High resolution single-shot EPI at 7T.
OBJECTIVE
Single-shot echo planar imaging (EPI) acquisitions at 7T are challenging due to increased distortions, signal dropouts, RF-power requirements, and reduced T2*. This study developed and tested pulse sequence and protocol modifications required to allow high resolution EPI for whole brain functional neuroimaging.


METHODS
Using geometric distortion correction methods, modified fat saturation, and parallel imaging, we acquired high resolution single-shot gradient-echo EPI data at 7T with different spatial resolution. The BOLD sensitivity was evaluated and quantified in a breath hold experiment.


RESULTS
Single-shot EPI data with isotropic resolution from 3 to 1.1 mm were acquired in human subjects. The RF-power deposition has been reduced to allow up to 22 slices per second. In addition, acoustic noise and helium boil-off have been reduced. A reduction of the fat saturation flip angle resulted in up to 20% signal gain without compromising the fat suppression quality. For the coil used, the BOLD sensitivity is highest for 2 or 1.4 mm isotropic resolution.


CONCLUSIONS
High resolution single-shot EPI in the whole brain can be performed at 7T with high efficiency, low signal dropout, and without major geometric distortions.
Speck
Oliver
O
Department of Biomedical Magnetic Resonance, Faculty of Natural Sciences/Institute for Experimental Physics, Otto-von-Guericke-University Magdeburg, Leipziger Str. 44, Haus 01, 39120 Magdeburg, Germany. oliver.speck@nat.uni-magdeburg.de
Stadler
J
J
Zaitsev
M
M
D000162:Acoustics; D000465:Algorithms; D016477:Artifacts; D001331:Automation; D001921:Brain / Q000473:pathology*; D001931:Brain Mapping / Q000379:methods; D017352:Echo-Planar Imaging / Q000295:instrumentation* / Q000379:methods*; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008432:Mathematical Computing; D016011:Normal Distribution; D019047:Phantoms, Imaging; D012119:Respiration; D012680:Sensitivity and Specificity