cladding along specific regions of the fiber bundle. The bend in relation to the stripped cladding causes the amount of light transmitted through the fiber to increase or decrease in relation to the magnitude and of the bend. One limitation of the technique is that one fiber is required for each direction desired to be measured.

0028Another technique is cross-coupling of a multi-core fiber, as described in <patcit id="pcit0013" dnum="US6888623B"><text>U.S. Patent No. 6,888,623</text></patcit> titled "Fiber Optic Sensor for Precision 3-D Position Measurement," issued on May 3, 2005. The cross coupling is a function of the shape of the fiber, and by analyzing the energy in each core, it is possible to determine the shape of the fiber.

0029In wavelength division multiplexing (WDM) Bragg gratings are written at various locations along a multicore fiber with different nominal center wavelengths. Each grating can be addressed independently by choosing the wavelength of light that is shone into the system to be close to the center wavelength of the grating. Strain (<i>i.e.,</i> bend) in the fiber near the grating will shift the center wavelength of the grating slightly, which can be measured by the shifts in the reflected spectra. A limitation of this technology is that the number of gratings that can be addressed is limited by the total range of wavelengths that the input light source can be scanned, and the minimum difference in nominal center wavelength, as governed by the amount of shift expected in the wavelengths due to strain in the multicore cable. <patcit id="pcit0014" dnum="US7317849B"><text>U.S. Patent No. 7,317,849</text></patcit> titled "Optical Fiber Sensor and Method," issued on January 8, 2008, further describes this technique.

0030Optical time domain reflectometry (OTDR) can be used as one solution to the limitations of the WDM technique. This solution allows many simultaneous measurements by writing many gratings at the same nominal center wavelength and using time delay of the reflectance to separate the spatial location of the gratings. The location of reflections in a fiber optic cable is determined by measuring the time-of-flight of light from a launch point into a fiber to receipt of a reflection back to the approximate point of launch. In principle, this technique could be used to isolate the same-center-wavelength gratings, however in practice, the position resolution available by this technique is often coarse.

0031In another more preferred technique OTDR uses multicore fiber where all gratings are written at roughly the same nominal wavelength, and the location of the grating is determined in the frequency domain by forming a resonant cavity between the reflection of the gratings and a high reflector at the proximal end of the fiber. This technique requires only one multicore fiber to produce a shape sensor, allows many gratings to be written at the same nominal center wavelength, and permits long fibers. Luna Innovations (www.lunainnovations.com) is an organization that is producing shape sensors built on this technique.

0032As used herein in, optical shape sensor includes any known optical shape sensor. Details of construction, operation and use of exemplary optical sensors may be found in, without limitation, <patcit id="pcit0015" dnum="US6376830B"><text>U.S. Patent No. 6,376,830</text></patcit> titled "System and Method for Measuring the Transfer Function of a Guided Wave Device," issued on April 23, 2002, <patcit id="pcit0016" dnum="US6426496B"><text>U.S. Patent No. 6,426,496</text></patcit> titled "High Precision Wavelength Monitor for Tunable Laser Systems," issued on July 30, 2002, <patcit id="pcit0017" dnum="US6856400B"><text>U.S. Patent No. 6,856,400</text></patcit> titled "Apparatus and Method for the Complete Characterization of Optical Devices Including Loss, Birefringence and Dispersion Effects" issued on February 15, 2005, <patcit id="pcit0018" dnum="US7113659B"><text>U.S. Patent No. 7,113,659</text></patcit> titled "Efficient Distributed Sensor Fiber," issued on September 26, 2006, and <patcit id="pcit0019" dnum="US7099015B"><text>U.S. Patent No. 7,099,015</text></patcit> titled "Fiber Optic Sensing Device for Measuring a Physical Parameter," issued on August 29, 2006.

0033When shape sensor <b>302</b> comprises an optical shape sensor, the axial orientation of the shape sensor from the proximal end through to the distal end must be aligned relative to the instrument <b>10,</b> as one method to increase the accuracy of the shape signal produced to correspond to the shape of the elongate body. As described above, working channel 26 runs down the center of instrument <b>10.</b> In one embodiment, the working channel is moved to an off-center position and the shape sensor is positioned to occupy the space formerly used by the working channel. Alternatively, the shape sensor <b>302</b> may be placed off-center in instrument <b>10.</b> However, all central shape sensor positions may create difficulties in maintaining the axial orientation of shape sensor <b>302,</b> because as instrument <b>10</b> bends the shape sensor can be compressed or stretched and is subject to breaking.

