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Gas Flow MRI Using Circulating Laser-Polarized129Xe

1999; Elsevier BV; Volume: 138; Issue: 1 Linguagem: Inglês

10.1006/jmre.1998.1675

1096-0856

Eike Brunner, Mathias Haake, Lana G. Kaiser, Alexander Pines, Jeffrey A. Reimer,

Advanced NMR Techniques and Applications

We describe an experimental approach that combines multidimensional NMR experiments with a steadily renewed source of laser-polarized129Xe. Using a continuous flow system to circulate the gas mixture, gas phase NMR signals of laser-polarized129Xe can be observed with an enhancement of three to four orders of magnitude compared to the equilibrium129Xe NMR signal. Due to the fact that the gas flow recovers the nonequilibrium129Xe nuclear spin polarization in 0.2 to 4 s, signal accumulation on the time scale of seconds is feasible, allowing previously inaccessible phase cycling and signal manipulation. Several possible applications of MRI of laser-polarized129Xe under continuous flow conditions are presented here. The spin density images of capillary tubes demonstrate the feasibility of imaging under continuous flow. Dynamic displacement profiles, measured by a pulsed gradient spin echo experiment, show entry flow properties of the gas passing through a constriction under laminar flow conditions. Further, dynamic displacement profiles of129Xe, flowing through polyurethane foams with different densities and pore sizes, are presented.