Doheny Image Reading Center, Doheny Eye Institute, Los Angeles, California; Department of Ophthalmology, David Geffen School of Medicine at the University of California-Los Angeles, Los Angeles, California.
Doheny Image Reading Center, Doheny Eye Institute, Los Angeles, California; Department of Ophthalmology, David Geffen School of Medicine at the University of California-Los Angeles, Los Angeles, California.
Ophthalmology. 2017 Jul;124(7):944-952. doi: 10.1016/j.ophtha.2017.02.006. Epub 2017 Mar 17.
To investigate the impact of multiple en face image averaging on quantitative measurements of the retinal microvasculature using optical coherence tomography angiography (OCTA).
Prospective, observational, cross-sectional case series.
Twenty-one healthy individuals with normal eyes.
Macular OCTA images were acquired from all participants using the Zeiss Cirrus 5000 with Angioplex OCTA software (Carl Zeiss Meditec, Dublin, CA). Nine OCTA cube scans per eye were obtained and 9 superficial retinal layer (SRL) and deep retinal layer (DRL) en face OCTA image slabs were averaged individually after registration. Quantitative parameters from the retinal microvasculature were measured on binarized and skeletonized OCTA images and compared with single OCTA images without averaging.
Vessel density (VD), vessel length density (VLD), vessel diameter index (VDI), and fractal dimension (FD).
Participants with artifact or poor image quality were excluded, leaving 18 eyes for the analysis. After averaging, qualitatively there was apparent reduction in background noise, and fragmented vessels in the images before averaging became continuous with smoother walls and showed sharper contrast in both the SRL and DRL. Binarized and skeletonized derivates of these averaged images also showed fewer line fragments and dots in nonvascular areas and more continuous vessel images than those of images without averaging. In both SRL and DRL, VD (P = 0.0010 and P = 0.0003, respectively), VLD (P < 0.0001 for both), and FD (P < 0.0001 for both) significantly decreased and VDI significantly increased after averaging (P < 0.0001 for both).
Averaging of multiple en face OCTA images improves image quality and also significantly impacts quantitative measurements. Reducing noise that could be misinterpreted as flow and annealing discontinuous vessel segments seem to be major mechanisms by which averaging may be of benefit.
利用光相干断层扫描血管造影术（OCTA）研究多次面平均对视网膜微血管定量测量的影响。
前瞻性、观察性、横断面病例系列研究。
21 名正常眼的健康个体。
使用 Zeiss Cirrus 5000 结合 Angioplex OCTA 软件（德国卡尔蔡司 Meditec 公司）对所有参与者的黄斑 OCTA 图像进行采集。每只眼获得 9 个 OCTA 立方体扫描，注册后分别对 9 个浅层视网膜层（SRL）和深层视网膜层（DRL）的面 OCTA 图像进行平均。在二值化和骨架化 OCTA 图像上测量视网膜微血管的定量参数，并与未经平均的单个 OCTA 图像进行比较。
血管密度（VD）、血管长度密度（VLD）、血管直径指数（VDI）和分形维数（FD）。
排除了有伪影或图像质量差的参与者，最终有 18 只眼纳入分析。平均化后，图像背景噪声明显减少，平均化前图像中的碎片状血管变得连续，血管壁更光滑，在 SRL 和 DRL 中对比度更清晰。这些平均化图像的二值化和骨架化衍生图像在非血管区域的线碎片和点也较少，血管图像更连续，而未经平均化的图像则较少。在 SRL 和 DRL 中，VD（P=0.0010 和 P=0.0003）、VLD（均 P<0.0001）和 FD（均 P<0.0001）显著降低，VDI 显著增加（均 P<0.0001）。
多次面 OCTA 图像平均化可改善图像质量，对定量测量也有显著影响。减少可能被误解为血流的噪声和退火不连续的血管段似乎是平均化可能有益的主要机制。
