In their seminal publication Brunner et al. have pioneered the distribution of the RF B1-field using the propagation of traveling waves within the bore of the 7 T MRI scanner. A common feature of most traveling-wave approaches is a waveguide mode excitation that relies on a closed-end antenna system at the bore end. We therefore propose an adaptive RF antenna system for the excitation (and control) of the fundamental circular waveguide mode (TE11), consisting of multiple «flat» composite right-/left-handed (CRLH) metamaterial ring antennas [cf. Fig.1(a)]that fully conforms to the inner surface of the MRI bore , and therefore yields no drawbacks in terms of patient’s comfort.