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Magnetization and diffusion effects in NMR imaging of hyperpolarized substances
Author(s) -
Gao JiaHong,
Lemen Lisa,
Xiong Jinhu,
Patyal Baldev,
Fox Peter T.
Publication year - 1997
Publication title -
magnetic resonance in medicine
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.696
H-Index - 225
eISSN - 1522-2594
pISSN - 0740-3194
DOI - 10.1002/mrm.1910370123
Subject(s) - nuclear magnetic resonance , magnetization transfer , magnetization , diffusion , diffusion mri , chemistry , magnetic resonance imaging , materials science , medicine , physics , magnetic field , radiology , thermodynamics , quantum mechanics
The special magnetization characteristics of hyperpolarized noble gases have led to an interest in using these agents for new MRI applications. In this note, the magnetization effects and NMR signal dependence of two noble gases, 3 He and 129 Xe, are modeled across a range of gradient‐echo imaging parameters. Pulse‐sequence analysis shows a wide variation in optimum flip angles between imaging of gas (e.g., 3 He or 129 Xe) in air spaces (e.g., trachea and lung) and in blood vessels. To optimize imaging of the air spaces, it is also necessary to reduce the otherwise substantial signal losses from diffusion effects by increasing voxel size. The possibility of using hyperpolarized 129 Xe for functional MRI (fMRI) is discussed in view of the results from the blood flow analysis. The short‐lived nature of the hyperpolarization opens up new possibilities, as well as new technical challenges, in its potential application as a blood‐flow tracer.