AtlasSeg: Atlas Prior Guided Dual-U-Net for Cortical Segmentation in Fetal Brain MRI

TL;DR

AtlasSeg is a novel dual-U-Net model that explicitly incorporates gestational age-specific atlas guidance and multi-scale attention mechanisms to improve fetal brain tissue segmentation accuracy across all gestational ages, especially in challenging early and late stages.

Contribution

The paper introduces AtlasSeg, a dual-U-Net architecture that explicitly integrates GA-specific atlas guidance and multi-scale spatial attention for improved fetal brain MRI segmentation.

Findings

Achieved highest average Dice score of 0.91 among tested networks.

Significantly improved segmentation accuracy in early and late gestational ages.

Demonstrated robustness to low-quality images with contrast changes and noise.

Abstract

Accurate automatic tissue segmentation in fetal brain MRI is a crucial step in clinical diagnosis but remains challenging, particularly due to the dynamically changing anatomy and tissue contrast during fetal development. Existing segmentation networks can only implicitly learn age-related features, leading to a decline in accuracy at extreme early or late gestational ages (GAs). To improve segmentation performance throughout gestation, we introduce AtlasSeg, a dual-U-shape convolution network that explicitly integrates GA-specific information as guidance. By providing a publicly available fetal brain atlas with segmentation labels corresponding to relevant GAs, AtlasSeg effectively extracts age-specific patterns in the atlas branch and generates precise tissue segmentation in the segmentation branch. Multi-scale spatial attention feature fusions are constructed during both encoding and decoding stages to enhance feature flow and facilitate better information interactions between two branches. We compared AtlasSeg with six well-established networks in a seven-tissue segmentation task, achieving the highest average Dice similarity coefficient of 0.91. The improvement was particularly evident in extreme early or late GA cases, where training data was scare. Furthermore, AtlasSeg exhibited minimal performance degradation on low-quality images with contrast changes and noise, attributed to its anatomical shape priors. Overall, AtlasSeg demonstrated enhanced segmentation accuracy, better consistency across fetal ages, and robustness to perturbations, making it a powerful tool for reliable fetal brain MRI tissue segmentation, particularly suited for diagnostic assessments during early gestation.