An RF field pattern with improved B₁ amplitude homogeneity

Providing uniform RF excitation across the sample is challenging in building high-field human MRI scanners. The traditional design strategy for the RF power transmission has been trying to achieve a spatial distribution of B₁ that is as uniform as possible in amplitude and direction. The fundamental limitation of this approach is that a constant solution of B ₁ is not available from the Maxwell equations at radio frequencies. Here, a new design strategy is introduced that takes advantage of solutions of the Maxwell equations that have a B₁ with uniform amplitude and varying direction in a lossless medium. In lossy media the B₁ amplitude also varies in space, but there is no intrinsic penalty in the homogeneity due to increases of the real part of the wave vector at higher fields. We demonstrate how it might be realized for RF excitation through a computer simulation for a uniform medium.