Andrew Hahn1, Andrew Nencka1, Daniel Rowe, 1,2
1Biophysics, Medical College of Wisconsin, Milwaukee, WI, United States; 2Mathematics, Statistics, and Computer Science, Marquette University, Milwaukee, WI
Estimations of main magnetic field inhomogeneity are often acquired for correction of image warping in echo planar images (EPI) resulting from vulnerability to off-resonance effects of EPI. Many established methods exist for field estimation, one of which involves two EPI acquisitions with different echo times. The method is fast, easily implemented and can be performed in-line with fMRI experiments. However, inconsistencies in the MRI scanner hardware, specifically with the RF pulse, as well as physiologic phenomena that alter the off-resonance characteristics between image acquisitions such as motion or respiration can induce errors in field maps estimated in this manner.