Fig. 4.

Simulated and experimentally measured absolute B ₁ ⁺ and relative B ₁ ⁻ field magnitude maps in an axial slice of a head-sized cylinder phantom: a B ₁ maps of a single power-matched CSA element arranged at the position corresponding to element 1 in Fig. 3; b B ₁ maps of a single element of the four-element CSA array (Fig. 3) with power-matched elements; c B ₁ maps of a single element of the comparable four-element C²ONTAR–CSA array. The absolute B ₁ ⁺ maps of current-controlled elements are normalized to the amplitude of the RF current of 1 A on the input port of the element. The B ₁ ⁺ maps of the power source-driven elements correspond to the absorbed power of P = 0.1091 W