For this study the investigators propose to include an additional CEST sequence in standard PET/MRI exam in order to obtain a cartography with biochemical informations from tissues in patients with glioma or brain metastases.
Standard Magnetic Resonance Imaging (MRI) is based on the excitation of hydrogen nuclei that are presents in water molecules, which abundance in human body allows for obtention of superior contrast. However, assessing the presence of other molecules than water in tissues is also of great clinical interest to probe metabolites related to physiological body function and pathological conditions.~Chemical exchange saturation transfer (CEST) allow to overcome some limitations of proton magnetic resonance spectroscopy (1H-MRS) by exploiting chemical properties of the targeted molecule through a continuous process of re-saturation and exchange, and thus detecting it with increased sensitivity, from two orders of magnitude. Moreover, CEST technique is based on imaging sequences and can therefore benefit from well-known fast acquisition strategies, as well as improved spatial resolution.