Fig. 1

Flow diagram of the MRI method for the measurement of the DTI-ALPS index. DTI data were preprocessed to generate FA maps and color-coded FA maps, and these images were normalized to a standard template where the location of the ROIs were initially determined. Subsequently, four 6 × 6 mm² ROIs were placed according to identified positions. Diffusivities in the directions of the x-, y-, and z-axis were recorded, and the DTI-ALPS index was calculated. DTI-ALPS, diffusion tensor image analysis along the perivascular space; FA, fractional anisotropy; DTI, Diffusion tensor image; ROI, region of interest