Abstract:
In an imaging method for medical diagnostics and a device operating according to this method, during an endoscopic examination of a body region of a patient with an endoscope, an image is generated with a non-endoscopic imaging method and the image field of the endoscope is determined and rendered in the image ( 28 ) with accurate position and orientation.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The invention concerns an imaging method for medical diagnostics as well as an imaging device operating according to this method. 
         [0003]    2. Description of the Prior Art 
         [0004]    In medical diagnostics, in a series of application cases different imaging methods are used simultaneously or successively in order to facilitate the diagnosis or to avoid misdiagnoses. For example, in urology it is known to implement both an endoscopic examination and an x-ray examination. In an endoscopic method, high-resolution, color, optical images are generated in real time in the viewing direction of the endoscope. Each image, however, offers only two-dimensional information of the state of a section of the inner surface of the cavity and no information from deeper slices or in other viewing directions. In an x-ray method, information is also acquired from regions that are not visible in an endoscopy image. The linking of individual or multiples endoscopic images with one or more x-ray images of the same body require on the part of the observer not only a precise knowledge of the anatomy but also a developed three-dimensional spatial sense that must first be learned and frequently leads to misinterpretations. Moreover, pathological structures often deviate in a complex manner from the standard, such that a linking of endoscopy images and x-ray images is made more difficult. 
         [0005]    One of the causes for these difficulties is that the methods normally used in addition to endoscopy (for example magnetic resonance methods or ultrasound methods in addition to the aforementioned x-ray methods) provide slice images of the examination subject, while in an endoscopy image only a boundary surface between an optically permeable medium and an optically impermeable medium is presented on a two-dimensional image plane. 
       SUMMARY OF THE INVENTION 
       [0006]    An object of the present invention is to provide an imaging method for medical diagnostics that makes the interpretation of image data acquired with endoscopic methods and non-endoscopic methods easier for the user. A further object of the invention is to provide a device operating according to such a method. 
         [0007]    The object according to the invention is achieved by an imaging method wherein, during an endoscopic examination of a body region of a patient, an image is generated of the body region with a non-endoscopic imaging method, and the image field of the endoscope is determined and rendered in the image with accurate position and orientation. 
         [0008]    Via this measure it is possible for the user to associate the structures identified in the endoscopy image or in the image with one another and to assess them with regard to their diagnostic relevance. 
         [0009]    In the present specification the term “image” is used exclusively for images that have been generated with a non-endoscopic imaging method, for example x-ray images, magnetic resonance images or ultrasound images. 
         [0010]    A particularly simple determination of the position and orientation of the image field of the endoscope is possible via comparison of the image of the endoscope generated with the non-endoscopic imaging method (i.e. the endoscope rendered in the image) with a stored three-dimensional model of the endoscope for the non-endoscopic method. This model is a three-dimensional image of the endoscope that has been generated with this method in a calibration. In such a model comparison, the model is rotated and displaced (shifted) with corresponding coordinate transformations until the image of the endoscope and the model projected on the image plane after the coordinate transformations show maximal correlation. The image field of the endoscope (which is projected in the image plane just like the model) is also linked with the model. 
         [0011]    As an alternative, the image coordinates of the image are determined in a fixed coordinate system and the position and orientation of the image field of the endoscope is measured in this fixed coordinate system with a position detection device. Due to this measure a model comparison is unnecessary and the image field can be projected into the image purely by calculation even if the endoscope itself is not visible in the image. 
         [0012]    The association of a structure rendered in the endoscopy image with a structure rendered in the image is made easier for the observer if the rendered image field is bounded by optically impermeable structures recognizable in the image. 
         [0013]    An additional facilitation for the user is achieved when a marker placed by the user in the endoscopy image is displayed in the image as a ray beam emanating from the endoscope or as an end point at an optically impermeable structure. 
         [0014]    As an alternative or in addition, an area selected by the user in the endoscopy image is displayed in the image as a beam emanating from the endoscope or as an end surface at an optically impermeable structure. 
         [0015]    In an embodiment of the invention, the marker or surface is automatically segmented with methods of image processing. 
         [0016]    If the image generated with a non-endoscopic imaging method is a 3D image, the image field of the endoscope can be visualized particularly vividly in spatial representation. 
         [0017]    A device according to the invention implements the method and achieves advantages that correspond to the advantages specified with regard to the method. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0018]      FIG. 1  schematically illustrates a device according to the invention. 
           [0019]      FIGS. 2 through 4  respectively show an image of an examination subject generated with a non-endoscopic imaging method, and an endoscopy image. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0020]    As shown in  FIG. 1 , a device according to the invention has an endoscopy apparatus  2  as well as an image generation system  4  operated according to a non-endoscopic method, in the example a C-arm x-ray apparatus with an x-ray source  6  and an x-ray receiver  8  that are arranged on a C-arm  9  (shown in dashes in the Figure). The C-arm  9  can be pivoted around an isocenter  10  such that a two-dimensional image (slice image) can be generated from a body region of a patient  12 . This pivot movement around an axis perpendicular to the plane spanned by the C-arm  9  (the plane of the drawing in  FIG. 1 ) is illustrated by a double arrow  14 . Moreover, if the C-arm  9  can be pivoted around an axis that lies in the plane spanned by it and is illustrated by the double arrow  16 , it is possible to also generate a 3D image data set from the body region of the patient  12 . 
