Abstract:
To improve the overall navigation process for minimally invasive repair of heart valve leaflets, an augmented reality technique capable of providing a robust three-dimensional context for transesophogeal echocardiography data has been developed. In the context of various embodiment of the invention, augmented reality essentially refers to a system in which the primary environment is virtual but the environment is augmented by real elements. In this real-time environment, the surgeon can easily and intuitively identify the tool, surgical targets, and high risk areas, and view tool trajectories and orientations.

Description:
RELATED APPLICATION 
     The present application claims the benefit of U.S. Provisional Application No. 61/565,795 filed Dec. 1, 2011, which is incorporated herein by reference. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to minimally invasive repair of heart valve leaflets. More particularly, the present invention relates to surgical navigation systems for minimally invasive repair of heart valve leaflets. 
     BACKGROUND OF THE INVENTION 
     Degenerative mitral valve disease (DMVD) is a common heart valve disorder in which there is incomplete valve closing, often resulting in shortness of breath, fluid retention, heart failure and premature death. DMVD is characterized by abnormal connective tissue of the mitral valve, resulting in weakening and rupture of the chordae tendonae (chords), the support structures of the mitral valve, preventing its natural closure. DMVD affects about 2% of the general population and severe, symptomatic DMVD is treated by surgical repair or replacement. Major advances in mitral repair surgery have improved short- and long-term outcomes of patients with this disease. Many such procedures can also benefit individuals having functional mitral valve disease. 
     Open heart cardiac surgery is highly invasive with a long recovery period, and not well tolerated by elderly or co-morbid patients. Recent innovations in minimally invasive and robotic mitral repair techniques employ sternal sparing approaches to reduce the invasiveness of the procedure, but still require the use of cardiopulmonary bypass which has many associated complications. While the emerging field of transcatheter mitral valve repair avoids the risks of conventional surgery and potentially offers hopes of beating heart mitral valve reconstruction, concerns about residual mitral insufficiency, durability and inadequate mitral valve repair have been raised. 
     Devices capable of performing off-pump, mitral valve repair for certain forms of DMVD, such as those disclosed in U.S. Patent Publication Nos. 2008/0188873, 2010/0174297, 2009/0105279 and 2009/0105751, have recently been developed. Such devices can use trans-apical access to approach and capture the prolapsed portion of the mitral valve leaflet, attach a suture and anchor it at the apex, constraining the flailing leaflet and eliminating the prolapse. Currently, this procedure relies exclusively on trans-esophageal echocardiography (TEE) guidance in the form of 2D single plane, bi-plane, and 3D imaging. While TEE has thus far proven adequate for the final positioning of the tool and grasping the leaflet, there have been concerns relating to the navigation of the tool from the apex to the target MV leaflet. TEE guidance can be problematic as it may not always be possible to maintain appropriate spatial and temporal resolution in 3D, and it may not always be possible using single 2D and 2D bi-plane views to simultaneously maintain both the tool tip and target site in the field of view. Using 2D echo it also can be difficult to ensure that the tool tip, rather than a cross section of the tool shaft, is visualized. Due to these navigation challenges, the tool can become caught in the region below the valve leaflet, risking leaflet perforation. 
     After extensive animal studies, the devices described in the above-referenced publications are currently undergoing preliminary in-human trials for the repair of flailing mitral valves. The procedure uses off-pump trans-apical left ventricle (LV) access. Correct leaflet capture is verified using a fiber-optic based detection mechanism. After leaflet capture has been verified, an ePTFE (expanded polytetrafluoroethylene) suture is pulled through the leaflet and the tool is retracted with both ends of the suture. The suture is fixed at the leaflet with a girth hitch knot, adjusted under Doppler echo to ensure minimum mitral regurgitation (MR) and then secured at the apex using a pledget. Multiple neochordae are typically used to ensure optimal valvular function. The single largest problem in navigating the device to the MV target region is that echo imaging must simultaneously keep the target region (MV line of coaptation) and the tool tip in view. 
     As noted above, traditional approaches for repairing and replacing mitral valves have relied on placing the patient on cardiopulmonary bypass (on-pump) and accessing the arrested heart directly via a median sternotomy. However, because this approach has the potential for major undesired neurological, vascular and immunological sequalae, there is a push towards performing such procedures in a minimally-invasive fashion. Preliminary experience on animals and humans has indicated that ultrasound guidance alone is often not sufficient for minimally invasive procedures. It would therefore be desirable for a system to provide enhanced surgical guidance in such minimally invasive procedures for repairing patient heart valves. 
