Identification of the optimal orientation of oblique sections through multiple parallel CT images.

A method for identifying the optimal orientation of images of oblique sections computed from a "stack" of parallel computed tomography (CT) scans is presented. The identification of the optimal orientation is facilitated by the display of the stack of cross-sectional images (volume image) in three dimensions. Moreover, by displaying the section image as a brightened plane within the volume, imaged anatomic landmarks may be utilized to guide the process of identifying the desired image plane orientation. The volume image display method, termed projection imaging, involves the numerical projection of the volume picture elements (voxels) of the three-dimensional (3-D) reconstruction onto a plane to form a two-dimensional projection image. For X-ray CT, these projections are analagous to, and appear very much like, conventional radiographs. The volume image is seen in three dimensions by appropriately viewing stereo-pair projections of the volume formed from viewpoints that are 2 to 8 degrees apart. The display of the 3-D reconstruction as a volume image eliminates the need for the observer to mentally reconstruct the spatial relationships of the oblique section to anatomic features within the volume.