Multimodal meta-learning for lung nodule classification under few-shot settings: a trustworthy AI framework with 2D–3D cross-modal alignment
摘要
Accurate classification of pulmonary nodule subtypes is vital for early lung cancer management. Yet, building reliable AI models remains challenging due to limited annotated data and the need to jointly exploit the complementary spatial cues offered by 2D CT slices and 3D volumetric scans. This work introduces a multimodal meta-learning framework for few-shot lung nodule classification, designed to enhance data-efficiency, fusion effectiveness, and interpretability. A contrastive 2D–3D cross-modal alignment module first harmonises slice-level and volume-level encoders into a unified latent space, enabling stable multimodal fusion under scarce supervision. A Prototypical Network-based episodic learner is then employed to support rapid adaptation to unseen nodules with only a few labelled samples. Beyond accuracy, the framework incorporates prototype-guided saliency mapping, fusion-margin analysis, and cognitive consistency metrics to assess the trustworthiness of model decisions. Experiments on a rare-data clinical cohort demonstrated that the proposed approach achieved 85.1% accuracy (95% CI [0.825, 0.877]) in a five-shot setting, surpassing single-modality and supervised baselines by 6–8%. Performance gains were statistically significant under the paired Wilcoxon signed-rank test (