     SUMMARY OF THE INVENTION 
     To improve the overall navigation process for minimally invasive repair of heart valve leaflets, an augmented reality technique capable of providing a robust three-dimensional context for transesophogeal echocardiography data has been developed. In the context of various embodiment of the invention, augmented reality essentially refers to a system in which the primary environment is virtual but the environment is augmented by real elements. In this real-time environment, the surgeon can easily and intuitively identify the tool, surgical targets, and high risk areas, and view tool trajectories and orientations. 
     In one embodiment, a surgical navigation system is provided to aid in conducting a heart valve repair procedure. System can include a heart valve repair device and medical imaging system including an imaging probe to provide real-time imaging of the anatomy of the patient. A tracking system can include one or more sensors incorporated into the heart valve repair device and imaging probe to track location and orientation data of those devices in real-time three-dimensional space. A computer processor can receive the imaging data from the imaging system and the location and orientation data from the tracking system and can also create virtual geometric models of the heart valve repair system and the imaging probe. At least one display device can present the virtual geometric models overlain onto the real-time imaging data in a common coordinate system showing the models moving in real-time based on the location and orientation data from the tracking system. 
     In a further embodiment, a surgical navigation system for use in aiding a surgical procedure can be provided. At least one sensor can be incorporated into an imaging probe of a medical imaging system and a heart valve repair device. Real-time imaging data can be acquired by the imaging system with the imaging probe. Virtual geometric models of the imaging probe and the heart valve repair device are also created. The virtual geometric models can then be overlain onto the imaging data in a common coordinate system. The location and orientation of the imaging probe and the heart valve repair device can subsequently be displayed in real-time three-dimensional space with tracking information obtained by the sensors. 
     The above summary of the various embodiments of the invention is not intended to describe each illustrated embodiment or every implementation of the invention. This summary represents a simplified overview of certain aspects of the invention to facilitate a basic understanding of the invention and is not intended to identify key or critical elements of the invention or delineate the scope of the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
       The embodiments of the present invention may be more completely understood in consideration of the following detailed description of various embodiments in connection with the accompanying drawings, in which: 
         FIG. 1  is a schematic representation of a surgical navigation system according to an embodiment of the present invention. 
         FIG. 2  is a perspective view of a surgical navigation system according to an embodiment of the present invention. 
         FIG. 3  is a partial view of a transesophageal echocardiogram probe that can be used with a surgical navigation system according to an embodiment of the present invention. 
         FIG. 4  is a perspective view of a heart valve repair system that can be used with a surgical navigation system according to an embodiment of the present invention. 
         FIG. 5A  is a partial perspective view of the heart valve repair system of  FIG. 4 . 
         FIG. 5B  is a partial perspective view of the heart valve repair system of  FIG. 4 . 
         FIG. 6  is a partial perspective view of a heart valve repair system for use with a surgical navigation system according to an embodiment of the present invention. 
         FIG. 7  is a partial perspective view of a heart valve repair system for use with a surgical navigation system according to an embodiment of the present invention. 
         FIG. 8  is a partial perspective view of a heart valve repair system for use with a surgical navigation system according to an embodiment of the present invention. 
         FIG. 9  is a partial perspective view of a heart valve repair system for use with a surgical navigation system according to an embodiment of the present invention. 
         FIG. 10  is a perspective view of a calibration system for a surgical navigation system according to an embodiment of the present invention. 
         FIG. 11  is a screenshot of a surgical navigation system according to an embodiment of the present invention. 
         FIG. 12  is a screenshot of a surgical navigation system according to an embodiment of the present invention. 
         FIG. 13  is a screenshot of a surgical navigation system according to an embodiment of the present invention. 
         FIG. 14  is a screenshot of a surgical navigation system according to an embodiment of the present invention. 
         FIG. 15  is a screenshot of a surgical navigation system according to an embodiment of the present invention. 
         FIG. 16  is a screenshot of a surgical navigation system according to an embodiment of the present invention. 
         FIG. 17  is a screenshot of a surgical navigation system according to an embodiment of the present invention. 
         FIG. 18  is a screenshot of a surgical navigation system according to an embodiment of the present invention. 
