Open birdcage coil for head imaging at 7T.

Area of Science:

• Magnetic Resonance Imaging (MRI)
• Radiofrequency (RF) Coil Engineering
• Biomedical Engineering

Background:

• Conventional birdcage coils face limitations in patient comfort and functional MRI integration.
• Improving RF coil design is crucial for advancing high-field MRI applications.
• Existing designs may compromise homogeneity or efficiency with modifications.

Purpose of the Study:

• To develop and validate a new birdcage coil geometry for 7 Tesla (T) brain imaging.
• The design aims to incorporate a large top window for enhanced patient comfort and functional MRI stimulus presentation.
• To ensure the new geometry does not compromise RF field homogeneity and transmit efficiency.

Main Methods:

• Theoretical description and design using the transfer matrix approach for a nonperiodic rung distribution.
• Full-wave simulations for coil adjustment and optimization.
• Experimental assembly, fine-tuning, matching, and validation on phantoms and in vivo.

Main Results:

• Optimized coil demonstrated good isolation (-14.9 dB) and symmetric circular polarized mode pattern.
• Experimental assessment confirmed competitive transmit efficiency and coverage compared to conventional coils.
• The opencage design maintained key performance metrics without significant degradation.

Conclusions:

• The proposed opencage coil is feasible for 7T brain imaging without compromising performance.
• Key parameters like B1 field homogeneity, transmit efficiency, and SAR were preserved.
• This design offers improved patient comfort and opens possibilities for enhanced fMRI studies and motion correction.