Fig. 3.

Comparison of FFT, iterative MB and iterative CPR approach for an in vivo brain scan. a Mild $B_0$ inhomogeneities (~ 600 Hz). (Top row) The FFT reconstruction results in a stretch of the brain along the readout direction (left-to-right). Both iterative CPR and iterative MB image reconstruction result in low errors in the estimated field map, and correct for the corresponding image deformations. The estimated $\mathrm{\Delta }{B}_0$ maps (middle row) and the differences with respect to that of the FFT approach (bottom row) show a similar improvement in the accuracy of the field map estimation when using the iterative CPR and MB approaches. The MB CS reconstruction for an undersampling factor of 2 shows the flexibility of the MB approach towards undersampling. b For strong $B_0$ inhomogeneities (~ 1500 Hz), here obtained by attaching an external magnet to the Faraday cage, the iterative MB approach still results in a uniform signal intensity, while the iterative CPR approach shows more signal shading in the lower-left corner of the brain