PolypSegNet: A modified encoder-decoder architecture for automated polyp segmentation from colonoscopy images

Colorectal cancer has become one of the major causes of death throughout the world. Early detection of Polyp, an early symptom of colorectal cancer, can increase the survival rate to 90%. Segmentation of Polyp regions from colonoscopy images can facilitate the faster diagnosis. Due to varying sizes, shapes, and textures of polyps with subtle visible differences with the background, automated segmentation of polyps still poses a major challenge towards traditional diagnostic methods. Conventional Unet architecture and some of its variants have gained much popularity for its automated segmentation though having several architectural limitations that result in sub-optimal performance. In this paper, an encoder-decoder based modified deep neural network architecture is proposed, named as PolypSegNet, to overcome several limitations of traditional architectures for very precise automated segmentation of polyp regions from colonoscopy images. For achieving more generalized representation at each scale of both the encoder and decoder module, several sequential depth dilated inception (DDI) blocks are integrated into each unit layer for aggregating features from different receptive areas utilizing depthwise dilated convolutions. Different scales of contextual information from all encoder unit layers pass through the proposed deep fusion skip module (DFSM) to generate skip interconnection with each decoder layer rather than separately connecting different levels of encoder and decoder. For more efficient reconstruction in the decoder module, multi-scale decoded feature maps generated at various levels of the decoder are jointly optimized in the proposed deep reconstruction module (DRM) instead of only considering the decoded feature map from final decoder layer. Extensive experimentations on four publicly available databases provide very satisfactory performance with mean five-fold cross-validation dice scores of 91.52% in CVC-ClinicDB database, 92.8% in CVC-ColonDB database, 88.72% in Kvasir-SEG database, and 84.79% in ETIS-Larib database. The proposed network provides very accurate segmented polyp regions that will expedite the diagnosis of polyps even in challenging conditions.