MRI acquisition
BEST
Participants completed pre-randomization MRI at the Vanderbilt University Institute for Imaging Sciences on a research-dedicated 3.0 T Philips Achieva whole-body scanner (Philips Medical Systems, Best, the Netherlands) using body coil radiofrequency transmission and a 32-channel head coil for reception. Structural imaging included a whole-brain T1-weighted MPRAGE image with TR = 8.75 ms, TE = 4.6 ms, flip angle = 9°, and spatial resolution = 0.89 × 0.89 × 1.2 mm