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Abstract #0356

Real-Time Shim Correction during Functional MRI Using a Volumetric Navigator

A Alhamud 1 , Paul Taylor 1,2 , Jia Fan 1 , Ernesta Meintjes 1 , and Andr J.W. van der Kouwe 3

1 Human Biology,MRC/UCT Medical Imaging Research Unit, University of Cape Town, Cape Town, Western Cape, South Africa, 2 African Institute for Mathematical Sciences (AIMS), Western Cape, South Africa, 3 Massachusetts General Hospital, Charlestown, Massachusetts, United States

During fMRI acquisition, magnetic field inhomogeneities may lead to severe signal dropouts and geometric distortions in fMRI images. The inhomogeneities are routinely minimized by shimming prior to fMRI scan. However, factors, which may include breathing, heating of the shim iron coils or subject motion, can alter the static shim and affect the BOLD measures. The purpose of this work is to introduce a technique to measure, report and correct in real-time magnetic field distortions as well as subject motion. This is achieved by acquiring two volumetric navigators to track motion and produce a field map after each fMRI volume acquisition.

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