Patent Publication Number: US-2021177299-A1

Title: Method And System For Providing Visual Guidance To An Operator For Steering A Tip Of An Endoscopic Device Towards One Or More Landmarks In A Patient

Description:
FIELD OF THE INVENTION 
     The present invention generally relates to endoscopic devices and in particular, to a method and system for providing visual guidance to an operator for steering a tip of an endoscopic device towards one or more landmarks in a patient. 
     BACKGROUND OF THE INVENTION 
     Minimally invasive surgical procedures are known to offer many benefits over traditional open surgery techniques, including less pain, shorter hospital stays, quicker return to normal activities, minimal scarring, reduced recovery time, and less injury to tissue. To perform such procedures, entry into the patient may be made through an incision or a natural body orifice. Both robotic and manually operated minimally invasive surgical devices may be used. 
     One example of a minimally invasive surgical robotic system is the da Vinci® Surgical System from Intuitive Surgical, Inc., of Sunnyvale, Calif. The da Vinci® Surgical System has a number of robotic arms that move attached medical devices, such as an image capturing device and Intuitive Surgical&#39;s proprietary EndoWrist® articulating surgical instruments, in response to movement of input devices by a surgeon viewing images captured by the image capturing device at a surgical site. Each of the medical devices may be inserted through its own minimally invasive incision into the patient and positioned to perform a medical procedure at the surgical site. The incisions are placed about the patient&#39;s body so that the surgical instruments may be used to cooperatively perform the medical procedure and the image capturing device may view it without their robotic arms colliding during the procedure. 
     An endoscope is a medical device that allows physicians to capture images of and diagnose problems with internal body organs by inserting the device either through a natural orifice or a surgeon created opening and guiding it to a target site within a patient. In some cases, it may also be used to perform medical procedures on the internal body organs. It may be steerable so that its distal tip is controllably oriented for navigation purposes. An image capturing device such as a stereoscopic or monoscopic camera may be provided at its distal tip so that images captured by the camera from that perspective may be viewed on a display screen by the surgeon. To perform various medical procedures at the target site, surgical tools, such as those used for cutting, grasping, cauterizing, etc., may extend out of the endoscope&#39;s distal tip. 
     The endoscope may be rigid such as those used in laparoscopy or it may be flexible so that it is capable of following the curvatures of body lumens. It may also be rigidizable and/or robotic. A rigidizable endoscope is an endoscope that has at least one section of its flexible body that can be made substantially rigid by a mechanical locking mechanism. A robotic endoscope is a flexible endoscope that has at least one section that bends under a computer controlled servo mechanism. It may also be a capsule like the EndoCapsule by Olympus or a tethered capsule in which case it is not controllably oriented for navigation purposes and gets moved in the patient anatomy by gravity, forces applied by the anatomy or by other surgical devices. 
     Natural Orifice Transluminal Endoscopic Surgery (“NOTES”) may employ a steerable endoscope to perform surgical procedures on patients. As an example, a flexible endoscope may be guided through one of the body&#39;s orifices and enter the abdomen from the inside of the patient, rather than through a minimally invasive incision from the outside. For example, in “transgastric” surgery, instruments are passed through the mouth and into the stomach. A gastrotomy is then performed so that the instruments may enter the abdomen and be used by the surgeon to perform a medical procedure within the abdominal cavity. Once the procedure is completed, the instruments are withdrawn along with any tissue removed during the procedure, and the entry point is closed back up. Because no incisions are made in the patient to accommodate entry of the endoscope, NOTES may be even less painful than surgery using minimally invasive incisions. Also, since it uses a natural body orifice instead of incisions to enter the body, it may result in reduced needs for general anesthetics and faster recovery times. 
     During the operation of a steerable endoscope, such as in a NOTES application, the endoscope tip may be turned multiple times and in different directions while moving towards a target site. As a consequence, the flexible endoscope may wind up looping around itself and disorienting the operator so as to make it difficult for the operator to keep track of the current direction of the endoscope tip if its captured image fails to clearly indicate its current direction with respect to the target site. In contrast, the operator may have a relatively rigid connection to the view in conventional laparoscopy. 
     If the operator accidentally moves the endoscope tip in the wrong direction, the tip may inadvertently perforate or otherwise damage tissue causing harm to the patient. Even if such harm is avoided by carefully moving the endoscope tip, additional time is required to repeatedly ascertain the true direction of the endoscope relative to the target site in the patient. Thus, the time required to perform the procedure is lengthened which adds to the cost of the surgery and increases health safety concerns. 
