# Semantic Segmentation of Brain Tumors Using a Local-Global Attention Model
## 4 Experiments and Results
### Ablation Studies
#### 4.5.4 The Effects of Hyperparameter P on Performance  
In this section, we discuss the impact of hyperparameter P on segmentation performance. As shown in Table 7, the optimal value of P is found to be 128, which demonstrates a 0.73% and 0.51% improvement in performance compared to the values of 64 and 256, respectively. Furthermore, the number of parameters with this particular setting is positioned in the mid-range, and there is only a marginal disparity in FLOPs.  
\begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline \multirow{2}{*}{**Feature Size**} & \multirow{2}{*}{**Params (M) (\(\downarrow\))**} & \multirow{2}{*}{**GFLOPs (\(\downarrow\))**} & \multicolumn{6}{c}{**Dice (\%) (\(\uparrow\))**} \\ \cline{6-10}  & & & **ET** & **TC** & **WT** & **Avg.** \\ \hline
[36,72,144,288] 1 & **57.9** & **438.8** & 79.83 & 77.11 & 88.53 & 81.82 \\
[48,96,192,384] & 72.9 & 771.8 & 80.42 & 77.74 & 88.14 & 82.10 \\
[60,120,240,480] & 83.9 & 1150.9 & **80.80** & **78.25** & **88.50** & **82.51** \\ \hline \hline \end{tabular}  
* The first number refers to the number of channels in Stage 1, with each subsequent number corresponding to the following stages. ET = Blue labels, TC = Blue labels + Red Labels, WT = Blue labels + Red Labels + Green Labels.  
\end{table}
Table 6: Ablation study of model width.  
\begin{table}
\begin{tabular}{c c c c c c c c c c c} \hline \hline \multirow{2}{*}{**Model**} & \multicolumn{2}{c}{**Blocks**} & \multirow{2}{*}{**Params (M) (\(\downarrow\))**} & \multirow{2}{*}{**GFLOPs (\(\downarrow\))**} & \multicolumn{6}{c}{**Dice (\%) (\(\uparrow\))**} \\ \cline{6-10}  & & & & & **ET** & **TC** & **WT** & **Avg.** \\ \hline Model 1 & & & 97.1 & 1234.5 & 79.14 & 76.36 & 87.39 & 80.96 \\ Model 2 & ✓ & & 99.8 & 1242.9 & 80.54 & 77.95 & 88.13 & 82.21 \\ Model 3 & & ✓ & **72.0** & 1199.5 & 80.24 & 77.39 & 87.95 & 81.86 \\ Ours & ✓ & ✓ & 83.9 & **1150.9** & **80.80** & **78.25** & **88.50** & **82.51** \\ \hline \hline \end{tabular}  
* ET = Blue labels, TC = Blue labels + Red Labels, WT = Blue labels + Red Labels + Green Labels.  
\end{table}
Table 4: Ablation study of each proposed block. ✓ denotes we employ the corresponding blocks.  
\begin{table}
\begin{tabular}{c c c c c c c c c c c} \hline \hline \multirow{2}{*}{**Setting**} & \multirow{2}{*}{**Stage 1**} & \multirow{2}{*}{**Stage 2**} & \multirow{2}{*}{**Stage 3**} & \multirow{2}{*}{**Stage 4**} & \multirow{2}{*}{**Bottom**} & \multirow{2}{*}{**Params (M) (\(\downarrow\))**} & \multirow{2}{*}{**GFLOPs (\(\downarrow\))**} & \multicolumn{6}{c}{**Dice (\%) (\(\uparrow\))**} \\ \cline{6-10}  & & & & & & **ET** & **TC** & **WT** & **Avg.** \\ \hline Setting 1 & & & & & & **ET** & **TC** & **WT** & **Avg.** \\ Setting 2 & ✓ & ✓ & & & & & **ET** & **TC** & **WT** & **Avg.** \\ Setting 3 & ✓ & ✓ & ✓ & ✓ & & & 83.0 & **1150.8** & 79.78 & 76.30 & 88.11 & 81.40 \\ Setting 4 & ✓ & ✓ & ✓ & ✓ & ✓ & & 83.9 & 1150.9 & **80.80** & **78.25** & **88.50** & **82.51** \\ \hline \hline \end{tabular}  
* ET = Blue labels, TC = Blue labels + Red Labels, WT = Blue labels + Red Labels + Green Labels.  
\end{table}
Table 5: Ablation study of SMA blocks. ✓ denotes we employ SMA blocks in corresponding stages.