A Nanoemulsion Based CEST Agent for Hyperpolarized 129Xe

Todd K. Stevens^1,2, Richard M. Ramirez^1,2, Alexander Pines^1,2

In this study, a novel and highly sensitive ¹²⁹Xe CEST contrast agent based on perfluorocarbon nanoemulsions is presented. CEST spectra for nanoemulsion droplet diameters ranging from 160 nm to 310 nm were used to demonstrate the dependence of the xenon exchange rates on the xenon diffusion transit times associated with the different sized droplets. Bloch modeling of the data allowed for determination of the escape probability of xenon atoms arriving at the surfactant boundary of the droplets (1.3%). Droplets of 210 nm and 310 nm diameters were detected at concentrations as low as 1 pM and 100 fM, respectively.