A Dixon water/fat separation technique, in particular in combination with a single-point acquisition scheme, avoids swaps of water and fat signals in the reconstructed MR images due to imperfections of the main magnetic field B0. Echo signals are generated and acquired in a pre-scan by subjecting an object (10) to a two or more point imaging sequence. A fat fraction map is derived from the echo signals of the pre-scan. Echo signals are generated and acquired in a clinical scan by subjecting the object (10) to a single-point imaging sequence. A field map estimate is derived from the fat fraction map and from the echo signals of the clinical scan. An MR image is reconstructed from the echo signals of the clinical scan. Signal contributions from fat and water are separated on the basis of the field map estimate.