Adjustable Subject-Specific Passive Shims using Optimized Distributions of Bismuth and Zirconium
Koch K, Rothman D, de Graaf R, Brown P
Low order spherical harmonic shims cannot globally compensate in-vivo field inhomogeneity near significant magnetic susceptibility boundaries. Subject-specific passive shims offer a means to globally compensate these higher-order effects. Through linear response theory, we have developed a method to optimize the placement of diamagnetic Bismuth and paramagnetic Zirconium elements. Here, we demonstrate the utility and accuracy of this method through the optimization, construction, and use of a global passive shim for the mouse brain.