     OBJECTS AND SUMMARY OF THE INVENTION 
     Accordingly, one object of one or more aspects of the present invention is a method, and a system for performing the method, of providing visual guidance to an operator for steering an endoscopic device towards one or more landmarks in a patient. 
     This and additional objects are accomplished by the various aspects of the present invention, wherein briefly stated, one aspect is a computer implemented method for providing guidance to steer an endoscopic device towards one or more landmarks in a patient, the method comprising: determining a current position of a reference point on the endoscopic device relative to a reference frame; determining a first vector from the current position of the reference point to a position of a first landmark relative to the reference frame; transforming the first vector from the reference frame to an image reference frame that corresponds to the perspective of an image capturing device disposed at a tip of the endoscopic device; and displaying a graphical representation of the transformed first vector along with a current image captured by the image capturing device on a display screen so as to indicate a direction to steer the tip of the endoscopic device towards the first landmark. 
     Another aspect is a system comprising: a display screen; an endoscopic device; and one or more processors adapted to determine a current position of a reference point on the endoscopic device relative to a reference frame, determine a first vector from the current position of the reference point to a position of a first landmark relative to the reference frame, transform the first vector from the reference frame to an image reference frame that corresponds to the perspective of an image capturing device disposed at a tip of the endoscopic device, and display a graphical representation of the transformed first vector along with a current image captured by the image capturing device on a display screen so as to indicate a direction to steer the tip of the endoscopic device towards the first landmark. 
     Additional objects, features and advantages of the various aspects of the present invention will become apparent from the following description of its preferred embodiment, which description should be taken in conjunction with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  illustrates a steerable endoscope system utilizing aspects of the present invention. 
         FIG. 2  illustrates a block diagram of a processing portion of a steerable endoscope system utilizing aspects of the present invention. 
         FIG. 3  illustrates a block diagram of a teleoperative portion of a steerable endoscope system utilizing aspects of the present invention. 
         FIG. 4  illustrates a flow diagram of a computer implemented method for assisting an operator in endoscopic navigation, utilizing aspects of the present invention. 
         FIG. 5  illustrates parts of a position determining portion of a steerable endoscope system utilizing aspects of the present invention. 
         FIG. 6  illustrates a primary display screen displaying an image captured by a steerable endoscope as viewed in a system utilizing aspects of the present invention. 
         FIG. 7  illustrates an auxiliary display screen displaying an anterior-posterior view of registered patient and endoscopic device models as generated by a system utilizing aspects of the present invention. 
         FIG. 8  illustrates an auxiliary display screen displaying an oblique view of patient and endoscopic device models as generated by a system utilizing aspects of the present invention. 
         FIG. 9  illustrates an auxiliary display screen displaying a lateral-medial view of patient and endoscopic device models as generated by a system utilizing aspects of the present invention. 
         FIG. 10  illustrates a primary display screen displaying an image captured by an endoscopic device in a main window area and an oblique view of patient and endoscopic device models in a picture-in-picture window area as generated by a system utilizing aspects of the present invention. 
         FIG. 11  illustrates a primary display screen displaying an image captured by an endoscopic device in a first area and an oblique view of patient and endoscopic device models in a second area as generated by a system utilizing aspects of the present invention. 
         FIG. 12  illustrates a flow diagram of a computer implemented method of providing directional guidance to maneuver an endoscopic device to one or more landmarks, utilizing aspects of the present invention. 
         FIG. 13  illustrates a flow diagram of a computer implemented method for establishing landmarks using an endoscopic device as it moves by the landmarks, utilizing aspects of the present invention. 
         FIG. 14  illustrates an oblique view of a patient torso with an endoscopic device inserted therein and examples of various landmarks as employed in a system utilizing aspects of the present invention. 
