## 3 Results
### Assessment of Intensity Variability and Segmentation Performance
#### 3.2.2 Comparison Amongst Brain Extraction Methods  
Initially, the differences between the BE methods with both BFC methods were assessed (Table 4), and significant differences in RBVs were identified among the methods, except for the hippocampus (\(\chi^{2}(4)\) = 7.116, \(p\) = 0.130) with N4 ITK correction, and for the hippocampus (\(\chi^{2}(4)\) = 8.160, \(p\) = 0.086) and amygdala (\(\chi^{2}(4)\) = 8.442, \(p\) = 0.077) with SPM-BFC. Post hoc tests were applied to statistically assess the differences obtained in between each BE method (Table 5). \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Brain Tissue** & **Bias Field Correction Method** & \(\chi^{2}\) & \(p\) & **[PERSON]’s \(W\)** \\ \hline \multirow{2}{*}{Cortical Grey Matter} & SPM-BFC & 49.565 & \textless{}0.001 * & 0.563 \\ \cline{2-5}  & N4 ITK & 30.032 & \textless{}0.001 * & 0.341 \\ \hline \multirow{2}{*}{White Matter} & SPM-BFC & 24.176 & \textless{}0.001 * & 0.275 \\ \cline{2-5}  & N4 ITK & 24.836 & \textless{}0.001 * & 0.282 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: [PERSON]’s two-way analysis of variance by ranks test statistics (Chi-squared (\(\chi^{2}\)), degrees of freedom (df = 4), \(p\)-value (\(p\)) and [PERSON]’s \(W\)) for evaluating the general differences regarding regional segmentation using five BE methods (Manual, BET2, SWS, HD-BET, and SynthStrip) with SPM-BFC and N4 ITK correction. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Brain Tissue** & **Brain Extraction Method** & \(Z\) & \(p\) \\ \hline \multirow{5}{*}{Hippocampus} & Manual & \(-1.353\) & 0.176 \\ \cline{2-5}  & BET2 & \(-2.345\) & 0.019 * \\ \cline{2-5}  & SWS & \(-0.046\) & 0.963 \\ \cline{2-5}  & HD-BET & \(-0.410\) & 0.682 \\ \cline{2-5}  & SynthStrip & \(-0.206\) & 0.837 \\ \hline \multirow{5}{*}{Amygdala} & Manual & \(-2.489\) & 0.013 * \\ \cline{2-5}  & BET2 & \(-2.111\) & 0.035 * \\ \cline{2-5}  & SWS & \(-1.845\) & 0.065 \\ \cline{2-5}  & HD-BET & \(-1.508\) & 0.132 \\ \cline{2-5}  & SynthStrip & \(-1.732\) & 0.083 \\ \hline \multirow{5}{*}{Cerebellum} & Manual & \(-0.676\) & 0.499 \\ \cline{2-5}  & BET2 & \(-0.598\) & 0.598 \\ \cline{2-5}  & SWS & \(-1.314\) & 0.189 \\ \cline{2-5}  & HD-BET & \(-0.219\) & 0.827 \\ \cline{2-5}  & SynthStrip & \(-0.564\) & 0.573 \\ \hline \multirow{5}{*}{Brainstem} & Manual & \(-2.234\) & 0.025 * \\ \cline{2-5}  & BET2 & \(-2.841\) & 0.005 * \\ \cline{1-1} \cline{2-5}  & SWS & \(-2.559\) & 0.010 * \\ \cline{1-1} \cline{2-5}  & HD-BET & \(-3.207\) & 0.001 * \\ \cline{1-1} \cline{2-5}  & SynthStrip & \(-3.317\) & \textless{}0.001 * \\ \hline \hline \end{tabular}
\end{table} 
Table 3: _Cont._ \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Brain Tissue** & **Bias Field Correction Method** & \(\chi^{2}\) & \(p\) & **Kendall’s \(W\)** \\ \hline Cerebral Spinal & \multicolumn{2}{c}{SPM-BFC} & 50.804 & \(<\)0.001 * & 0.577 \\ \cline{2-6} Fluid & N4 ITK & 40.545 & \(<\)0.001 * & 0.461 \\ \hline Deep Nuclear & \multicolumn{2}{c}{SPM-BFC} & 31.852 & \(<\)0.001 * & 0.362 \\ \cline{2-6} Grey Matter & N4 ITK & 30.378 & \(<\)0.001 * & 0.345 \\ \hline Hippocamp & SPM-BFC & 8.160 & 0.086 & 0.093 \\ \cline{2-6}  & N4 ITK & 7.116 & 0.130 & 0.081 \\ \hline Amygdala & SPM-BFC & 8.442 & 0.077 & 0.096 \\ \cline{2-6}  & N4 ITK & 11.067 & 0.026 * & 0.126 \\ \hline Cerebellum & \multicolumn{2}{c}{SPM-BFC} & 55.486 & \(<\)0.001 * & 0.631 \\ \cline{2-6}  & N4 ITK & 54.740 & \(<\)0.001 * & 0.622 \\ \hline Brainstem & \multicolumn{2}{c}{SPM-BFC} & 35.186 & \(<\)0.001 * & 0.400 \\ \cline{2-6}  & N4 ITK & 35.675 & \(<\)0.001 * & 0.405 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: _Cont._