Metamaterial Antennas Enhance MRI of the Eye and Occipital Brain.

Abstract

A metamaterial-integrated radio frequency antenna (MTMA), implemented in planar and bend configurations, enables high-resolution MRI of the eye, orbit, and occipital brain at 7.0 T. Its dual-layer co-planar architecture integrates a two-channel transceive loop with a metamaterial layer composed of subwavelength epsilon-negative unit cells. These unit cells were custom-designed based on classical split-ring resonators for operation at 7.0 T. Electromagnetic simulations, including human voxel models, guided the design and characterization of the MTMA's electromagnetic behavior. Both MTMA configurations were benchmarked against conventional loop coil arrays in phantoms and in vivo for experimental validation, demonstrating enhanced transmit (B₁ ⁺) efficiency and receive sensitivity enabled by the metamaterial layer through resonant near-field coupling. MRI safety was verified through SAR simulations, bio-thermal modeling, Magnetic Resonance thermometry, and fiber-optic sensors, confirming compliance with safety guidelines. The Bend-MTMA enabled in vivo human MRI of the eye and orbit in healthy volunteers, including B₁ ⁺ mapping, and provided diagnostic T₁- and T₂-weighted imaging in volunteers with retinal pathology and sinus cysts, demonstrating clinical applicability. The Planar-MTMA enabled occipital lobe MRI in human volunteers, achieving superior signal coverage and transmit performance. The modular unit cell design enables tuning across MRI magnetic field strengths, establishing a clinically translatable metamaterial-integrated antenna platform for ocular and neurological imaging.