Uji Akihito, Balasubramanian Siva, Lei Jianqin, Baghdasaryan Elmira, Al-Sheikh Mayss, Sadda SriniVas R
Doheny Image Reading Center, Doheny Eye Institute, Los Angeles, California.
Department of Ophthalmology, David Geffen School of Medicine at UCLA (University of California, Los Angeles).
JAMA Ophthalmol. 2017 Nov 1;135(11):1197-1204. doi: 10.1001/jamaophthalmol.2017.3904.
Imaging of the choriocapillaris in vivo is challenging with existing technology. Optical coherence tomography angiography (OCTA), if optimized, could make the imaging less challenging.
To investigate multiple en face image averaging on OCTA images of the choriocapillaris.
DESIGN, SETTING, AND PARTICIPANTS: Observational, cross-sectional case series at a referral institutional practice in Los Angeles, California. From the original cohort of 21 healthy individuals, 17 normal eyes of 17 participants were included in the study. The study dates were August to September 2016.
All participants underwent OCTA imaging of the macula covering a 3 × 3-mm area using OCTA software (Cirrus 5000 with AngioPlex; Carl Zeiss Meditec). One eye per participant was repeatedly imaged to obtain 9 OCTA cube scan sets. Registration was first performed using superficial capillary plexus images, and this transformation was then applied to the choriocapillaris images. The 9 registered choriocapillaris images were then averaged. Quantitative parameters were measured on binarized OCTA images and compared with the unaveraged OCTA images.
Vessel caliber measurement.
Seventeen eyes of 17 participants (mean [SD] age, 35.1 [6.0] years; 9 [53%] female; and 9 [53%] of white race/ethnicity) with sufficient image quality were included in this analysis. The single unaveraged images demonstrated a granular appearance, and the vascular pattern was difficult to discern. After averaging, en face choriocapillaris images showed a meshwork appearance. The mean (SD) diameter of the vessels was 22.8 (5.8) µm (range, 9.6-40.2 µm). Compared with the single unaveraged images, the averaged images showed more flow voids (1423 flow voids [95% CI, 967-1909] vs 1254 flow voids [95% CI, 825-1683], P < .001), smaller average size of the flow voids (911 [95% CI, 301-1521] µm2 vs 1364 [95% CI, 645-2083] µm2, P < .001), and greater vessel density (70.7% [95% CI, 61.9%-79.5%] vs 61.9% [95% CI, 56.0%-67.8%], P < .001). The distribution of the number vs sizes of the flow voids was skewed in both unaveraged and averaged images. A linear log-log plot of the distribution showed a more homogeneous distribution in the averaged images compared with the unaveraged images.
Multiple en face averaging can improve visualization of the choriocapillaris on OCTA images, transforming the images from a granular appearance to a level where the intervascular spaces can be resolved in healthy volunteers.
利用现有技术对脉络膜毛细血管进行活体成像具有挑战性。光学相干断层扫描血管造影（OCTA）若经过优化，可使成像难度降低。
研究对脉络膜毛细血管OCTA图像进行多次表面投影图像平均处理的效果。
设计、地点和参与者：在加利福尼亚州洛杉矶一家转诊机构进行的观察性横断面病例系列研究。在最初的21名健康个体队列中，纳入了17名参与者的17只正常眼睛进行研究。研究日期为2016年8月至9月。
所有参与者使用OCTA软件（配备AngioPlex的Cirrus 5000；卡尔蔡司医疗技术公司）对黄斑区进行OCTA成像，覆盖面积为3×3毫米。对每位参与者的一只眼睛进行重复成像，以获得9组OCTA立方体扫描图像。首先使用浅层毛细血管丛图像进行配准，然后将此变换应用于脉络膜毛细血管图像。然后对9张配准后的脉络膜毛细血管图像进行平均处理。在二值化的OCTA图像上测量定量参数，并与未平均的OCTA图像进行比较。
血管管径测量。
本分析纳入了17名参与者的17只眼睛（平均[标准差]年龄为35.1[6.0]岁；9名[53%]为女性；9名[53%]为白种人/白人），图像质量足够。单张未平均的图像呈现颗粒状外观，血管形态难以辨别。平均处理后，脉络膜毛细血管的表面投影图像呈现出网状外观。血管的平均（标准差）直径为22.8（5.8）微米（范围为9.6 - 40.2微米）。与单张未平均的图像相比，平均后的图像显示出更多的血流信号缺失区域（1423个血流信号缺失区域[95%置信区间，967 - 1909]对1254个血流信号缺失区域[95%置信区间，825 - 1683]，P <.001），血流信号缺失区域的平均尺寸更小（911[95%置信区间，301 - 1521]平方微米对1364[95%置信区间，645 - 2083]平方微米，P <.001），以及更高的血管密度（70.7%[95%置信区间，61.9% - 79.5%]对61.9%[95%置信区间，56.0% - 67.8%]，P <.001）。在未平均和平均后的图像中，血流信号缺失区域的数量与尺寸分布均呈偏态。分布的线性对数 - 对数图显示，与未平均的图像相比，平均后的图像分布更均匀。
多次表面投影平均处理可改善OCTA图像上脉络膜毛细血管的可视化效果，使图像从颗粒状外观转变为在健康志愿者中能够分辨血管间隙的水平。