         FIG. 15  illustrates a primary display screen displaying a current image captured by an endoscopic device and graphical representations of various vectors indicating directions to corresponding landmarks along with an image associated with one of the landmarks, according to a method utilizing aspects of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       FIG. 1  illustrates, as an example, a system  100  including a steerable endoscope  110 , one or more fiber optic cables  120  inserted in the endoscope  110 , a position processor  130 , an image processor  140 , an image capturing device  141 , a display processor  150 , a primary display screen  600 , and an auxiliary display screen  160 . Although shown as separate units, the position processor  130 , image processor  140  and display processor  150  may each be implemented as hardware, firmware, software or a combination thereof, which interact with or are otherwise executed by one or more computers, such as the one or more computers  200  depicted in  FIG. 2 . The primary and auxiliary display screens,  600  and  160 , are preferably computer monitors capable of displaying three-dimensional images to an operator of the system  100 . However, for cost considerations, either or both of the primary and auxiliary display screens,  600  and  160 , may be a standard computer monitor capable of only displaying two-dimensional images. 
     The endoscope  110 , in this example, has a flexible body  114 , a steerable tip  112  at its distal end  111  and a handle or electromechanical interface  116  at its proximal end  115 . Control cables (not shown) or other control means typically extend from the handle or electromechanical interface  116  to the steerable tip  112  so that the tip  112  may be controllably bent or turned as shown for example by dotted line versions of the bent tip  112 . Although a steerable endoscope is described in this example, the present invention is not to be limited to endoscopes of this type and may be practiced with other endoscopic devices (such as rigid, rigidizable, robotic, or capsule endoscopes) as well. 
     A stereoscopic or monoscopic camera  141  is provided at the distal end  111  for capturing images that are transmitted to and processed by the image processor  140  and/or display processor  150  and displayed on the primary display screen  600  and/or auxiliary display screen  160  according to the various aspects of the invention as described herein. One of a plurality of fiber optic cables  120  may be coupled at its proximal end to a light source (not shown) for illumination purposes at the distal end  111 . Others of the fiber optic cables  120  may be configured with bend or shape sensors such as Fiber Bragg Gratings (or other strain sensors such as those employing Rayleigh scattering) so that light passing through the fiber optic cable is processed by the position processor  130  to determine a current position and shape of the endoscope  110  including the orientation of its distal tip  112 . In addition to the fiber optic cables  120  extending through the endoscope  110 , one or more additional fiber optic cables (not shown) configured with strain sensors may be attached to the endoscope  110  so as to provide position information of the endoscope  110  at the attachment point. 
     When the steerable endoscope  110  is manipulated manually by an operator, a handle  116  is used with appropriate levers or other control mechanism(s) for controllably orienting the endoscope tip  112  by pulling appropriate cables (not shown) which couple such control mechanisms of the handle  116  to the tip  112 . On the other hand, when the steerable endoscope  110  is manipulated teleoperatively by an operator, an electromechanical interface  116  is used instead of a handle. 
     As shown in  FIG. 3 , the electromechanical interface  116  allows the endoscope  110  to be electrically and mechanically coupled to a robot arm  301  whose movement is controlled by a controller  302  in response to operator manipulation of an input device  303 . Either or both the interface  116  and the robot arm  301  include motors that drive the cables used to steer the endoscope tip  112 . In addition to controlling bending of the endoscope&#39;s tip  112 , the robot arm  301  may also be configured to insert/retract the endoscope  110  into and out of an aperture (e.g., natural orifice or minimally invasive incision) in the patient, rotate the endoscope  110  about its central axis, and/or rotate the electromechanical interface  116  about a pivot point at the aperture. The controller  302  is preferably implemented as hardware, firmware or software (or a combination thereof) in the one or more computers  200  along with the processors  130 ,  140 ,  150 . 
     Details on the determination of the endoscope&#39;s position and bending using Fiber Bragg Gratings may be found, for examples, in U.S. 2007/0156019 A1 entitled “Robotic Surgery System Including Position Sensors Using Fiber Bragg Gratings”, U.S. 2008/0212082 A1 entitled “Fiber Optic Position and/or Shape Sensing Based on Rayleigh Scatter”, U.S. 2008/0218770 A1 entitled “Robotic Surgical Instrument and Methods using Bragg Fiber Sensors”, and U.S. application Ser. No. 14/164,829 entitled “Fiber Optic Shape Sensor, each of which is incorporated herein by reference. Details on a conventional steerable endoscope may be found for example in U.S. Pat. No. 6,869,396 B2 entitled “Steerable Endoscope and Improved Method of Insertion”. 
       FIG. 4  illustrates, as an example, a flow diagram of a computer implemented method  400  for assisting an operator in endoscopic navigation of the steerable endoscope  110  towards a site in a patient. The computer in this case is preferably the one or more computers  200  that include the processors  130 ,  140 ,  150 . 
