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Signal Dynamics in Magnetic Resonance Imaging of the Lung with Hyperpolarized Noble Gases

✍ Scribed by Harald E. Möller; X.Josette Chen; Mark S. Chawla; Bastiaan Driehuys; Laurence W. Hedlund; G.Allan Johnson

Publisher
Elsevier Science
Year
1998
Tongue
English
Weight
348 KB
Volume
135
Category
Article
ISSN
1090-7807

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✦ Synopsis

The nonequilibrium bulk magnetic moment of hyperpolarized (HP) noble gases generated by optical pumping has unique characteristics. Based on the Bloch equations, a model was developed describing the signal dynamics of HP gases used in magnetic resonance imaging (MRI) of the lung with special consideration to the breathing cycle. Experimental verification included extensive investigations with HP 3 He and 129 Xe during both inspiration and held breath in live guinea pigs. Radial acquisition was used to investigate the view variations with a temporal resolution of 5 ms. Agreement between theoretical predictions and in vivo results was excellent. Additionally, information about effects from noble gas diffusion and spin-lattice relaxation was obtained. In vivo results for T 1 were 28.8 ؎ 1.8 s for 3 He and 31.3 ؎ 1.8 s for 129 Xe. Comparison with in vitro data indicated that relaxation in the pulmonary gas space is dominated by dipolar coupling with molecular oxygen. The results provide a quantitative basis for optimizing pulse sequence design in HP gas MRI of the lung.

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