Whole Brain Field Homogenization with Localized Electrical Coils

Christoph Juchem¹, Terence W. Nixon¹, Mark Abildgaard¹, Scott McIntyre¹, Douglas L. Rothman¹, Robin A. de Graaf¹

Strong field distortions created by largely varying magnetic susceptibility conditions in the human head pose a major limitation in the study of brain areas like the prefrontal cortex as they hamper whole brain imaging and spectroscopy. The distortions are usually minimized by a set of low-order spherical harmonic shim functions. Based on field simulations, we show that largely improved whole brain shimming can be achieved with a set of 100 circular electrical coils placed directly around the head of the subject. Shim fields can be generated that exhibit a strength and complexity that by far exceeds the capabilities of the not problem-oriented, spherical harmonic functions.