Toward 19F magnetic resonance thermometry: spin–lattice and spin–spin-relaxation times and temperature dependence of fluorinated drugs at 9.4 T
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This study examines the influence of the environmental factor temperature on the 19F NMR characteristics of fluorinated compounds in phantom studies and in tissue.
Materials and methods
19F MR mapping and MR spectroscopy techniques were used to characterize the 19F NMR characteristics of perfluoro-crown ether (PFCE), isoflurane, teriflunomide, and flupentixol. T1 and T2 mapping were performed, while temperature in the samples was changed (T = 20–60 °C) and monitored using fiber optic measurements. In tissue, T1 of PFCE nanoparticles was determined at physiological temperatures and compared with the T1-measured at room temperature.
Studies on PFCE, isoflurane, teriflunomide, and flupentixol showed a relationship between temperature and their physicochemical characteristics, namely, chemical shift, T1 and T2. T1 of PFCE nanoparticles was higher at physiological body temperatures compared to room temperature.
The impact of temperature on the 19F NMR parameters of fluorinated compounds demonstrated in this study not only opens a trajectory toward 19F MR-based thermometry, but also indicates the need for adapting MR sequence parameters according to environmental changes such as temperature. This will be an absolute requirement for detecting fluorinated compounds by 19F MR techniques in vivo.
KeywordsMagnetic resonance Fluorine MR 19F MR Thermometry Spin–lattice relaxation
CP would like to thank Yiyi Ji for helpful discussions on thermometry. TN wishes to acknowledge the support provided by the European Research Council (ERC advanced Grant, ThermalMR, EU project 743077). SW wishes to acknowledge the support provided by the Germany Research Council (DFG WA2804).
Study conception and design: CP, PR, TE, TN, and SW. Acquisition of data: CP, TE, LS, and SW. Drafting of manuscript: CP, PR, TE, LS, TN, and SW. Critical revision: CP, PR, TE, LS, TN, and SW.
This study was funded (in part) by the Deutsche Forschungsgemeinschaft to SW (DFG WA2804). TN received funding from the European Research Council (ERC advanced Grant, ThermalMR, EU project 743077).
Compliance with ethical standards
Conflict of interest
Thoralf Niendorf is founder and CEO of MRI.TOOLS GmbH, Berlin, Germany.
Statement of human/animal rights
All animal experiments were conducted in accordance with procedures approved by the Animal Welfare Department of the State Office of Health and Social Affairs Berlin (LAGeSo), and conformed to national and international guidelines to minimize discomfort to animals (86/609/EEC).
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