Effective delivery of the traveling wave to distant locations in the body at 7T

Introduction The possibility of application of the traveling wave concept for MRI experiments on a whole body at ultra high fields was recently confirmed by the experiments in Zürich and Utrecht [1, 2]. In these experiments excitation and reception is carried out by a single antenna situated at the beginning of the cavity of a 7 Tesla MR scanner which guides traveling waves along its longitudinal axis. The radiated traveling wave first travels through air and then starts to propagate in a (human) body. A strong damping of the wave occurs during the passage through the body and prohibits excitation of the parts which are located far from the antenna, e. g. the pelvic area. Here, we propose a new concept to deliver a maximum B1 + power to the intended region for RF excitation using the waveguide with a coaxial inner conductor. Such waveguide is created by the RF shield of the MR scanner and the inserted cylindrical conductive layer that shields part of the body, e.g. the legs. Due to this conductive shield the radiated wave initially does not penetrate into the body and, thus, the undesirable premature wave attenuation is prevented.