Christoph Juchem1, Terence W. Nixon1, Mark Abildgaard1, Scott McIntyre1, Douglas L. Rothman1, Robin A. de Graaf1
1Diagnostic Radiology, MRRC, Yale University School of Medicine, New Haven, CT, USA
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.