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FIG 2. Two-dimensional illustration in a cut plane of the 3D dataset. The blue lines represent the contours in the cut plane of a blood vessel (ellipsoid) and an aneurysm (circle).
A, -B, Manual thresholding: different threshold levels change the contours of the vessel and the aneurysm.
Gradient-edge detection: voxels with high gradient values are white and voxels with low gradient values are black. In homogeneous parts of the volume, some gradient differences are present, caused by image noise (C). After the small gradient differences are filtered, the contours are unchanged (D).
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