Abstract:
A bone registration system is disclosed. The bone registration system may have a device including a scanner arranged to scan a target surface area of bone to obtain scan data and a first communication component. The registration system may have also a first marker positionable on a first portion of bone. The first marker may include a second communication component arranged to transmit a location signal for indicating a position of the first marker in a plurality of dimensions relative to the device. The system may have also a registration unit that compares the scan data with surface data of the bone to generate position data identifying overlapping elements of the scan data relative to the surface data, determines location data from the location signal and determines a location of the first marker on a surface of the bone using the position data and the location data.

Description:
PRIORITY CLAIM 
       [0001]    The present application claims priority to U.S. Provisional Application Ser. No. 61/499,838 entitled “Ultrasound CT Registration for Positioning” filed on Jun. 22, 2011 and U.S. Provisional Application Ser. No. 61/499,849 entitled “Ultrasound CT Registration for Positioning” filed on Jun. 22, 2011, the entire disclosures of which are incorporated herein by reference. 
     
    
     BACKGROUND 
       [0002]    CT (Computed Tomography) is often used to image bones as this permits the construction of high definition three-dimensional images. These high definition images facilitate understanding of fractures, ligament injuries and dislocations and assist in the formulation of treatment strategies. CT scanners, however, are large, bulky devices which are inconvenient for use during treatment procedures. Although ultrasound imaging devices are less bulky and more convenient for use during procedures, the images produced by these devices are less accurate and comprehensive than those produced by CT scanners. 
       SUMMARY OF THE INVENTION 
       [0003]    The present invention relates to a bone registration system. The bone registration system may have a device including a scanner arranged to scan a target surface area of bone to obtain scan data and a first communication component. The registration system may have also a first marker positionable on a first portion of bone. The first marker may include a second communication component arranged to transmit a location signal for indicating a position of the first marker in a plurality of dimensions relative to the device. The system may have also a registration unit that compares the scan data with surface data of the bone to generate position data identifying overlapping elements of the scan data relative to the surface data, determines location data from the location signal and determines a location of the first marker on a surface of the bone using the position data and the location data. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0004]      FIG. 1  shows a schematic drawing of a system according to a first exemplary embodiment of the present invention; 
           [0005]      FIG. 2  shows a perspective view of the system according to the first exemplary embodiment of the present invention; 
           [0006]      FIG. 3  shows a perspective view of a system according to a second exemplary embodiment of the present invention; 
           [0007]      FIG. 4  shows a schematic drawing of the system according to the second exemplary embodiment of the present invention; 
           [0008]      FIG. 5  shows a perspective view of a system according to a third exemplary embodiment of the present invention; and 
           [0009]      FIG. 6  shows a schematic drawing of the system according to the third exemplary embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0010]    The present invention may be further understood with reference to the following description and the appended drawings, wherein like elements are referred to with the same reference numerals. The present invention relates to a system and method for registering a location of a bone marker on a bone for subsequent treatment of the bone. In particular, the present invention relates to a system and method for determining the relative locations of a handheld device and one or more markers to register the location of a marker on a bone with CT data of the bone. Once a position of the one or more marker on a bone is registered, during a treatment procedure, the movement of the marker may be tracked and the tracking information used to manipulate previously obtained CT image data to accurately track and display the position of one or more portions of bone during a procedure. 
         [0011]    As will be described in greater detail hereinafter, the present invention is directed to a system and method for registering a location of the one or more markers positioned on the bone with the CT image data to aid in performing of a medical procedure (e.g., a bone fixation procedure, etc.). The exemplary system and method according to the invention permits the registration of the location of the one or more markers quickly and easily via an intra-operative procedure. Exemplary embodiments of the present invention describe a system and method utilizing a portable device to obtain data which is registered to establish the location of first and second markers on first and second portions of bone on a CT image so that, as the first portion of bone is manipulated during a treatment procedure, movement data may be used to manipulate the CT image to show the movement of the bone. It will be understood by those of skill in the art that although the exemplary embodiments describe first and second markers as positioned on first and second portions of a bone, respectively, the first and second markers may also be positioned on first and second bones that are adjacent to one another or on any other substantially rigid body structures so that a previously obtained CT image of the structures may be manipulated to show motion of the structures during a procedure. 
