Department of Computer Science, Brunel University London, Kingston Lane, Uxbridge, UB83PH, UK.
J Med Syst. 2019 Nov 13;43(12):336. doi: 10.1007/s10916-019-1452-9.
Early diagnosis of retinal OCT images has been shown to curtail blindness and visual impairments. However, the advancement of ophthalmic imaging technologies produces an ever-growing scale of retina images, both in volume and variety, which overwhelms the ophthalmologist ability to segment these images. While many automated methods exist, speckle noise and intensity inhomogeneity negatively impacts the performance of these methods. We present a comprehensive and fully automatic method for annotation of retinal layers in OCT images comprising of fuzzy histogram hyperbolisation (FHH) and graph cut methods to segment 7 retinal layers across 8 boundaries. The FHH handles speckle noise and inhomogeneity in the preprocessing step. Then the normalised vertical image gradient, and it's inverse to represent image intensity in calculating two adjacency matrices and then the FHH reassigns the edge-weights to make edges along retinal boundaries have a low cost, and graph cut method identifies the shortest-paths (layer boundaries). The method is evaluated on 150 B-Scan images, 50 each from the temporal, foveal and nasal regions were used in our study. Promising experimental results have been achieved with high tolerance and adaptability to contour variance and pathological inconsistency of the retinal layers in all (temporal, foveal and nasal) regions. The method also achieves high accuracy, sensitivity, and Dice score of 0.98360, 0.9692 and 0.9712, respectively in segmenting the retinal nerve fibre layer. The annotation can facilitate eye examination by providing accurate results. The integration of the vertical gradients into the graph cut framework, which captures the unique characteristics of retinal structures, is particularly useful in finding the actual minimum paths across multiple retinal layer boundaries. Prior knowledge plays an integral role in image segmentation.
视网膜 OCT 图像的早期诊断已被证明可以减少失明和视力障碍。然而,眼科成像技术的进步使得视网膜图像的规模不断扩大,无论是在数量还是种类上,都超过了眼科医生对这些图像进行分割的能力。虽然有许多自动化方法,但斑点噪声和强度不均匀性会对这些方法的性能产生负面影响。我们提出了一种全面的、全自动的 OCT 图像视网膜层注释方法,该方法由模糊直方图双曲线化(FHH)和图割方法组成,用于分割 7 个视网膜层和 8 个边界。FHH 在预处理步骤中处理斑点噪声和不均匀性。然后使用归一化的垂直图像梯度及其倒数来计算两个邻接矩阵中的图像强度,然后 FHH 重新分配边缘权重,使边缘沿着视网膜边界的成本较低,图割方法确定最短路径(层边界)。该方法在 150 个 B 扫描图像上进行了评估,我们的研究中使用了每个部位 50 个颞部、中央凹和鼻侧的图像。该方法在所有(颞部、中央凹和鼻侧)部位都表现出了很高的容忍度和适应性,能够处理视网膜层轮廓变化和病理一致性的问题。该方法在分割视网膜神经纤维层时还实现了很高的准确性、灵敏度和 Dice 得分,分别为 0.98360、0.9692 和 0.9712。该注释可以通过提供准确的结果来辅助眼部检查。将垂直梯度集成到图割框架中,捕捉到视网膜结构的独特特征,特别有助于找到跨越多个视网膜层边界的实际最小路径。先验知识在图像分割中起着不可或缺的作用。