Fig. 5.

Simulation (a and b) and experimental (c and d) ${\text{B}}_1^{+}$ efficiency $\left({\text{B}}_1^{+}/\surd \text{W}\right)$ maps of the 16-channel dipole and the 16-channel asymmetric sleeve antenna arrays with a phantom. The results are shown in the axial, coronal, and sagittal planes. For the experimental data (c and d), a threshold was applied for better data display purpose. Note: Due to the reduced interaction among the coaxial cables and antennas of the 16-channel asymmetric sleeve antenna array, the sagittal image shows more field distortion compared to the 16-channel dipole antenna array. Red arrows indicate ROIs where values are measured. The measurements are listed below the corresponding set of figures for comparison. Green dots indicate the position of individual element of the arrays.