         [0012]    As shown in  FIG. 1 , a system  100  according to an exemplary embodiment of the present invention comprises a handheld device  102  configured to obtain and transmit ultrasound data  120  (e.g., ultrasound image data) to a tracking system  104 . The tracking system  104  registers the ultrasound data  120  with CT data  122  (e.g., a CT image) obtained prior to collection of the ultrasound data  120  to determine a location on the CT data  122  corresponding to the position of the handheld device  102  relative to the CT image, such as a bone, represented by the CT data  122 . As would be understood by those skilled in the art, the handheld device  102  may use any known portable ultrasound imaging device including, for example, an ultrasound scanner  110  for obtaining ultrasound images. The handheld device  102  also has an electromagnetic sensor  112  for sensing an electromagnetic field emitted from a signal emitter  114  of a field generator  200 . The electromagnetic signal emitter  114  generates an electromagnetic field that is also sensed by a first marker electromagnetic sensor  124  of a first marker  106 . An electromagnetic sensor  112  of the handheld device  102  and the first marker sensor  124  communicate with the tracking system  104  by sending thereto device data  126  and marker data  128 , respectively, in response to receiving the signal emitted by the signal emitter  114 . The device data  126  and marker data  128  provide information on the locations of the device  102  and marker  106 , respectively, relative to the field generator  200 . The tracking system  104  uses the device and marker data  126 ,  128  to determine a position of the first marker  106  relative to the handheld device  102 . 
         [0013]    Using the collected information, the tracking system  104  registers (e.g., correlates) the ultrasound data  120  to the CT data  122  to identify the location of the handheld device  102  relative to, for example, a bone; registers the location of the handheld device  102  relative to the first marker  106 , and determines a location of the first marker  106  on the image represented by the CT data  122 , which may be shown on a display  118 . In a further embodiment, the electromagnetic signal emitter  114  communicates with a second marker electromagnetic sensor  125  of a second marker  132  to determine the location of the second marker  132  relative to the handheld device  102  to determine a location of the second marker  132  relative to, for example, an image of a bone  108  represented by the CT data  122 . Thus, in an embodiment where the first and second markers  106 ,  132  are located on first and second portions of a fragmented bone, the locations of the first and second markers  106 ,  132  on the bone may be registered prior to a manipulation of the fragments. Such registration may result in the first and second markers  106 ,  132  being used to track movement of the first and second portions of the bone relative to one another by manipulating the CT data  122  to display the motion by moving relative to one another portions of the image represented by the CT data  122  corresponding to the first and second portions of the bone  108 . For example, the CT data  122  may be manipulated to show relative movement between the first and second portions of bone  108  on the display  118  based on the movement of the first and second markers  106 ,  132 . 
         [0014]    The scanner  110  of the handheld device  102  may take a 2D ultrasound image to obtain ultrasound data  120 . The system  100  then looks through the ultrasound data  120  for portions bearing a similarity of contour to portions of the image represented by the CT data  122  to identify portions of the ultrasound data  120  and the CT data  122  which correspond to the same portion of the bone  108 . The ultrasound data  120  and the CT data  122  may, however, have several points of similarity, requiring the handheld device  102  to take several 2D ultrasound images over discrete periods of time to ensure correct registration between these identified portions of data representing the same portion of the bone  108 . The number of 2D ultrasound images required may depend, for example, on the homogeneity of the contour of the bone and the level of detail in the ultrasound and CT data  120 ,  122 , respectively. For example, for long bones with large substantially homogeneous areas, more ultrasound scanning may be required to obtain the registration between the ultrasound and CT data  120 ,  122 , respectively. Thus, several candidate locations of the CT data  122  may be identified and additional ultrasound data  120  (e.g., ultrasound images) collected until one of the several candidate locations is confirmed as correctly corresponding to a selected portion of the image represented by the CT data  122 . 
         [0015]      FIG. 2  depicts a use of the system  100  for registering the location of first and second markers  106 ,  132  on a bone  108  with a CT image of the bone  108 . The electromagnetic sensor  112  provides device data  126 , which includes a position and/or orientation of the handheld device  102  relative to the field generator  200 . In particular, as would be understood by those skilled in the art, a known sensor may be employed as the sensor  112  to provide data on an angular orientation of the handheld device  102  in  6  dimensions, which includes first, second and third dimensions indicating a distance on X, Y and Z axes between the handheld device  102  and the field generator  200  and three dimensions relating to the angular rotation (i.e., Roll-Pitch-Yaw) of the handheld device  102  relative to the field generator  200 . This device data  126  is similarly transmitted to the tracking station  104 . 
         [0016]    The electromagnetic signal emitter  114  of the field generator  200  communicates with the first electromagnetic sensor  124  and the tracking station  104  to provide marker data  128 , which includes a position and/or orientation of the first marker  106  relative to the signal emitter  114 . In particular, the signal emitter  114  emits a signal to the first marker electromagnetic sensor  124 , which senses the position and/or orientation of the first marker  106  in 6 dimensions relative to the field generator  200 . The 6 dimensions include 3 dimensions relating to a distance of the signal emitter  114  from the first marker electromagnetic sensor  124  along X, Y and Z axes and three dimensions relating to the angular rotation (i.e., Roll-Pitch-Yaw) of the signal emitter  114  relative to the first marker electromagnetic sensor  124 . This marker data  128  is then transmitted to the tracking station  104 . 
