# COMA: Propagating Complementary Multi-Level Aggregation Network for Polyp Segmentation
## 4 Discussion
### CMM and BPM Visualization
#### 4.3.1 Complementary Masking Visualization  
To verify the effectiveness of the complementary multi-level aggregation, we sampled random channels from the low- and high-level representations and compared them after applying complementary information. In Figure 3-CMM, (a) and (b) denote relatively low-level and high-level features, respectively, whereas (c) is the complementary information masked by the high-level representation. We observed that the polyp regions were enhanced, and the discrepancy was diminished between (a)-(b) and (d)-(e) when applying the complementary information. The CMM in the first decoder propagated the refined representations to the next CMM and the second decoder. Following the complementary propagation, the second decoder could present the polyp regions under the discrepancy reduced representations.  
\begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline
**Dataset** & **BPM Combination** & **\#Params** & **mDice** & **mIoU** & \(\mathbf{S_{m}}\) & \(\mathbf{E_{m}}\) & **MAE** \\ \hline \multirow{4}{*}{CVC-ClinicDB} & \(E_{1}^{(1)},D_{1}^{(1)}\) & 31.10 M & 0.927 & 0.884 & 0.944 & 0.983 & 0.0070 \\  & \(E_{1}^{(1)},D_{1}^{(1)}\) & 31.10 M & 0.930 & 0.889 & 0.949 & 0.984 & 0.0068 \\  & \(E_{1}^{(1)},D_{1}^{(4)}\) & 31.10 M & **0.933** & **0.891** & **0.956** & **0.985** & **0.0066** \\  & \(E_{1}^{(1)},D\,^{\dagger}\) & 33.32 M & 0.928 & 0.885 & 0.954 & 0.982 & 0.0070 \\ \hline \multirow{4}{*}{Kvasir} & \(E_{1}^{(1)},D_{1}^{(1)}\) & 31.10 M & **0.905** & **0.855** & **0.924** & **0.955** & **0.027** \\  & \(E_{1}^{(1)},D_{3}^{(1)}\) & 31.10 M & 0.891 & 0.842 & 0.915 & 0.945 & 0.029 \\  & \(E_{1}^{(1)},D_{4}^{(1)}\) & 31.10 M & 0.901 & 0.852 & 0.919 & 0.951 & **0.027** \\  & \(E_{1}^{(1)},D\,^{\dagger}\) & 33.32 M & 0.903 & 0.852 & 0.920 & 0.954 & 0.028 \\ \hline \multirow{4}{*}{ColonDB} & \(E_{1}^{(1)},D_{1}^{(1)}\) & 31.10 M & **0.762** & **0.697** & **0.852** & 0.883 & **0.037** \\  & \(E_{1}^{(1)},D_{3}^{(1)}\) & 31.10 M & 0.738 & 0.677 & 0.840 & 0.864 & 0.039 \\  & \(E_{1}^{(1)},D_{4}^{(1)}\) & 31.10 M & 0.754 & 0.689 & 0.849 & **0.897** & **0.037** \\  & \(E_{1}^{(1)},D\,^{\dagger}\) & 33.32 M & 0.753 & 0.684 & 0.849 & 0.887 & 0.037 \\ \hline \multirow{4}{*}{ETIS} & \(E_{1}^{(1)},D_{2}^{(1)}\) & 31.10 M & 0.679 & 0.619 & 0.830 & 0.830 & 0.016 \\  & \(E_{1}^{(1)},D_{3}^{(1)}\) & 31.10 M & **0.714** & **0.656** & **0.845** & 0.858 & **0.015** \\  & \(E_{1}^{(1)},D\,^{\dagger}\) & 31.10 M & 0.711 & 0.648 & 0.844 & **0.887** & **0.015** \\  & \(E_{1}^{(1)},D\,^{\dagger}\) & 33.32 M & 0.697 & 0.629 & 0.840 & 0.851 & 0.024 \\ \hline \multirow{4}{*}{CVC-T} & \(E_{1}^{(1)},D_{2}^{(1)}\) & 31.10 M & 0.880 & 0.814 & 0.933 & 0.979 & 0.007 \\  & \(E_{1}^{(1)},D_{3}^{(1)}\) & 31.10 M & 0.898 & 0.835 & 0.939 & 0.981 & 0.007 \\ \cline{1-1}  & \(E_{1}^{(1)},D_{4}^{(1)}\) & 31.10 M & **0.906** & **0.843** & **0.945** & **0.988** & **0.006** \\ \cline{1-1}  & \(E_{1}^{(1)},D\,^{\dagger}\) & 33.32 M & 0.869 & 0.800 & 0.926 & 0.984 & 0.011 \\ \hline \hline \end{tabular}
\end{table}
Table 8: Comparison of COMMA performance with regard to BPM combinations. \(\dagger\) indicates that the boundary information was extracted through an independent boundary decoder, as in previous methods [20; 23].