Kugelman Jason, Alonso-Caneiro David, Read Scott A, Vincent Stephen J, Collins Michael J
Contact Lens and Visual Optics Laboratory, School of Optometry and Vision Science, Queensland University of Technology, Brisbane, Queensland, Australia.
Biomed Opt Express. 2018 Oct 26;9(11):5759-5777. doi: 10.1364/BOE.9.005759. eCollection 2018 Nov 1.
The manual segmentation of individual retinal layers within optical coherence tomography (OCT) images is a time-consuming task and is prone to errors. The investigation into automatic segmentation methods that are both efficient and accurate has seen a variety of methods proposed. In particular, recent machine learning approaches have focused on the use of convolutional neural networks (CNNs). Traditionally applied to sequential data, recurrent neural networks (RNNs) have recently demonstrated success in the area of image analysis, primarily due to their usefulness to extract temporal features from sequences of images or volumetric data. However, their potential use in OCT retinal layer segmentation has not previously been reported, and their direct application for extracting spatial features from individual 2D images has been limited. This paper proposes the use of a recurrent neural network trained as a patch-based image classifier (retinal boundary classifier) with a graph search (RNN-GS) to segment seven retinal layer boundaries in OCT images from healthy children and three retinal layer boundaries in OCT images from patients with age-related macular degeneration (AMD). The optimal architecture configuration to maximize classification performance is explored. The results demonstrate that a RNN is a viable alternative to a CNN for image classification tasks in the case where the images exhibit a clear sequential structure. Compared to a CNN, the RNN showed a slightly superior average generalization classification accuracy. Secondly, in terms of segmentation, the RNN-GS performed competitively against a previously proposed CNN based method (CNN-GS) with respect to both accuracy and consistency. These findings apply to both normal and AMD data. Overall, the RNN-GS method yielded superior mean absolute errors in terms of the boundary position with an average error of 0.53 pixels (normal) and 1.17 pixels (AMD). The methodology and results described in this paper may assist the future investigation of techniques within the area of OCT retinal segmentation and highlight the potential of RNN methods for OCT image analysis.
在光学相干断层扫描(OCT)图像中对单个视网膜层进行手动分割是一项耗时的任务,而且容易出错。人们对高效且准确的自动分割方法进行了研究,提出了多种方法。特别是,最近的机器学习方法聚焦于卷积神经网络(CNN)的应用。循环神经网络(RNN)传统上应用于序列数据,最近在图像分析领域也取得了成功,这主要归功于其在从图像序列或体数据中提取时间特征方面的有效性。然而,此前尚未有关于其在OCT视网膜层分割中的潜在应用的报道,并且其在从单个二维图像中提取空间特征方面的直接应用也较为有限。本文提出使用一种经过训练的循环神经网络作为基于图像块的图像分类器(视网膜边界分类器),结合图搜索(RNN-GS)来分割健康儿童OCT图像中的七个视网膜层边界以及年龄相关性黄斑变性(AMD)患者OCT图像中的三个视网膜层边界。探索了使分类性能最大化的最优架构配置。结果表明,在图像呈现清晰序列结构的情况下,对于图像分类任务,RNN是CNN的一个可行替代方案。与CNN相比,RNN的平均泛化分类准确率略高。其次,在分割方面,RNN-GS在准确性和一致性方面与先前提出的基于CNN的方法(CNN-GS)相比具有竞争力。这些发现适用于正常数据和AMD数据。总体而言,RNN-GS方法在边界位置方面产生的平均绝对误差更小,正常数据的平均误差为0.53像素,AMD数据的平均误差为1.17像素。本文所描述的方法和结果可能有助于未来对OCT视网膜分割领域技术的研究,并突出了RNN方法在OCT图像分析中的潜力。