Shim Navigators for Accurate Detection of the B0 Magnetic Field Inhomogeneities using Reference MGE Images

Iulius Dragonu¹, Daniel Nicolas Splitthoff¹, Nicoleta Baxan¹, Paul Freitag², Jrgen Hennig¹, Maxim Zaitsev¹

The B0 magnetic field may change during the experiment for several reasons: physiological motion, such as breathing, subject motion and hardware imperfections, such as passive shim element heating. Changes in B0 homogeneities can lead to unwanted signal fluctuations in EPI time course acquisitions. As suggested previously, shim navigators may allow the detection of magnetic field evolution. It has been demonstrated that the phase of a projection is not necessarily proportional to the B0 field inhomogeneities along the direction of that projection. In this work, we propose a method for detection of zero- and first-order in plane shims (f0, A11 and B11) based on shim navigators and reference multi gradient echo images.