     In  401 , a patient computer model stored in memory  155  is referenced to a fixed reference frame (i.e., one that does not move during the medical procedure to be performed using the endoscope  110 ) by first referencing points on a live patient who is generally prone on an operating table with the fixed reference frame, then associating the referenced points with corresponding points on the patient computer model. 
     For example, using a pointer device whose tip position may be readily determined in the fixed reference frame (such as the endoscope&#39;s tip  112 ), the operator may move the pointer device so that it first touches the mouth of the patient to establish a first reference point corresponding to the mouth of the patient computer model. The operator may then move the pointer device so that it next touches the right and left crest of the iliac of the patient to establish a second reference point corresponding to the right and left crest of the iliac of the patient computer model. Other points such as the navel and the left and right arm pits may also be used to establish more reference points. By referencing the patient computer model to the patient in this manner, the proper size (i.e., length and width) of the patient computer model may also be established as well as its alignment with the patient and its position in the fixed reference frame. Thus, with just a few points, the patient computer model may be properly scaled and aligned (i.e., conformed) with the patient using model information in an anthropometry database in the memory  155 . 
     Several patient computer models may be stored in memory  155 . For example, a number of generic patient computer models may be stored so that a different model may be used depending on the age, sex, size, etc., of the patient. Preferably, each of the models is a three-dimensional computer model including at least a head and torso (such as seen in  FIGS. 7-9 ) so that all natural orifices are included as well as potential target sites for performing diagnostic or surgical procedures on a patient. Three-dimensional computer models of the actual patient may also be stored and used with the present system if available, such as may be generated using a Computed Tomography (CT) scan. Alternatively, the surgeon or assistant may move the distal tip  112  over the surface of the patient&#39;s body to map its profile and provide sufficient information to the position processor  130  to generate information for a three-dimensional computer model of the patient which it stores in the memory  155 . 
     In  402 , a determination is made whether or not the operator has issued a start guidance command. The operator may issue the start guidance command in any one of a number of ways such as depressing an input button or flipping a switch on the input device  303  when the steerable endoscope  110  is being controlled teleoperatively, or depressing an input button or flipping a switch on the handle  116  when the steerable endoscope  110  is being controlled manually. Other ways may include voice actuation using a microphone and voice recognition processor (not shown) that may be implemented in or operatively coupled to the one or more computers  200 ; a foot pedal (not shown) that may be depressed by the operator so as to turn on or off the guidance; and a graphical user interface using the auxiliary display screen  160 , the primary display screen  600  or another display screen (not shown) that the operator may interact with using an input device. 
     If the determination in  402  is NO (i.e., navigation guidance mode has not been initiated by the operator), then the method loops through  402  each process cycle (or other programmed cycle) until a YES determination is made, at which time, the method proceeds to  403 . 
     In  403 , the current position and shape (e.g., bending) of the endoscope  110  is determined by the position processor  130  using information received from one or more optical fibers configured with shape sensors that has been inserted in the flexible body  114  of the endoscope  110 . As an example of one such optical fiber, referring to  FIG. 5 , the distal end of an optical fiber  501  extends to the endoscope&#39;s tip  112  and its proximal end is attached to a base point  502  whose position in the fixed reference frame is known or readily determinable by the position processor  130 . Preferably, the position processor  130  is also attached or otherwise coupled to the base point  502  so that the processor  130  may receive information from the bend sensors of the optical fiber  501  at that point. 
     Since the length of the fiber optic cable  501  is known, its proximal end is fixed to a known location, and its distal end extends out to the endoscope&#39;s tip  112 , the current position and orientation of the tip  112  in the fixed reference frame may be readily determined from the current bending of the optical fiber  501  as indicated by information received from the bend sensors. Although only one fiber optic cable  501  is shown for illustrative purposes, multiple fibers or a single fiber with multiple cores configured with strain sensors are preferably employed for determining the shape of the endoscope body  114  and distal tip  112 , such as described using shape sensors in previously incorporated by reference U.S. 2007/0156019 A1, U.S. 2008/0212082 A1, and U.S. application Ser. No. 12/164,829. 
