Background

: Ground glass nodule (GGN) segmentation is one of the important and challenging tasks in diagnosing early-stage lung adenocarcinomas. Manually delineation of 3D GGN in computed tomography (CT) image is a subjective, laborious and tedious task, which presents poor repeatability.

Purpose

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.

Methods

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 pre-processing 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 the CT scans. Then, a 3D attentional cascaded residual network (ACRU-Net) was proposed to develop the deep learning-based segmentation model by using residual network and 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.

Results

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 that of 3D residual U-Net and ACRU-Net without CRF optimization.

Conclusions

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.

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