XeNA: An automated ‘open-source’ 129Xe hyperpolarizer for clinical use

• Published in: Magnetic resonance imaging Vol. 32; no. 5; pp. 541 - 550
• Main Authors: Nikolaou, Panayiotis, Coffey, Aaron M., Walkup, Laura L., Gust, Brogan M., Whiting, Nicholas, Newton, Hayley, Muradyan, Iga, Dabaghyan, Mikayel, Ranta, Kaili, Moroz, Gregory D., Rosen, Matthew S., Patz, Samuel, Barlow, Michael J., Chekmenev, Eduard Y., Goodson, Boyd M.
• Format: Journal Article
• Language: English
• Published: Elsevier Inc 01.06.2014
• Subjects: Hyperpolarization; Laser-polarized xenon; Lung imaging; MRI; Optical pumping; Optical pumping; MRI; Laser-polarized xenon; Hyperpolarization; Lung imaging
• ISSN: 0730-725X; 1873-5894
• DOI: 10.1016/j.mri.2014.02.002

Here we provide a full report on the construction, components, and capabilities of our consortium’s “open-source” large-scale (~1L/h) 129Xe hyperpolarizer for clinical, pre-clinical, and materials NMR/MRI (Nikolaou et al., Proc. Natl. Acad. Sci. USA, 110, 14150 (2013)). The ‘hyperpolarizer’ is automated and built mostly of off-the-shelf components; moreover, it is designed to be cost-effective and installed in both research laboratories and clinical settings with materials costing less than $125,000. The device runs in the xenon-rich regime (up to 1800Torr Xe in 0.5L) in either stopped-flow or single-batch mode—making cryo-collection of the hyperpolarized gas unnecessary for many applications. In-cell 129Xe nuclear spin polarization values of ~30%–90% have been measured for Xe loadings of ~300–1600Torr. Typical 129Xe polarization build-up and T1 relaxation time constants were ~8.5min and ~1.9h respectively under our spin-exchange optical pumping conditions; such ratios, combined with near-unity Rb electron spin polarizations enabled by the high resonant laser power (up to ~200W), permit such high PXe values to be achieved despite the high in-cell Xe densities. Importantly, most of the polarization is maintained during efficient HP gas transfer to other containers, and ultra-long 129Xe relaxation times (up to nearly 6h) were observed in Tedlar bags following transport to a clinical 3T scanner for MR spectroscopy and imaging as a prelude to in vivo experiments. The device has received FDA IND approval for a clinical study of chronic obstructive pulmonary disease subjects. The primary focus of this paper is on the technical/engineering development of the polarizer, with the explicit goals of facilitating the adaptation of design features and operative modes into other laboratories, and of spurring the further advancement of HP-gas MR applications in biomedicine.