title: Molecular hydrogen and catalytic combustion in the production of hyperpolarized 83Kr and 129Xe MRI contrast agents.
abstract: Hyperpolarized (hp) (83)Kr is a promising MRI contrast agent for the diagnosis of pulmonary diseases affecting the surface of the respiratory zone. However, the distinct physical properties of (83)Kr that enable unique MRI contrast also complicate the production of hp (83)Kr. This work presents a previously unexplored approach in the generation of hp (83)Kr that can likewise be used for the production of hp (129)Xe. Molecular nitrogen, typically used as buffer gas in spin-exchange optical pumping (SEOP), was replaced by molecular hydrogen without penalty for the achievable hyperpolarization. In this particular study, the highest obtained nuclear spin polarizations were P =29% for(83)Kr and P= 63% for (129)Xe. The results were reproduced over many SEOP cycles despite the laser-induced on-resonance formation of rubidium hydride (RbH). Following SEOP, the H2 was reactively removed via catalytic combustion without measurable losses in hyperpolarized spin state of either (83)Kr or (129)Xe. Highly spin-polarized (83)Kr can now be purified for the first time, to our knowledge, to provide high signal intensity for the advancement of in vivo hp (83)Kr MRI. More generally, a chemical reaction appears as a viable alternative to the cryogenic separation process, the primary purification method of hp(129)Xe for the past 2 1/2 decades. The inherent simplicity of the combustion process will facilitate hp (129)Xe production and should allow for on-demand continuous flow of purified and highly spin-polarized (129)Xe.
authors.affiliation: Sir Peter Mansfield Imaging Centre, Division of Respiratory Medicine, School of Medicine, University of Nottingham, Nottingham NG7 2RD, United Kingdom;
authors.forename: Nicola J
authors.initials: NJ
authors.lastname: Rogers
authors.affiliation: Sir Peter Mansfield Imaging Centre, Division of Respiratory Medicine, School of Medicine, University of Nottingham, Nottingham NG7 2RD, United Kingdom; Department of Chemical and Environmental Engineering, University of Nottingham, Nottingham NG7 2RD, United Kingdom;
authors.forename: Fraser
authors.initials: F
authors.lastname: Hill-Casey
authors.affiliation: Sir Peter Mansfield Imaging Centre, Division of Respiratory Medicine, 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 Imaging Centre, Division of Respiratory Medicine, 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 Imaging Centre, Division of Respiratory Medicine, School of Medicine, University of Nottingham, Nottingham NG7 2RD, United Kingdom;
authors.forename: Clémentine
authors.initials: C
authors.lastname: Lesbats
authors.affiliation: Department of Chemical and Environmental Engineering, University of Nottingham, Nottingham NG7 2RD, United Kingdom;
authors.forename: Sean P
authors.initials: SP
authors.lastname: Rigby
authors.affiliation: Ecole Supérieure de Physique et Chimie Industrielles, Université Pierre et Marie Curie, 75005 Paris, France.
authors.forename: Jacques
authors.initials: J
authors.lastname: Fraissard
authors.affiliation: Sir Peter Mansfield Imaging Centre, Division of Respiratory Medicine, 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 Imaging Centre, Division of Respiratory Medicine, School of Medicine, University of Nottingham, Nottingham NG7 2RD, United Kingdom; Thomas.Meersmann@Nottingham.ac.uk.
authors.forename: Thomas
authors.initials: T
authors.lastname: Meersmann
mesh_terms: D002384:Catalysis; D003287:Contrast Media; D006859:Hydrogen / Q000737:chemistry*; D007726:Krypton / Q000737:chemistry*; D008279:Magnetic Resonance Imaging; D014978:Xenon / Q000737:chemistry*
chemical_list: D003287:Contrast Media; D014978:Xenon; D007726:Krypton; D006859:Hydrogen
keywords: chemical looping combustion; cryogenic separation; hyperpolarized noble gas contrast agents; pulmonary imaging; spin-exchange optical pumping