Variable Flip Angle 3D-GRASE for Increased Spatial Coverage and Improved Point Spread Function in High Resolution fMRI at 7T
Valentin G. Kemper 1 , Federico De Martino 1 , An T. Vu 2 , David A. Feinberg 3 , Essa Yacoub 2 , and Rainer Goebel 1
Department of Cognitive Neuroscience,
Maastricht University, Maastricht, Limburg, Netherlands,
Center for Magnetic Resonance Research, University of
Minnesota, Minneapolis, Minnesota, United States,
Wills Institute of Neuroscience, University of
California, Berkeley, United States
Variable flip angle (VFA) refocusing schemes for
Inner-Volume 3D-GRASE were designed to improve spatial
coverage and point-spread along the partition direction
in high-resolution functional MRI at 7T. Phase graph
theory was used to calculate signal contributions from
spin-echoes and stimulated echoes along the echo train.
The simulations yield point-spread functions, which are
in good agreement with such estimated from non-phase
encoded acquisitions. In a simple visual activation
experiment, almost twice the number of slices were
acquired per echo train while maintaining the temporal
signal to noise ratio, functional sensitivity, and
point-spread properties of a reference acquisition with
conventional 180 refocusing.
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