# Self-Isolated Dual-Mode High-Pass Birdcage RF Coil for Proton and Sodium MR Imaging at 7 T MRI
## 3 Results
### MR Imaging Experiments  
Figure 6 illustrates an FA map of the phantom acquired using \({}^{1}\)H STBC RF coil, \({}^{23}\)Na STBC RF coil, and \({}^{1}\)H/\({}^{23}\)Na DMBC RF coil. For the \({}^{1}\)H images, the FA map uniformity of 63.4% with \({}^{1}\)H STBC RF coil and 59.8% with \({}^{1}\)H/\({}^{23}\)Na DMBC RF coil were achieved. Similarly, for \({}^{23}\)Na FA mapping, the uniformity was high at 87.8% for \({}^{23}\)Na STBC RF coil, with \({}^{1}\)H/\({}^{23}\)Na DMBC RF coil achieving a nearly equivalent uniformity of 84.4%.  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline  & \multicolumn{2}{c}{\({}^{1}\)H RF coil} & \multicolumn{2}{c}{\({}^{23}\)Na RF coil} \\ \cline{2-5}  & **STBC Coil** & **DMBC Coil** & **STBC Coil** & **DMBC Coil** \\ \hline Isolation Coef. (S12) & \(-\)19.10 dB & \(-\)19.23 dB & \(-\)20.71 dB & \(-\)20.31 dB \\ \hline Impedance (Z11) & \(50-\) j 2.33 & \(50-\) j 2.52 & \(50-\) j 1.81 & \(50+\) j 1.14 \\ \hline Impedance (Z22) & \(50-\) j 1.25 & \(50-\) j 3.34 & \(50-\) j 0.79 & \(50-\) j 1.27 \\ \hline Q-factor & 820.01 & 736.37 & 981.52 & 860.34 \\ \hline \hline \end{tabular}
\end{table}
Table 3: _Cont._  
Figure 5: Simulated B\({}_{1}^{+}\)-field maps in 3D human Duke model (left-axial; center-coronal; right-sagittal) at (**a**) \({}^{1}\)H and (**b**) \({}^{23}\)Na resonant frequency; simulated SAR maps in Duke model (left-axial; center-coronal; right-sagittal) at (**c**) \({}^{1}\)H and (**d**) \({}^{23}\)Na resonant frequency.  
In the assessment of the RF coil performance for \({}^{1}\)H MRI, SNR maps using \({}^{1}\)H STBC and \({}^{1}\)H/\({}^{23}\)Na DMBC RF coils are presented in Figure 7. The mean SNR value in ROI was 83.3 for \({}^{1}\)H STBC RF coil and 77.9 for \({}^{1}\)H/\({}^{23}\)Na DMBC RF coil, indicating a 6.5% SNR reduction with the DMBC RF coil.  
Similarly, for the \({}^{23}\)Na MRI test, the SNR maps of a human head are presented in Figure 8. The maps compare MR images acquired using \({}^{23}\)Na STBC and \({}^{1}\)H/\({}^{23}\)Na DMBC RF coil. The mean SNR values within the cerebrospinal fluid (CSF) ROI were 41.9 vs. 39.8 for STBC \({}^{23}\)Na and \({}^{1}\)H/\({}^{23}\)Na DMBC RF coil, respectively. This minor difference represents a nominal 5.4% reduction in SNR with the \({}^{1}\)H/\({}^{23}\)Na DMBC RF coil, which is nearly comparable to the performance of the \({}^{23}\)Na STBC RF coil.  
Figure 8: SNR maps of \({}^{23}\)Na MR images of an in vivo human head using (**a**) \({}^{23}\)Na STBC RF coil and (**b**) \({}^{1}\)H/\({}^{23}\)Na DMBC RF coil. Red circles overlaid on CSF designate the area for SNR measurement.  
Figure 6: \({}^{1}\)H FA map (nominal FA: 60\({}^{\circ}\)) of phantom obtained using (**a**) \({}^{1}\)H STBC RF coil and (**b**) \({}^{1}\)H/\({}^{23}\)Na DMBC RF coil. \({}^{29}\)Na FA map (nominal FA: 45\({}^{\circ}\)) obtained using (**c**) \({}^{23}\)Na STBC RF coil and (**d**) \({}^{1}\)H/\({}^{23}\)Na DMBC RF coil.  
Figure 7: SNR maps of in vivo human head \({}^{1}\)H MR images acquired with (**a**) \({}^{1}\)H STBC RF coil and (**b**) \({}^{1}\)H/\({}^{23}\)Na DMBC RF coil. Red circles indicate the ROI for the SNR measurement.