         FIG. 19  is a screenshot of a surgical navigation system according to an embodiment of the present invention. 
         FIG. 20  is a screenshot of a surgical navigation system according to an embodiment of the present invention. 
         FIG. 21  is a flowchart depicting steps of heart valve repair process according to an embodiment of the present invention. 
     
    
    
     While the present invention is amenable to various modifications and alternative forms, specifics thereof have been shown by way of example in the drawings and will be described in detail. It should be understood, however, that the intention is not to limit the present invention to the particular embodiments described. On the contrary, the invention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the present invention. 
     DETAILED DESCRIPTION 
     In the following detailed description of the present invention, numerous specific details are set forth in order to provide a thorough understanding of the present invention. However, one skilled in the art will recognize that various embodiments of the present invention may be practiced without these specific details. In other instances, well-known methods, procedures, and components have not been described in detail so as to not unnecessarily obscure aspects of the present invention. 
     According to an embodiment of the present invention, a visualization environment uses tracking technology to locate both a heart valve repair tool and a transesophageal echocardiogram (TEE) probe in 3D space, making it possible to represent real-time echo images with virtual geometric models of both devices and interactively defined anatomy within a common coordinate system. Exemplary repair tools can include those disclosed in U.S. Patent Publication Nos. 2008/0188873, 2010/0174297, 2009/0105279 and 2009/0105751, each of which is incorporated by reference. Sensors from, for example, the Aurora (Northern Digital, Waterloo, Canada) magnetic tracking system (MTS) can be integrated into the repair tool and onto the TEE probe of a, for example, Philips iE33 ultrasound. 
     Geometric models of each device can be created with appropriate computer software and the tools appropriately calibrated. One embodiment of such geometric models can be implanted using the Visualization Toolkit (http://www.vtk.org/doc/release/5.0/html/classes.html) using spline filters and STL file readers found in the open-source VTK software libraries, which is incorporated by reference herein. Specifically, classes such as the vtkSTLREader and vtkSplineFilter can be utilized, each of which is incorporated by reference. Axes with 10 mm markings can be projected from the virtual representation of the tool, indicating the forward trajectory of the tool and the direction of the opening jaws. The system greatly facilitates a surgeons&#39; ability to plan the tool trajectory towards a desired target site, such as a heart valve. 
     In addition to representations of the tools, tracking the TEE image data makes it possible to define anatomy of interest (aortic valve annulus, target location (e.g., mitral valve line of coaptation), and regions to be avoided (e.g., mitral valve annulus) for contextual purposes. In the case of mitral valve repair, the objective is to identify the plane of the mitral valve annulus in order to be able to navigate the repair tool quickly and safely to the appropriate place within the valve annulus to proceed with the repair under. With regard to an aortic valve repair, a primary issue is identifying the critical structures associated with the valve so that a new valve can be placed in such a way that it does not block the coronary vessels fed by the coronary ostia and positioned appropriately with respect to the base of the aorta. In both types of procedures, target points can be indentified with ultrasound shown as three dimensional locations in space that can be fitted with lines, rigs or planes to identify the location of the coronary ostia, annuli of the valves, the line or plane defining the base of the valve or any calcifications near the aortic valve. As will be described further herein, each of these marked regions can be updated to reflect its motion during the procedure, using motion models acquired from pre-operative images, by extracting motion parameters from the intra-operative ultrasound images, or by implanting and tracking one or more magnetically or sonically traced fiducial markers secured close to or on the respective target region. 
     This augmented reality system is designed to assist the surgeon with three related navigation tasks of; planning the access point and trajectory; maintaining a safe and direct entry through the mitral valve commisure into the left atrium, and establishing the correct tool orientation at the line of coaptation so the repair device can grasp the flailing leaflet. As shown in  FIG. 21  such a process  10  includes, prior to making the apical entry incision, the echocardiographer identifying a minimal number of tie-points along the pertinent anatomy (aortic valve annulus, mitral valve annulus, line of coaptation) at step  12 . From these coordinates, at step  14  a series of coordinates are generated to represent these features in virtual space. Next, the surgeon uses a desired trajectory projection of the repair tool determined at step  16  to plan the optimal entry point and orientation at step  18 . After apical access at step  20 , the surgeon simply orients and points the tool trajectory towards the desired target site and advances the tool at step  22 , monitoring the virtual representations as seen on the real-time echo image data at step  24 . By overlaying the virtual elements on the real echo image data, the surgeon is able to assess the accuracy and reliability of the virtual representations in real time. Once at the desired target location at step  26 , the procedure can return to the standard workflow for carrying out the repair procedure at step  28 , since additional guidance is no longer needed. In addition, any relevant structure that can be identified within or surrounding the heart in ultrasound, with a tracked electrophysiological device or which can be identified in preoperative image and registered into the ultrasound coordinate frame can be similarly incorporated into the system. 
