Analytical Sciences

Stability Enhancement of ¹²⁹Xe Hyperpolarizing System Using Alkali Metal Vapor in Spin-Exchange Optical Pumping Cell to Achieve High NMR Sensitivity

Hideaki FUJIWARA,*,** Hirohiko IMAI,*** and Atsuomi KIMURA*

*Division of Health Sciences, Graduate School of Medicine, Osaka University, 1-6 Yamadaoka, Suita, Osaka 565-0871, Japan
**MR MedChem Research, LLC, 2-11-28 Aoshinke, Minoo, Osaka 562-0024, Japan
***Department of Systems Science, Graduate School of Informatics, Kyoto University, Yosihda-Honmachi, Sakyo, Kyoto 606-8501, Japan

Hyperpolarized (HP) ¹²⁹Xe NMR and MRI have enabled ¹²⁹Xe studies with extraordinarily enhanced sensitivity, stimulating new developments in magnetic resonance in chemistry, physics, biology and medicine. However, the standard method of HP ¹²⁹Xe production inevitably demands Rb vapor for the excitation, which has made the method very sensitive to impurities such as water or oxygen. This is the case especially in the recirculating system. In the present study, stability of the hyperpolarizing system is discussed by proposing the “cell decay constant”, which symbolizes the decay rate of the NMR signal obtained from the system. The cell decay constant is effectively decreased to 1/3 by introducing separated chambers and mechanical stirring of the alkali metals used in the system, making it effective for accumulating FIDs over 30 to 100 h. The newly developed hyperpolarizing system has been successfully applied for newly detecting a broad signal at 190 ppm with an industrial material Nanofiber.

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