This pipeline is similar to the one on the previous page, but highlights our ability to extract the cortical surface of the brain and derive both regional thickness measures as well as vertex-wise measures (in other words, thickness at every point on the cortical surface). We generate both volume and thickness measures as they often provide unique information about brain atrophy.

For surface analysis, the 3D T1-weighted MRI scans from the tissue classification stage undergo:

• Cortical surface extraction using a modified version of the fully-automated CLASP (Constrained Laplacian Anatomic Segmentation using Proximity) algorithm, which generates an inner and outer cortical surface
• Computation of thickness (as the distance between the inner and outer surfaces) for each vertex of the cortical surface
• Vertex-wise and ROI-based statistical analysis