     One embodiment of a surgical navigation system  100  as described above is depicted in  FIGS. 1 and 2 . The primary components of the system include a magnetic tracking system  102 , an ultrasound imaging system  104  and a computer  106  with one or more output monitors  108 . A TEE probe  110  of the ultrasound imaging system  104  can be integrated with the magnetic tracking system  102 . A heart valve repair device  112  can also interface with the magnetic tracking system  102 . 
     The magnetic tracking system  102  can utilize sensors interfacing with each of the TEE probe  110  and the heart valve repair device  112  to track the location and orientation of those tools with respect to the magnetic field generator  117  of the system  102 , which can be placed on the operating room table underneath the patient. This information can be used to place both the TEE probe  110  and the heart valve repair device  112  into a common virtual environment. Each of the sensors can communicate with the magnetic sensor control unit  116  that is linked to each sensor by a sensor interface unit  118 . In one embodiment, the system  102  uses the Northern Digital Aurora magnetic tracking system. In such an embodiment, the magnetic tracking system  102  is controlled using NDI API software  113  and interfaces with the navigation application suite  111  on the computer  106  with AIGS API software  114 . The system can utilize three tracked sensors, one mounted to the TEE probe  110  and two mounted to the heart valve repair device. In other embodiments, greater or fewer sensors can be used with each device. Although described as using a magnetic tracking system  102  to track the ultrasound probe and surgical tools, it should be understood that various other tracking systems could be utilized in accordance with the present invention. For example, other types of tracking that could be used include acoustic, radio-frequency, fiber optic, image based and x-ray. 
     Referring now to  FIG. 3 , there can be seen a TEE probe  110  that can be used with embodiments of the present invention. The TEE probe  110  includes an ultrasound transducer that interacts with the ultrasound system  104  to provide echo images, as is known in the art. In the present invention, at least one sensor  130  is mounted to the TEE probe  110 . Sensor  130  can be a six degree of freedom, magnetically tracked sensor. In one embodiment, as shown in  FIG. 3 , the sensor  130  is mounted on a side surface of the probe  110 . In other embodiments, the sensor  130  can be mounted on an upper or lower surface of the probe or integrated inside the probe casing. Sensor  130  can be mounted to probe  110  with an adhesive, such as, for example a Loctite 3554 UV cured adhesive. Sensor  130  can be permanently or removably mounted to probe  110 . In one embodiment, sensor  130  can be a single use, disposable sensor that can be utilized due to potential sensor damage and cleaning/sterilization issues that can arise with long term use. Sensor  130  can also be integrated into a removably mountable cap that can be mounted to the probe  110  during a procedure and then removed for cleaning prior to a subsequent procedure. 
       FIGS. 4-9  depict a heart valve repair device  112  that can be used with embodiments of the present invention. Device  112  generally includes a handle assembly  140  and a capture assembly  142  with an elongate shaft  144  extending therebetween. An actuator  146  is located at a proximal end of the device  112  for operating capture assembly  142 . As can be seen in  FIGS. 5A and 5B , capture assembly  142  can include a first clamping jaw  148  and a second clamping jaw  150 . Clamping jaws  148 ,  150  are slidably disposably relative to each other with actuator and can be used to capture tissue, such as a heart valve leaflet, therebetween. Once tissue is captured between clamping jaws  148 ,  150  a needle  152  can penetrate the tissue to insert a suture  154  into the tissue. Further details of heart valve repair devices useable with the present invention are disclosed in U.S. Patent Publication No. 20090105751, which is incorporated by reference herein. Although one specific heart valve repair device is shown, it should be understood that the present invention can be adapted for use with any type of heart valve repair device. 
