MRI acquisition
All structural brain MRIs were acquired in a 3-Tesla MR system (General Electric PET/MRI equipment, USA). Volumetric images were based on T1-weighted sequences using a 3D fast-field echo pulse sequence with the following parameters: field of view (FOV) of 25.6, time of repetition (TR) of 7.7 ms, time of echo (TE) of 3.1 ms, and 202 slices.