Figure 3
From: Distortion correction using topup algorithm by single k-space (TASK) for echo planar imaging
Overall process to estimate B0 field map. A single phase-corrected k-space was divided into two halves and reconstructed to images by POCS. To compensate for the signal suppression by insufficient k-space information, an iterative procedure of automatic brain masking and uniformity correction was applied. Finally, the topup method with the two final input images with opposite distortions could estimate the B0 field map.