     In  404 , a computer model that is indicative of the current configuration of the flexible endoscope  110  is generated using a model of the endoscope stored in the memory  155  and modifying it to reflect the shape information received from the optical fibers configured as shape sensors. Preferably, both the stored and generated computer models of the endoscope  110  are three-dimensional models. 
     In  405 , the patient computer model generated in  401  and the endoscope computer model generated in  404  are displayed together properly registered with respect to each other according to their respective positions in the fixed reference frame on the auxiliary display screen  160 . Thus, the operator of the steerable endoscope  110  is provided a view of the current shape of the endoscope  110  relative to the patient&#39;s body in order to provide guidance to the operator for navigating the endoscope  110  to a target site within the patient. A visual indication of the target site may also be displayed as well as computer models or other indications of any anatomic structures or body lumens that the endoscope  110  may encounter or pass through in its path to the target site. 
     The manner in which the patient and endoscope computer models are displayed on the auxiliary display screen  160  is preferably selectable by the operator using any one or more of a number of well known techniques such as clickable icons and pull down menus provided on the auxiliary display screen  160  and/or primary display screen  600 . For example, icons may be provided on the auxiliary display screen  160  so that the operator may select an anterior-posterior view  750 , oblique view  751 , or lateral-medial view  752  of the patient and endoscope  110 , such as shown respectively in  FIGS. 7, 8 and 9 , by clicking on the appropriate icon using a computer mouse or other suitable device. 
     Referring to  FIG. 7 , the anterior-posterior view  750  of the patient computer model  720  and endoscope computer model  710  is shown along with indications of various landmarks along the endoscope&#39;s path (e.g., mouth entry, esophagus, stomach entry, and colon) on the auxiliary display screen  160 . In addition, real-time images captured by the endoscope  110  (such as the captured image  650  shown in  FIG. 6  being displayed on a primary display screen  600 ) may also be displayed on the auxiliary display screen  160  adjacent to (or appearing to emanate from) the distal end  711  of the endoscope computer model  710 . 
     In addition to (or alternative of) displaying the patient and endoscope computer models,  720  and  710 , on the auxiliary display screen  160 , the computer models may be displayed on the primary display screen  600  along with the captured image  650 . For example, the oblique view  751  may be shown as a picture-in-picture insert to the captured image  650  on the primary display screen  600  as shown in  FIG. 10  or it may be shown in an adjacent window to that of the captured image  650  on the primary display screen  600  as shown in  FIG. 11 . 
     Referring back to  FIG. 4 , in  406 , a determination is made whether or not the operator has issued a stop guidance command. The operator may issue the stop guidance command in any one of a number of ways similar to, but complementary of those in which the operator issues the start guidance command. 
     If the determination in  406  is NO (i.e., navigation guidance mode has not been stopped by the operator), then the method loops back to  403  to update the current position and bend of the endoscope  110  and display a computer model of it along with the computer model of the patient for the next process cycle (or other programmed cycle). On the other hand, if the determination in  406  is YES (i.e., navigation guidance mode has been stopped by the operator), then the method proceeds to  407  in which the display processor  150  either causes the computer models of the patient and endoscope to no longer be displayed on the auxiliary display screen  160  and/or primary display screen  600  or freezes them on the display screen. 
     During the whole endoscopic procedure, starting from the insertion of the endoscope  110  in the patient&#39;s body, the proposed method and invention stores in the memory device  155  digital versions of images periodically captured by the camera  141  (at the distal tip  112  of the endoscope  110 ) together with the three-dimensional (3-D) position and orientation information of the camera  141  (as determined by the position processor  130 ) with respect to the patient anatomy at the times (e.g., at a processing rate of 30 HZ) that the images were captured. Timestamps indicating the times are also stored in the memory device  155 . The resulting database provides endoscopic images tagged by their respective 3-D locations in the fixed reference frame that can be accessed at any successive time by the display processor  150  for the purpose of computing synthetic two-dimensional (2-D) and three-dimensional (3-D) views of the visited anatomy. Thus, a full recording of the endoscopic procedure may be stored in the memory device  155  (preferably a mass storage device, such as a hard drive, for this application) that may be played back on the display screens  600  and  160  for educational and/or archival purposes. 
