“…In recent years, deep learning methods, especially the Convolutional Neural Networks (CNN), have demonstrated state-of-the-art performance in many image segmentation tasks, including segmentation of medical images (Cai et al, 2016;Cha et al, 2016;Hu et al, 2017;Milletari et al, 2017Milletari et al, , 2016Zhu et al, 2017). Several groups (Ibragimov and Xing, 2017;Ren et al, 2018) used deep learning method in OARs segmentation, but the improvement over traditional methods are not significant, and currently the superiority of deep learning approach in the OARs segmentation task is not fully revealed.…”