Toward (19)F magnetic resonance thermometry: spin-lattice and spin-spin-relaxation times and temperature dependence of fluorinated drugs at 9.4 T

OBJECTIVE: This study examines the influence of the environmental factor temperature on the (19)F NMR characteristics of fluorinated compounds in phantom studies and in tissue. MATERIALS AND METHODS: (19)F MR mapping and MR spectroscopy techniques were used to characterize the (19)F NMR characteristics of perfluoro-crown ether (PFCE), isoflurane, teriflunomide, and flupentixol. T(1) and T(2) mapping were performed, while temperature in the samples was changed (T = 20-60 °C) and monitored using fiber optic measurements. In tissue, T(1) of PFCE nanoparticles was determined at physiological temperatures and compared with the T(1)-measured at room temperature. RESULTS: Studies on PFCE, isoflurane, teriflunomide, and flupentixol showed a relationship between temperature and their physicochemical characteristics, namely, chemical shift, T(1) and T(2). T(1) of PFCE nanoparticles was higher at physiological body temperatures compared to room temperature. DISCUSSION: The impact of temperature on the (19)F NMR parameters of fluorinated compounds demonstrated in this study not only opens a trajectory toward (19)F 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 (19)F MR techniques in vivo.