FIGURE 4.

Average and coefficient of variation (CV) of the transmit field magnitude $\left(\left|{\text{B}}_1^{+}\right|\right)$ inside the fetus across different body models. CP mode: circularly polarized birdcage mode, RFS: optimal RF shim setting for average $\left|{\text{B}}_1^{+}\right|$ or $\left|{\text{B}}_1^{+}\right|$ CV with no SAR restrictions (red triangle or star in Figure 2), RFS, improved SAR: optimal RF shim setting for average $\left|{\text{B}}_1^{+}\right|$ or $\left|{\text{B}}_1^{+}\right|$ CV that also improves maternal and fetal SAR compared with CP mode of the corresponding model (black triangle or star in Figure 2). The percentages of improvement in average $\left|{\text{B}}_1^{+}\right|$ and $\left|{\text{B}}_1^{+}\right|$ CV when using RF shimming compared with CP mode are noted above the bar graphs