Fig 6: 3rd-order shim-induced Fuzzy Ripples as a function of echo spacing, dual-polarity averaging, 3rd order shim.
A) The Fuzzy Ripple artifact varies with the echo spacing of the EPI readout. Consequently, the strength of this artifact can be reduced by adjusting the readout protocol, although such adjustments may compromise TE and readout efficiency.
B) The Fuzzy Ripples induced by the third-order shim can be mitigated by disconnecting its circuit. Opening this circuit reduces the inductive coupling between the third-order shim and the gradient and reduces Fuzzy Ripple artifacts.
C) As indicated by Figures 3 and 4, dual polarity averaging can counteract the Fuzzy Ripples induced by the third-order shim. This approach can mitigate fuzzy ripples, even for the most problematic echo spacings with the third-order shim still connected. Though, faint residual fuzzy ripples remain.
Acquisition parameters of data presented here are mentioned in methods section 3.5. Supplementary Figure S3 presents a reproduction of the results shown here.