Abstract:
A method for displaying colonography images includes presenting a series of oblique images of the colon at sequential locations along the colon centerline. Each image is generally centered on the centerline, presents a field of view generally perpendicular to the centerline, and is oriented with the bottom of the colon down.

Description:
REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims the benefit of U.S. provisional application Ser. No. 60/881,294, filed Jan. 19, 2007 and entitled Oblique Centerline Following Display Of CT Colonography Images, which is incorporated herein in its entirety by reference 
     
    
     TECHNICAL FIELD 
       [0002]    The invention is a method and system for processing colonography image data and displaying colonography images. 
       BACKGROUND 
       [0003]    Colonography, the use of electronic imaging technologies such as computed tomography (CT) to generate images of a patient&#39;s colon for purposes of colorectal cancer screening, is generally known. By way of example, these technologies are disclosed in the Johnson et al. U.S. Pat. Nos. 6,928,314 and 7,035,681, the Zalis U.S. Pat. No. 6,947,784, the Vining U.S. Pat. Nos. 6,909,913 and 7,149,564, and PCT publication no. WO 2007/030132, all of which are incorporated herein by reference. Briefly, this methodology involves obtaining a series of CT images of adjacent portions or slices of the colon. A radiologist then studies each of the images to identify any pre-cancerous polyps. Alternatively, a computer can effectively create a simulated intraluminal flight through the colon (this is also known as virtual colonoscopy). Colonography has been demonstrated to be a highly efficacious approach for detecting colorectal polyps. 
         [0004]    Readers of CT colonography data sometimes prefer to maintain a small field of view, to maximize conspicuity of small polyps. However, this requires them to manually follow the colon throughout the abdomen and pelvis. Manually following the colon as it curves through the body can at times be difficult and may distract the reader from his or her primary task, which is to locate polyps and lesions within the colon. The reader may also sometimes recenter the segment of interest in the workstation display, further complicating the primary task. Conversely, the need for such recentering may be reduced if the image is viewed at a large field of view, but then any polyps may be more difficult to identify. 
       SUMMARY 
       [0005]    The invention is an improved method and system for processing and displaying colonography image data. In one embodiment of the invention the image data is processed to identify a centerline of the colon. A series of oblique image data sets representative of images of the colon at sequential locations along the centerline is generated. Each image is generally centered on the centerline, presents a field of view generally perpendicular to the centerline and is oriented with the bottom of the colon down. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0006]      FIG. 1  is an image of a colon with a centerline traversing the length of the colon. 
           [0007]      FIGS. 2A-2C  are oblique centerline-following and bottom down images of a colon at a series of sequential positions within the colon in accordance with one embodiment of the invention. 
           [0008]      FIG. 3  is a schematic illustration of the imaging method of the invention. 
       
    
    
     DESCRIPTION OF THE INVENTION 
       [0009]    This invention is a display technique based on the automatic generation of a midline trace or centerline of the colon and then the display of a sequence of images that are centered on this trace, are perpendicular to it, and follow along it. This displays the colon in true cross section along its entire length, as if it had been straightened and sliced perpendicular to its long axis. Such a viewing technique can enhance the prominence of polyps sticking out into the lumen of the colon. The technique can help keep the observer&#39;s attention focused on the colon, and display the colon at an optimal size and in an optimal plane for lesion detection. This can result in faster reading times with less disruption of concentration, and may yield both time savings and improvements in accuracy. 
         [0010]    A centerline trace is shown in  FIG. 1 , and many techniques for generating such a trace are known and described in the literature. A small (and in some embodiments adjustable) field of view of an oblique slice through the data that is perpendicular to the trajectory of the centerline at this position is displayed around the current centerline position. The oblique slice is then rotated so that gravity points to the bottom of the image. This ensures a consistent orientation between slices, and also ensures that liquid content within the colon appears at the bottom of the image, where radiologists typically expect to see it. 
         [0011]    The radiologist controls the centerline position currently observed and field of view (e.g., the size of the field of view) with a mouse, slider bar or other keyboard or GUI control. As the radiologist advances through the centerline, the image shown is constantly updated to be from the slice corresponding to the current centerline position and centered on its location.  FIGS. 2A-2C  illustrate oblique centerline following, displaying sample views at three closely spaced points along the centerline in the transverse colon. As the radiologist scans along the centerline, the current centerline point (bright dot in the figure) remains at the center of the image, and a relatively small field of view is displayed around it, maintaining the current segment of interest in the center of the display. The images shown in  FIGS. 2A-2C  were generated at four point increments along the centerline, and have a field of view approximately 80 mm wide. Liquid stool contents always appears at the bottom of the images in  FIGS. 2A-2C . 
         [0012]    The field of view (FOV) is preferably large enough to show sufficient detail in the image, yet small enough so that the reader can view the image relatively quickly. The appropriate size FOV can be determined. Alternatively, GUI or other controls can be installed to make this adjustable by the user. Navigational aids to orient the user as to the current location, such as a full rendering of the colon ( FIG. 1 ) with an arrow or marker showing the current position, can be included. The display system can automatically keep track of whether all necessary slices have been viewed, and alert the user when some areas of the colon have not been observed. 
         [0013]      FIG. 3  is a schematic illustration of oblique colon following in accordance with the invention. The images are generated orthogonal to the colon centerline and are centered on the lumen. The displayed images are rotated so that gravity points downward. 
         [0014]    Although the invention is described with reference to preferred embodiments, those skilled in the art will recognize that changes can be made in form and detail without departing from the spirit and scope of the invention.