MAEMC-NET: A hybrid self-supervised learning method for predicting the malignancy of solitary pulmonary nodules from CT images

Tianhu Zhao ¹ Yong Yue ² Hang Sun ³ Jingxu Li ⁴ Yanhua Wen ⁵ Yu-Dong Yao ⁶ Wei Qian ¹ Yubao Guan ⁵ Shouliang Qi ^1*

• ¹ Northeastern University, Shenyang, China
• ² Department of Radiology, Shengjing Hospital of China Medical University, Shenyang, Liaoning Province, China
• ³ Shenyang Ligong University, Shenyang, Liaoning Province, China
• ⁴ Department of Radiology, The First Affiliated Hospital of Guangzhou Medical University, Guangzhou, China
• ⁵ Fifth Affiliated Hospital of Guangzhou Medical University, Guangzhou, Guangdong Province, China
• ⁶ Department of Electrical & Computer Engineering, Schaefer School of Engineering & Science, Stevens Institute of Technology, Hoboken, New Jersey, United States

Pulmonary granulomatous nodules (PGN) often exhibit similar CT morphological features to solid lung adenocarcinomas (SLA), making preoperative differentiation challenging. This study introduces MAEMC-NET, a model integrating generative (Masked AutoEncoder) and contrastive (Momentum Contrast) self-supervised learning to learn CT image representations of intra-and inter-solitary nodules. A generative self-supervised task of reconstructing masked axial CT patches containing lesions was designed to learn intra-and inter-slice image representations. Contrastive momentum is used to link the encoder in axial-CT-patch path with the momentum encoder in coronal-CT-patch path. A total of 494 patients from two centers were included. MAEMC-NET achieved an area under curve (95% Confidence Interval) of 0.962 (0.934-0.973). These results not only significantly surpass the joint diagnosis by two experienced chest radiologists (77.3% accuracy) but also outperform the current state-of-the-art methods. The model performs best on medical images with a 50% mask ratio, showing a 1.4% increase in accuracy compared to the optimal 75% mask ratio on natural images. The proposed MAEMC-NET effectively distinguishes between benign and malignant solitary pulmonary nodules and holds significant potential to assist radiologists in improving the diagnostic accuracy of PGN and SLA.