EPI Undistortion Using an Echo Spacing Fitting Method
Liu X, Zhong J
University of Rochester
Echo planar imaging (EPI) suffers severe geometry and intensity distortions because of its inherently long acquisition window in the phase encoding direction. In this work, we propose an Echo Spacing Fitting (ESF) EPI undistortion method using two images collected with different echo spacing times and phase gradient directions. It is shown that the previously proposed phase-reversal undistortion method is a special case of the ESF method. This algorithm performs well in correcting distorted EPI image due to field inhomogeneity. More accurate correction can be achieved if 3 or more images with different echo spacing times are acquired.