         [0017]    The tracking station  104  may be a computer or other processing arrangement including a processor  116  and a display  118 . The ultrasound data  120 , CT data  122 , device data  126  and marker data  128  may, for example, be saved to a memory  130  of the tracking station  104  and may be used to register the first marker  106  to the CT data  122 . The processor  116  correlates the ultrasound data  120  and the CT data  122  to determine a position of the handheld device  102  relative to image of the bone  108  in the CT data  122 . The processor  116  may then determine a location of the first marker  106  relative to the CT data  122  using the device data  126  and marker data  128 . The location of the first marker  106  may also be displayed on the display  118 . The processor  106  may register in real-time the ultrasound and CT data  120 ,  122 , respectively, and determine the location of the first marker  106  on the image represented by the CT data  122  so that a system user may be provided with real-time information regarding completion of the registration process. 
         [0018]    After registration of the first marker  106 , a second marker  132  may be positioned on a second portion of the bone  108 . Thus, when registration of the first marker  106  has been completed, the registration procedure discussed above may be repeated for the second marker  132  to register a location thereof. Once the locations of both the first and second markers  106 ,  132 , respectively, have been determined relative to the CT data  122 , relative movement between the first and second markers  106 ,  132  may be continuously tracked and monitored such that a manipulated CT image showing the relative movement of the first and second portions of the bone  108  may be displayed on the display  118  observable by a surgeon or other user to visualize the reduction of a fracture. 
         [0019]    The embodiment depicted by  FIGS. 1 and 2  has been described for a situation where the bone  108  in which the first and second markers  106 ,  132  are positioned is fractured. The fracture could result in two, three, four, etc., bone fragments in each of which a marker is positioned and its location subsequently registered so that at some point later the relative movement of the markers, and therefore the bone fragment associated with the marker, can be tracked on the CT image whilst the bone fragments are moved. An alternate use of the registration system  100  arises when a bone is in one piece, but it is to be divided by an osteotomy into two or more pieces. In this situation, the registered location of the first marker  106  can be used to identify and register the location of the second and each subsequent marker with the CT data by determining the locations of the second and subsequent markers relative to the first marker with reference to the registered location of the first marker  106 . 
         [0020]    Referring again to  FIG. 2 , a first exemplary technique utilizing the system  100  is shown. An electromagnetic field generator  200  emits an electromagnetic field capable of being sensed in the 6 dimensions described earlier. The electromagnetic field generator  200  comprises at least two coils (not shown). It is noted that although the embodiment of  FIG. 2  is depicted with only the first marker  106  including a first sensor  124 , the second marker  132  or any plurality of additional markers may be used without deviating from the scope of the invention. The handheld device  102  is connected to the tracking station  104  by, for example, a wired or wireless connection. The first marker  106  may also be connected to the tracking station  104  via a wired connection, although a wireless connection is also envisioned. The embodiment of  FIG. 2  operates in a manner substantially similar to the mode of operation disclosed above. 
         [0021]    Specifically, a CT scan of the bone  108  is made and the CT data  122  is provided to the tracking system  104 . The first marker  106  is positioned on a first portion of the bone  108  and the ultrasound seamier  110  is used to scan the first portion of the bone  108 . It is noted that the position of the first marker  106  as depicted is exemplary only and that the first marker  106  may be positioned anywhere on the bone  108  without deviating from the scope of the invention. The ultrasound and device data  120 ,  126 , respectively, along with marker data  128  for the first marker  106  is transmitted to the tracking station  104  and stored, for example, in a memory  130  and accessed via the processor  116  as required. The processor  116  compares and correlates the ultrasound and CT data  120 ,  122  to register the data—i.e., determine overlapping elements in the ultrasound and CT data  120 ,  122 . Then, using the device data  126  which indicates a position of the handheld device  102  relative to the field generator  200  and the marker data  128 , which indicates a location of the first marker  106  relative to the field generator  200 , the processor  116  determines a location of the first marker  106  relative to the CT data  122 . Specifically, the processor  116  identifies a position and orientation in 3D space relative to the field generator  200  of the first marker  106  to determine marker data  128 , and the first sensor  112  of the handheld device  102  to determine device data  126 . The processor  116  uses the marker data  128  and device data  126  to determine the relative location of the first marker  106  to the handheld device  102 . The processor  116  uses also the ultrasound data  120  to link the location of the handheld device  102  to the CT data  122  to determine the relative location of the handheld device  102  to the bone  108  in the CT image. Knowing the location of the first marker  106  relative to the handheld device  102  and the location of the handheld device  102  relative to the CT image of the bone  108 , the processor determines the location of the first marker  106  relative to the CT image of the bone  108  and thereby registers the location of the first marker  106  on the CT data  122  and, therefore, the bone  108 . The relative location of the first marker  106  and the CT data  122  may be displayed on the display  118 . 
