Department of Ophthalmology, New England Eye Center, Tufts Medical Center, 800 Washington Street, Box 450, Boston, MA, 02111, USA.
Department of Ophthalmology, University of Colorado, Denver, CO, USA.
Sci Rep. 2020 Sep 21;10(1):15368. doi: 10.1038/s41598-020-72358-z.
Binarization is a critical step in analysis of retinal optical coherence tomography angiography (OCTA) images, but the repeatability of metrics produced from various binarization methods has not been fully assessed. This study set out to examine the repeatability of OCTA quantification metrics produced using different binarization thresholding methods, all of which have been applied in previous studies, across multiple devices and plexuses. Successive 3 × 3 mm foveal OCTA images of 13 healthy eyes were obtained on three different devices. For each image, contrast adjustments, 3 image processing techniques (linear registration, histogram normalization, and contrast-limited adaptive histogram equalization), and 11 binarization thresholding methods were independently applied. Vessel area density (VAD) and vessel length were calculated for retinal vascular images. Choriocapillaris (CC) images were quantified for VAD and flow deficit metrics. Repeatability, measured using the intra-class correlation coefficient, was inconsistent and generally not high (ICC < 0.8) across binarization thresholds, devices, and plexuses. In retinal vascular images, local thresholds tended to incorrectly binarize the foveal avascular zone as white (i.e., wrongly indicating flow). No image processing technique analyzed consistently resulted in highly repeatable metrics. Across contrast changes, retinal vascular images showed the lowest repeatability and CC images showed the highest.
二值化是视网膜光相干断层扫描血管造影 (OCTA) 图像分析的关键步骤，但各种二值化方法产生的指标的可重复性尚未得到充分评估。本研究旨在检查使用先前研究中应用的不同二值化阈值方法在多个设备和丛中产生的 OCTA 量化指标的可重复性。对 13 只健康眼睛的三个不同设备的连续 3×3mm 黄斑 OCTA 图像进行了研究。对于每个图像，分别应用对比度调整、3 种图像处理技术（线性配准、直方图归一化和对比度限制自适应直方图均衡化）和 11 种二值化阈值方法。计算视网膜血管图像的血管面积密度 (VAD) 和血管长度。量化脉络膜毛细血管 (CC) 图像的 VAD 和血流不足指标。使用组内相关系数测量的可重复性不一致，通常在二值化阈值、设备和丛之间不高（ICC<0.8）。在视网膜血管图像中，局部阈值往往错误地将黄斑无血管区二值化为白色（即错误地表示为血流）。没有一种图像处理技术始终产生高度可重复的指标。在对比度变化方面，视网膜血管图像的可重复性最低，CC 图像的可重复性最高。
