The ultimate goal of this project is to develop a commercially available source of highly nuclear spin polarized 129Xe for use in clinical MRl and MRS. Such a source must be capable of producing 1 liter 129Xe doses polarized to a level in excess of 20%. We have developed a prototype device which employs continuous-flow hyperpolarization and subsequent cryogenic accumulation and storage of the polarized 129Xe. While this prototype has been invaluable for initial development work, its performance is not yet sufficient for clinical use. The routine availability of polarized 129Xe is expected to make possible a wide array-of new clinical imaging applications - most notably high-resolution functional imaging of lung ventilation and perfusion. During phase I of this project we intend to investigate numerous avenues for increasing the degree of polarization level presently achieved (roughly 10% for 0.4 liters). In particular we will address the gas mixture composition, optimal laser absorption levels, high-purity optical cell manufacture, and a measurement of 129Xe depolarization in the solid phase. Several calibrated polarimetry stations will be used to diagnose 129Xe polarization throughout the entire system. Data gathered in this preliminary period will be used to identify critical polarization and production rate bottlenecks that must be addressed in Phase II.
Highly polarized 129Xe can be inhaled and imaged in a single breath-hold. Calculations indicate that the pulmonary blood vessels can also be visualized. Near-term clinical applications include complete functional imaging of lung ventilation and perfusion. Future applications include sinus imaging, colon imaging, myocardial perfusion, kidney perfusion, and white matter perfusion.
