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Abstract #0836

Inter-slice current constrained B0 shim optimization for high order dynamic shim updating with strongly reduced eddy currents

Michael Schwerter1, Chan Hong Moon2, Hoby Hetherington2, Jullie Pan2, Lutz Tellmann1, Jörg Felder1, and N. Jon Shah1,3

1Institute of Neuroscience and Medicine, Medical Imaging Physics (INM-4), Forschungszentrum Jülich, Jülich, Germany, 2Department of Radiology, University of Pittsburgh, Pittsburgh, PA, United States, 3Faculty of Medicine, Department of Neurology, RWTH Aachen University, Aachen, Germany

Dynamic shim updating using spherical harmonics is an effective B0 shim technique, but known to induce eddy currents which degrades the achievable shim quality. Current DSU implementations therefore use pre-emphasis which requires additional hardware and time-consuming system calibrations. To reduce eddy current generation, we have implemented an optimization algorithm which limits the maximum inter-slice shim current change. It is based on the assumption that a smooth variation of shim currents with small current steps will substantially reduce eddy currents. Simulations and initial experiments have shown that eddy currents can be drastically reduced without significant impact on the achievable shim quality.

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