Dennis F R Heijtel1,2, Peter van Gelderen1, Jeff H. Duyn1, Jacco A. de Zwart1
1Advanced MRI, LFMI, NINDS, National Institutes of Health, Bethesda, MD, USA; 2Department of Biomedical Engineering, Eindhoven University of Technology, Eindhoven, Netherlands
Static magnetic field homogeneities negatively affect image quality, in particular at high magnetic field strength. For human brain imaging, predominant sources of such inhomogeneities are the nasal cavity and ear canals. With the current technology, active shim coils cannot adequately compensate for these spatial field perturbations. We investigated the feasibility of generalized passive shimming based on a cylindrical array of ferrous particles, placed in between transmit and receive coil array, for improved field homogeneity in human brain imaging at 7 T. Results (n=34) show consistently improved field homogeneity, albeit limited (~12%), predominantly due to volunteer-to-volunteer variability.
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