     A first synthetic 2-D view can be computed by assembling (stitching together) multiple endoscopic images taken from neighboring 3-D locations into a single larger panoramic image according to the well known Computer Vision technique known as mosaicking (see for instance the seminal work by R. Szeliski, H. Y. Shum, Creating full view panoramic image mosaics and environment maps, In  Proc. of ACM SIGGRAPH,  1997.) Endoscopic panoramas allow improved endoscopic navigation by providing a larger field of view then the endoscopic camera is capable of hence delivering greater awareness of the surrounding anatomy to the surgeon. Thus, the captured images shown in various figures herein on the primary display screen  600  are preferably panoramic images generated by the display processor  150  by mosaicking images retrieved from the memory device  155  which are representative of the most recently captured images by the camera  141 . 
     As an additional endoscopic navigation tool, graphical indications showing steering directions to previously defined landmarks in the patient are also provided as an aspect of the present invention. 
       FIG. 12  illustrates, as an example, a flow diagram of a computer implemented method  1200  for providing directional guidance to maneuver the steerable endoscope  110  to one or more landmarks in a patient. The computer in this case is preferably the one or more computers  200  that include the processors  130 ,  140 ,  150 . 
     In  1201 , a determination is made whether or not the operator has turned on a landmarks directional guidance mode. The operator may turn on and/or off this mode in any one of a number of ways such as depressing an input button or flipping a switch on the input device  303  when the steerable endoscope  110  is being controlled teleoperatively, or depressing an input button or flipping a switch on the handle  116  when the steerable endoscope  110  is being controlled manually. Other ways may include voice actuation using a microphone and voice recognition processor (not shown) that may be implemented in or operatively coupled to the one or more computers  200 ; a foot pedal (not shown) that may be depressed by the operator so as to turn on or off the mode; and a graphical user interface (GUI)  202  using the display screen  600  that the operator may interact with using an input device  201  as shown in  FIG. 2  to turn on and off the mode as well as specify other aspects or parameters of the method as described herein. 
     If the determination in  1201  is NO (i.e., landmark directional guidance is turned off), then the method loops through  1201  each process cycle (or other programmed cycle) until a YES determination is made, at which time, the method proceeds to  1202 . 
     In  1202 , the current position of the endoscope tip  112  in a fixed reference frame (i.e., a reference frame that does not move during the performance of a medical procedure using the endoscope  110 ) is determined by the position processor  130  using information received from the optical fibers configured with strain sensors (e.g., optical fiber  501  in  FIG. 5 ) that have been inserted in the flexible body  114  of the endoscope  110 . 
     The current position and orientation of the endoscope tip  112  may be readily determined in the fixed reference frame (for example, as previously explained in reference to  403  of  FIG. 4 ) from the current bending of the optical fibers as indicated by information received from their strain sensors since their lengths are known, their proximal ends are fixed to a known location (such as fiber  501  to base point  502  as shown in  FIG. 5 ), and their distal ends extend to the endoscope&#39;s tip  112 . 
     In  1203 , a vector connecting the current position of the endoscope tip  112  to the position of each landmark to which guidance indications are to be provided is determined by the display processor  150  using the endoscope tip position determined in  1202  and landmark positions stored in the memory device  155 . 
     Typically, the landmarks are established by the operator as he or she guides the steerable endoscope  110  along its path from an entry point to a target site in the patient. As an example,  FIG. 14  shows an oblique view of a patient&#39;s head and torso where the steerable endoscope  110  has entered through the patient&#39;s mouth and its tip  112  guided to a target site. In this example, the endoscope  110  has been guided through the esophagus to the patient&#39;s stomach. The stomach was then entered and the endoscope  110  guided to the target site. Along the way, landmarks are established at the mouth entry and stomach entry using a method such as described below in reference to  FIG. 13 . 
     Alternatively, the positions of landmarks within the patient may be based upon preoperative measured data such as generated by Computer Axial Tomography (CAT), Magnetic Resonance Imaging (MRI), or X-rays. In this case, the patient&#39;s body (as he or she is lying down on the operating room table) is referenced to the fixed reference frame and the landmarks are registered with the patient&#39;s body so that their positions are determinable in the fixed reference frame by their respective positions in the patient&#39;s body. The landmark positions are then stored in the memory device  155  (or other storage device accessible to the display processor  150 ). Although establishing landmarks in this manner may be time consuming and expensive, it allows the method described herein to provide directional guidance to landmarks in front of the endoscope tip  112  (i.e., between the current position of the endoscope tip and the target site), not just behind it (i.e., between the entry point into the patient and the current position of the endoscope tip). 
