Generalized Non-Linear SENSE Shimming

Daniel Nicolas Splitthoff¹, Maxim Zaitsev¹

With the SENSE Shimming (SSH) approach a method was introduced recently that allows for estimating B0 field inhomogeneities based on a reference image and a series of points on a single free induction decay (FID). In the original approach the temporal evolution of the FID data is explained by field inhomogeneities, using linear approximations. Effects caused by relaxation and those caused by inhomogeneities can therefore not be distinguished and values can only be given relative to a baseline measurement. We here present an extension to the method, which takes into account a larger range of the FID in order to explain not only B0 inhomogeneities but relaxation as well and which therefore allows for accurate field map estimation based on a reference image and a single FID. Since the signal equation is non-linear, the linear fitting of the original approach has to be replaced by a non-linear optimization. The feasibility of the method is shown on in vivo data.