Maximilian N. Diefenbach1, Stefan Ruschke1, Hendrik Kooijman2, Anh T. Van3, Ernst J. Rummeny1, Axel Haase3, and Dimitrios C. Karampinos1
1Department of Diagnostic and Interventional Radiology, Technische Universität München, Munich, Germany, 2Philips Healthcare, Hamburg, Germany, 3Zentralinstitut für Medizintechnik, Technische Universität München, Munich, Germany
To avoid swaps in water-fat imaging a pre-processing step to standard fieldmap estimation methods is proposed. Based on spherical harmonic expansion the shimfield and the inhomogeneities of the main magnetic field are calculated. Thereby obtained details of the field inside the empty scanner are used to calculate an object-based fieldmap based on the tissue geometry and the susceptibility of tissue and air. The superposition of these three contributions to the fieldmap serves as an initial estimate for the water-fat separation algorithm and can reduce swaps in cases of large FOVs and when shimming is used.