     In  1204 , the vectors determined in  1203  are then transformed from the fixed reference frame to a reference frame associated with the endoscope tip  112  (or camera  141 ) by the display processor  150 . 
     In  1205 , 3-D arrows (or other graphical representations) indicative of the transformed vectors determined in  1204  are generated by the display processor  150 . The directions of the 3-D arrows are referenced to the endoscope tip&#39;s reference frame so that they correspond to directions that the operator should steer the endoscope&#39;s tip  112  using the handle or electromechanical interface  116  as previously described. 
     The sizes of the 3-D arrows, on the other hand, may be generated so as to be proportional to the magnitudes of the translated vectors so that landmarks further away are represented by larger arrows. As an alternative, the sizes may be generated so as to be inversely proportional to the magnitudes of the translated vectors so that landmarks further away are represented by smaller arrows. As yet another alternative, the sizes may be generated so as to each have the same length (such as shown by arrows  1511 ,  1512  and  1513  in  FIG. 15 ). 
     The 3-D arrows may also be color-coded so that the color of each arrow is uniquely associated with a particular anatomic structure. For example, referring to  FIG. 15 , a 3-D arrow  1511  indicating a steering direction towards the mouth entry landmark may be colored red, a 3-D arrow  1512  indicating a steering direction towards the stomach entry landmark may be colored yellow, and 3-D arrow  1513  indicating a steering direction towards the colon entry landmark may be colored blue. Alternatively, the edges of the display screen  600  may be colored to correspond to landmarks. The color schemes used herein may be operator defined or correspond to the color scheme used on MR viewers. 
     In  1206 , the 3-D arrows (or other graphical representations) generated in  1205  and a current image (as currently captured at the endoscope tip  112  and processed by the image processor  140  or a panoramic image as previously described using mosaicking of the current and previously captured images) are displayed on the primary display screen  600  by the display processor  150 . In addition, previously captured images of the landmarks may also be selectively or automatically retrieved from the memory device  155  and displayed adjacent or otherwise proximate to their respective 3-D arrows. The positions of the 3-D arrows may be displayed on the display screen  600  so as to relate to the orientations of the translated vectors so that, for example, arrows pointing to the left are positioned on the left side of the image and arrows pointing to the right are positioned on the right side of the image. Alternatively, the 3-D arrows may all be positioned near the same side of the image or spaced around the image. In the case where edges of the display screen  600  may be colored to correspond to landmarks, the 3-D arrow corresponding to each landmark is displayed adjacent its respective colored edge so that the association of the 3-D arrow and landmark is clear. 
     In addition to showing the landmarks as 3-D arrows on or near the current endoscope image on the primary display screen  600 , the landmarks can be displayed together with the 3-D patient and endoscope computer models being displayed on the auxiliary display screen  160  wherein positions of stored landmarks may be shown in their proper locations relative to the patient computer model. The landmarks may be indicated, for example, by a text label with the landmark name, a thumbnail image with the stored endoscope image captured with the landmark, a small graphic icon related to the type of landmark, or with an approximate 3-D model of the landmark. 
     Selection of which, if any, landmark images are to be displayed may be made by the operator, for example, using the input device  201  and GUI  202  to select one display option from a menu including: all landmark images to be displayed, no landmark images displayed, and only nearest landmark image to be displayed. Alternatively, the operator may not be provided an option and the choice pre-selected and programmed into the display processor  150 . Position, size, color and other options for displaying the 3-D arrows on the display screen  600  may be selected by the operator using the input device  201  and GUI  202  as shown in  FIG. 2 . 
     As an example of such displaying,  FIG. 15  shows the display screen  600  having a current image  1501  (i.e., an image currently captured by the endoscope  110  or a panoramic image as described elsewhere herein) displayed on it along with arrows  1511 ,  1512  and  1513  respectively providing directional guidance to the mouth entry, stomach entry and colon entry landmarks. In addition, a previously captured image  1523  of the colon entry landmark is shown being displayed in a window adjacent to its associated arrow  1513 , which happens to be the nearest landmark to the current position of the endoscope tip  112 . 
     In  1207 , a determination is made whether or not the operator has turned off the landmark directional guidance mode. The operator may turn off the mode in any one of a number of ways similar to, but in an opposite manner of those in which the operator turned on the landmark guidance mode (e.g., placing a switch in an “off” vs. “on” position). 
