Hiroyuki Takeda1, Boklye Kim2
1Radiology, University of Michigan, Ann Arbor, MI, United States; 2Radiology, University of Michigan, ann arbor, MI, United States
In practice, the field map dynamically changes with head motion during the scan, and such a changing field leads to variations in geometric distortions in EPI. A previous retrospective approach of approximating a dynamic field map by applying rigid body transformations to an observed static field map may be insufficient in the presence of significant out-of-plane rotations. Our approach is to retrospectively estimate the objects susceptibility map from an observed high-resolution static field map using an estimator derived from a probability density function of non-uniform noise. This approach is capable of finding the susceptibility map regardless of the wrapping effect.