         [0022]    Once the first marker  106  has been registered relative to the CT data  122 , the registration process may be repeated for any number of additional markers (not shown) using the same process as described for registering the first marker  106 . For each additional marker, the ultrasound scanner  110  is used to scan that bone portion in which the bone marker to be registered is located. In this way, movement of a bone fragment during the registration procedure may be compensated. In the situation where the bone  108  is in one piece, a position of the second marker  132  may be detected relative to the first marker  106  to determine a location of the second marker  132  relative to the CT data  122 . The relative location of the second marker  132  may also be displayed on the display  118 . As those skilled in the art will understand, this relative registration process may be used in, for example, osteotomy procedures where the bone  108  is in one piece and the first marker communicates with the second marker to register a location thereof. It is noted, however, that for osteotomy procedures a user may also register the first and second markers individually with the tracking station  104 . 
         [0023]    In another embodiment of the invention, the registration process may be used for the treatment of scoliosis, with the first and second markers positioned on two different bones, e.g., vertebrae of the spine. In such an embodiment, the first and second markers are individually registered with the tracking station  104 , as also described in greater detail earlier. Thus, once the locations of both the first and second markers  106 ,  132  have been determined, the user may move the first and second bones relative to one another and, consequently, move the first and second markers  106 ,  132 , relative to one another. The motion between the first and second markers  106 ,  132  is used to manipulate the image represented by the CT data  122  so the movement between the first and second bones represented by the motion of the markers  106 ,  132  is shown on the display  118  so that a user may monitor movement of bones during treatment. The exemplary system and method according to the invention compensates for inadvertent movement of the bones or fragments since the location of the first and second markers  106 ,  132  is taken relative to the field generator  200  and not relative to a position thereof within the body. In yet another scoliosis fixation procedure, 3D ultrasound may be used bypassing the need for a build up a 3D image using slices of a 2D ultrasound image, as those skilled in the art will understand. A fixation procedure for a fractured bone may use a registration process substantially similar to that used for a scoliosis fixation procedure, with the first and second markers positioned on separate portions of the fractured bone. 
         [0024]    In an exemplary embodiment, the handheld device  102  the ultrasound scanner may include a Siemens X150 for ultrasound scanning and a VF 10-5 vector transducer. The processor  116  may utilize the live MMGIFusion software developed by Princeton SCR for data acquisition and visualization and the IVUS (Interventional Ultrasound) software prototype developed at CAMP, Technical University of Munich and SCR, Princeton for automatic CT-Ultrasound registration. It will be understood by those of skill in the art, however, that this an exemplary embodiment only and that other systems may be utilized so long as they facilitate use of the system  100 , as described above. 
         [0025]      FIGS. 3-4  depict another exemplary marker registration system and method according to the invention. The system and method of  FIGS. 3-4  includes a first marker  106  positionable on the bone  108  including a first marker electromagnetic sensor  124 . In this embodiment the field generator  200  is located on the handheld device  102 . The handheld device  102  and first marker electromagnetic sensor  124  are connected to the tracking station  104  by a wired or wireless connection. The system and method of  FIG. 3  operates similarly to that disclosed above with respect to  FIGS. 1 and 2 . However, since the field generator  200  is located on the handheld device  102 , the position and orientation in 6 dimensions of the first marker  106  relative to the field generator  200  provides the processor  116  with the marker data  128 . For the system of  FIGS. 3-4 , the processor  116  can register the location of one or more markers without a first sensor associated with the handheld device  102  and device data  126 . Specifically, the first marker electromagnetic sensor  124  provides marker data  128  including a position and/or orientation of the first marker  106  relative to the handheld device  102 , compares the ultrasound data  120  to the CT data  122  and registers a position and/or orientation of the handheld device  102  relative to the CT image of the bone  108 . The marker data  128  and the registered location of the handheld device  102  is then used to register a location of the first marker  106  on the image represented by the CT data  122  by correlating marker data with the registered location of the handheld device  102  relative to the CT image of the bone  108 . 
         [0026]      FIGS. 5-6  depict a system and method according to another embodiment of the invention. The system and method are substantially the same as described for  FIGS. 3-4  with the exception that field generator  200  is replaced with an optical field generator  400  (e.g., light emitting array). Specifically, the handset  102  may communicate with an optical tracking instrument  300  connected to the first marker  106 . The optical tracking instrument  300  aids in location and registration of the first marker  106  with the tracking station  104  in accordance with the method described with respect to the embodiment depicted by  FIGS. 3-4 . 
         [0027]    It will be apparent to those skilled in the art that various modifications and variations can be made in the structure and the methodology of the present invention, without departing from the spirit or the scope of the invention. Thus, it is intended that the present invention come within the scope of the appended claims and their equivalents.