Abstract:
Navigation through a network of body passages, such as through the airways, is improved by a method of displaying information which provides a fly-through visualization of the passageway. As landmarks or waypoints are passed, the view changes to a next segment in a planned pathway to a target. Such a visualization technique avoids tunnel vision, such as that encountered while using real-time endoscopes.

Description:
RELATED APPLICATIONS 
       [0001]    This application claims priority to U.S. Provisional Application Ser. No. 61/028,098 filed Feb. 12, 2008 entitled Controlled Perspective Guidance Method, which is hereby incorporated herein by reference. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    Identifying and treating lung tissue abnormalities presents challenges that are somewhat unique to the lungs. If a tissue lesion or tumor is to be identified and excised surgically, the chest wall must be opened to provide access to the lungs. Opening the chest wall is a common procedure but one that presents risks of infection and lengthy recovery time, nonetheless. 
         [0003]    A desirable alternative to surgery, in terms of reducing patient trauma, is to identify and excise the tumor endoscopically. Endoscopic surgery in the lungs, however, means that the complicated bronchial maze must be navigated. Endoscopes have cameras at their distal tips that provide a physician a real-time image through the end of the endoscope while the endoscope is being advanced through the bronchial system. However, typical endoscopes are too wide to be advanced deep into the lungs as the diameters of the airways decrease toward the alveoli. 
         [0004]    In order to assist in navigating deep in the lungs, systems, such as that described in U.S. Pat. No. 7,233,8202, incorporated herein in its entirety, have been developed that include a sensor at the distal tip of a probe. The sensor interacts with a field generator to provide a real-time indication of its location in a three-dimensional space encompassing the lungs. The real-time indication is superimposed on a computer image of the bronchial tree (known as a “virtual bronchial tree”) so that the location indication generated by the sensor is useful to the physician. 
         [0005]    Heretofore, the location data has been presented to the physician as though the sensor is actually an endoscope. Hence, the virtual bronchial tree image is presented from the perspective of the tip of the sensor and as the sensor is advanced, the image of the virtual bronchial tree moves past the sides of the sensor and disappears. 
         [0006]    The difficulty when viewing navigation progress in this manner, as is true with an endoscope as well, is that the physician has tunnel vision. No peripheral vision is available. Thus, if the end of the sensor is adjacent a branch, the branch may not appear on the screen. The physician wanting to see to the sides of the endoscope or, in the virtual sense, the sensor, must either retract the probe or turn it in the direction of the branch. 
         [0007]    This visualization problem becomes even more confusing when considering first that the sensor is moving with the cardiac rhythm and breathing cycle of the patient and second that the sensor often twists when the steering mechanism is activated. The cardiac rhythm and breathing cycle cause jittering of the virtual image, which can be very disorienting. With regards to the use of the steering mechanism, most steerable probes have a tip that can be turned in one to four directions. This means that in order to turn the tip in a desired direction, it may be necessary to rotate the tip around its longitudinal axis up to 180 degrees prior to deflection. This will cause the image being viewed to flip and then turn. The physician can easily become disoriented after a few turns while trying to navigate to a lesion. 
         [0008]    There is a need to provide more useable data display for use in navigating a probe through a virtual bronchial tree. 
       SUMMARY OF THE INVENTION 
       [0009]    The system and method of the present invention provides more useable visual presentation to a physician using an intra-body navigation system. Generally, the system and method of the present invention uses a system of planned waypoints along a planned route through the bronchial tree in order to incrementally advance the image presented to the physician. 
         [0010]    Thus, a physician using the system and method of the present invention will see an image of the bronchial tree and an image of the sensor being advanced through the airways to a subsequent waypoint. Once the sensor has reached the next waypoint and has been turned down an appropriate branch, the image perspective will be advanced to that next waypoint. Rather than the images being presented as though there were a camera mounted on the sensor, which may be moving in a chaotic, erratic fashion, the images of the virtual bronchial tree are presented in a controlled manner, for example as though cameras are mounted on each of the waypoints. 
