Enhancing B1+ at 7T MRI by combining a compact metamaterial devised from artificial dielectric with a TIAMO-like acquisition

Motivation: Local signal enhancement at 7T MRI can benefit from passively added metamaterial while optimally combined with B1-shim configuration of the multi-channel transmit coils. Passively added metamaterial needs to be compact for easy integration in the tight coil-to-patient settings. Goal(s): Our goal was to design a compact metamaterial and examine local signal enhancement with B1-shim configurations. Approach: AD comprising of hexagonally placed conductive sub-units was designed and integrated in a resonant metamaterial at 298 MHz. Scans with TIAMO-like shimming were acquired. Results: The TIAMO-like two scans configurations showed higher enhancement than using only CP-mode and the enhancement reached larger region-of-interest . Impact: We demonstrated a new compact and thin AD and metamaterial configuration that does not require lumped elements for 7T MRI. Importantly, we showed that the use of B1-shim can further increase the achieved enhancement.