title: (19)F spin-lattice relaxation of perfluoropolyethers: Dependence on temperature and magnetic field strength (7.0-14.1T).
abstract: Fluorine ((19)F) MRI of perfluorocarbon-labeled cells has become a powerful technique to track the migration and accumulation of cells in living organisms. It is common to label cells for (19)F MRI with nanoemulsions of perfluoropolyethers that contain a large number of chemically equivalent fluorine atoms. Understanding the mechanisms of (19)F nuclear relaxation, and in particular the spin-lattice relaxation of these molecules, is critical to improving experimental sensitivity. To date, the temperature and magnetic field strength dependence of spin-lattice relaxation rate constant (R1) for perfluoropolyethers has not been described in detail. In this study, we evaluated the R1 of linear perfluoropolyether (PFPE) and cyclic perfluoro-15-crown-5 ether (PCE) at three magnetic field strengths (7.0, 9.4, and 14.1T) and at temperatures ranging from 256-323K. Our results show that R1 of perfluoropolyethers is dominated by dipole-dipole interactions and chemical shift anisotropy. R1 increased with magnetic field strength for both PCE and PFPE. In the temperature range studied, PCE was in the fast motion regime (ωτc<1) at all field strengths, but for PFPE, R1 passed through a maximum, from which the rotational correlation time was estimated. The importance of these measurements for the rational design of new (19)F MRI agents and methods is discussed.
authors.affiliation: Russell H. Morgan Dept. of Radiology and Radiological Science, Division of MR Research, The Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA; Dept. of Oncology, The Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA; Cellular Imaging Section, Institute for Cell Engineering, The Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA.
authors.forename: Deepak K
authors.initials: DK
authors.lastname: Kadayakkara
authors.affiliation: Department of Chemistry, University of Pittsburgh, Pittsburgh, PA 15260, USA.
authors.forename: Krishnan
authors.initials: K
authors.lastname: Damodaran
authors.affiliation: Department of Biological Sciences, Carnegie Mellon University, Pittsburgh, PA 15213, USA; Pittsburgh NMR Center for Biomedical Research, Carnegie Mellon University, Pittsburgh, PA 15213, USA.
authors.forename: T Kevin
authors.initials: TK
authors.lastname: Hitchens
authors.affiliation: Russell H. Morgan Dept. of Radiology and Radiological Science, Division of MR Research, The Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA; Dept. of Oncology, The Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA; Dept. of Biomedical Engineering, The Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA; Dept. of Chemical & Biomolecular Engineering, The Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA; Cellular Imaging Section, Institute for Cell Engineering, The Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA. Electronic address: jwmbulte@mri.jhu.edu.
authors.forename: Jeff W M
authors.initials: JW
authors.lastname: Bulte
authors.affiliation: Department of Radiology, University of California at San Diego, La Jolla, CA 92093, USA.
authors.forename: Eric T
authors.initials: ET
authors.lastname: Ahrens
mesh_terms: D003287:Contrast Media / Q000737:chemistry / Q000528:radiation effects; D004987:Ethers / Q000737:chemistry* / Q000528:radiation effects*; D066235:Fluorine-19 Magnetic Resonance Imaging / Q000379:methods*; D005466:Fluorocarbons / Q000737:chemistry* / Q000528:radiation effects*; D006801:Humans; D060526:Magnetic Fields; D008422:Materials Testing; D011829:Radiation Dosage; D013696:Temperature
chemical_list: D003287:Contrast Media; D004987:Ethers; D005466:Fluorocarbons; C078113:perfluoropolyether
keywords: (19)F MRI; (19)F NMR; (19)F cellular MRI; Cell tracking; Fluorine-19 MRI; Perfluorocarbons; R(1); Spin–lattice relaxation; T(1)