         [0011]    In one embodiment, rhythmic movement (movement caused by the breathing cycle, cardiac cycle, or patient movement) is visualized by tying the perspective of the video image to the visible portion of the bronchial tree such that there is no viewable relative movement between the “camera” and the bronchial tree. Rather, all rhythmic movement is visualized by showing movement of the probe. Hence, if the bronchial tree moves in such a manner that it affects the relative position of the probe within the airways, the probe is seen as moving. This provides the physician with a more accurate perception of the location of the probe. 
         [0012]    In another embodiment, calculations and visualization are simplified by incorporating the reality that while the probe is being advanced through a section of the airways that contains no branches, the probe will be automatically guided by the sidewalls of the airway. Hence, no particularly useful information is gleaned from an image that is showing rhythmic movement. In this embodiment, a simplified view of the sensor being advanced through the center of the airway is provided until the sensor reaches a fork. Once the fork is reached, the probe will be shown as veering down one of the available branches. In this way, the physician knows which branch the probe has entered. A preferred aspect of this embodiment provides a highlighted representation of the target branch, as determined in a pre-operative planning stage. 
         [0013]    In another embodiment, the airway is represented by a simple tunnel with the next waypoint or branch highlighted somehow. As the probe is advanced, the highlighted waypoint increases in size to simulate getting closer. As the probe appears to pass the highlighted waypoint, the view switches, either manually or automatically, to a new airway with the next waypoint highlighted in the distance. 
         [0014]    In yet another aspect of the present invention, an overlay or second window is displayed giving a schematic diagram of the bronchial tree and the entire path to the target shown. Preferably, an indication of the present sensor location is shown, thereby providing the physician with an indication of the probe&#39;s progress towards the target. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0015]      FIG. 1  is a diagram of an example of a location system that may be used with the present invention; and 
           [0016]      FIGS. 2-22  are examples of displayed images of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0017]    Referring now to the figures and first to  FIG. 1 , there is shown a location system  10 . Though the navigation display system and method of the present invention may be used with any location system having virtual capabilities, a description of a location system  10  is provided by way of example. 
         [0018]    The location system  10  generally includes a locatable guide  20 , a location board  40 , and a control system  80 . The locatable guide  20  is a probe having a receiver that generally includes a plurality of (preferably three) field component sensors  22 ,  24  and  26 . Each of the field sensor components is arranged for sensing a different component of an electromagnetic field generated by the location board  40 . 
         [0019]    The location system  10  also includes the location board  40 . The location board  40  is a transmitter of electromagnetic radiation. The location board  40  includes a stack of three substantially planar rectangular loop antennas  42 ,  44  and  46  connected to drive circuitry  48 . Drive circuitry  48  includes appropriate signal generators and amplifiers for driving each of the loop antennas  42 ,  44  and  46  at their corresponding frequencies. The electromagnetic waves generated by the location board  40  are received by the locatable guide  20  and converted into electrical signals that are then sent to the control system  80 . 
         [0020]    The control system  80  generally includes reception circuitry  82  and a display  86 . The reception circuitry has appropriate amplifiers and A/D converters. The reception circuitry  82  and the driving circuitry  48 , which may be considered part of the control system  80 , are controlled by a controller/processor  84  that typically is an appropriately programmed computer. The controller/processor  84  directs the generation of transmitted signals by driving circuitry  48 . The controller/processor  84  also generates video signals, which are sent to the display  86 . 
         [0021]    Having introduced the basic system  10  on which the present invention is practiced, attention can now be focused on the manner in which the controller/processor  84  presents information on the display  86 . 
         [0022]    Preferably, all of the embodiments of the present invention have the ability to display an overview of the bronchial tree. This overview may be obtained from subjective sources such as CT images or objective sources such as medical atlases, etc. An example of such an overview  100  is provided in  FIG. 2 . The overview  100  may be displayed on a split screen or on a separate monitor. The overview may also be presented in a separate window on the display  86  but it is likely that a physician would benefit from being able to constantly monitor the overview  100 . The overview  100  includes an indication of a targeted lesion  102  and a path  104  to the lesion  102 . The path  104  is determined in a pre-operative planning stage, either manually or automatically, or a combination thereof (semi-automatically, for example). 
         [0023]    The path  104  includes a plurality of waypoints or turning points  106   a - d  enroute to the lesion  102 . Navigation to these waypoints  106   a - d  is supplemented by identifiable anatomical landmarks  107   a - e , typically bifurcations, trifurcations, or forks. 
