Water-fat separation is a particularly important problem for magnetic resonance imaging.Although many methods have been proposed,the reliability is still challenging.In this work,we have presented a method based on the combination of the branch-cut method and multigrid algorithm to get a more robust performance of water-fat separation.First,the branch-cut method is applied to identify residues,which violates the requirement that the interacting phase gradient around a closed path be zero.Residues and branch...