Magnetic resonance imaging (MRI) of optically polarized 3He and 129Xe has already found application in imaging of the gas space in lungs with encouraging results. Given the sensitivity of its NMR parameters to the local environment Xe would also be an excellent probe for the study of tissues in living organisms. One of the major challenges for medical applications using hyperpolarized (HP) Xe is its efficient delivery to the blood while maintaining the large non-equilibrium spin polarization acquired during optical pumping. Previous practice has involved the introduction of HP gas into the organism through the respiratory system. More efficient methods for the local delivery may include pre-dissolving of HP Xe in a liquid or the production of microbubbles with subsequent injection into the organism. This may open up further applications such as vascular imaging or functional (perfusion) studies. The objective of the project is therefore threefold: (1) the preparation of systems of biological compatibility suited for an efficient delivery of HP Xe to the vascular system, (2) the measurement of 129Xe chemical shifts and relaxation times T1 for the decay of the spin polarization in vivo and during delivery as well as the investigation of the dynamics of the exchange of Xe between the carrier system and its biological environment, and (3) the development of strategies for vascular imaging and perfusion studies in a live animal.
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