     Repair device  112  as used with the present invention can incorporate two sensors in addition to the sensor  130  utilized with the TEE probe  112 . In one embodiment, a first sensor  156  can be disposed with a rubber cylinder positioned within a groove  158  in the shaft  144  of the device near the handle assembly  140 . This sensor can be a five degree of freedom magnetic sensor that is used to track the opening and closing of the capture assembly  142  clamping jaws  148 ,  150 . A second sensor  160  can also be disposed in a groove  162  in the shaft  144 . The second sensor  160  can be a six degree of freedom magnetic sensor that is used to track the movement of the repair device  112  itself. In one embodiment, the second sensor  160  can be held in the groove by an adhesive. Each sensor  156 ,  160  includes corresponding wires  164 ,  166  through which the positional data is transmitted that are routed out of the tool  112  and back to the sensor interfaces  118  and sensor control unit  116 . In one embodiment, the wires  164  for the first sensor are fixed to the shaft  144  at location  164   a  and again adjacent the exit point of wires  164  from device at location  164   b , with a length of slack  164   c  that allows the sensor to move along the shaft  144  when actuator  146  is employed to move the clamping jaws  148 ,  150 . Wires  166  for second sensor  160  can be adhered to the shaft  144  until the wires  166  exit the device  112 . Wires  164 ,  166  can exit through an opening  168  in the body of the repair tool  112 . In one embodiment, opening includes a grommet through which the wires  164 ,  166  extend. 
     One or both of the heart valve repair device  112  and the TEE probe  110  can be calibrated for use with the system  100 . In this context, calibration refers to the process of defining the coordinate frame of a device relative to the magnetic tracking sensors or other sensors used to track the device. Heart valve repair device  112  can be calibrated with a calibration jig  170  such as shown in  FIG. 10 . The jig  170  is configured such that the tip of the repair device  112  is always in the same location when held in the jig  170 . In one embodiment, the jig  170  can comprise two milled acrylic blocks. A reference sensor  172  is positioned near the tip of the repair device  112  and can be rigidly mounted to the jig  170 . In one embodiment, the sensor can be an NDI Aurora sensor. The jig  170  can also include a series of divots  174  milled into the jig  170  near the tip of the repair device  112 . In one embodiment, eight spherical divots are milled in a non-symmetrical pattern. A geometric model of the jig  170  can be created from a micro-CT of the jig, with the origin of the model defined at the repair device  112  tip and the z-axis extending along the long axis of the repair device  112 . Using the micro-CT data, the locations of the milled divots are then defined for the model. Then, a magnetically tracked tool  176  is used to calibrate the repair device  112  by interfacing the tool  176  with each of the divots  174 . In one embodiment, a tip  178  of the tool  176  can be shaped to fit within the divots  174 . In one embodiment, the device  112  can be provided to an end user having been pre-calibrated for use during production. 
     The TEE probe  110  can be calibrated by using a magnetically tracked tool intersecting the ultrasound image plane. In one embodiment, the magnetically tracked tool can be a previously calibrated repair device  112 . In one embodiment, the computer  106  can monitor the accuracy of the calibration during a surgical procedure and warn the users of potential inaccuracies in the model. In such an embodiment, the system could also intra-operatively correct calibration errors during the procedure. 
     The ultrasound image data acquired by the TEE probe  110  is transmitted from the ultrasound system  104  to the computer  106  for integration into the virtual scene created with the system  100 . The data can be transferred from the ultrasound system  104  to the computer with a converter  120 . In one embodiment, the converter is the Epiphan DVI2USB converter. In such an embodiment, the converter  120  can be managed by the Epiphan Application Program Interface  121 . 
     The computer  106  operates to integrate image data from the ultrasound system  104  with tracking information from the magnetic tracking system  102  to present virtual representations of the heart valve repair tool  112  and TEE probe  110  in a common 3D environment. Using the tracked TEE image data, geometric models of pertinent anatomy, such as mitral and aortic valve annuli, are added to provide the surgeon with a significantly more intuitive environment for performing the surgical procedure, as will be described in more detail below. 
     In one embodiment, two monitors  108  are used to provide a split screen view of the system. In such an embodiment, one monitor can be used for viewing by the surgeon and the other can be used by the echocardiographer and technician. In other embodiments, only one monitor can be used or more than two monitors can be used. 
