| 摘要 |
An imaging apparatus (A) generates volume image data which is stored in an image memory (B). An image memory access controller (30) withdraws selected pixel values from the volume image memory which it provides at a video processor (20) to formulate the appropriate video signals for display on a video monitor (C). An operator defines a volume on an operator controller (32). A plurality of interconnected polygons define the three-dimensional volume specified by the operator. The video processor converts these defined polygons into an appropriate display on the monitor. The polygons are selected to define a subregion to be viewed. The polygons are rotated about one or more of (x), (y), and (z) axes, scaled, and translated along these axes to select an orientation from which the polygon and enclosed data is to be viewed. The rotation, scaling and translation is stored (38, 40, 42). From each pixel interior to the projection of a visible polygon onto the screen, the coordinates of a sample in the polygon are calculated via the inverse of the stored rotation, scaling, and translation. The computed tomography (CT) value of sample and that of its neighbours are retrieved, interpolated, weighted with the surface gradient and illuminated on the screen. The polygons are compared and hidden surfaces removed (54). If retrieved pixel values are retrieved that correspond to air or other tissue that is not to be viewed, the access control means continues to step along the translated and rotated viewing direction ray until a pixel value is found which meets the air and non-viewed tissue viewing criteria (62). For a more lifelike image, shading is added (64) to data corresponding to one or more of the polygons. <IMAGE> |
