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Abstract #1096

Why is 7T fMRI in the entorhinal cortex so difficult and what can we do about it?

Nadine N Graedel1, Oliver Warrington1, Barbara Dymerska1, Vahid Malekian1, Oliver Josephs1, Peter Kok1, and Martina F Callaghan1
1Wellcome Centre for Human Neuroimaging, UCL Queen Square Institute of Neurology, University College London, London, United Kingdom


Functional MRI in the entorhinal cortex is very challenging due to large and geometrically complex B0 field inhomogeneity. As a result, a quarter of voxels are lost due to T2*-driven dephasing and/or because the echo is pushed outside of the acquisition window. Additionally, off-resonant voxels suffer from poor excitation efficiency with frequency-selective binomial pulse excitation, which are preferred for fat suppression for SAR and time efficiency. We empirically demonstrate substantial signal, and consequently tSNR, gains in off-resonance regions by reducing binomial pulse order (from 1-3-3-1 to 1-2-1 or 1-1) that match numerical predictions.

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