     The computer  106  can operate a software platform that provides an augmented reality viewpoint for a surgeon performing a procedure, such as repair of a heart valve. The software platform provides the system for integrating the real-time information from the magnetic tracking system  102  with the real-time information from the ultrasound system  104 ,  110 . The information is displayed on a user interface  200  on the one or more computer monitors  108  showing the ultrasound image data with dynamic virtual geometric representations of surgical tools  202  and anatomy  204  as will be discussed in more detail with regard to  FIGS. 11-20 . 
     To establish the user interface, the software platform must render the various components for display on the interface. The body or shaft  144  of the heart valve repair device  112  can be rendered on the system as a solid shape derived from CAD drawings of the device. Either a portion of the length of the body of the device (e.g., 2 cm or 4 cm) or the full body can be rendered. The tip or capture assembly  142  can also be generated from CAD drawings using the same calibration matrix as the body. The location where the needle  152  used by the device to penetrate tissue exits from the shaft  144  can be marked with a sphere  206 . The sphere can define two axes, a first axis  208  can be aligned with the direction of the tool trajectory and a second axis  210  can be orthogonal to the first axis  208 . Repair device  112  can be displayed either as opaque or transparent object. In one embodiment, the device  112  automatically fades to transparency as it approaches target tissue, with distances at which this occurs selectable by the user. In such an embodiment, the sphere marker  206  showing the location of the needle can remain opaque at all times. 
       FIG. 13  depicts an opening screen  220  of the user interface  200  according to an embodiment of the present invention. Opening screen  220  can include a general functions render pane  222  that allows rendering of an object to be manipulated and a module render pane  224  for displaying specific operations that can be undertaken in a given module. The scene render pane  226  will display the navigation data for a given procedure. A drop down menu  228  can be used to access the user interfaces for various modules. 
     A tracked tool module  230  is displayed in  FIG. 14 . A tracked tools dialog window  232  shown in  FIGS. 15-18  can be opened by selecting the corresponding button  233  on the tracked tool module  230 . A tracker pull down menu  234  can be used to select a specific tracked tool. Once a tool is selected, tracker control buttons  236  can be used to control tracking of the tool. The opacity of all tools can be controlled with the global tool opacity slider  238 . Opacity of a specific tool can also be adjusted on the tracked tool module  230  by selecting from the tool pull down bar  240  and using the corresponding slider  242 . Display of the selected tool in wireframe and display of the tool axes can also be turned off and on with corresponding check boxes  244 ,  246  on the tracked tool module  230 . 
       FIGS. 15-18  display various aspects of the tracked tools dialog window  232 , which can provide the basic functionality of the tracked tool module  230  as well as additional functionality. A tracker pane  248  of the window  232  is shown in  FIG. 15 , and includes a tracker pull down menu  234  and tracker control buttons  235 . A tool pull down menu  240  allows selection of a specific tool. A new tracking system box  251  allows a new system to be added with an initialize tracker button  250  to actuate the new system. A specific configuration for a tracking can be loaded or saved with buttons in the configuration box  252 . 
     A tool actor pane  252  of the tracked tools dialog window  232  is shown in  FIG. 16 . The tool actor pane  252  allows all virtual actors to be interactively modified in real time. The tool actor can be selected from a tool actor dropdown  254  and a new tool can be rendered with the add tool button  256  after an acting tool is selected. Various information on the tool can be provided and modified in the information box  258 . Callbacks for the tool are contained in a callbacks box  260 . Video sources for use with the tracked tool can be added, removed and viewed in the video sources box  262 . 
     The tool calibration matrix  266  is displayed on a tool calibration pane  264  of the dialog box  232  as shown in  FIG. 17 . The matrix can be manually entered into the boxes or can be copied and pasted into a text box  268 . Various matrix controls  270  for manipulating the data are also provided. A tip calibration box  272  can allow calibration of a tool tip and can also display the root mean squared error of the calibration  274 . The orientation and tip location of a tool can also be obtained from a previously saved tool with the orientation box  276 . A command box  278  can alternatively be used to manually calibrate the rotation and translation controls. The tracked tools dialog window  232  can also include a video capture pane  280  as shown in  FIG. 18 . This pane can provide for selection of a specific source video card from a pull down menu  282  and display information  284  about the source. 
