Improving traveling-wave RF fields inside magnetic resonance imaging bores by incorporating dielectric loadings

The next-generation magnetic resonance imaging (MRI) systems at ultra-high static magnetic fields (magnetic flux densities), B0 > 3 T, and ultra-high Larmor frequencies, ƒ0 > 127.8 MHz, utilize RF excitation magnetic fields, B1, in the form of traveling waves (TWs) in the MRI bore. Hence, the images of subjects are generated and received by far-field coils, namely, by excitation probes that essentially operate as antennas, in place of the traditional quasi-static, near-field RF coils used in 3-T clinical MRI scanners (e.g., birdcage coils). When compared to traditional, quasi-static, MRI systems, TW MRI systems can provide more homogeneous B1 field distribution, better signal-to-noise ratio, larger field of view, more comfort for patients, etc. Moreover, it is possible to potentially benefit from the advantages of TW concepts also at relatively lower (but still considered high) field strengths (e.g., B0 = 3 T; ƒ0 = 127.8 MHz), in order to address challenges and enable substantial improvements of current clinical MRI scanners at 3 T.