         [0021]    An endoscope  20  with which it is possible to optically observe a section of the internal surface of a wall  30  of a cavity  18  is inserted via a bodily orifice into said cavity  18  of the body  12 . The lateral edge  19  of an image field  22  acquired by the endoscope  20  is drawn in dashes in  FIG. 1 . 
         [0022]    Starting from the wall  30  of the cavity  18 , in the example a pathological tissue zone  24  (for example a tumor) extends into a region lying behind the wall  30  (i.e. outside of the cavity  18 ). In the shown example this pathological tissue zone  24  lies in the image field  22  of the endoscope  20  and is recognizable as a planar structure  240  of the inner surface in an endoscopy image  26  acquired in this position of the endoscope  20 , which planar structure  240  is in fact emphasized relative to the surroundings but whose unambiguous assessment is not possible without further measures. 
         [0023]    Among other things, the contour of the wall  30  of the cavity  18  (which contour forms an optically impermeable structure) as well as further structures  32  situated in the slice plane are recognizable in a non-endoscopic image  28  (in the example a two-dimensional x-ray slice image) generated with the image generation system  4 . A structure  242  that extends into the tissue and that reflects pathological tissue zones  24  is now recognizable for the user in this image  28 . Moreover, the endoscope  20  is visible in the image  28  in the shown exemplary embodiment. 
         [0024]    Using a three-dimensional model of the endoscope  20  stored in a memory  40  of the image generation system  4 , the position of the endoscope  20  (and therefore of the image field  22 ) relative to an image coordinate system x B , y B  associated with the image generation system  4  is now determined by comparison of the image of the endoscope  20  with this model. The image field  22  is mixed into the image  28  with accurate position and orientation (i.e. is visibly emphasized for the user) with an image processing software implemented in a control and evaluation device  42  of the image generation system  4 . For example, the entire image field  22  is colored for this purpose. Alternatively, it is also possible to exclusively display the edge  19  of the image field  22  as boundary rays in the image  28 . 
         [0025]    Moreover, in the shown example both the edge  19  and the image field  22  end at the contour (recognizable in the image  28 ) of the wall  30  of the cavity  18  in order to visualize to the observer that only a surface region corresponding to this contour is visible in the endoscopy image  26 . Alternatively or additionally, it is possible to emphasize the end surface of the image field  22  at the optically impermeable structure (wall  30 ). 
         [0026]    By comparison of endoscopy image  26  and image  28 , the observer now recognizes that the flat structure  240  visible in the endoscopy image  26  belongs to the structure  242  extending deep into the tissue in image  28 , and the observer can in this manner now clearly associate both structures  240 ,  242  with one another and, for example, better assess their volume extent since the endoscopy image  26  and the image  28  impart size impressions in slice planes perpendicular to one another. 
         [0027]    Moreover, in the shown example a position detection device  50  is associated with the endoscope  20 , with which position detection device  50  the position and orientation of the endoscope  20  (and therefore also the position and orientation of the image field  22 ) can be determined in a fixed coordinate system x, y, z with the use of sensors (not shown in the Figure) arranged in the region of the endoscope tip. Given a known relationship between the image coordinate system x B , y B  of the image  28  and the fixed coordinate system x, y, z, it is possible to enter the image field  22  into the image  28  with correct position without it being necessary to store a model of the endoscope  20 . 
         [0028]    The observer now has the possibility to mark an area of interest to him or her in the endoscopy image, which area encompasses the structure  240  in the example. This area  52  is relayed from a control and evaluation device  54  of the endoscopy apparatus  2  to the control and evaluation device  42  of the image generation system  4  and is mixed into the image  28  with the image processing software, for example in the form of a limited image field  56  shown in hatching or in the form of boundary rays  58  drawn in dashes, as is illustrated in  FIG. 2 . 
         [0029]    As an alternative to this, the observer can also place a marker  60  at a single point of interest to the observer, which marker  60  is then shown either as a sight line or ray  62  (drawn in dashes) ending at the wall  30  or likewise as an end point  61  of this ray  62  at the wall  30 , i.e. the optically impermeable structure in the image  28 . 
         [0030]    However, in principle it is also possible that the area  52  of interest or the marker is automatically segmented with methods of image processing. 
         [0031]    Situations in which the endoscope  20  is visible in the image (slice image) are presented in  FIGS. 1 through 3 . This is not necessarily the case since the tip of the endoscope can also be located in a plane lying outside of the slice plane. 
         [0032]    A situation in which the tip of the endoscope is arranged outside of the plane of the drawing (the image plane of image  28 ) shown in  FIG. 1  and the optical axis of the video camera integrated into the endoscope is aligned perpendicular to the slice plane is presented in  FIG. 4 . In this case the image field  22  of the endoscope is a circular area (an ellipse given angled orientation of the optical axis) and the observer can in any case learn the information that a synthesis of the two images is not possible upon consideration of the image of the endoscopy image  26  and the image  28 . 
         [0033]    In the exemplary embodiment, two-dimensional slice images are generated by an image generation system  4 . However, the method can be used with particularly great advantage even when the image generation system  4  generates a three-dimensional image data set of the examination subject  12 . Then the normally conical image field  22  of the endoscope can be spatially mixed into the 3D data set and the orientation of the user is significantly facilitated. 
         [0034]    The invention is also not limited to the flexible endoscope depicted in the exemplary embodiment. In principle the endoscope can also be executed rigidly or as an endoscopy capsule. 
         [0035]    Although modifications and changes may be suggested by those skilled in the art, it is the intention of the inventors to embody within the patent warranted hereon all changes and modifications as reasonably and properly come within the scope of their contribution to the art.