A weakly supervised inpainting-based learning method for lung CT image segmentation

Recently, various fully supervised learning methods are successfully applied for lung CT image segmentation. However, pixel-wise annotations are extremely expert-demanding and labor-intensive, but the performance of unsupervised learning methods are failed to meet the demands of practical applications. To achieve a reasonable trade-off between the performance and label dependency, a novel weakly supervised inpaintingbased learning method is introduced, in which only bounding box labels are required for accurate segmentation. Specifically, lesion regions are first detected by an object detection network, then we crop them out of the input image and recover the missing holes to normal regions using a progressive CT inpainting network (PCIN). Finally, a post-processing method is designed to get the accurate segmentation mask from the difference image of input and recovered images. In addition, real information (i.e., number, location and size) of the bounding boxes of lesions from the dataset guides us to make the training dataset for PCIN. We apply a multi-scale supervised strategy to train PCIN for a progressive and stable inpainting. Moreover, to remove the visual artifacts resulted from the invalid features of missing holes, an initial patch generation network (IPGN) is proposed for holes initialization with generated pseudo healthy image patches. Experiments on the public COVID-19 dataset demonstrate that PCIN is outstanding in lung CT images inpainting, and the performance of our proposed weakly supervised method is comparable to fully supervised methods.

Automated summary

Recently, fully supervised learning methods have been successfully used for lung CT image segmentation. However, pixel-wise annotations are demanding and time-consuming, while unsupervised learning methods fail to meet practical requirements. To address this, a novel weakly supervised inpainting-based learning method is introduced, which only requires bounding box labels for accurate segmentation. The method detects lesion regions, recovers missing holes, and applies post-processing for accurate segmentation. Experiments on a COVID-19 dataset demonstrate the outstanding performance of the proposed method in lung CT image inpainting.