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= Fixing Common Topological Defects = <<TableOfContents>> == Motivation == After the initial surface is inflated, any topological defects must be corrected before proceeding. This is often an iterative process where the surface is inflated, viewed, fixed, and reinflated until the surface looks smooth and continuous in all regions. Topological defects can have many different forms. Some look like holes or tunnels in the surface. Others appear as dimples, bumps, or handles. They are created when there are holes in the segmentation, fill errors, areas of non-white matter classified as white matter, and areas where islands of white matter are cut off entirely from the main volume, or disconnect and then reconnect later. Non-cortical structures that adjacent to the cortex (such as the fornix, basal ganglia, and lateral ventricle) can cause large topological defects. All of these are problematic when generating a spherical representation of the cortex, because they represent areas of non-unique mapping to the sphere. In each case, the region must be fixed before inter-subject averaging and morphological studies. The automatic topology corrector can only correct minor errors. == Manual == * Holes * WM classified as non-WM * Fix by filling * Example: filling ventricle * Handles * non-WM classified as WM * Fix by cutting * Example: removing optic nerve * (Other areas: fornix, basal ganglia, temporal strands) == Automatic == |
- Diff for "FSTutorial/FixingDefects"