Studying flow dispersion through porous media by novel molecular contrast NMR imaging Water in a highly 1H spin-polarized state is proposed as a novel and authentic contrast agent to visualize perfusion of water through flow columns by magnetic resonance imaging (MRI). We developed an approach based on dynamic nuclear polarization (DNP) and a portable instrument to amplify the 1H MRI signal of water by >130 fold, in continuous-flow, under ambient conditions and at 0.35 Tesla. Because we utilize highly polarized stable radicals that are immobilized onto a gel matrix, the hyperpolarized water exiting the gel column is perfectly radical-free. Songi Han University of California Santa Barbara Santa Barbara, CA 93106 ACS PRF# 45861-G9 flow 1 ml/min 1.5 ml/min 2 ml/min 1 mm DNP off DNP on DNP on DNP on The images illustrate that the transient and mechanical flow dispersion of pure water entering the water-filled tube packed with molecular sieve beads can be directly visualized without using tracers molecules, but through the hyper-polarization of water’s MRI signal. Hyper-polarization represents an ideal contrast mechanism to highlight the ubiquitous and specific function of water because the physiological and macroscopic function of water is not altered by the degree of magnetization.