Figure 5. B₁⁺ maps in phantom at 3.0 T.

Central axial partition of the 3D B₁⁺ maps obtained with methods A-E in phantom at 3.0 T using a birdcage TX/RX coil. Identical repetition times (TR = 30 ms) and SAR levels were used for all methods. The same partition of the B₁⁺ map acquired for comparison with the DAM with TR = 500 ms is also shown (F). All maps are normalized to their nominal B₁⁺ given in Table 1 in µT. The typical central spot of the birdcage TX/RX coil is visible. The contour plots (with contour increment of 0.05) show that the B₁⁺ distributions obtained from the phase-based methods are consistent with the DAM. Methods: A – Optimized low-flip-angle method , B – Phase-sensitive method , C – ΦFA-CUP method , D – Bloch-Siegert method, E – Orthogonal-pulses method, F – Double Angle method.