Guided field Map Estimation and Image Correction for MRI with LargeMagnetic Field Inhomogeneity

Many methods deployed for Magnetic Resonance Imaging (MRI) suffer from degraded image quality when the static magnetic field (B₀) is nonuniform, as B₀ inhomogeneity causes different types of image artifacts and distortions. Image correction methods require a prior estimate of the field map. In this work, we study the problem of static B₀ inhomogeneity estimation from distorted and undistorted image pairs, despite undistorted images being noisy. The estimated field map is later utilized to correct distorted images. The efficacy of the proposed approach is demonstrated for different encoding methods in the presence of large magnetic field inhomogeneity via extensive simulations.