Polarized Xenon in Rat Lungs and Body Tissues

We observed  NMR spectra in the thorax of living rats breathing the laser-polarized gas (see Fig. 1), and obtained NMR images of laser-polarized 129Xe gas inside the rat lung gas space (see Fig. 2). We found three well-resolved 129Xe-tissue NMR resonances, in addition to the 129Xe gas resonance in the lung gas space. We identified these tissue resonances as 129Xe in solution in pulmonary tissue, red blood cells, and plasma & adipose tissue. Once xenon inhalation was stopped, the three 129Xe tissue resonances were observed to decay with different time constants ranging from 11 to 50 seconds – i.e., longer than the blood circulation time in the animal. This experiment showed that it should be possible to perform dissolved-state 129Xe MRI in animals (subsequently achieved by Swanson, Chupp, and collaborators at U. Mich.) and humans. It also provides strong supporting evidence for our current efforts to use 129Xe gas-tissue exchange as a minimally invasive tool for imaging of the lung’s surface area and function.

Top – Fig. 1: 129Xe NMR spectra from the thorax of a rat breathing the laser-polarized gas. Spectral peaks A, B, and C are 129Xe in solution in plasma/adipose tissue, pulmonary tissue, and red blood cells, respectively. Polarization decay after cessation of breathing is shown at right.
Bottom – Fig. 2: Axial slice NMR lung images of a living rat. (a) Temporal sequence of laser-polarized 129Xe NMR images from the lung gas space. (b) The summed image from the six images shown in (a). (c) Conventional proton NMR image of a corresponding slice. Note the complimentary nature of the noble gas and proton images.

Note: These experiments were performed in close collaboration with scientists at the MR Division of the Brigham and Women’s Hospital.

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