The lungs, with their low density and diffuse surface, have proven difficult to image. Quantitative determination of the surface to volume ratio, an indicator for emphysema, would be particularly useful. MRI imaging sequences can determine the extent to which gas diffusion over large distance is restricted by boundaries. Work is underway to develop a precise, noninvasive measure of the degeneration of the gas exchange walls in emphysemic lungs by restricted xenon diffusion. Although excellent MRI images of the brain are possible, it is difficult to distinguish between gray matter, which is responsible for cognitive function, and white matter, which is associated with motor function.
Xenon is highly soluble in the blood and in white matter of the brain.
Tens of seconds after inhaling xenon, a concentration accumulates in the white matter, allowing selective imaging of this important structure. Xenon is a known anesthetic. By producing images of xenon concentrations and measuring small shifts in the xenon resonance frequency that characterize the local chemistry, we hope to determine the mechanism for anesthesia. We also hope to contribute to the discovery of new diagnostic techniques for understanding white matter degeneration and disease, such as Parkinson's disease. We have begun collaborating with teams at the Brigham and Women's Hospital and the Harvard-Smithsonian Astrophysical Observatory to develop these promising techniques.