Single-Frequency Birdcage Coils for Deep Tissue Perfluorocarbon Magnetic Resonance Imaging in Mice

Area of Science:

• Magnetic Resonance Imaging
• Biomedical Engineering
• Cellular Biology

Background:

• Fluorine-19 (¹⁹F) MRI is crucial for in vivo cell tracking using perfluorocarbons (PFCs).
• Optimizing radiofrequency (RF) hardware is essential for enhancing deep tissue ¹⁹F MR detection and anatomical imaging.

Purpose of the Study:

• To develop and evaluate novel mouse-specific RF coils for improved dual ¹H anatomical and deep tissue ¹⁹F MR imaging.
• To compare the performance of single-frequency ¹H and ¹⁹F coils against dual-frequency coils for PFC detection.

Main Methods:

• Construction of three linearly polarized birdcage RF coils: dual-frequency ¹H/¹⁹F, and sequential single-frequency ¹H and ¹⁹F coils.
• Benchmarking RF coil quality factors, homogeneity, and sensitivity against a commercial dual-frequency surface coil.
• In vivo assessment using PFC nanoemulsion injected into mice, evaluating signal-to-noise ratios (SNRs) and contrast-to-noise ratios (CNRs) at varying depths.

Main Results:

• Single-frequency birdcage coils demonstrated more uniform coverage and higher SNRs for ¹⁹F detection compared to dual-frequency coils.
• The single-frequency ¹H coil significantly increased CNR in anatomical images (p < 0.001).
• The single-frequency ¹⁹F coil showed significantly higher SNR in lymph nodes (p < 0.01) and improved PFC detectability, with performance degrading linearly with depth for surface coils (R² = 0.6352).

Conclusions:

• Novel single-frequency RF coils significantly enhance deep tissue ¹⁹F MR imaging performance in mice.
• These coils improve PFC detectability and SNR in lymph nodes compared to dual-frequency coils.
• The findings highlight limitations of surface coils for deep tissue ¹⁹F quantification and advocate for specialized coil designs.