Multiband multislice GE‐EPI at 7 tesla, with 16‐fold acceleration using partial parallel imaging with application to high spatial and temporal whole‐brain fMRI

Abstract

Parallel imaging in the form of multiband radiofrequency excitation, together with reduced k-space coverage in the phaseencode direction, was applied to human gradient echo functional MRI at 7 T for increased volumetric coverage and concurrent high spatial and temporal resolution. Echo planar imaging with simultaneous acquisition of four coronal slices separated by 44mm and simultaneous 4-fold phase-encoding undersampling, resulting in 16-fold acceleration and up to 16-fold maximal aliasing, was investigated. Task/stimulusinduced signal changes and temporal signal behavior under basal conditions were comparable for multiband and standard single-band excitation and longer pulse repetition times. Robust, whole-brain functional mapping at 7 T, with 2 3 2 3 2mm 3 (pulse repetition time 1.25 sec) and 1 3 1 3 2mm 3 (pulse repetition time 1.5 sec) resolutions, covering fields of view of 256 3 256 3 176mm 3 and 192 3 172 3 176mm 3 , respectively, was demonstrated with current gradient performance.

The prestimulus default mode network state predicts cognitive task performance levels on a mental rotation task

“…T1‐weighted anatomical scans were obtained for each participant using a three‐dimensional magnetization‐prepared rapid‐acquisition gradient‐echo (MPRAGE) sequence (192 slices, slice thickness = 1 mm, no gap, TR = 2,250 ms, TE = 2.21 ms, FA = 9°, FOV = 256 × 256 mm 2 , matrix size = 256 × 256, total scan time = 8 min 26 s). Functional images were acquired using multiband (MB) accelerated echo‐planar imaging (EPI) (Moeller et al., 2010), obtaining one resting state run (900 volumes, 48 slices, voxel dimensions = 2.5 mm isotropic, no gap, TR = 1,000 ms, TE = 31 ms, FA = 62°, FOV = 224 × 224 mm 2 , matrix size = 89.6 × 89.6, MB factor = 4, slice order = interleaved) and four to five mental rotation task runs (equal scanning parameters, 880 volumes).…”

Quantitative mapping of the per‐axon diffusion coefficients in brain white matter

“…The spin‐echo echo‐planar scan with nominal flip angle of ${78}^{°}$ and refocusing flip angle of ${160}^{°}$ was performed using a multiband sequence 38, 39, 40 with slice acceleration factor of 3. The diffusion data were acquired with in‐plane phase encoding in both right‐to‐left and left‐to‐right directions.…”

“…The acquisition time was circa $36\hspace{0.17em}\min$. After unaliasing the simultaneously acquired slices channel by channel 38, 39, 40, SENSE1 multiple‐coil combination was applied 41 and the magnitude signal was stored. The dataset used in the study came from an adult male in the age group between 25 and 35 years.…”

Striatal subdivisions that coherently interact with multiple cerebrocortical networks

“…T1‐weighted structural images were obtained for anatomical reference (resolution = 0.8 × 0.8 × 0.8 mm 3 ). Functional images were obtained using multiband gradient‐echo echo‐planar sequences (Feinberg et al, 2010; Moeller et al, 2010; Xu et al, 2013; TR = 4.0 s, TE = 41.6 ms, flip angle = 73º, FOV = 160 × 160 mm 2 , matrix size = 128 × 128, 120 contiguous slices, voxel size = 1.25 × 1.25 × 1.25 mm 3 , multiband factor = 4). We acquired 100 volumes in each fMRI run at the resting state and repeated the process for 10 runs in each of the 10 daily sessions.…”