Kadayakkara Deepak K, Damodaran Krishnan, Hitchens T Kevin, Bulte Jeff W M, Ahrens Eric T
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.
Department of Chemistry, University of Pittsburgh, Pittsburgh, PA 15260, USA.
J Magn Reson. 2014 May;242:18-22. doi: 10.1016/j.jmr.2014.01.014. Epub 2014 Feb 10.
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.
全氟碳标记细胞的氟（¹⁹F）磁共振成像已成为追踪活生物体中细胞迁移和聚集的强大技术。用含有大量化学等价氟原子的全氟聚醚纳米乳液对细胞进行¹⁹F磁共振成像标记很常见。了解¹⁹F核弛豫机制，特别是这些分子的自旋晶格弛豫，对于提高实验灵敏度至关重要。迄今为止，全氟聚醚的自旋晶格弛豫速率常数（R1）对温度和磁场强度的依赖性尚未得到详细描述。在本研究中，我们在三个磁场强度（7.0、9.4和14.1T）以及256 - 323K的温度范围内评估了线性全氟聚醚（PFPE）和环状全氟-15-冠-5醚（PCE）的R1。我们的结果表明，全氟聚醚的R1主要由偶极-偶极相互作用和化学位移各向异性决定。PCE和PFPE的R1均随磁场强度增加。在所研究的温度范围内，PCE在所有场强下都处于快速运动状态（ωτc<1），但对于PFPE，R1经过一个最大值，据此估计了旋转相关时间。讨论了这些测量对于合理设计新型¹⁹F磁共振成像剂和方法的重要性。
