Kidney abnormality segmentation in thorax-abdomen CT scans

TL;DR

This paper presents a deep learning approach for accurate kidney and abnormality segmentation in thorax-abdomen CT scans, outperforming human observers in kidney parenchyma segmentation and providing a foundation for further improvements in abnormality detection.

Contribution

The study introduces novel modifications to 3D U-Net and combines it with nnUNet, achieving state-of-the-art segmentation performance on kidney structures and abnormalities.

Findings

Achieved Dice scores of 0.965 and 0.947 for kidney parenchyma segmentation.

Top model scored 0.585 for abnormality segmentation, close to human score of 0.664.

Proposed methods outperform previous approaches and human observers in key metrics.

Abstract

In this study, we introduce a deep learning approach for segmenting kidney parenchyma and kidney abnormalities to support clinicians in identifying and quantifying renal abnormalities such as cysts, lesions, masses, metastases, and primary tumors. Our end-to-end segmentation method was trained on 215 contrast-enhanced thoracic-abdominal CT scans, with half of these scans containing one or more abnormalities. We began by implementing our own version of the original 3D U-Net network and incorporated four additional components: an end-to-end multi-resolution approach, a set of task-specific data augmentations, a modified loss function using top-$k$, and spatial dropout. Furthermore, we devised a tailored post-processing strategy. Ablation studies demonstrated that each of the four modifications enhanced kidney abnormality segmentation performance, while three out of four improved kidney parenchyma segmentation. Subsequently, we trained the nnUNet framework on our dataset. By ensembling the optimized 3D U-Net and the nnUNet with our specialized post-processing, we achieved marginally superior results. Our best-performing model attained Dice scores of 0.965 and 0.947 for segmenting kidney parenchyma in two test sets (20 scans without abnormalities and 30 with abnormalities), outperforming an independent human observer who scored 0.944 and 0.925, respectively. In segmenting kidney abnormalities within the 30 test scans containing them, the top-performing method achieved a Dice score of 0.585, while an independent second human observer reached a score of 0.664, suggesting potential for further improvement in computerized methods. All training data is available to the research community under a CC-BY 4.0 license on https://doi.org/10.5281/zenodo.8014289