Distribution and dynamics of laser-polarized ¹²⁹Xe magnetization in vivo

The first magnetic resonance imaging studies of laser-polarized ¹²⁹Xe, dissolved in the blood and tissue of the lungs and the heart of Sprague-Dawley rats, are described. ¹²⁹Xe resonances at 0, 192, 199, and 210 ppm were observed and assigned to xenon in gas, fat, tissue, and blood, respectively. One-dimensional chemical-shift imaging (CSI) reveals xenon magnetization in the brain, kidney, and lungs. Coronal and axial two-dimensional CSI show ¹²⁹Xe dissolved in blood and tissue in the thorax. Images of the blood resonance show xenon in the lungs and the heart ventricle. Images of the tissue resonance reveal xenon in lung parenchyma and myocardium. The ¹²⁹Xe spectrum from a voxel located in the heart ventricle shows a single blood resonance. Time-resolved spectroscopy shows that the dynamics of the blood resonance match the dynamics of the gas resonance and demonstrates efficient diffusion of xenon gas to the lung parenchyma and then to pulmonary blood. These observations demonstrate the utility of laser-polarized ¹²⁹Xe to detect exchange across the gas-blood barrier in the lungs and perfusion into myocardial tissue. Applications to measurement of lung function, kidney perfusion, myocardial perfusion, and regional cerebral blood flow are discussed. Magn Reson Med 42:1137–1145, 1999. © 1999 Wiley-Liss, Inc.