Oliver Speck1, J Stadler, M Zaitsev. 1. 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
Abstract
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. MATERIALS AND 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. CONCLUSION: 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.
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. MATERIALS AND 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. CONCLUSION: 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.
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