title: Automated transfer and injection of hyperpolarized molecules with polarization measurement prior to in vivo NMR.
abstract: Hyperpolarized magnetic resonance via dissolution dynamic nuclear polarization necessitates the transfer of the hyperpolarized molecules from the polarizer to the imager prior to in vivo measurements. This process leads to unavoidable losses in nuclear polarization, which are difficult to evaluate once the solution has been injected into an animal. We propose a method to measure the polarization of the hyperpolarized molecules inside the imager bore, 3 s following dissolution, at the time of the injection, using a precise quantification of the infusate concentration. This in situ quantification allows for distinguishing between signal modulations related to variations in the nuclear polarization at the time of the injection and signal modulations related to physiological processes such as tissue perfusion. In addition, our method includes a radical scavenging process that leads to a minor reduction in sample concentration and takes place within a couple of seconds following the dissolution in order to minimize the losses due to the presence of paramagnetic polarizing agent in the infusate. We showed that proton exchange between vitamin C, the scavenging molecule and the deuterated solvent shortens the long carboxyl (13)C longitudinal relaxation time in [1-(13)C]acetate. This additional source of dipolar relaxation can be avoided by using deuterated ascorbate. Overall, the method allows for a substantial gain in polarization and also leads to an extension of the time window available for in vivo measurements.
authors.affiliation: Institute of Physics of Biological System, École Polytechnique Fédérale de Lausanne, Lausanne, Switzerland.
authors.forename: Tian
authors.initials: T
authors.lastname: Cheng
authors.forename: Mor
authors.initials: M
authors.lastname: Mishkovsky
authors.forename: Jessica A M
authors.initials: JA
authors.lastname: Bastiaansen
authors.forename: Olivier
authors.initials: O
authors.lastname: Ouari
authors.forename: Patrick
authors.initials: P
authors.lastname: Hautle
authors.forename: Paul
authors.initials: P
authors.lastname: Tordo
authors.forename: Ben
authors.initials: B
authors.lastname: van den Brandt
authors.forename: Arnaud
authors.initials: A
authors.lastname: Comment
mesh_terms: D000818:Animals; D001205:Ascorbic Acid / Q000737:chemistry; D001331:Automation; D002247:Carbon Isotopes; D016166:Free Radical Scavengers / Q000378:metabolism; D046911:Macromolecular Substances / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D008297:Male; D011522:Protons; D051381:Rats; D017207:Rats, Sprague-Dawley; D012815:Signal Processing, Computer-Assisted
chemical_list: D002247:Carbon Isotopes; D016166:Free Radical Scavengers; D046911:Macromolecular Substances; D011522:Protons; D001205:Ascorbic Acid
keywords: 13C MRS; DNP; hyperpolarization; in vivo; proton exchange; radical scavenging; rodents; vitamin C