Cause of ventricles and brainstem performance trend divergence across domains

Ascertain the reasons why the ventricles and brainstem labels exhibit different performance trends compared to other tissue labels when comparing in-domain versus out-of-domain fetal brain MRI segmentation results in the FeTA 2022 evaluation.

Background

The authors observe that, unlike most labels which perform slightly better out-of-domain, the ventricles and brainstem show a differing trend in evaluation metrics. Understanding this divergence is important for improving label-specific robustness and overall clinical reliability of segmentation.

This observation emerges from detailed per-label analysis of in-domain and out-of-domain performance, suggesting label-specific sensitivities to domain shifts or reconstruction differences.