Whole brain, high resolution multiband spin-echo EPI fMRI at 7T: A comparison with gradient-echo EPI using a color-word Stroop task

• Published in: NeuroImage (Orlando, Fla.) Vol. 97; pp. 142 - 150
• Main Authors: Boyacioğlu, Rasim, Schulz, Jenni, Müller, Nils C.J., Koopmans, Peter J., Barth, Markus, Norris, David G.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier Inc 15-08-2014; Elsevier Limited
• Subjects: BOLD; Brain; CNR; Neurosciences; Noise; Orbito-frontal; Physiological noise; PINS; Sensitivity; Studies; Physiological noise; Orbito-frontal; Sensitivity; BOLD; PINS; CNR
• ISSN: 1053-8119; 1095-9572
• DOI: 10.1016/j.neuroimage.2014.04.011

A whole brain, multiband spin-echo (SE) echo planar imaging (EPI) sequence employing a high spatial (1.5mm isotropic) and temporal (TR of 2s) resolution was implemented at 7T. Its overall performance (tSNR, sensitivity and CNR) was assessed and compared to a geometrically matched gradient-echo (GE) EPI multiband sequence (TR of 1.4s) using a color-word Stroop task. PINS RF pulses were used for refocusing to reduce RF amplitude requirements and SAR, summed and phase-optimized standard pulses were used for excitation enabling a transverse or oblique slice orientation. The distortions were minimized with the use of parallel imaging in the phase encoding direction and a post-acquisition distortion correction. In general, GE-EPI shows higher efficiency and higher CNR in most brain areas except in some parts of the visual cortex and superior frontal pole at both the group and individual-subject levels. Gradient-echo EPI was able to detect robust activation near the air/tissue interfaces such as the orbito-frontal and subcortical regions due to reduced intra-voxel dephasing because of the thin slices used and high in-plane resolution.
•Whole brain, high resolution comparison of SE and GE EPI with task fMRI at 7T•Multiband SE acquisition without SAR problems is possible at 7T with PINS RF pulses.•GE EPI shows higher efficiency and higher CNR in most brain areas at 7T.•GE EPI can detect activation near the air/tissue interfaces with thinner slices.