Dixon type water/fat separation mr imaging with improved fat shift correction

Abstract

The invention relates to a method of Dixon-type MR imaging. It is an object of the invention to provide an MR imaging technique using bipolar readout magnetic field gradients with an improved estimation of the main field inhomogeneity to eliminate residual artifacts. In accordance with the invention, a method of MR imaging of an object placed in a main magnetic field within an examination volume of a MR device is proposed, wherein the method comprises the steps of: —subjecting the object () to an imaging sequence to generate at least two sets of echo signals at two or more different echo times using bipolar pairs of readout magnetic field gradients, one set of echo signals being generated at a first echo time (TE) and the other set of echo signals being generated at a second echo time (TE), —acquiring the echo signals from the object (), —reconstructing a first image from the echo signals attributed to the first echo time (TE) and a second image from the echo signals attributed to the second echo time (TE), —computing modified first and second images by compensating for a fat shift in the reconstructed first and second images respectively, —estimating phase errors in the acquired echo signals on the basis of the first and second images and the modified first and second images using a signal model including the resonance spectra of fat and water and the spatial variation of the main magnetic field, and —reconstructing a water image and/or a fat image by separating the signal contributions of fat and water to the acquired echo signals using the estimated phase errors. Moreover, the invention relates to a MR device () and to a computer program to be run on a MR device ().