0034There are a number of techniques that may be employed to ensure that the shape sensor is positioned to minimize damage and provide accurate signals representing the shape of all or a portion of the elongate body. Referring to <figref idref="f0004"><b>FIG. 4</b></figref><b>,</b> optical shape sensor <b>402</b> extends along a portion of the flexible elongate body in a spiral pattern, comprising a single full spiral turn along a single articulating segment <b>28.</b> In other embodiments, optical shape sensor <b>402</b> can extend in a spiral pattern for an integral number of full spiral turns, so long as the axial orientation of the shape sensor from the proximal end through to the distal end of the shape sensor relative to the instrument is maintained, as needed by the specific technical requirements of a particular optical shape sensor. Optical shape sensor can extend in a spiral pattern along only a single articulating segment <b>28,</b> as shown in <figref idref="f0004"><b>FIG. 4</b></figref><b>,</b> or can extend in a spiral pattern along multiple articulating segments of the elongate body, including along the entire length of the elongate body. In one embodiment, when the shape sensor spirals along multiple articulating segments, the shape sensor spirals for an integral number of full spiral turns for each articulating segment. This maintains the axial orientation along each articulating segment <b>28,</b> and collectively, therefore, along the elongate body.

0035The spiraling of optical shape sensor <b>402</b> along a portion of the flexible elongate body adds a naturally occurring twist to the optical shape sensor, which disrupts the axial orientation of the shape sensor as it runs along the flexible elongate body. As such, a counter twist must be induced in the optical shape sensor to remove the natural twist caused by the spiraling path along the elongate body and maintain the axial orientation of the shape sensor from the proximal end through to the distal end relative to the elongate body.

0036As further shown in <figref idref="f0004"><b>FIG. 4</b></figref><b>,</b> optical shape sensor <b>402</b> can include at least one indicator <b>404</b> on at least the proximal and distal ends of the shape sensor. The indicators <b>404</b> can be aligned throughout articulating segment <b>28</b> to maintain the axial orientation of the shape sensor proximal end and the shape sensor distal relative to the articulating segment <b>28.</b> In the embodiment of <figref idref="f0004"><b>FIG. 4</b></figref><b>,</b> indicators <b>404</b> are physical indicators, such as tabs extending from the shape sensor. These tabs can be fitted into clips <b>406,</b> which holds optical shape sensor <b>402</b> in place on each end of articulating segment <b>28</b> and maintains the axial orientation of the proximal end of the shape sensor relative to the distal end of the shape sensor. In this configuration, however, as described above, if the shape sensor is spiraled along articulating segment, the axial orientation of the shape sensor from the proximal end through to the distal end must still be aligned relative to the articulating segment, such as by inducing a counter twist in the shape sensor. In another embodiment, the physical indicators can be grooves designed to mate with the ends of the articulating segments. In yet another embodiment, indicators <b>404</b> can be a visual marker on the shape sensor itself, such as a colored or dotted line that runs the length of the shape sensor, for example. It should be understood that the shape sensor is illustrated on the elongate body for purposes of describing the relative position of the sensor to the elongate body or segment thereof. In some embodiments, the shape sensor is integrated into the elongate body, a sleeve that fits over or is joined to the elongate body or on, within, or about one or more of the articulating segments.

0037Shape sensor <b>302</b> described above is not limited to being an optical shape sensor. Referring to <figref idref="f0005"><b>FIG. 5</b></figref><b>,</b> alternatively, resistance changing flexible bands can be implemented in elongate body <b>12.</b> As known in the art, resistance changing flexible bands change resistance when stretched. One example of resistance changing flexible bands are Stretch Sensors™, available from Images SI Inc. (http://www.imagesco.com/sensors/stretch-sensor.html). As shown in <figref idref="f0005"><b>FIG. 5</b></figref><b>,</b> flexible band sensors <b>502</b> can extend along the length of articulating segment <b>28</b> of elongate body <b>12.</b> Pairs of flexible band sensors <b>502</b> can run along first and second pairs of hinges <b>204</b> and <b>206</b> for each bending plane (x- plane and y- plane) of articulating segment <b>28.</b> In this embodiment, the flexible band sensors will experience a resistance gain and a resistance decrease during articulation. The resistance delta between of the flexible band sensors <b>502</b> can be determined or measured and used to determine the shape of each articulating segment <b>28.</b> Thus, the flexible band sensors <b>502</b> can provide a shape signal to controller <b>30,</b> as described above, corresponding to the shape of at least a portion of elongate body <b>12.</b>

