AttENT: Domain-Adaptive Medical Image Segmentation via Attention-Aware Translation and Adversarial Entropy Minimization

Due to the intrinsic domain shift among different modalities, it is nontrivial to directly apply a well-trained model into other cross-modality medical images. Unsupervised domain adaptation (UDA) has the potential to reduce such domain shift. However, existing UDA methods try to align domains in either image level or in feature level, failing to consider the unified relationship between cross-modality images and their corresponding features. In this paper, we propose a novel UDA framework for domain adaptive medical image segmentation. The proposed framework synergizes both pixel space and entropy space for domain alignment. Specifically, in the pixel space, we introduce the attention mechanism into CycleGAN, and enhance the semantic and geometric consistency of the target organs during the image style transformation. In entropy space, we utilize entropy minimization principle to force consistent image segmentation between well-annotated source domain and non-annotated target domain. The aligned ensemble of two representation spaces enables a well-trained segmentation model to effectively transfer from source domain to target domain. The experimental results demonstrate the effectiveness of the proposed method. For the task of multi-organs segmentation from cross-modality medical images, our proposed framework achieves state-of-the-art performance, with some specific metric even superior to those of supervised methods. The code is available at https://github.com/lichen14/AttENT.