Fluorine-19 fast recovery fast spin echo imaging for mapping 5-fluorouracil

In vivo detection of teriflunomide-derived fluorine signal during neuroinflammation using fluorine MR spectroscopy

Background: Magnetic resonance imaging (MRI) is indispensable for diagnosing neurological conditions such as multiple sclerosis (MS). MRI also supports decisions regarding the choice of disease-modifying drugs (DMDs). Determining in vivo tissue concentrations of DMDs has the potential to become an essential clinical tool for therapeutic drug monitoring (TDM). The aim here was to examine the feasibility of fluorine-19 (¹⁹F) MR methods to detect the fluorinated DMD teriflunomide (TF) during normal and pathological conditions.

Methods: We used ¹⁹F MR spectroscopy to detect TF in the experimental autoimmune encephalomyelitis (EAE) mouse model of multiple sclerosis (MS) in vivo. Prior to the in vivo investigations we characterized the MR properties of TF in vitro. We studied the impact of pH and protein binding as well as MR contrast agents.

Results: We could detect TF in vivo and could follow the ¹⁹F MR signal over different time points of disease. We quantified TF concentrations in different tissues using HPLC/MS and showed a significant correlation between ex vivo TF levels in serum and the ex vivo¹⁹F MR signal.

Conclusion: This study demonstrates the feasibility of ¹⁹F MR methods to detect TF during neuroinflammation in vivo. It also highlights the need for further technological developments in this field. The ultimate goal is to add ¹⁹F MR protocols to conventional ¹H MRI protocols in clinical practice to guide therapy decisions.

Toward 19F 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 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 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, T₁ and T₂. T₁ of PFCE nanoparticles was higher at physiological body temperatures compared to room temperature.

DISCUSSION

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.

Double-tuned radiofrequency coil for (19)F and (1)H imaging

We developed a double-tuned radiofrequency (RF) coil using a novel circuit method to double tune for fluorine-19 (19F) and 1H magnetic resonance imaging, whose frequencies are very close to each other. The RF coil consists of 3 parallel-connected series inductor capacitor circuits. A computer simulation for our double-tuned RF coil with a phantom demonstrated that the coil has tuned resonant frequency and high sensitivity for both 19F and 1H. Drug distribution was visualized at 7 tesla using this RF coil and a rat administered perfluoro 15-crown-5-ether emulsion. The double-tune RF coil we developed may be a powerful tool for 19F and 1H imaging.