• Tetsuya Wakayama, Masakazu Kitamoto, Tsuyoshi Ueyama, Hirohiko Imai, Michiko Narazaki, Atsuomi Kimura, and Hideaki Fujiwara.
• Department of Medical Physics and Engineering, Division of Health Sciences, Graduate School of Medicine, Osaka University, Osaka, Japan. waka@sahs.med.osaka-u.ac.jp
• J Magn Reson Imaging. 2008 Apr 1; 27 (4): 777-84.

PurposeTo apply a continuous flow-type hyperpolarizing (CF-HP) system to lung imaging and investigate the feasibility of hyperpolarized (129)Xe MRI at a low xenon concentration.Materials And MethodsUnder two conditions where a 3% or 70% xenon gas mixture was constantly supplied, gas- and dissolved-phase (129)Xe images and diffusion-weighted (129)Xe-gas images were obtained from the mouse lung. Signal-to-noise ratio (SNR) of the (129)Xe images and the apparent diffusion coefficient (ADC) of xenon were compared between the two gas mixtures.ResultsThe SNR of gas- and dissolved-phase images were 28.9 +/- 5.2 and 12.0 +/- 2.0, respectively, using the 70% xenon gas mixture, while they were 22.9 +/- 4.8 and 6.8 +/- 0.6, using the 3% mixture. The ADC of xenon using the 3% xenon gas mixture was approximately 1.5 times higher than that using the 70% one. These results indicated that the high ADC increases the apparent replenishment rate of gas-phase magnetization, thus resulting in a reduction of the SNR loss induced by diluting xenon with quenching gases.ConclusionThe CF-HP system is useful for lung imaging at an extremely low concentration of xenon, which enables one to fully restrain an anesthetic effect of xenon and to reduce consumption of xenon in a measurement.(c) 2008 Wiley-Liss, Inc.

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