High-Resolution Mapping of Neuronal Activation with Balanced SSFP at 9.4 Tesla

Purpose: This work investigates the feasibility of high-resolution functional imaging of the human brain using passband balanced steady state free precession (SSFP) at 9.4 Tesla (T). To this end, the temporal signal stability, blood-oxygen-level-dependent (BOLD)-related signal changes and sensitivity to frequency offsets were evaluated. Methods: Three-dimensional slab selective and nonselective balanced SSFP have been implemented with minimized repetition time and high temporal resolution using parallel imaging, partial Fourier acquisition and elliptical scanning. Using a volume repetition time of approximately 3 s, a visual checker board stimulation was applied for 6 min. Temporal signal stability of balanced SSFP and BOLD response-related signal changes and sensitivity to frequency changes were evaluated. Results: Activation could be detected in all volunteers with BOLD-related signal changes from 3% to 6%. At 1 mm isotropic resolution, the thermal noise SNR0 was 67 and the total temporal noise variation tSNR was 45 supporting a very high signal stability of balanced SSFP. No significant changes of activation at different offresonance frequencies were detected. Conclusion: High spatial and temporal resolution balanced SSFP at 9.4T to detect functional activation is feasible. Activation patterns and signal changes are stable and reproducible across subjects within the visual cortex, and comparable to reported values of SE-EPI at 7T and 9.4T. (C) 2015 Wiley Periodicals, Inc.