Development of a fast method for quantitative measurement of hyperpolarized 129Xe dynamics in mouse brain |
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Authors: | Imai Hirohiko Kimura Atsuomi Akiyama Kazue Ota Chikako Okimoto Kazuki Fujiwara Hideaki |
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Institution: | Department of Medical Physics and Engineering, Area of Medical Technology and Science, Division of Health Sciences, Graduate School of Medicine, Osaka University, 1-7 Yamadaoka, Suita, Osaka, 565-0871, Japan. |
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Abstract: | A fast method has been established for the precise measurement and quantification of the dynamics of hyperpolarized (HP) xenon‐129 (129Xe) in the mouse brain. The key technique is based on repeatedly applying radio frequency (RF) pulses and measuring the decrease of HP 129Xe magnetization after the brain Xe concentration has reached a steady state due to continuous HP 129Xe ventilation. The signal decrease of the 129Xe nuclear magnetic resonance (NMR) signal was well described by a simple theoretical model. The technique made it possible to rapidly evaluate the rate constant α, which is composed of cerebral blood flow (CBF), the partition coefficient of Xe between the tissue and blood (λi), and the longitudinal relaxation time (T1i) of HP 129Xe in the brain tissue, without any effect of depolarization by RF pulses and the dynamics in the lung. The technique enabled the precise determination of α as 0.103 ± 0.018 s‐1 (± SD, n = 5) on healthy mice. To investigate the potential of this method for detecting physiological changes in the brain of a kainic acid (KA) ‐induced mouse model of epilepsy, an attempt was made to follow the time course of α after KA injection. It was found that the α value changes characteristically with time, reflecting the change in the physiological state of the brain induced by KA injection. By measuring CBF using 1H MRI and 129Xe dynamics simultaneously and comparing these results, it was suggested that the reduction of T1i, in addition to the increase of CBF due to KA‐induced epilepsy, are possible causes of the change in 129Xe dynamics. Thus, the present method would be useful to detect a pathophysiological state in the brain and provide a novel tool for future brain study. Copyright © 2011 John Wiley & Sons, Ltd. |
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Keywords: | hyperpolarized 129Xe brain kainic acid epilepsy cerebral blood flow mouse ASL FAIR |
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