         [0024]    During navigation to the target lesion  102 , an virtual interior view of the airway will be displayed along with the overview  100 . This interior view may be realistic, constructed from CT scans, for example, or may be very basic (schematic). Additionally, this may be presented as a perspective or parallel geometric view (i.e. with or without a vanishing point). Hence, in a preferred embodiment,  FIGS. 3 ,  5 ,  7 ,  9 ,  11 ,  13 ,  15 , and  17 - 22  show an interior display which will be presented with the overview  100 . Various embodiments of the present invention will be demonstrated using the same path  104  and target lesion  102  from  FIG. 2 . 
         [0025]    A first embodiment is shown in  FIGS. 3-16 . In this embodiment, the display is shown from a viewpoint just over or beyond the distal tip of the locatable guide. The display remains centered in the airway and does not twist or otherwise move with the movement of the locatable guide except in an axial direction.  FIG. 3  shows the first landmark  107   a  and the first waypoint  106   a . Because the waypoints are turning points and not (necessarily) physical landmarks, the waypoints may be displayed as suspended points that indicate to the physician that upon reaching the waypoint, the physician needs to steer the probe in the next direction. Alternatively, the waypoints need not be displayed. In order to ease navigation, the correct airway will be highlighted somehow, as shown. Optionally, the highlighted airway could change color or blink when the probe reaches the waypoint to indicate a direction change is needed. To further assist with navigation, the position of the locatable guide is shown as an arrowhead  108 , or some other indication, on the overview  100  as shown in  FIG. 4 . 
         [0026]      FIG. 5  shows that as the locatable guide is advanced the features of the bifurcation marked as landmark  107   a  grow larger, indicating that the locatable guide is nearing the waypoint  106   a . The airway along the path remains highlighted to assist the physician in navigating to the lesion  102 . Also, as seen in  FIG. 6 , the arrowhead  108  continues to advance along the path. It is envisioned that the arrowhead  108  may always be depicted along the desired path, thereby providing only an indication of how far along the path the locatable guide has been advance, or more preferably, the arrowhead may float independent of the path, thereby providing indication of the location of the locatable guide in the event that the physician has advanced the tip of the probe down an incorrect airway. 
         [0027]    After the probe has passed through the opening of the correct airway, the view changes to that shown in  FIG. 7 , with the next waypoint  106   b  highlighted and an adjacent landmark  107   b  in the distant field view. Optionally, a more distant bifurcation  110  is depicted, giving depth to the perspective view of the airway. This bifurcation labeled for reference purposes in  FIG. 8 , which corresponds to the view in  FIG. 7 . The arrowhead  108  is still visible in  FIG. 8  but has not advanced considerably past its position in  FIG. 6 , because crossing the threshold of a waypoint to a different view may be accomplished with a minute actual advancement of the locatable guide. 
         [0028]      FIG. 9  shows the steady growth of the features  110 ,  107   b  and  106   b  as the locatable guide is advanced.  FIG. 10  shows that the arrowhead  108  is close to approaching the waypoint  106   b.    
         [0029]    Upon passing waypoint  106   b , the view changes to that shown in  FIG. 11 . Landmark  107   c  is visible with the correct airway containing waypoint  106   c  highlighted.  FIG. 12  is the corresponding overview  100  with arrowhead  108  located just past waypoint  106   b  and pointing in the direction of the next waypoint  106   c.    
         [0030]    Upon passing landmark  107   c , the view changes to that shown in  FIG. 13 . Landmark  107   d  is visible with the correct airway highlighted. Notably, waypoint  106   c  has not yet been reached and still appears in the distance. This illustrates that landmarks may be used as trigger points to update the views. This is useful for long straight passages that result in passing several anatomical features. Alternatively, only waypoints may be used as trigger points.  FIG. 14  shows that the arrowhead has advanced past waypoint  106   c.    
         [0031]      FIG. 15  provides the view after passing landmark  107   d  and corresponds with the overview  100  shown in  FIG. 16 . Optionally, the target  102 , which is now visible, is highlighted in a different color or pattern than the various waypoints. It is also preferable to provide an indication when the tip of the probe is within an operational proximity to the target  102 , such that the physician knows that the appropriate task (biopsy, ablation, excision, etc.) may be performed without further advancing or orienting the probe. 
