A cascade attention network for liver lesion classification in weakly-labeled multi-phase CT images

Abstract

Focal liver lesion classification is important to the diagnostics of liver disease. In clinics, lesion type is usually determined by multi-phase contrast-enhanced CT images. Previous methods of automatic liver lesion classification are conducted on lesion-level, which rely heavily on lesion-level annotations. In order to reduce the burden of annotation, in this paper, we explore automatic liver lesion classification with weakly-labeled CT images (i.e. with only image-level labels). The major challenge is how to localize the region of interests (ROIs) accurately by using only coarse image-level annotations and accordingly make the right lesion classification decision. We propose a cascade attention network to address the challenge by two stages: Firstly, a dual-attention dilated residual network (DADRN) is proposed to generate a class-specific lesion localization map, which incorporates spatial attention and channel attention blocks for capturing the high-level feature map’s long-range dependencies and helps to synthesize a more semantic-consistent feature map, and thereby boosting weakly-supervised lesion localization and classification performance; Secondly, a multi-channel dilated residual network (MCDRN) embedded with a convolutional long short-term memory (CLSTM) block is proposed to extract temporal enhancement information and make the final classification decision. The experiment results show that our method could achieve a mean classification accuracy of 89.68%, which significantly mitigates the performance gap between weakly-supervised approaches and fully supervised counterparts.