Multi-modal MRI Acquisition Protocol

Data acquisition was performed on a Philips Ingenia Elition X 3 T MRI system (Philips Healthcare, Best, NL; R5.6.1.0) using a 32-channel head coil. The imaging protocol consisted of magnetization prepared rapid gradient echo (MPRAGE), fluid-attenuated inversion recovery (FLAIR), 3D gradient and spin echo (GRASE) with 48 echoes for myelin water imaging (Prasloski et al., 2012b (link)), and 3D gradient echo with three echoes and ten MT-pulses for ihMT (Girard et al., 2015 (link)). Three 3D multi-echo gradient echo data sets with T1-, PD-, and MT-weighting, including B1-mapping, were acquired for multi-parameter mapping (Tabelow et al., 2019 (link)). Diffusion-weighted imaging (DWI) data were acquired with a multiband accelerated single-shot spin echo version of an echo-planar imaging sequence with two diffusion shells (32 gradient directions at b = 711 s/mm² and 64 gradient directions at b = 2000s/mm² with 12 interleaved b = 0 s/mm²). In each participant, MPRAGE and FLAIR were scanned first. The order of all other sequences was permuted across participants. Detailed scanning parameters can be found in the supplementary methods and in Supplementary Table X1.