A hierarchical teacher-student learning framework with adaptive cross-modal fusion for brain tumor segmentation

Accurate brain tumor segmentation plays an important role in clinical diagnosis, treatment planning, and therapeutic response monitoring. Multi-modal MRI provides complementary structural and functional information, but existing methods remain limited by their inadequate exploitation of cross-modal complementarity and their inability to effectively handle modality-specific disparities and redundant information. To address these challenges, this paper proposes a novel hierarchical teacher-student learning framework with adaptive cross-modal fusion. MRI modalities are grouped into teacher modalities (Flair and T1c) and student modalities (T2 and T1) based on their intrinsic tumor-related characteristics. Central to this framework is the Modality Guidance Module (MGM), which consists of two key components designed to achieve multi-modal feature distillation. Within MGM, the Modality Enhancement Module (MEM) extracts highly discriminative features from teacher modalities. While the Modality Fusion Module (MFM) leverages these features to guide and refine the learning of student modalities. To further capture inter-modal dependencies, a Cross-Modal Fusion Module (CMFM) is introduced to adaptively integrate complementary information across all modalities. Extensive experiments on the BraTS 2018, 2019 and 2020 datasets demonstrate that the proposed method achieves superior performance compared with state-of-the-art approaches. Beyond brain tumor segmentation, the hierarchical teacher-student paradigm and adaptive fusion strategy also hold potential for broader multi-modal image analysis tasks.