Abstract:
The present continuation-in-part application shows several specific embodiments of the invention and claims described in the parent patent application. In particular, it shows certain specific geometries of a dental-attached localizer which would be convenient for ear, nose, and throat (ENT) surgical applications or other localization applications related to the front of the face, the skull base, and similar areas. The localizer described in this continuation-in-part has rods and diagonals which allow quasi-coronal CT or other tomographic slices to be made through the face, skull base, and neck anatomy so as to locate structures accurately and repeatedly relative to the coordinate reference frame established by the dental impression piece.

Description:
[0001]    This application is a Continuation-In-Part of application Ser. No. 08/263,650, filed Jun. 20, 1994.  
     
    
     
       BACKGROUND TO THE INVENTION AND CONTINUATION-IN-PART  
         [0002]    In the parent patent application, a system and method were described involving a dental impression means attached to which a localizer structure is implemented for the purpose of giving reference indicia in tomographic slices through the patient&#39;s head and neck region so as to transform or map the image data from said tomographic or 3D volumetric data sets to a coordinate frame associated with said dental impression means. The parent application was general and included applications in neurosurgery, ENT, radiation therapy, and repeated radiographic imaging.  
           [0003]    The use in ENT surgery frequently involves taking CT X-ray tomographic slices which are essentially parallel to the plane of face, that is, in a nearly coronal aspect relative to the head. Typically the patient is lying prone; that is, with his stomach downward, on the CT scanning table, and his face looking into the aperture of the scanner. In this configuration, the slices are nearly coronal. It is an objective in ENT surgery to use the tomographic slices to coordinate insertion of tools into critical areas around the nose, sinuses, eyes, and skull base. Great precision is required, since these are dangerous and delicate areas, where 1 or 2 millimeters error in positioning could be harmful or fatal.  
           [0004]    Thus, it is an objective of this continuation-in-part to provide embodiments of the claimed invention of the parent application which would be suitable and convenient for the ENT coronal slice application. Furthermore, it is an object of this continuation-in-part, also as claimed in the previous invention, to provide physical index points on the tomographic localizer attached to the dental impression piece which can be used to calibrate, re-calibrate, and locate stereotactic tools, radiation machines, or other instrumentation such as a microscope or ultrasonic head relative to the patient&#39;s anatomy at the time of surgery, and all coordinated and cooperatively related to the image slice data and mapping thereof into the frame of reference of the dental impression means.  
       
    
    
     DESCRIPTION OF THE FIGURES  
       [0005]    [0005]FIG. 1 shows a dental-based localizer structure with angled and canted rods and diagonal elements which can enable target localization in axial or coronal slices through the patient&#39;s head and face.  
         [0006]    [0006]FIG. 2 shows another embodiment of a localizer which provides indicia for tomographic slicing in a nearly coronal aspect, as well as index points for referencing a stereotactic instrument during surgery.  
     
