Microstrip RF surface coil design for extremely high-field MRI and spectroscopy

Area of Science:

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

Background:

• Conventional radiofrequency (RF) surface coils used in high-field MRI (7 Tesla) face challenges with radiation loss and sample loading perturbations.
• Existing coil designs can be complex, costly, and difficult to fabricate, limiting their widespread adoption in research and clinical settings.
• There is a need for improved RF coil designs that enhance sensitivity, penetration, and B1 symmetry at ultra-high field strengths.

Purpose of the Study:

• To develop and characterize a novel microstrip RF surface coil for in vivo proton and other nuclei NMR applications at 7T.
• To evaluate the performance, including signal-to-noise ratio (SNR), penetration, and B1 symmetry, of the new coil design.
• To demonstrate the convenience and efficiency of the microstrip coil for high-field MRI/MRS research and clinical applications.

Main Methods:

• A purely distributed-element and transmission line design was employed, featuring a thin conductor and ground plane separated by a low-loss dielectric.
• Theoretical description of the microstrip RF coil principles was provided to guide design.
• Gradient-recalled echo images were acquired using single- and two-turn microstrip coils on phantoms and human brains at 7T for performance evaluation.

Main Results:

• The microstrip RF coil demonstrated reduced radiation loss and sample loading perturbations compared to conventional coils.
• The coil exhibited a high Q factor, small physical size, no RF shielding requirement, lower cost, and ease of fabrication.
• The two-turn design significantly improved B1 symmetry, and the optimal dielectric thickness (H) was found to be approximately 7 mm, yielding comparable B1 penetration to conventional coils.

Conclusions:

• The novel microstrip RF surface coil design offers a practical and efficient solution for high-field MRI/MRS at 7T.
• This coil technology enhances convenience and efficiency for researchers and clinicians, potentially improving diagnostic capabilities.
• The microstrip coil's performance characteristics, including SNR and B1 symmetry, make it a valuable advancement in RF coil development.