Travelling wave approach for high field magnetic resonance imaging

A theoretical investigation of the travelling-wave approach for high field magnetic resonance imaging (MRI) is presented. The travelling wave probes excite the fields in the longitudinal direction of the bore, so that the effects of the attenuation constant due to high permittivity and lossy tissue need to be calculated. In addition, the travelling wave modes should affect the B₁⁺ field homogeneity inside high permittivity and lossy tissue. The full-field solution of infinite waveguide loaded with a lossy dielectric cylinder for 7T travelling wave phenomenon is presented. The transcendental equation was solved numerically to find the attenuation and propagation constants. Results indicate that, the B₁⁺ field is independent of the antenna type, other than the magnitude as the purpose is just exciting modes. In this paper, the traveling wave probes were designed, fabricated, and tested for 7-tesla (7T) MRI.