Figure 8.

Dual channel transmit RF coil in quadrature excitation mode uses the same RF amplitude A₁ and a 90º phase shift between the channels (a). Quadrature excitation results in reduced signal in the left lobe of the liver (arrow) due to dielectric effects (b). Using optimised elliptical polarisation with two different RF amplitudes, A₁ and A₂, and an $\alpha °$phase shift between the channels (c) results in an improved image uniformity (d).