Method for fat characterization using MRI images acquired using a multiple gradient-echo sequence with bipolar gradients

A device for monitoring the proportion of unsaturated fatty acids and proportion of saturated fatty acids in a region of interest in a subject, the device comprising:

• a magnetic resonance imaging system adapted to image the region of interest in the subject by using a magnetic resonance imaging technique, the magnetic resonance imaging technique involving successive echoes of a multiple-gradient echo sequence with bipolar readout gradients, to obtain images and
• a controller adapted to:
• receive the obtained images of the region of interest from the magnetic resonance imaging system, each image associating to each pixel of the image the amplitude of the measured signal in the magnetic resonance imaging technique and the phase of the measured signal in the magnetic resonance imaging technique,
• unwrap the phase of each image, to obtain unwrapped images,
• extract a complex signal over echo time for at least one pixel of the unwrapped images, to obtain at least one extracted complex signal,
• calculate fat characterization parameters by using a fitting technique applied on a model,
• the model being a function which associates to a plurality of parameters each extracted complex signal, the plurality of parameters comprising at least two fat characterization parameters, the magnitude error generated by the use of the bipolar readout gradients and the phase error generated by the use of the bipolar readout gradients,
• the fitting technique being a non-linear least-square fitting technique using pseudo-random initial conditions, and
• quantify the proportion of unsaturated fatty acids and proportion of saturated fatty acids in the region of interest in the subject based on the calculated fat characterization parameters.