Volumetric segmentation of ground glass nodule based on 3D attentional cascaded residual U‐Net and conditional random field

Ground glass nodule (GGN) segmentation is one of the important and challenging tasks in diagnosing early-stage lung adenocarcinomas. Manually delineating of 3D GGN in a computed tomography (CT) image is a subjective, laborious, and tedious task, which presents poor repeatability.To reduce the annotation burden and improve the segmentation performance, this study proposes a 3D deep learning-based volumetric segmentation model to segment the GGN in CT images.A total of 379 GGNs were retrospectively collected from the public database, Shanghai Pulmonary Hospital (SHPH), and Fudan University Shanghai Cancer Center (FUSCC). First, a series of image preprocessing techniques involving image resampling, intensity normalization, 3D nodule patch cropping, and data augmentation, were adopted to generate the input images for the deep learning model by using CT scans. Then, a 3D attentional cascaded residual network (ACRU-Net) was proposed to develop the deep learning-based segmentation model by using the residual network and the atrous spatial pyramid pooling module. To improve the model performance, a voxel-based conditional random field (CRF) method was used to optimize the segmentation results. Finally, a balanced cross-entropy and Dice combined loss function was applied to train and build the segmentation model.Testing on SHPH and FUSCC datasets, the proposed method generates the Dice coefficients of 0.721 ± 0.167 and 0.733 ± 0.100, respectively, which are higher than those of 3D residual U-Net and ACRU-Net without CRF optimization.The results demonstrated that combining 3D ACRU-Net and CRF effectively improved the GGN segmentation performance. The proposed segmentation model may provide a potential tool to help the radiologist in the segmentation and diagnosis of 3D GGN.