Hyperpolarized ¹²⁹Xe MRI using isobutene as a new quenching gas

Abstract

The use of a quenching gas, isobutene, with a low vapor pressure was investigated to enhance the utility of hyperpolarized (129) Xe (HP Xe) MRI. Xenon mixed with isobutene was hyperpolarized using a home-built apparatus for continuously producing HP Xe. The isobutene was then readily liquefied and separated almost totally by continuous condensation at about 173 K, because the vapor pressure of isobutene (0.247 kPa) is much lower than that of Xe (157 kPa). Finally, the neat Xe gas was continuously delivered to mice by spontaneous inhalation. The HP Xe MRI was enhanced twofold in polarization level and threefold in signal intensity when isobutene was adopted as the quenching gas instead of N2 . The usefulness of the HP Xe MRI was verified by application to pulmonary functional imaging of spontaneously breathing mice, where the parameters of fractional ventilation (ra ) and gas exchange (fD ) were evaluated, aiming at future extension to preclinical studies. This is the first application of isobutene as a quenching gas for HP Xe MRI.

Enabling Clinical Technologies for Hyperpolarized 129Xenon Magnetic Resonance Imaging and Spectroscopy

“…Other methods of CF delivery have been investigated, including operating without 4 He as a buffer gas [45] and using very low 129 Xe concentrations [46] . Fujiwara et al [47, 48] . showed that possible alternatives to N 2 can be used successfully as quenching gases this way, including isobutene, furan, and butane, and Meersmann et al [49, 50] .…”

“…Other methods of CF delivery have been investigated, including operating without 4 He as ab uffer gas [45] and using very low 129 Xe concentrations. [46] Fujiwara et al [47,48] showed that possible alternatives to N 2 can be used successfully as quenching gases this way,i ncluding isobutene,f uran, and butane,and Meersmann et al [49,50] demonstrated amethod of removing N 2 without the need for cryo-collection. However, due to the complexities (and potential toxicities) that such alternative methods may bring to the SEOP process,they may not be suitable for implementation in ac linical setting.…”

Enabling Clinical Technologies for Hyperpolarized 129Xenon Magnetic Resonance Imaging and Spectroscopy

“…Other methods of CF delivery have been investigated, including operating without 4 He as ab uffer gas [45] and using very low 129 Xe concentrations. [46] Fujiwara et al [47,48] showed that possible alternatives to N 2 can be used successfully as quenching gases this way,i ncluding isobutene,f uran, and butane,and Meersmann et al [49,50] demonstrated amethod of removing N 2 without the need for cryo-collection. However, due to the complexities (and potential toxicities) that such alternative methods may bring to the SEOP process,they may not be suitable for implementation in ac linical setting.…”

Continuous flow production of concentrated hyperpolarized xenon gas from a dilute xenon gas mixture by buffer gas condensation

“…Any reaction also seems to be very slow for the unsaturated hydrocarbon isobutene used here. In fact, degradation of the SEOP cell using the isobutene mixture was adequately slow and at an acceptable level to complete in vivo experiments with a sufficient number of mice, e.g., 50 mice 25 .…”

“…The aim of this work is to develop a new method to concentrate HP 129 Xe gas from a dilute Xe gas mixture using a new buffer gas for SEOP that is capable of continuously delivering highly spin polarized undiluted 129 Xe gas for use in performing NMR or MRI measurement continuously with improved sensitivity. We reported a study on pulmonary functional imaging in mice using HP 129 Xe generated using a system based on the concept described here 25 . In the present study, we focus on the basic aspects of the methodology based on a detailed analysis of Xe polarization, Rb polarization and Rb-Xe spin exchange process in the use of a new quenching gas comparing them with the conventional N 2 .…”