7 t mri scanner

Structural and functional MRI was collected using a Siemens 7 T MRI scanner. High-resolution functional data were acquired using a multiband gradient-echo T2* echo planar imaging (EPI) sequence with a 1.5 × 1.5 × 1.5 mm resolution; multiband acceleration factor 3; repetition time (TR) 1962 ms; echo time (TE) 20 ms; flip angle 66°; and a GRAPPA acceleration factor 2. Field of view (FOV) was adjusted to cover the whole-brain with axial orientation and a fixed angulation of −30° (anterior-to-posterior phase encoding direction; 96 slices). Additionally, a single-measurement, whole-brain, functional image was acquired prior to the main functional image (with similar orientation). This pre-saturation scan was later used to improve registration of the main functional image to the whole brain. Structural data were acquired with a T1-weighted MP-RAGE sequence with a 0.7 × 0.7 × 0.7 mm resolution; GRAPPA acceleration factor 2; TR 2200 ms; TE 3.02 ms; and inversion time (TI) 1050 ms. To correct for field inhomogeneities a separate Fieldmap sequence was acquired with a 2 × 2 × 2 mm resolution; TR 620 ms; TE1 4.08 ms; TE2 5.10 ms. Finally, to regress out the effect of physiological noise in functional data, cardiac and respiratory frequencies were collected by pulse oximetry and respiratory bellows.

Experiments were conducted in a Siemens 7 T MRI scanner using a 32-channel head coil with internal head cage at New York University Center for Biomedical Imaging. High-resolution (1.0 mm isotropic voxels) T1-weighted MPRAGE images were acquired with the following parameters: FOV 256 mm, 192 sagittal slices, TR 3000 ms, TE 4.49 ms, flip angle 6°, fat suppression on. For intensity normalization, proton density (PD) images were acquired with the following parameters: FOV 256 mm, 192 sagittal slices, 1.0 mm isotropic voxels, TR 1760 ms, TE 2.57 ms, flip angle 6°, bandwidth 280 Hz/Px. Blood oxygen level-dependent (BOLD) fMRI images were acquired with the following parameters: FOV 192 mm, 54 oblique slices covering all of cortex, voxel size 2.0 mm × 2.0 mm, slice thickness 2.0 mm with distance factor 10%, TR 2000 ms, TE 25 ms, multiband factor 2, GRAPPA acceleration 2, phase encoding direction P- > A, flip angle 50°.

Anatomical magnetic resonance imaging (MRI) data were acquired for all subjects on a Siemens 7 T MRI scanner using a 32-channel head coil with internal head cage at New York University Center for Biomedical Imaging. High-resolution (1.0 mm isotropic voxels) T1-weighted MPRAGE images were acquired with the following parameters: FOV 256 mm, 192 sagittal slices, TR 3000 ms, TE 4.49 ms, flip angle 6°, fat suppression on. Stimulation sites were determined based on each subject’s anatomical MRI, using the Brainsight Neuronavigation system (Rogue Research Inc.). Each subject’s MRI data were registered to the standard MNI space using custom AFNI scripts for nonlinear transform. After the targeted coordinates were applied in MNI space, the MRI was transformed back into the individual subject’s head space for physical targeting. A mark was made on the skin at the scalp location nearest to the target region for placement of the tDCS anode. These methods closely follow those published in a previous study from our lab^{23 (link)}.

We acquired MRI data on a head-only 7 T MRI scanner (Siemens, Germany), equipped with a head gradient-insert (AC84, 80 mT m⁻¹ maximum gradient strength; 350 mT m⁻¹ slew rate) and a 32-channels receive coil with tight transmit sleeve (Nova Medical, Massachusetts, USA). T2*-weighted functional images were acquired using SMS acquisition with voxel resolution of 1.5 mm isotropic, with a matrix size of 146 × 146 × 75, which resulted in a field of view of 219(AP) × 219(LR) × 112.5(FH) mm. Repetition time (TR) was 1.25 s, echo time (TE) was 0.023 s, flip angle was 60° and bandwidth was 1903 Hz Px⁻¹. Slices were oriented transversally with an anterior-to-posterior phase-encoding direction. Numerosity runs contained 265 TRs whereas the other runs 304. Additionally, at the end of each run we acquired 3 volumes with the opposite phase encoding direction. High-resolution T1-weighted images were also obtained using MP2RAGE pulse sequence optimized for 7 T (voxel size = 0.6 × 0.6 × 0.6 mm, matrix size = 320 × 320 × 256, TI₁/TI₂ = 750/2350 ms, α₁/α₂ = 4/5°, TR_MP2RAGE/TR/TE = 5500/6000/4.94 ms).