0038In an alternative embodiment, shape sensor <b>302</b> can comprise a plurality of flex sensors, such as those made by FlexPoint (www.flexpoint.com) or SpectraSymbol (www.spectrasymbol.com). As shown in <figref idref="f0006"><b>FIG. 6</b></figref><b>,</b> flex sensors <b>602</b> and <b>604</b> (flex sensors <b>604</b> are provided along hinges <b>204</b> but obscured from view in <figref idref="f0006"><b>FIG. 6</b></figref>) can be attached to hinges <b>206</b> and <b>204</b> of each link <b>200,</b> respectively, to provide a signal to the controller <b>30</b> a signal indicative of the angle of articulation. Flex sensors <b>602</b> and <b>604</b> are flat and bend in one plane, but are essentially not bendable in the orthogonal plane. Thus, in this embodiment, flex sensors <b>602</b> and <b>604</b> are aligned so the bending plane of each pair of links <b>200</b> is approximately parallel with the bending plane of the flex sensor across each hinge. As described above, the flex sensors <b>602</b> and <b>604</b> can provide a shape signal to controller <b>30</b> corresponding to the shape of at least a portion of elongate body <b>12.</b>

0039In yet another embodiment, a potentiometer (POT) can be used to measure joint angles as yet another technique for determining the shape of all or a portion of the elongate body. Similar to the embodiments described above, A POT-purchase assembly can be provided at each hinge of the articulating segments <b>28.</b> In this embodiment, the POT has a wiper that brushes against a carbon film thereby changing the resistance output from the POT. The wiper is attached to a slotted piece, which is fixed on hinges <b>204</b> and <b>206</b> between adjacent links <b>200</b> of articulating segments <b>28.</b> Articulation of links <b>200</b> turns the slotted piece and causes the wiper to brush against the carbon film and change the resistance output of the POT as described. This resistance can be provided as a shape signal to controller <b>30,</b> as described above, corresponding to the shape of at least a portion of elongate body <b>12.</b> An alternative to a POT sensor is the use of an optical encoder, as will be appreciated by the skilled artisan.

0040Another alternative device and technique for shape sensing includes using magnetic sensors, or alternatively sensors that detect variations in magnetic fields generated by a transmitter. Ascension Technology Corporation (http://www.ascension-tech.com/) is developing sensors suited to the purposes described herein. <patcit id="pcit0020" dnum="US11242048A" dnum-type="L"><text>U.S. Patent Appln. Ser. No. 1 1/242,048</text></patcit> titled "DC Magnetic-Based Position and Orientation Monitoring System for Tracking Medical Instruments," filed on October 4, 2005, also discloses this technology. The magnetic sensors can be placed at intervals along elongate body 12, in accordance with an embodiment of the present invention. The spatial orientation of and movements detected by the magnetic sensors may be used to indicate, determine or measure the shape of all or a portion of the elongate body. In the same manner as described above, the magnetic sensors can provide a shape signal to controller 30 corresponding to the shape of at least a portion of elongate body 12.

0041<figref idref="f0007">FIG. 7</figref> shows a flowchart illustrating an exemplary method of controlling an instrument having an elongate body according to an example. Certain details and features have been left out of flowchart 700 that are apparent to a person of ordinary skill in the art. For example, a step may consist of one or more substeps or may involve specialized equipment or materials, as known in the art.

0042The following description of flowchart 700 includes references to instrument 10 of <figref idref="f0001">FIG. 1</figref> and system 300 of <figref idref="f0003">FIG. 3</figref>, since the method steps in flowchart 700 are implemented utilizing an instrument such as instrument 10. At step 702 of flowchart 700, a control signal is outputted to a controller to change the shape of an instrument having an elongate body. As described above, a user can input a control signal into user input device 42, which can transmit the control signal to controller 30, for example. In one embodiment, controller 30 is in communication with actuator 304 to direct the movement of elongate body 12.

0043At step 704 of flowchart 700, the shape of at least a portion of the elongate body is sensed with a shape sensor. As described above, shape sensor 302 provides a shape signal corresponding to the shape of at least one of articulating segments 28. In one example, shape sensor 302 runs along the entire length of elongate body 12 to provide a shape signal corresponding to the shape of the entire length of elongate body 12. However, in another example, instrument 10 is inserted into a patient so shape sensor 302 need not run along the entire length of elongate body 12, but rather, only be sufficiently long to indicate the shape of the portion of elongate body 12 inserted into the patient.

0044At step 706 of flowchart 700, the shape signal corresponding to the shape of the portion of the elongate body is outputted from the shape sensor to the controller. In one example, the outputting step can further include the step outputting the shape signal to a video display to display an output representing the shape of the portion of the elongate body. As described above, system 300 can include a video display configured to receive the shape signal from shape sensor 302 and display an output representing the shape of a portion of elongate body 12. Thus, the user can guide, steer or direct movement or alteration of the shape of the instrument 10 by monitoring the shape of elongate body 12 as it is displayed on the video display.

