Zoomed functional imaging in the human brain at 7 Tesla with simultaneous high spatial and high temporal resolution.
Functional neuroimaging in the human brain using noninvasive magnetic resonance methods has the potential of providing highly resolved maps of neuronal activation. Decreasing the voxel size and obtaining simultaneously high temporal resolution is a major challenge and is mainly limited by sensitivity. Here, signal-to-noise gains at high magnetic fields (7 Tesla) and an optimized surface coil setup are combined with a novel approach for zoomed functional imaging in the visual cortex. For echoplanar imaging, the acquisition time and segmentation was shortened fourfold by using a reduced field-of-view. An adiabatic outer-volume suppression method, BISTRO, was used to obliterate signal outside the area-of-interest achieving effective suppression even for inhomogeneous B1-fields. A single-shot acquisition was performed at submillimeter resolution in the human brain, while simultaneously maintaining a high temporal resolution of 125 ms. Functional studies with and without field-of-view reduction were performed. Activation and percent change maps were compared with respect to spatial extent, t values and percentage changes of the BOLD contrast. The detection of functional activation was found to be equal within the inter-series variability for the two acquisition schemes. Thus, single-trial BOLD responses were detected for the first time robustly at a 500 x 500 microm2 in plane and 250 ms temporal resolution, significantly expanding the possibilities of event-related functional imaging in the human brain. The magnetization transfer effect induced by the outer-volume suppression pulses was investigated and found to be increased during neuronal activity.
Pfeuffer
Josef
J
Center for Magnetic Resonance Research, University of Minnesota Medical School, 2021 6th Street S.E., Minneapolis, Minnesota 55455, USA. josef.pfeuffer@tuebingen.mpg.de
van de Moortele
Pierre-Francois
PF
Yacoub
Essa
E
Shmuel
Amir
A
Adriany
Gregor
G
Andersen
Peter
P
Merkle
Hellmut
H
Garwood
Michael
M
Ugurbil
Kamil
K
Hu
Xiaoping
X
D000465:Algorithms; D001921:Brain / Q000033:anatomy & histology* / Q000166:cytology / Q000502:physiology; D017352:Echo-Planar Imaging; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008279:Magnetic Resonance Imaging / Q000295:instrumentation / Q000379:methods*; D010775:Photic Stimulation; D015203:Reproducibility of Results; D014793:Visual Cortex / Q000033:anatomy & histology* / Q000166:cytology / Q000502:physiology; D014794:Visual Fields / Q000502:physiology