Reducing the ambiguity of field inhomogeneity and chemical shift effect for fat–water separation by field factor

Abstract

PurposeTo reduce the ambiguity between chemical shift and field inhomogeneity with flexible TE combinations by introducing a variable (field factor).Theory and MethodsThe ambiguity between chemical shift and field inhomogeneity can be eliminated directly from the multiple in‐phase images acquired at different TEs; however, it is only applicable to few echo combinations. In this study, we accommodated such an implementation in flexible TE combinations by introducing a new variable (field factor). The effects of the chemical shift were removed from the field inhomogeneity in the candidate solutions, thus reducing the ambiguity problem. To validate this concept, multi‐echo MRI data acquired from various anatomies with different imaging parameters were tested. The derived fat and water images were compared with those of the state‐of‐the‐art fat–water separation algorithms.ResultsRobust fat–water separation was achieved with the accurate solution of field inhomogeneity, and no apparent fat–water swap was observed. In addition to the good performance, the proposed method is applicable to various fat–water separation applications, including different sequence types and flexible TE choices.ConclusionWe propose an algorithm to reduce the ambiguity of chemical shift and field inhomogeneity and achieved robust fat–water separation in various applications.