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.