Predicting Optimal Properties of CEST MRI Agents Under Practical Experimental Conditions

¹Department of Radiology, Harvard Medical School, Athinoula A. Martinos Center for Biomedical Imaging, Charlestown, MA, USA; ²Russell H. Morgan Department of Radiology & Radiological Science, Johns Hopkins University School of Medicine, Baltimore, MD; ³F. M. Kirby Center for functional Brain Imaging, Kennedy Krieger Institute , Baltimore, MD, USA; ⁴F. M. Kirby Center for functional Brain Imaging, Kennedy Krieger Institute, Baltimore, MD, USA

Chemical exchange saturation transfer (CEST) imaging provides a sensitivity enhancement mechanism that allows measurement of microenvironment properties through dilute labile groups. Because in general CEST MRI contrast increases with the chemical exchange rate, there has been great interest in developing DIACEST/LIPOCEST/PARACEST agents with fast exchange rates. Here, we have examined CEST MRI contrast under practical experimental conditions, and derived the optimal properties of CEST agents at different exchangeable proton shifts from water using both analytical solutions and numerical simulations. In addition we have validated these experimentally for two different types of exchangeable protons.