Segmentation of Mediastinal Lymph Nodes in CT with Anatomical Priors
This work addresses the cumbersome task of identifying lymph nodes for clinicians monitoring diseases like lung cancer, offering a potential tool for improved patient outcomes in initial staging CT scans, though it is incremental as it builds on existing segmentation methods with added anatomical priors.
The paper tackled the problem of segmenting mediastinal lymph nodes in CT scans, which is challenging due to shape and appearance variations, by leveraging anatomical priors from 28 structures. The result was a 3D cascade nnUNet model achieving a Dice score of 72.2 ± 22.3 for nodes with short axis diameter ≥ 8mm, representing a 10-point improvement over a current approach on the same test dataset.
Purpose: Lymph nodes (LNs) in the chest have a tendency to enlarge due to various pathologies, such as lung cancer or pneumonia. Clinicians routinely measure nodal size to monitor disease progression, confirm metastatic cancer, and assess treatment response. However, variations in their shapes and appearances make it cumbersome to identify LNs, which reside outside of most organs. Methods: We propose to segment LNs in the mediastinum by leveraging the anatomical priors of 28 different structures (e.g., lung, trachea etc.) generated by the public TotalSegmentator tool. The CT volumes from 89 patients available in the public NIH CT Lymph Node dataset were used to train three 3D nnUNet models to segment LNs. The public St. Olavs dataset containing 15 patients (out-of-training-distribution) was used to evaluate the segmentation performance. Results: For the 15 test patients, the 3D cascade nnUNet model obtained the highest Dice score of 72.2 +- 22.3 for mediastinal LNs with short axis diameter $\geq$ 8mm and 54.8 +- 23.8 for all LNs respectively. These results represent an improvement of 10 points over a current approach that was evaluated on the same test dataset. Conclusion: To our knowledge, we are the first to harness 28 distinct anatomical priors to segment mediastinal LNs, and our work can be extended to other nodal zones in the body. The proposed method has immense potential for improved patient outcomes through the identification of enlarged nodes in initial staging CT scans.