Opencage radio frequency coil for magnetic resonance imaging

We present a volume radio frequency coil for Magnetic Resonance Imaging that provides access to the region of interest. While the conventional birdcage coil is composed of a periodic array of similar unit cells making a cylindrical structure, the proposed coil, called “opencage,” is made of an aperiodic array of metamaterial based unit cells presenting different geometries and characteristics. We develop here a dedicated approach based on Bloch impedance matching and phase balance for the design of the opencage coil. We perform full-wave numerical simulations to validate this concept. An experimental demonstration of the opencage coil for small animal imaging at 7 Tesla is presented. The results of the in-vitro, in-vivo imaging and $B1+$ map reconstruction achieved with a preclinical MRI scanner are presented. We show that $B1+$ field homogeneity and amplitude generated by the opencage coil are comparable to those of a conventional birdcage coil of the same size.