Slice-selective gradient-encoded CEST spectroscopy for monitoring dynamic parameters and high-throughput sample characterization.

Chemical Exchange Saturation Transfer (CEST) NMR is an increasingly used technique for generating molecule or microenvironment specific signal contrast. To characterize CEST agents and to extract parameters such as temperature and pH, it is often required to resolve the spectral dimension. This is achieved by recording so called CEST- or z-spectra, where the spectral CEST information is conventionally acquired point by point, leading to long acquisition times. Here, we employ gradient-encoding to substantially accelerate the acquisition process of z-spectra in phantom experiments, reducing it to only two scans. This speedup allows us to monitor dynamic processes such as rapid temperature changes in a PARACEST sample that would be inaccessible with the conventional encoding. Furthermore, we combine the gradient-encoding approach with multi-slice selection, thus reserving one spatial dimension for the simultaneous investigation of heterogeneous PARACEST sample packages within one experiment. Hence, gradient-encoded CEST might be of great use for high-throughput screening of CEST contrast agents.