Realization of ¹⁹F MRI oximetry method using perfluorodecalin.

Area of Science:

• Medical Imaging
• Biophysics
• Fluorine Chemistry

Background:

• ¹⁹F magnetic resonance imaging (MRI) offers unique advantages for oximetry due to the high gyromagnetic ratio of ¹⁹F nuclei.
• Perfluorodecalin (PFD) is a clinically approved compound with potential applications in ¹⁹F MRI oximetry.
• Accurate oxygen tension (pO₂) measurements are crucial for understanding physiological processes and disease states, particularly in oncology.

Purpose of the Study:

• To evaluate the technical feasibility of using perfluorodecalin (PFD) for ¹⁹F MRI oximetry at a high magnetic field (7.05 T).
• To determine optimal parameters for PFD-based ¹⁹F MRI oximetry, including sample volume and excitation methods.
• To assess the in vivo performance of PFD for measuring oxygen levels in healthy and tumor-bearing rodent brains.

Main Methods:

• ¹⁹F T₁ relaxation time measurements were performed on PFD samples with varying oxygen concentrations (0%, 21%, 100%) at 21°C and 37°C.
• In vivo ¹⁹F MRI studies were conducted on rats, including one healthy control and two with C6 brain gliomas.
• Selective excitation of PFD's trans-isomer ¹⁹F nuclei (CF₂ groups) was employed for accurate oximetry.

Main Results:

• Optimal PFD volume for reliable T₁ measurements was determined to be 30 μl, with a standard deviation not exceeding 5%.
• Selective excitation of PFD's ¹⁹F nuclei at approximately -140 ppm (relative to TFA) is crucial for the oximetry method.
• In vivo studies demonstrated a decrease in pO₂ from ~38 mmHg in healthy rat brains to near 0 mmHg in advanced-stage gliomas.

Conclusions:

• The study confirms the feasibility of using perfluorodecalin (PFD) for ¹⁹F MRI oximetry.
• PFD-based ¹⁹F MRI oximetry can successfully detect reduced oxygen levels in brain tumors.
• This technique holds potential for non-invasive assessment of tumor hypoxia.