0045At step 708 of flowchart 700, the movement of the elongate body is directed in response to the control signal and the shape signal. As described above, controller 30, being in communication with both user input device 42 and shape sensor 302, can direct the movement of at least one of the articulating segments 28 in response to the control signal from user input device 42 and the shape signal from shape sensor 302 to provide a closed- loop feedback control system for controlling instrument 10.

0046In other examples, the method can further include the step of creating a surgical opening in a patient. A surgical opening can be created in a patient into which instrument 10 can be inserted and controlled using the system described above. The surgical opening can also be a natural body orifice, or an opening created after first passing at least a portion of the elongate body through a natural or created opening in the body. Additionally, the method can further include the step of sensing the shape of least a portion of the elongate body beyond the surgical opening, and outputting the shape signal to a video display to display an output representing the shape of the portion of the elongate body beyond the surgical opening.

0047In addition to sensing the shape of the elongate body, optical sensors can be used to determine the depth of insertion of the elongate body from a particular predefined point. This information can also be used to construct the three dimensional shape of the elongate body, as previously described. Two or more shape sensors may be used to determine the depth of insertion of an instrument. Consider a pair of shape sensors. Each sensor is capable of providing x,y,z position within an x,y,z coordinate system. One sensor is placed at a fixed location and is used as a reference location. In one example, the x,y,z tip position of the first sensor is used as the point of reference. The point of reference may be placed at, on or near a natural or surgically created opening in the body. The point of reference sensor may be positioned adjacent a surgically created opening created within the body after entering the body through a natural opening or a surgically created opening. The reference point may be positioned at or near a natural opening even if a surgical opening is created and utilized elsewhere. For example, the reference point may be at or near the mouth when an opening is created in the stomach or at another point in the alimentary canal. Additionally, the reference point opening may be created and the shape sensor and flexible instrument positioned and used in support of NOTES, as described in copending patent application serial number <patcit id="pcit0021" dnum="WO11522305A"><text>1 1/522,305 filed September 14, 2006</text></patcit> titled "Methods and Apparatus Useful in Performing Transluminal and Other Procedures." The second sensor is attached to an instrument. The instrument passes near the tip of the first sensor. The x, y, z position of the second instrument is known. Next, compare the x,y,z positions along the instrument until one matches or most nearly corresponds to the x,y,z position of the tip. The x,y,z position on the instrument is then used to determine the position of the instrument relative to the reference point or the depth that the instrument has been inserted beyond the reference point. Additionally, the shape of the second instrument is also known based on information from the second shape sensor. The path, organ or portion of the body traversed relative to the reference point may also be determined using the depth of insertion and the shape of the second shape sensor. Similar techniques may also be used while the instrument is being withdrawn or manipulated.

0048In an alternative example, the techniques described herein may be used to measure the relative location of a shape sensor with respect to another position sensor that is not a shape sensor. For example, if the anus was placed in a known location on an operating room table, and the shape sensor's base is located in a known location with respect to an operating room table, depth of insertion could be determined entirely using a single shape sensor in the scope, and the second sensor is the "ruler" formed by the known relative locations of the anus and the base of the shape sensor.

0049It would be possible to discern velocity, acceleration and higher order derivatives from this arrangement as well. Use of multiple sensors could be used to provide redundancy, consistency / error checking, and lower error and lower signal noise through various stochastic estimation techniques (such as extended Kalman filters, Unscented Transform filters, Weiner filtering, H_infmity optimal estimation and the like).

0050As for additional details pertinent to the various embodiments described herein, materials and manufacturing techniques may be employed as within the level of those with skill in the relevant art. The same may hold true with respect to method-based aspects of the invention in terms of additional acts commonly or logically employed. There are additional system requirements needed to ensure the full integration and proper operation of a shape sensor with the elongate body and associated control system optical shape sensors, for example require a light source and a perfect components to ensure the light source is focused or provided to the optical sensor. These and other conventional components are also included as part of the system 300 as needed by the technical requirements of the particular shape sensor or sensors being used.

0051Also, it is contemplated that any optional feature of the inventive variations described may be set forth and claimed independently, or in combination with any one or more of the features described herein. Likewise, reference to a singular item, includes the possibility that there are plural of the same items present. More specifically, as used herein and in the appended claims, the singular forms "a," "and," "said," and "the" include plural referents unless the context clearly dictates otherwise. It is further noted that the claims may be drafted to exclude any optional element. As such, this statement is intended to serve as antecedent basis for use of such exclusive terminology as "solely," "only" and the like in connection with the recitation of claim elements, or use of a "negative" limitation. Unless defined otherwise herein, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The breadth of the present invention is not to be limited by the subject specification, but rather only by the plain meaning of the claim terms employed.

0052It is intended that the following claims define the scope of the invention and that methods and structures within the scope of these claims and their equivalents be covered thereby.