     An anatomical feature module  286  is shown in  FIG. 19 . A drop down menu  288  and associated controls allow a specific anatomical feature to be selected, added or removed, such as for example, the mitral valve or the aortic valve. Various controls  290  can be used to adjust the rendering of the anatomical feature  289 . A plurality of function keys  292  is also provided. Keys  292  can be used to manage tie points  294 , which can be denoted by small spheres on the interface  200 . Tie points  294  can be one or more 3-dimensional points representing a tracked location on an anatomical landmark such as the annulus of the mitral valve or aortic valve or other structure as described earlier. The tie points can be used to create a model of the structure with a suitable curve. Tie points can also be displayed to represent specific points on the structure, such as a desired grasping point along a valve leaflet. The save/load data buttons  296  allow tie points to be saved into the system or loaded from memory. A manage data menu  298  allows the tie point data to be edited and removed. In an alternative embodiment, tie points can be selected and defined on the ultrasound device  104 , rather than on the computer  106 . 
     In one embodiment, anatomical structures can be tracked as they move, either by using image-based tracking or by introducing tracked sensors close or attached to the anatomical structures. The tracking information can be used to dynamically update the virtual representations of the anatomy created with the tie points. An advantage of updating the target regions dynamically during the procedure is that in the case of mitral valve repair, the repairing instrument is less likely to be inadvertently guided into an inappropriate structure, causing potential damage. In the case of the aortic valve, the advantage of dynamically moving the target structures is that the procedure can be carried out without temporarily stopping the heart or inducing rapid pacing, both of which would stop the target motion, but would add additional risk to the patient. 
     A repair device module  271  is shown in  FIG. 20 . The scene render pane  226  displays the tracked repair tool  112  and TEE probe  110 . Functions buttons  273  can be used to control various aspects of the devices. Various viewpoints from which the user can view the procedure can be selected and modified with viewpoints controls  275 . The scene render pane  226  can display viewpoints in various ways, including a single view, a split, two pane view and a four pane view. The viewpoint of the virtual camera for a specific view can be controlled with the computer mouse, which can rotate, pan, zoom, etc. the view, to allow the user to define a specific view. One view that can be utilized is a barrel view, which sets the camera a set distance, such as 10 cm, above the repair tool  112  aligned along the main axis of the tool  112 . Barrel view can be activated with a corresponding function button  273 . In an alternative embodiment, rather than the user defining and controlling the viewing angles for the augmented virtual reality scene, the viewing angles can be automated for a specific type of procedure. Views can also be based on pre-operatively acquired data. In an alternative embodiment, the images can be displayed stereoscopically to the observer. Navigation output controls  277  provide tracking and control of data relating to navigation of the repair device  112  to the target tissue structure and grasping controls  279  provide tracking and control of data relating the grasping function of the repair tool  112  clamping jaws  148 ,  150 . These tracking functions can be activated manually, or can be performed automatically and can provide for recording, storage and later playback. Automatic opacity of the tool at specific distances from the target site can be controlled with opacity controls  281 . 
     It has been found that a surgical navigation system such as system  100  can significantly reduce the surgical time needed to perform a minimally invasive procedure, such as repair of a heart valve leaflet. In one study, the mean task completion time fell by a factor of almost six when using such a system. Such a system also leads to more direct navigation paths to the target tissue, which results in a safer procedure. For example, in repair of a heart valve leaflet, a repair device can inadvertently enter an area dangerous to a patient, such as the left ventricular outflow tract or cause damage to the leaflet itself when the path to the tool is not guided as described herein. 
     Although described herein as providing surgical navigation for capturing heart valve leaflets, embodiments of the present invention can also be applied to targeting any intracardiac structure for repair or replacement, such as full valve replacement or other structural heart repair. Sutures and other repair devices can be delivered via the disclosed system for repair purposes. 
     In a further embodiment, a surgical navigation system as described herein can be utilized as a training system. Thus, in lieu of utilizing the system to aid in guiding an actual surgical procedure, the system can be utilized to train surgeons, echocardiographers and others for performing heart repair procedures. 
     Various embodiments of systems, devices and methods have been described herein. These embodiments are given only by way of example and are not intended to limit the scope of the present invention. It should be appreciated, moreover, that the various features of the embodiments that have been described may be combined in various ways to produce numerous additional embodiments. Moreover, while various materials, dimensions, shapes, implantation locations, etc. have been described for use with disclosed embodiments, others besides those disclosed may be utilized without exceeding the scope of the invention.