    
     DESCRIPTION OF THE INVENTION  
       [0007]    Referring to FIG. 1A, a localizer is shown which is an embodiment of the present invention and the invention described and claimed in the parent application. Included in the invention components is a dental tray  1101 , attached to which is a platform  1120 . The platform supports vertical, horizontal, and diagonal elements. The vertical elements  1110 ,  1111 ,  1116 ,  1118 , together with the diagonal elements  1105 ,  1115 ,  1114 , and  1108 , give rise to varying index points in tomographic scans so as to determine a mapping from a two-dimensional slice image in an axial plane or quasi-axial plane to a three-dimensional coordinate system associated with the dental tray  1101 , which is directly molded to the teeth and thus directly affixed to the patient&#39;s skull via the patient&#39;s upper and/or lower teeth. Also shown in FIG. 1A are horizontal rods  1104 ,  1106 ,  1107 , and  1109 , which enable a quasi-coronal plane such as plane  1102  to include index data that in turn enables a mapping from a quasi-coronal slice through the patient&#39;s face and related anatomy so as to map the data from this CT image slice to the coordinate reference frame associated with the dental tray  1101 .  
         [0008]    [0008]FIG. 1B shows the index data as it might appear from a quasi-axial CT slice through the anatomy and the localizer of FIG. 1A. The index points from the vertical rods are shown by spots  1133 ,  1134 ,  1132 , and  1130 , and the index marks from the diagonal rods are shown as  1136 ,  1139 ,  1138 , and  1131 . The patient&#39;s anatomy is also shown by the outline  1137 . The position of the index points and their relative location enable such a two-dimensional planar data set as FIG. 1B to be mapped into the three-dimensional coordinate system relative to the dental tray  1101  and the attached platform  1120  according to the teachings and invention of Russell Brown, U.S. Pat. No. 4,608,977. Such a mapping is alluded to in the invention of the parent patent application with respect to this type of implementation. Furthermore, shown in FIG. 1C is a front-on view of the localizer of FIG. 1A, and here is shown the horizontal rods  1140 ,  1142 ,  1143 , and  1145 , as well as the diagonals  1141  and  1144  which enabled a quasi-coronal slice such as  1102  to include sufficient index data to map from such a quasi-coronal slice, again to the dental and platform coordinate system of elements  1101  and  1120 . For example, in FIG. 1B there is shown a slice through such a structure which is not perfectly parallel to the vertical rods of the localizer, and there are the associated index points  1150 ,  1152 ,  1153 , and  1155  associated with the horizontal rods and the index points  1151  and  1154  associated with the diagonal elements. The fact that the lines associated with the point pairs  1150 ,  1152  and  1155 ,  1153  are not parallel indicates that the plane of the slice is not parallel to the vertical rods. The location of all of these index points and the relationship of the angle included between the line elements  1150  to  1152 , compared to the line element  1153  to  1154 , give further indication about the inclination of the plane relative to the localizer, and thus the mapping alluded to above can be done. Thus, each point of the anatomy, illustrated by  1157 , can be so mapped into the frame of reference of the dental tray.  
         [0009]    Referring to FIG. 2, another embodiment of the invention of the parent patent application is shown with a localizer, including a dental try  1201  attached cooperatively to rod and diagonal structures. In this case, the horizontal rods are illustrated by  1203 ,  1224 ,  1207 ,  1124 ,  1125 ,  1210 ,  1211 , and  1218 , and the diagonal rod elements are illustrated by elements  1204 ,  1205 ,  1208 ,  1212 , and  1217 . A mathematical plane, illustrated by the dashed plane  1202 , is shown in a nearly coronal aspect to the patient&#39;s face, and it intersects these various structures at the points  1220 ,  1221 ,  1222 ,  1224 ,  1225 ,  1226 ,  1227 ,  1228 ,  1229 ,  1230 ,  1232 . FIG. 2B illustrates how these index points would look in a typical two-dimensional X-ray CT slice, such as plane  1202 . Index marks for the horizontal rods are  1240 ,  1243 ,  1244 ,  1246 ,  1247 ,  1250 , and the index points for the diagonal elements are illustrated as  1241 ,  1242 ,  1245 ,  1248 , and  1249 . The patient&#39;s anatomy is illustrated by the diagram  1251 . By determining the two-dimensional coordinate positions of each of these index points, as well as any points in the anatomy in a two-dimensional slice, a transformation, calculation, or mapping can be made by computer, manually, or graphically between this data set and the three-dimensional coordinate reference frame of the dental tray and its associated attachment structure to the diagonal and horizontal rods. The pattern of the index points from the diagonal and parallel rods shown in FIG. 2B make determinable not only the coordinate point mapping but also the inclination of the plane of the slice. FIG. 2 shows a lateral elevation view of the patient&#39;s head with the localizer structure in place. Horizontal rods are illustrated by  1263  and  1266  on one side of the head, The diagonal rods  1264  and  1265  are also shown for the structure on one side of the face and head. The projected plane of two CT slices is shown by  1262  and  1261 . The intersection points for each of