“…After ROI extraction, the reviewed studies commonly use GM tissue mean intensities, or volumes, of brain ROIs as features from PET, MRI, fMRI or other modalities [198]. Other measures include subcortical volumes [199,200], grey matter densities [201,202], cortical thickness [203,204], brain glucose metabolism [205,206], cerebral amyloid-β accumulation [207,208], and the average regional CMRGlc [209] for PET. The hippocampus is of particular interest in the reviewed papers; ROI-based methods have used 3D data and morphological measurements of its cortical thickness, curvature, surface area, and volume.…”