CACFormer: A Hybrid CNN-Transformer Architecture Guided by Channel Attention for 3D Medical Image Segmentation

Vision Transformer has achieved significant performance improvements in natural image segmentation tasks owing to its superior global modeling capabilities. However, applying vision Transformers to 3D medical image segmentation is challenging because of the quadratic computational complexity of the self-attention mechanism and their limited generalization on small-scale datasets. To address these limitations, we propose a hybrid CNN-Transformer architecture guided by channel attention, referred to as CACFormer, for 3D medical image segmentation. Specifically, we design a simple and effective channel attention module to guide the fusion of local and global features in each channel. This module adaptively assigns weights to each channel based on its semantic contribution to accurate segmentation. Meanwhile, we introduce a novel linear Transformer variant that integrates a linear attention mechanism with tanh activation. This design encourages the model to focus on the target regions and produce robust segmentation outcomes. The effectiveness and competitive generalization of the proposed framework are validated across five benchmark datasets. On AMOS2022, CACFormer achieves an average Dice score of 89.71%, outperforming 3D UX-Net (89.30%) while reducing inference time from 3.77 s to 2.49 s (a 33.95% reduction). On BraTS2021, CACFormer attains an average Dice score of 90.20%, comparable to TransBTS (90.33%), with 28.54% fewer parameters and 15.22% faster inference time (from 0.46 s to 0.39 s), demonstrating a favorable trade-off between performance and efficiency. Moreover, CACFormer demonstrates competitive cross-dataset generalization, achieving an average Dice score of 86.50% on BraTS2021 when trained on BraTS2019, significantly out-performing TransBTS (47.90%). Index Terms-3D Medical Image.