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Dynamics of magnetization in hyperpolarized gas MRI of the lung

✍ Scribed by G. Allan Johnson; Gordon Cates; X. Josette Chen; Gary P. Cofer; Bastiaan Driehuys; Will Happer; Laurence W. Hedlund; Brian Saam; Mark D. Shattuck; John Swartz

Publisher
John Wiley and Sons
Year
1997
Tongue
English
Weight
680 KB
Volume
38
Category
Article
ISSN
0740-3194

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✦ Synopsis

Abstract

The magnetization in hyperpolarized gas (HP) MRI is generated by laser polarization that is independent of the magnet and imaging process. As a consequence, there is no equilibrium magnetization during the image acquisition. The competing processes of gas inflow and depolarization of the spins lead to large changes in signal as one samples k‐space. A model is developed of dynamic changes in polarization of hyperpolarized ^3^He during infusion and in vivo imaging of the lung and verified experimentally in a live guinea pig. Projection encoding is used to measure the view‐to‐view variation with temporal resolution <4 ms. Large excitation angles effectively sample the magnetization in the early stages of inflow, highlighting larger airways, while smaller excitation angles produce images of the more distal spaces. The work provides a basis for pulse sequences designed to effectively exploit HP MRI in the lung.

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