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Abstract #0612

INSTANT (INtegrated Shimming and Tip-Angle NormalizaTion): 3D flip-angle mitigation using joint optimization of RF and shim array currents

Mads Sloth Vinding1,2, Torben Ellegaard Lund1,2, Jason P Stockmann3,4, and Bastien Guérin3,4
1Department of Clinical Medicine, Aarhus University, Aarhus, Denmark, 2Center of Functionally Integrative Neuroscience, Aarhus University Hospital, Aarhus, Denmark, 3A. A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Charlestown, MA, United States, 4Harvard Medical School, Boston, MA, United States

We generalize a composite pulse approach used with an RF/multi-coil shim array, whereby we optimize the RF and shim array waveforms played simultaneously for 3D flip-angle homogenization at 7 Tesla in the human head. We show that this approach yields shorter pulses at a given excitation error than when optimizing the RF alone. In other words, the original intuition of the composite pulse approach of RF pulses surrounding DC shim current blips is extended to concurrent RF and shim current and the additional degrees-of-freedom played as continuous shim waveforms significantly improves the excitation quality (uniform 90º excitation).

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