these planes are illustrated as  1271 ,  1277 ,  1273 , and  1278  for plane  1261  and as  1270 ,  1277 ,  1272 , and  1279  for the plane  1262 . The relationship of these points can be seen to change, depending on the angle of the plane and the position of the plane, and it is this kind of varying relationship of the index points, one relative to the other, which enables the full plane inclination angles as well as mapping of points within the plane to be done according to the patent of Brown. Also, the use of the horizontal rods in this particular example and in the example of FIG. 1 in conjugation with the diagonal rods make it possible to do the mapping easily for an arbitrary CT slice plane. Not shown in FIG. 2C are the index points for the upper elements  1207 ,  1208 , and  1202  with their associated image fiducial points  1244 ,  1245 , and  1246 . These may also be used for an appropriate transformation of coordinates. With the use of two diagonals as shown on each of the side structures of FIG. 2A, the top upper N-shaped structure gives added information which is duplicated but may improve accuracy. The upper N-shaped structure is not essential for these quasi-coronal slices, but is shown here for completeness, as it may be desired to have only one diagonal element on each of the structures to the left and right of the patient&#39;s head. It should also be pointed out that not all of these rods and diagonal elements are necessary to do the mapping or transformation; nor is it necessary to do a full computer code matrix transformation to perform the mapping. A simple triangular plate structure, single rod and single diagonal structure, varying numbers of rod and diagonal structures on the left, right, top, and other portions of the head, curvilinear rod or diagonal elements, spiral structures, arrays of index points, arrays of rods and pins of varying lengths and configurations could all be used to implement the basic invention of this continuation-in-part and of its parent patent application. They are all embodiments of graphic reference means which may be attached to a dental reference frame that can be seen in tomographic or three-dimensional imaging processes that enable the frame of reference of the data from the image processing means to be transformed or mapped into the coordinate reference frame associated with the patient&#39;s anatomy, in this case the skull, which is attached to the dental tray.  
         [0010]    The devices such as those illustrated in FIG. 1 and FIG. 2 are particularly convenient in the ENT field, where quasi-coronal slices through the patient&#39;s head are used. They provide an accurate and detailed mapping from the slice data to the patient&#39;s anatomy which can then be used in turn to provide accurate approach, angulation, and calculation to targets and paths through the patient&#39;s nose, mouth, or other facial aspects into interior anatomical target points for surgery. Use for maxofacial, nasal, pituitary, acoustic, head, throat, and larynx surgery is an obvious application, as discussed in the parent application. The extrapolation to stereotactic target coordination for radiation therapy is also a consequence and application, as described in the parent application. Furthermore, in the diagram of FIG. 2A there are reference points or positions illustrated by  1282 ,  1285 ,  1280 , and  1281 , which are identifiable physical points of known or determinable coordinates associated with the localizer structure that can be accessed during the imaging and also potentially during the surgical, set-up, or calibration phase of the treatment or surgery. As illustrated in the parent invention, these points can be touched off by or located from, for example, a stereotactic digitizer or navigator which may be mechanical, optical, ultrasonic, radiofrequency, magnetic, or otherwise coupled to an interface to a computer graphic workstation, thereby enabling that navigator to be calibrated relative to the patient&#39;s anatomy and recalibrated, if necessary, by simple insertion of the dental tray into the patient&#39;s mouth.  
         [0011]    Included within the scope of this continuation-in-part and in the parent application is use of such identifiable physical points associated with the localizer and/or the dental applicator. Those skilled in the art can make further variations of this present disclosed embodiments for the use in ENT surgery and surgery and therapy in and around the face. It should be noted that although the embodiments in FIG. 1 and FIG. 2 show what is called horizontal rods and diagonal rods thereto, it is possible to make such a localizer to function as described by having only what one would say is diagonal rods; that is, rods that are angled one relative to the other, and not necessarily sets of parallel rods at all. For example, systems of V-shaped rods could be used or merely a single V-shaped structure could be used to give an index of the position of the tomographic slice. The combination of V-shaped or N-shaped structures, or other structures thereof, could be used in conjugation with additional knowledge about the orientation of the CT image plane such as its degree of parallelity to external apparatus to effect such a data mapping. Combinations of index points and rods could be used to effect the purpose which is claimed in this continuation-in-part and the parent invention.  
         [0012]    Having described the continuation-in-part, I therefore claim as letters patent to this invention the following: