Linear phase-error correction for improved water and fat separation in dual-echo dixon techniques

Large and spatially‐linear phase errors along the frequency‐encode direction may be induced by several common and hard‐to‐avoid system imperfections such as eddy currents. For data acquired in dual‐echo Dixon techniques, the linear phase error can be more aggravated when compared to that acquired in a single echo and can pose challenges to a phase‐correction algorithm necessary for successful Dixon processing. In this work, we propose a two‐step process that first corrects the linear component of the phase errors with a modified Ahn‐Cho algorithm (Ahn CB and Cho ZH, IEEE Trans. Med. Imaging 6:32, 1987) and then corrects the residual phase errors with a previously‐developed region‐growing algorithm (Ma J, Magn. Res. Med. 52:415, 2004). We demonstrate that successive application of the two‐step process to data from a dual‐echo Dixon technique provides a “1‐2 punch” to the overall phase errors and can overcome local water and fat separation failures that are observed when the region‐growing–based algorithm is applied alone. Magn Reson Med 60:1250–1255, 2008. © 2008 Wiley‐Liss, Inc.