CEST MRI

Magnetic resonance imaging (MRI) with indirect detection through chemical exchange saturation transfer (CEST) has developed into a mature technique with unique features for quantitative imaging since many biophysical and biochemical parameters of molecular reporters are linked to exchange-coupled magnetization pools. The CEST approach also greatly improves the sensitivity of MRI and has become a valuable technique in diagnostic imaging for various tissue parameters and synthetic molecular reporters. It uses an induced signal loss in an abundant spin pool to capture information from a dilute spin pool through an actively driven saturation transfer process. This enables a much better signal than direct readout of the magnetization from the low-concentration analyte. This chapter provides an introduction into the concepts of CEST and its different “flavors” considering a continuously growing library of agents, quantitative evaluation for contributing physicochemical parameters, and advanced encoding techniques. CEST applications nowadays rely on endogenous and synthetic agents that are both discussed here. The inclusion of spin hyperpolarization as another signal amplification concept illustrates special features that come with the increased dynamic range and extended timescale that magnetization from hyperpolarized nuclei provides.