Besides its classical water-related images, MRI is able to give metabolic information mainly thanks to two approaches. The first one is classical magnetic resonance spectroscopy imaging (MRSI) which leads to one NMR spectrum per image voxel. The second one is chemical exchange saturation transfer (CEST) contrast which gives a map weighed by the metabolite exchangeable protons. CEST MRI monitors the water signal intensity in function of the saturation frequency in a so-called z-spectrum. Saturating the signal at the frequency of exchangeable protons partially saturates the water signal leading to its decrease. Each contrast presents its own advantages and drawbacks. However, both methods have the same limitation, which concerns the excellent homogeneity of the magnetic field required over the entire image.