Direct and Independent Estimation of B0 Components Based on Raw EPI Data

Frederik Testud¹, Iulius Dragonu¹, Jrgen Hennig¹, Maxim Zaitsev¹

GE EPI is a widely used imaging technique, but is very sensitive to B₀ field inhomogeneities. To correct for temporal changes of B₀, real-time measuring methods are necessary, such as estimating gradient maps of B₀ from raw EPI data. Here a filter scheme is presented to calculate local B₀ gradients. The local gradient in the readout direction is estimated independently from the gradient in the phase encoding direction by finding the contour lines of the gradients. This method is compared with previously introduced raw data based techniques and shown to perform better or equally well.