Deep learning architectures for multiphase CT image segmentation

The article provides a comprehensive systematic analysis of modern deep learning architectures for automatic segmentation of multiphase CT images. The specific features of multiphase data are considered in detail, the main of which are spatial mismatches (offsets) between phases caused by patient movements and the different nature of the accumulation of contrast agent in pathological tissues at different phases. These features make direct adaptation of classical segmentation methods ineffective and require the development of specialized architectures. The article traces the evolution of approaches: from basic convolutional networks (U-Net, 3D U-Net, nnU-Net) and hybrid models (TransUNet, UNETR) combining convolutions and transformers to specialized solutions. Special attention is paid to models with mechanisms of cross-attention between phases, such as PA-ResSeg, M3Net and MULLET, which allow for implicit alignment of features and adaptive merging of information from different phases without explicit registration (alignment) of images. The paper also analyzes the comparative advantages of various data fusion strategies from different phases (early, late, cross-interaction), discusses issues of computational efficiency and availability of open datasets. Key trends and promising areas of development of the field have been identified, including the use of fundamental models (MedSAM, VoxTell) and modal-agnostic learning. It is concluded that further progress in the field of multiphase segmentation of CT images is associated with the creation of computationally efficient architectures capable of integration into the real clinical process to support diagnostic solutions.

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