Automatic Segmentation of Clinical Target Volume and Organs-at-Risk for Breast Conservative Radiotherapy Using a Convolutional Neural Network

Abstract

Objective

Delineation of clinical target volume (CTV) and organs at risk (OARs) is important for radiotherapy but is time-consuming. We trained and evaluated a U-ResNet model to provide fast and consistent auto-segmentation.

Methods

We collected 160 patients’ CT scans with breast cancer who underwent breast-conserving surgery (BCS) and were treated with radiotherapy. CTV and OARs were delineated manually and were used for model training. The dice similarity coefficient (DSC) and 95th percentile Hausdorff distance (95HD) were used to assess the performance of our model. CTV and OARs were randomly selected as ground truth (GT) masks, and artificial intelligence (AI) masks were generated by the proposed model. Two clinicians randomly compared CTV score differences of the contour. The consistency between two clinicians was tested. Time cost for auto-delineation was evaluated.

Results

The mean DSC values of the proposed method were 0.94, 0.95, 0.94, 0.96, 0.96 and 0.93 for breast CTV, contralateral breast, heart, right lung, left lung and spinal cord, respectively. The mean 95HD values were 4.31mm, 3.59mm, 4.86mm, 3.18mm, 2.79mm and 4.37mm for the above structures, respectively. The average CTV scores for AI and GT were 2.89 versus 2.92 when evaluated by oncologist A (P=0.612), and 2.75 versus 2.83 by oncologist B (P=0.213), with no statistically significant differences. The consistency between two clinicians was poor (kappa=0.282). The time for auto-segmentation of CTV and OARs was 10.03 s.

Conclusion

Our proposed model (U-ResNet) can improve the efficiency and accuracy of delineation compared with U-Net, performing equally well with the segmentation generated by oncologists.

Keywords:

• clinical target volume
• organ at risk
• auto-segmentation
• breast cancer radiotherapy
• clinical evaluation

Abbreviations

BC, breast cancer; BCS, breast conserving surgery; WBI, whole-breast irradiation; CTV, clinical target volume; OARs, organs at risk; ROIs, regions of interest; ABAS, atlas-based auto-segmentation; CNNs, convolutional neural networks; DIR, deformable image registration; GT, ground truth; AI, artificial Intelligence; DICOM, digital imaging and communications in medicine; ESTRO, European Society for Radiotherapy and Oncology; RTOG, Radiation Therapy Oncology Group.

Disclosure

Ms Qi Chen, Mr Shaobin Wang,and Mr Yu Chen are employees of MedMind Technology Co. The authors report no other conflicts of interest in this work.