IEEE J Biomed Health Inform. 2019 May;23(3):1151-1162. doi: 10.1109/JBHI.2018.2852635. Epub 2018 Jul 3.
The level set based deformable models (LDM) are commonly used for medical image segmentation. However, they rely on a handcrafted curve evolution velocity that needs to be adapted for each segmentation task. The Convolutional Neural Networks (CNN) address this issue by learning robust features in a supervised end-to-end manner. However, CNNs employ millions of network parameters, which require a large amount of data during training to prevent over-fitting and increases the memory requirement and computation time during testing. Moreover, since CNNs pose segmentation as a region-based pixel labeling, they cannot explicitly model the high-level dependencies between the points on the object boundary to preserve its overall shape, smoothness or the regional homogeneity within and outside the boundary. We present a Recurrent Neural Network based solution called the RACE-net to address the above issues. RACE-net models a generalized LDM evolving under a constant and mean curvature velocity. At each time-step, the curve evolution velocities are approximated using a feed-forward architecture inspired by the multiscale image pyramid. RACE-net allows the curve evolution velocities to be learned in an end-to-end manner while minimizing the number of network parameters, computation time, and memory requirements. The RACE-net was validated on three different segmentation tasks: optic disc and cup in color fundus images, cell nuclei in histopathological images, and the left atrium in cardiac MRI volumes. Assessment on public datasets was seen to yield high Dice values between 0.87 and 0.97, which illustrates its utility as a generic, off-the-shelf architecture for biomedical segmentation.
基于水平集的可变形模型(LDM)常用于医学图像分割。然而,它们依赖于手工制作的曲线演化速度,需要针对每个分割任务进行调整。卷积神经网络(CNN)通过以端到端的方式学习稳健的特征来解决这个问题。然而,CNN 采用了数百万个网络参数,这在训练过程中需要大量的数据来防止过拟合,并增加了测试时的内存需求和计算时间。此外,由于 CNN 将分割视为基于区域的像素标记,因此它们不能显式地建模对象边界上的点之间的高级别依赖关系,以保持其整体形状、平滑度或边界内外的区域同质性。我们提出了一种基于递归神经网络的解决方案,称为 RACE-net,以解决上述问题。RACE-net 对在恒定平均曲率速度下演变的广义 LDM 进行建模。在每个时间步,使用受多尺度图像金字塔启发的前馈架构来近似曲线演化速度。RACE-net 允许以端到端的方式学习曲线演化速度,同时最小化网络参数、计算时间和内存需求的数量。RACE-net 在三个不同的分割任务上进行了验证:彩色眼底图像中的视盘和杯、组织病理学图像中的细胞核、以及心脏 MRI 容积中的左心房。在公共数据集上的评估表明,Dice 值在 0.87 到 0.97 之间,这说明了它作为生物医学分割的通用、现成架构的实用性。