Enhancement of transmit and receive efficiencies with hybridized meta-atom in 7T head coil
Résumé
Background B1 homogeneity in 7T MRI remains an important challenge in order to fully benefit from the signal enhancement due to the stronger magnetization available in ultra-high field scanners. High-dielectric constant pads have been proposed and optimized for passive shimming purposes [1-3]. Common formulations of dielectric pads for 7T applications are based on BaTiO 3 mixed with water. They present some drawbacks such as performance decay over time and toxicity. While previous studies tackled directly the formulation problem introducing new dielectric materials and solvent [4], we adopted a new approach based on metamaterials [5]. We demonstrated that the hybridization of four parallel metallic wires arranged on a square unit cell provides the ability to control radiofrequency field inside a 7T head birdcage. In the present work, we show that these hybridized meta-atom (HMA) can be used to improve MRI acquisition in the presence of a head receive array routinely used for in vivo MRI protocol.
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