Arya Malvika, Rebhun Carl B, Alibhai A Yasin, Chen Xuejing, Moreira-Neto Carlos, Baumal Caroline R, Reichel Elias, Witkin Andre J, Duker Jay S, Sadda SriniVas R, Waheed Nadia K
Ophthalmic Surg Lasers Imaging Retina. 2018 Oct 15;49(10):S5-S17. doi: 10.3928/23258160-20180814-02.
To assess variability in vessel density (VD) measurements across three optical coherence tomography angiography (OCTA) devices to identify a methodology that offers the least amount of variation in VD, and to assess the effect of averaging of multiple scans on VD variability.
Fifteen eyes of eight healthy individuals were imaged consecutively on three OCTA devices. Segmentations at the superficial, deep, and full retinal layers were generated. Repeat scans for each retinal layer were registered and averaged to generate one OCTA image. Two different automated thresholding techniques were used to calculate vessel area density (VAD) from binarized images and vessel skeleton density (VSD) from skeletonized images. Vessel length, a linear measure of the combined lengths of vessels, was calculated. Foveal avascular zone (FAZ) area was measured.
All three OCTA devices were significantly different (P < .0001). This finding remained after averaging images (P < .0001). VSD was more repeatable within a device but less reproducible across devices. Conversely, VAD demonstrated less repeatability but greater reproducibility. Differences in VSD between devices were systematic and attributable to differences in resolution. Vessel length, unaffected by resolution, demonstrated no significant differences between the devices (P > .107). There was no significant difference in FAZ area across devices (P = .51). After averaging images, VD was significantly different from the single images for each device and plexus (P < .05) but remained within 1% of the value of a single scan.
OCTA devices show variability in VD for healthy individuals. With greater repeatability, VSD appeared useful for following a patient on one device. VAD and vessel length seemed ideal for comparing vessel parameters between OCTA devices. After averaging multiple scans, VSD remained within 1% of a single scan, for which clinical significance remains to be determined. Caution is advised when comparing quantitative analyses across OCTA devices. [Ophthalmic Surg Lasers Imaging Retina. 2018;49:S5-S17.].
评估三种光学相干断层扫描血管造影（OCTA）设备在测量血管密度（VD）时的变异性，以确定一种使VD变异性最小的方法，并评估多次扫描平均化对VD变异性的影响。
对8名健康个体的15只眼睛依次使用三种OCTA设备进行成像。生成视网膜浅层、深层和全层的分割图像。对每个视网膜层的重复扫描进行配准并平均，以生成一张OCTA图像。使用两种不同的自动阈值技术从二值化图像计算血管面积密度（VAD），从骨架化图像计算血管骨架密度（VSD）。计算血管长度，即血管总长度的线性测量值。测量黄斑无血管区（FAZ）面积。
所有三种OCTA设备均存在显著差异（P <.0001）。图像平均化后这一结果依然存在（P <.0001）。VSD在同一设备内的重复性更高，但在不同设备间的再现性较低。相反，VAD的重复性较低但再现性较高。不同设备间VSD的差异具有系统性，且归因于分辨率的差异。不受分辨率影响的血管长度在各设备间无显著差异（P >.107）。不同设备间FAZ面积无显著差异（P =.51）。图像平均化后，每种设备和视网膜神经纤维层的VD与单张图像相比均有显著差异（P <.05），但仍在单次扫描值的1%以内。
OCTA设备在健康个体的VD测量中存在变异性。VSD重复性更高，似乎有助于在同一设备上对患者进行随访。VAD和血管长度似乎是比较不同OCTA设备血管参数的理想指标。多次扫描平均化后，VSD仍在单次扫描值的1%以内，其临床意义尚待确定。在比较不同OCTA设备的定量分析结果时建议谨慎。[《眼科手术、激光与视网膜成像》。2018；49：S5 - S17。]
