Flexible metasurface boosts performance of bio-inspired surface coil for 7 T preclinical MRI

This work presents a bio-inspired, floral-patterned surface coil for ultra-high-field preclinical MRI, enhanced by a flexible split-ring metasurface that boosts SNR without passive tuning. When the coil is loaded with a saline-solution phantom, RF impedance matching is degraded, leading to a reduction in performance. To quantify this degradation, we evaluated the noise factor (NF) and SNR from phantom images. The NF ratios demonstrate the metasurface's advantages: without metasurface, NF_cir/NF_bio=1.02 (where NF_cir and NF_bio correspond to the circular and bio-inspired coils, respectively); with metasurface and phantom, NF_cirMS/NF_bioMS=3.52 (where the subscript MS denotes the addition of the metasurface), indicating drastic noise reduction. SNR results show that the bio-inspired coil alone provides a 28% improvement over a conventional circular coil, while adding the metasurface yields an additional 44% enhancement (84% overall). These results highlight the potential of combining bio-inspired geometries with flexible metasurfaces for high-sensitivity ultra-high-field MRI.