EBG structure to improve the B1 efficiency of stripline coil for 7 Tesla MRI

This paper presents the first application of an EBG structure to improve the B1 efficiency of strip-line coils used for 7-Tesla Magnetic Resonance Imaging (MRI). The proposed offset multilayer electromagnetic band gap (EBG) structure is utilized as a high impedance surface behind an extended half-wavelength (meandered) dipole. It operates at 300MHz, the magnetic resonance frequency at 7 T, and comprises of electrically small cells of only 7.5% of the free-space wavelength. The reflection phase coefficient and the dispersion diagram were used to characterize the EBG structure. The MRI strip-line coil backed by our EBG structure is successful in exhibiting a stronger B₁-field inside a phantom than the original design using a metallic conductor (PEC) ground plane for the coil. The quantitative improvement in B₁ efficiency amounts to 47%.