         [0032]    Another presentation embodiment is shown in  FIGS. 17-22 . In this embodiment, rather than indicating the advancement of the probe by producing a growing effect for the various features, a virtual image of the probe itself is provided and the viewpoint remains fixed just beyond each waypoint. Optionally, the physician may be given the option to advance the waypoint manually, in the event that two waypoints are spaced apart such that the image of the next waypoint is difficult to see. 
         [0033]      FIG. 17  shows the first landmark  107   a  and the tip of the locatable guide or probe  112 . In order to ease navigation, the correct airway will be highlighted somehow, as shown. To further assist with navigation, the position of the locatable guide is shown as an arrowhead  108 , or some other indication, on the overview  100  as shown in  FIG. 4 . 
         [0034]      FIG. 18  shows that as the locatable guide is advanced the features of the bifurcation marked as landmark  107   a  remain the same size, but more of the probe  112  becomes visible, as though the probe  112  is advancing past and away from the viewpoint. The probe  112  is approaching the waypoint  106   a  and the physician can see that the probe  112  is turned toward the correct airway. Also, as seen in  FIG. 6 , the arrowhead  108  continues to advance along the path. It is envisioned that the arrowhead  108  may always be depicted along the desired path, thereby providing only an indication of how far along the path the locatable guide has been advance, or more preferably, the arrowhead may float independent of the path, thereby providing indication of the location of the locatable guide in the event that the physician has advanced the tip of the probe down an incorrect airway. Preferably, as shown in  FIG. 19 , in the event that the probe  112  is advanced down an incorrect airway, the viewpoint will not change to the next viewpoint. Rather, the probe  112  remains visible and is shown as advancing down the incorrect airway. This provides the physician with an easily understood indication that the probe should be retracted and advanced down the illuminated or highlighted airway. Preferably, the virtual probe  112  is constantly representative of the position and orientation of the actual probe. 
         [0035]    After the probe has passed through the opening of the correct airway, the view changes to that shown in  FIG. 20 , with the next waypoint  106   b  highlighted in the distant field view. Optionally, a more distant bifurcation  110  is depicted, giving depth to the perspective view of the airway. This bifurcation labeled for reference purposes in  FIG. 8 , which corresponds to the view in  FIG. 20 . The arrowhead  108  is still visible in  FIG. 8  but has not advanced considerably past its position in  FIG. 19 , because crossing the threshold of a waypoint to a different view may be accomplished with a minute actual advancement of the locatable guide. 
         [0036]      FIG. 21  shows the advancement of the probe  112  to a point where the probe may be steered toward the highlighted airway. Preferably, as the probe is steered, the virtual probe  112  is depicted as deflecting in the direction that the actual probe is deflected.  FIG. 10  shows that the arrowhead  108  is close to approaching the waypoint  106   b.    
         [0037]      FIG. 22  provides the view after passing waypoint  106   c  and corresponds with the overview  100  shown in  FIG. 16 . Optionally, the target  102 , which is now visible, is highlighted in a different color or pattern than the various waypoints. It is also preferable to provide an indication when the tip of the probe is within an operational proximity to the target  102 , such that the physician knows that the appropriate task (biopsy, ablation, excision, etc.) may be performed without further advancing or orienting the probe. Alternatively, as shown in  FIG. 22 , the probe  112  itself is highlighted to show that the probe is in operational proximity to the target lesion  102 . 
         [0038]    Although the invention has been described in terms of particular embodiments and applications, one of ordinary skill in the art, in light of this teaching, can generate additional embodiments and modifications without departing from the spirit of or exceeding the scope of the claimed invention. For example, it is envisioned that the controlled perspective imaging method of the present invention could be used with a system that uses a navigation device other than a locatable guide, such as an optical navigation system. Using inputs such as identifiable landmarks and bronchoscope depth, through image processing the display method of the present invention could be utilized to provide a more user-friendly navigational interface. Accordingly, it is to be understood that the drawings and descriptions herein are proffered by way of example to facilitate comprehension of the invention and should not be construed to limit the scope thereof.