CEST MRI for Molecular Imaging of Brain Metabolites

As a sensitive MRI method, Chemical Exchange Saturation Transfer (CEST) MRI based on endogenous contrast has been increasingly utilized for molecular imaging of various metabolites. Among these applications, the authors have described CEST MRI for molecular imaging of brain metabolites in this review, including brain glutamate, the most abundant excitatory neurotransmitter; creatine, a key molecular of bioenergetics; and myo-inositol, a biomarker of glial cells. Those metabolites conventionally have been quantified with MR spectroscopy methods. Compared to MR spectroscopy, CEST methods typically provide a few hundred to a few thousand fold enhancement in sensitivity, enabling twodimensional imaging or mapping of metabolites at high resolution. In this review, the authors have also reviewed the preliminary applications of these molecular imaging methods. Finally, the challenges related to CEST MRI for molecular imaging in general are discussed.