Figure 7.

Simulated (2D) average magnetic environment of a water proton inside and outside myelinated axons running perpendicular to the magnetic field (and the image plane). For isotropic susceptibility, both environments have cylindrical symmetry and lead to similar local fields (and thus frequencies). For anisotropic susceptibility, an asymmetry is observed that is reversed between the two water environments. This will lead to frequency differences between environments. Thick and thin plot lines show horizontal and vertical profiles respectively. Spatial scale of environment is 7-fold expanded compared to that of magnetization in left column. The average magnetic environment was calculated as described in caption of Fig. 6.