title: Cryogenics free production of hyperpolarized 129Xe and 83Kr for biomedical MRI applications.
abstract: As an alternative to cryogenic gas handling, hyperpolarized (hp) gas mixtures were extracted directly from the spin exchange optical pumping (SEOP) process through expansion followed by compression to ambient pressure for biomedical MRI applications. The omission of cryogenic gas separation generally requires the usage of high xenon or krypton concentrations at low SEOP gas pressures to generate hp (129)Xe or hp (83)Kr with sufficient MR signal intensity for imaging applications. Two different extraction schemes for the hp gasses were explored with focus on the preservation of the nuclear spin polarization. It was found that an extraction scheme based on an inflatable, pressure controlled balloon is sufficient for hp (129)Xe handling, while (83)Kr can efficiently be extracted through a single cycle piston pump. The extraction methods were tested for ex vivo MRI applications with excised rat lungs. Precise mixing of the hp gases with oxygen, which may be of interest for potential in vivo applications, was accomplished during the extraction process using a piston pump. The (83)Kr bulk gas phase T1 relaxation in the mixtures containing more than approximately 1% O2 was found to be slower than that of (129)Xe in corresponding mixtures. The experimental setup also facilitated (129)Xe T1 relaxation measurements as a function of O2 concentration within excised lungs.
authors.affiliation: Sir Peter Mansfield Magnetic Resonance Centre, School of Medicine, University of Nottingham, Nottingham NG7 2RD, United Kingdom.
authors.forename: Theodore
authors.initials: T
authors.lastname: Hughes-Riley
authors.affiliation: Sir Peter Mansfield Magnetic Resonance Centre, School of Medicine, University of Nottingham, Nottingham NG7 2RD, United Kingdom.
authors.forename: Joseph S
authors.initials: JS
authors.lastname: Six
authors.affiliation: Sir Peter Mansfield Magnetic Resonance Centre, School of Medicine, University of Nottingham, Nottingham NG7 2RD, United Kingdom.
authors.forename: David M L
authors.initials: DML
authors.lastname: Lilburn
authors.affiliation: Sir Peter Mansfield Magnetic Resonance Centre, School of Medicine, University of Nottingham, Nottingham NG7 2RD, United Kingdom.
authors.forename: Karl F
authors.initials: KF
authors.lastname: Stupic
authors.affiliation: Sir Peter Mansfield Magnetic Resonance Centre, School of Physics and Astronomy, University of Nottingham, Nottingham NG7 2RD, United Kingdom.
authors.forename: Alan C
authors.initials: AC
authors.lastname: Dorkes
authors.affiliation: Nottingham Respiratory Research Unit, University of Nottingham, Nottingham NG5 1PB, United Kingdom.
authors.forename: Dominick E
authors.initials: DE
authors.lastname: Shaw
authors.affiliation: Sir Peter Mansfield Magnetic Resonance Centre, School of Medicine, University of Nottingham, Nottingham NG7 2RD, United Kingdom.
authors.forename: Galina E
authors.initials: GE
authors.lastname: Pavlovskaya
authors.affiliation: Sir Peter Mansfield Magnetic Resonance Centre, School of Medicine, University of Nottingham, Nottingham NG7 2RD, United Kingdom. Electronic address: Thomas.Meersmann@Nottingham.ac.uk.
authors.forename: Thomas
authors.initials: T
authors.lastname: Meersmann
mesh_terms: D000465:Algorithms; D000818:Animals; D003287:Contrast Media; D005740:Gases; D007090:Image Interpretation, Computer-Assisted; D007554:Isotopes; D007726:Krypton / Q000737:chemistry*; D008168:Lung / Q000033:anatomy & histology; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D010100:Oxygen / Q000737:chemistry; D051381:Rats; D017207:Rats, Sprague-Dawley; D012121:Respiration, Artificial; D012413:Rubidium / Q000737:chemistry; D014979:Xenon Isotopes / Q000737:chemistry*
chemical_list: D003287:Contrast Media; D005740:Gases; D007554:Isotopes; D014979:Xenon Isotopes; D007726:Krypton; D012413:Rubidium; D010100:Oxygen
keywords: Cryogenic separation; Hyperpolarization; Kr-83; Krypton-83; Lung imaging; Oxygen partial pressure; Pulmonary MRI; Spin-exchange optical pumping; T(1) relaxation; Xe-129; Xenon-129