     If the determination in  1207  is NO (i.e., landmark directional guidance mode has not been turned off by the operator), then the method loops back to  1202  to update the landmark directional vectors (e.g.,  1511 ,  1512 ,  1513  in  FIG. 15 ) as the endoscope tip  112  is being guided to the target site and display updated graphical representations of the translated vectors on the display screen  600  along with a current image captured by the endoscope  110 . On the other hand, if the determination in  1207  is YES (i.e., landmark direction guidance mode has been turned off by the operator), then the method proceeds to  1208  in which the display processor  150  causes the graphical representations of the translated vectors and any corresponding landmark captured images to no longer be displayed on the display screen  600 . 
     It is to be appreciated that even though landmark directional guidance mode may be turned off, the operator may still be guiding the steerable endoscope  110  towards the target site and continually updated images captured at the endoscope tip  112  (and processed by image processor  130 ) may still be displayed on the display screen  600  by the display processor  150 . For example, referring to  FIG. 15 , the display screen  600  may still have the current or panoramic image  1501  displayed on it, but the arrows  1511 ,  1512 ,  1513  and landmark image  1523  are no longer displayed after the operator turns off the landmark directional guidance mode. 
     It is also to be appreciated that the operator may interactively establish landmarks for which directional guidance is to be provided at any time while guiding the steerable endoscope  110  towards the target site. In particular, landmark establishment may be performed while landmark directional guidance mode is turned on as well as off. 
       FIG. 13  illustrates, as an example, a computer implemented method  1300  for establishing anatomic structure landmarks as the steerable endoscope  110  is being guided through a patient&#39;s body. As in the case of the method  1200  described in reference to  FIG. 12 , the computer in this case is preferably the one or more computers  200  that include the processors  130 ,  140 ,  150 . In particular, it is preferably performed by the display processor  150  concurrently with other activities performed by the display processor  150  as described herein. 
     In  1301 , a landmark establishment request is received from the operator. The operator may initiate the request in any one of various well known interactive techniques including those previously described in reference to turning on and off the landmark directional guidance mode (but preferably a different one so as not confuse the two actions). 
     In  1302 , the current position of the endoscope tip  112  in the fixed reference frame is determined. Note that if the landmark directional guidance mode is turned on, this action is the same as  1202  of method  1200  and therefore, it does not have to be performed since the result from  1202  may be used in this case (i.e., it does not have to be performed a second time or twice in the same process cycle). 
     In  1303 , the current position of the endoscope tip  112  is then stored in the memory device  155  and referenced as the position of the landmark whose establishment has been requested. In  1304 , a current image captured at the endoscope tip  112  is identified as an image of the landmark and in  1305 , information of the image is also stored in the memory device  155  and referenced as the image of the landmark whose establishment has been requested. 
     As may be appreciated in performing the method  1300 , the order in which actions  1302  and  1304  occur is not important. In fact, the image processor  140  may process captured images at a different rate than that in which the position processor  130  determines current positions of the endoscope tip  112 . Therefore, the two actions may differ in the time as well as in the order in which they may each occur. In any event, upon receiving the landmark establishment request in  1301 , the next determined position of the endoscope tip  112  is stored in the memory device  155  and the next captured image received from the image processor  130  is stored in the memory device  155  without concern about which one occurs first. 
     In addition to the establishment of landmarks while navigating the endoscope  110  towards a target site within the patient, anatomic structures (such as the esophagus, stomach, colon, etc.) may be measured using position information of the endoscope tip  112  as it moves from one end of the anatomic structure to the other. Information of the measured anatomic structure may than be used to align and size 3-D models or preoperative measured data of the anatomic structures to their proper positions inside the patient&#39;s body and display the structures together with the 3-D patient computer model on the auxiliary display screen  160 . As an example,  FIG. 14  shows how the measured positions of the mouth and stomach entry landmarks have been used, together with the intermediate shape of the endoscope, to align and size a 3-D model of the esophagus connecting the mouth to the stomach entry. The esophagus model is then displayable as a 3-D curved tube  1401 , together with the 3-D models of the patient and the endoscope  110  on the auxiliary display screen  160 . 
     Although the various aspects of the present invention have been described with respect to one or more preferred embodiments, it will be understood that the invention is entitled to full protection within the full scope of the appended claims.