Automated Segmentation of Liver and Liver Tumors with SwinUNETR and UNET Neural Networks on ¹⁸F-FDG PET/CT

To develop and evaluate automated segmentation models for the liver and hepatic tumors on ¹⁸F-fluorodeoxyglucose positron emission tomography/computed tomography (¹⁸F-FDG PET/CT) using SwinUNETR and residual UNET architectures, and to assess their accuracy in complex clinical cases.

In this single-center retrospective study, 100 patients (48 males, 52 females; mean age 61±14 years) with ¹⁸F-FDG-avid hepatic lesions from various primary malignancies were included. Liver segmentation was performed on non-contrast CT images using pairs of SwinUNETR and residual UNET models, and tumor segmentation was performed on masked PET images using separately trained pair of SwinUNETR and residual UNET model. Model performance was evaluated using the dice similarity coefficient (DSC), volumetric bias, and Bland-Altman analysis for metabolic tumor volume (MTV) and total lesion glycolysis (TLG).

For liver segmentation, SwinUNETR achieved a median DSC of 97.59% (range: 95.41-98.93%) with a median volumetric bias of -0.94% (LoA: -3.76% to +0.50%), while residual UNET achieved a median DSC of 97.85% (range: 94.81-98.80%) with a median volumetric bias of -0.34% (LoA: -2.63% to +1.16%). For tumor segmentation, SwinUNETR achieved a median DSC of 92.62% (range: 80.75-97.46%), an MTV bias of -8.60% (LoA: -31.62% to +1.21%), and a TLG bias of -6.40% (LoA: -25.58% to +0.76%). Residual UNET achieved a median DSC of 93.07% (range: 80.74-98.18%), MTV bias of -4.33% (LoA: -24.36% to +10.12%), and TLG bias of -11.10% (LoA: -30.8% to +4.52%). Most MTV and TLG measurements were within ±10% of reference values.

Both SwinUNETR and Residual UNET achieved excellent liver segmentation accuracy and clinically acceptable tumor segmentation performance on ¹⁸F-FDG PET/CT, with SwinUNETR showing slightly better performance in liver volumetric measurements. These open-source models could be integrated into clinical workflows to automate segmentation tasks, facilitate treatment planning for liver-directed therapies, and support reproducible quantitative imaging analyses.