A Large Convolutional Neural Network for Clinical Target and Multi-organ Segmentation in Gynecologic Brachytherapy with Multi-stage Learning

Mingzhe Hu; Yuan Gao; Yuheng Li; Ricahrd LJ Qiu; Chih-Wei Chang; Keyur D. Shah; Priyanka Kapoor; Beth Bradshaw; Yuan Shao; Justin Roper; Jill Remick; Zhen Tian; Xiaofeng Yang

arXiv · 2506.01073

A Large Convolutional Neural Network for Clinical Target and Multi-organ Segmentation in Gynecologic Brachytherapy with Multi-stage Learning

Mingzhe Hu·Yuan Gao·Yuheng Li·Ricahrd LJ Qiu·Chih-Wei Chang·Keyur D. Shah·Priyanka Kapoor·Beth Bradshaw·Yuan Shao·Justin Roper·Jill Remick·Zhen Tian·Xiaofeng Yang

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Abstract

Purpose: Accurate segmentation of clinical target volumes (CTV) and organs-at-risk is crucial for optimizing gynecologic brachytherapy (GYN-BT) treatment planning. However, anatomical variability, low soft-tissue contrast in CT imaging, and limited annotated datasets pose significant challenges. This study presents GynBTNet, a novel multi-stage learning framework designed to enhance segmentation performance through self-supervised pretraining and hierarchical fine-tuning strategies. Methods: GynBTNet employs a three-stage training strategy: (1) self-supervised pretraining on large-scale CT datasets using sparse submanifold convolution to capture robust anatomical representations, (2) supervised fine-tuning on a comprehensive multi-organ segmentation dataset to refine feature extraction, and (3) task-specific fine-tuning on a dedicated GYN-BT dataset to optimize segmentation performance for clinical applications. The model was evaluated against state-of-the-art methods using the Dice Similarity Coefficient (DSC), 95th percentile Hausdorff Distance (HD95), and Average Surface Distance (ASD). Results: Our GynBTNet achieved superior segmentation performance, significantly outperforming nnU-Net and Swin-UNETR. Notably, it yielded a DSC of 0.837 +/- 0.068 for CTV, 0.940 +/- 0.052 for the bladder, 0.842 +/- 0.070 for the rectum, and 0.871 +/- 0.047 for the uterus, with reduced HD95 and ASD compared to baseline models. Self-supervised pretraining led to consistent performance improvements, particularly for structures with complex boundaries. However, segmentation of the sigmoid colon remained challenging, likely due to anatomical ambiguities and inter-patient variability. Statistical significance analysis confirmed that GynBTNet's improvements were significant compared to baseline models.

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Mingzhe Hu, Yuan Gao, Yuheng Li, Ricahrd LJ Qiu, Chih-Wei Chang, Keyur D. Shah, Priyanka Kapoor, Beth Bradshaw, Yuan Shao, Justin Roper, Jill Remick, Zhen Tian, Xiaofeng Yang. 2025-06-01. A Large Convolutional Neural Network for Clinical Target and Multi-organ Segmentation in Gynecologic Brachytherapy with Multi-stage Learning. https://arxiv.org/abs/2506.01073

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