Using Inductively-Coupled Dipole Pairs as Array Elements for Improving Whole-Brain Coverage at 9.4T

Motivation: At ultra-high fields, homogeneity of brain MRI is deteriorated by the subject-specific non-uniform distribution of RF magnetic field B1+. Goal(s): To design a 9.4T eight-channel transceiver dipole array with improved homogeneity of B1+ in the axial direction with better whole-brain coverage. Approach: We used an array consisting of paired passively coupled folded-end dipoles. We numerically optimized the B1+ homogeneity by adjusting the overlap between the folded ends of the active and passive dipoles and the load impedance of the passive one. Results: The proposed array demonstrated improved B1+ whole-brain homogeneity including the upper C-spine compared to several state-of-the-art dipole and loop arrays. Impact: The presented antenna element of coupled folded dipoles can be used in designing UHF array coils with improved longitudinal whole-brain coverage. Such coils can be beneficial for studies where imaging of the entire brain including the upper C-spine is required.