A Modified Reversed Gradient Method using the Displacement Map Concept for Geometric Distortion Correction in EPI
Chang H, Chuang T, Huang T, Chung H, Chen C
National Taiwan University
Reversed gradient method (RG) relies on using gradient with reversed polarity that produces distortion in opposite direction, from which the information on the difference in spatial displacements is then used to correct for distortion. However, RG is problematic in regions with low signals. We proposed a modified RG using the concept of displacement map to solve this problem. Our modified scheme uses 2D surface fitting to smooth the displacement map, it hence has advantages of less computing time with eddy current correction capability. The corrected EPI images show good preservation of quality even near the skull base.