Optimizing Traveling Wave RF Excitation for in Vivo Use

Cornelis A.T. van den Berg¹, Hugo Kroeze¹, Bart L. van de Bank¹, Bob van den Bergen¹, Peter R. Luijten¹, Jan J.W. Lagendijk¹, Dennis W.J. Klomp¹

Traveling waves has recently been introduced as a fundamentally new RF excitation concept for high field MRI. A great challenge is to achieve a sufficient transmit field at distant locations in the body since the wave is dampened during its passage through the body. In this study it is demonstrated by means of simulations and in-vivo experiments that dielectric insets can be used to generate 1.7 to 3 times higher B1+ field per unit power. Furthermore, it was found that an incoming wave reflects strongly at air-tissue interfaces in the shoulders region resulting in B1+ field focusing in the neck.