Near-unity nuclear polarization with an open-source 129 Xe hyperpolarizer for NMR and MRI

• Published in: Proceedings of the National Academy of Sciences - PNAS Vol. 110; no. 35; pp. 14150 - 14155
• Main Authors: Nikolaou, Panayiotis, Coffey, Aaron M., Walkup, Laura L., Gust, Brogan M., Whiting, Nicholas, Newton, Hayley, Barcus, Scott, Muradyan, Iga, Dabaghyan, Mikayel, Moroz, Gregory D., Rosen, Matthew S., Patz, Samuel, Barlow, Michael J., Chekmenev, Eduard Y., Goodson, Boyd M.
• Format: Journal Article
• Language: English
• Published: 27-08-2013
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.1306586110

Lung diseases comprise the third leading cause of death in the United States and could benefit from new imaging modalities. “Hyperpolarized” xenon-129 can overcome the ordinarily weak MRI signals from low-density species in lung space or dissolved in tissue; however, clinical progress has been slowed by the difficulty in preparing large amounts of hyperpolarized xenon with high magnetization, as well as the cost and limited availability of xenon hyperpolarization devices. We describe a unique low-cost “open-source” xenon “hyperpolarizer,” characterize its ability to produce xenon-129 with high magnetization, and demonstrate its utility for human lung imaging.
The exquisite NMR spectral sensitivity and negligible reactivity of hyperpolarized xenon-129 (HP
129
Xe) make it attractive for a number of magnetic resonance applications; moreover, HP
129
Xe embodies an alternative to rare and nonrenewable
3
He. However, the ability to reliably and inexpensively produce large quantities of HP
129
Xe with sufficiently high
129
Xe nuclear spin polarization (
P
Xe
) remains a significant challenge—particularly at high Xe densities. We present results from our “open-source” large-scale (∼1 L/h)
129
Xe polarizer for clinical, preclinical, and materials NMR and MRI research. Automated and composed mostly of off-the-shelf components, this “hyperpolarizer” is designed to be readily implementable in other laboratories. The device runs with high resonant photon flux (up to 200 W at the Rb D
1
line) in the xenon-rich regime (up to 1,800 torr Xe in 500 cc) in either single-batch or stopped-flow mode, negating in part the usual requirement of Xe cryocollection. Excellent agreement is observed among four independent methods used to measure spin polarization. In-cell
P
Xe
values of ∼90%, ∼57%, ∼50%, and ∼30% have been measured for Xe loadings of ∼300, ∼500, ∼760, and ∼1,570 torr, respectively.
P
Xe
values of ∼41% and ∼28% (with ∼760 and ∼1,545 torr Xe loadings) have been measured after transfer to Tedlar bags and transport to a clinical 3 T scanner for MR imaging, including demonstration of lung MRI with a healthy human subject. Long “in-bag”
129
Xe polarization decay times have been measured (
T
1
∼38 min and ∼5.9 h at ∼1.5 mT and 3 T, respectively)—more than sufficient for a variety of applications.