Encoding matching criteria for cross-domain deformable image registration.

Background: Most existing deep learning-based registration methods are trained on single-type images to address same-domain tasks, resulting in performance degradation when applied to new scenarios. Retraining a model for new scenarios requires extra time and data. Therefore, efficient and accurate solutions for cross-domain deformable registration are in demand.

Purpose: We argue that the tailor-made matching criteria in traditional registration methods is one of the main reason they are applicable in different domains. Motivated by this, we devise a registration-oriented encoder to model the matching criteria of image features and structural features, which is beneficial to boost registration accuracy and adaptability.

Methods: Specifically, a general feature encoder (Encoder-G) is proposed to capture comprehensive medical image features, while a structural feature encoder (Encoder-S) is designed to encode the structural self-similarity into the global representation. Moreover, by updating Encoder-S using one-shot learning, our method can effectively adapt to different domains. The efficacy of our method is evaluated using MRI images from three different domains, including brain images (training/testing: 870/90 pairs), abdomen images (training/testing: 1406/90 pairs), and cardiac images (training/testing: 64770/870 pairs). The comparison methods include traditional method (SyN) and cutting-edge deep networks. The evaluation metrics contain dice similarity coefficient (DSC) and average symmetric surface distance (ASSD).

Results: In the single-domain task, our method attains an average DSC of 68.9%/65.2%/72.8%, and ASSD of 9.75/3.82/1.30 mm on abdomen/cardiac/brain images, outperforming the second-best comparison methods by large margins. In the cross-domain task, without one-shot optimization, our method outperforms other deep networks in five out of six cross-domain scenarios and even surpasses symmetric image normalization method (SyN) in two scenarios. By conducting the one-shot optimization, our method successfully surpasses SyN in all six cross-domain scenarios.

Conclusions: Our method yields favorable results in the single-domain task while ensuring improved generalization and adaptation performance in the cross-domain task, showing its feasibility for the challenging cross-domain registration applications. The code is publicly available at https://github.com/JuliusWang-7/EncoderReg.