Fig. 1.
Representative ΔB0 brain field map acquired at 7 T overlaid on a reference structural image. The FOV has been shimmed with 1st and 2nd order spherical harmonics on a 7 T Siemens scanner. The residual B0 inhomogeneity is particularly severe in regions bordering the sinuses, ear canals, and oral cavity, especially the orbitofrontal cortex, inferior temporal lobes, and brainstem. The standard deviation of ΔB0 within the masked region of the ΔB0 field map, σB0Global, is 51.9 Hz. Field maps are acquired using a two-echo gradient echo sequence with 2.4 × 2.4 mm in-plane resolution, 2 mm slices, and ΔTE = 1.02 ms.