Al-Sheikh Mayss, Ghasemi Falavarjani Khalil, Akil Handan, Sadda SriniVas R
Doheny Image Reading Center, Doheny Eye Institute, Los Angeles, CA USA.
Department of Ophthalmology, David Geffen School of Medicine, University of California - Los Angeles, Los Angeles, CA USA.
Int J Retina Vitreous. 2017 May 15;3:13. doi: 10.1186/s40942-017-0068-9. eCollection 2017.
To study the impact of image quality on quantitative measurements and the frequency of segmentation error with optical coherence tomography angiography (OCTA).
Seventeen eyes of 10 healthy individuals were included in this study. OCTA was performed using a swept-source device (Triton, Topcon). Each subject underwent three scanning sessions 1-2 min apart; the first two scans were obtained under standard conditions and for the third session, the image quality index was reduced using application of a topical ointment. En face OCTA images of the retinal vasculature were generated using the default segmentation for the superficial and deep retinal layer (SRL, DRL). Intraclass correlation coefficient (ICC) was used as a measure for repeatability. The frequency of segmentation error, motion artifact, banding artifact and projection artifact was also compared among the three sessions.
The frequency of segmentation error, and motion artifact was statistically similar between high and low image quality sessions (P = 0.707, and P = 1 respectively). However, the frequency of projection and banding artifact was higher with a lower image quality. The vessel density in the SRL was highly repeatable in the high image quality sessions (ICC = 0.8), however, the repeatability was low, comparing the high and low image quality measurements (ICC = 0.3). In the DRL, the repeatability of the vessel density measurements was fair in the high quality sessions (ICC = 0.6 and ICC = 0.5, with and without automatic artifact removal, respectively) and poor comparing high and low image quality sessions (ICC = 0.3 and ICC = 0.06, with and without automatic artifact removal, respectively).
The frequency of artifacts is higher and the repeatability of the measurements is lower with lower image quality. The impact of image quality index should be always considered in OCTA based quantitative measurements.
研究图像质量对光学相干断层扫描血管造影（OCTA）定量测量及分割误差频率的影响。
本研究纳入10名健康个体的17只眼睛。使用扫频源设备（Triton，拓普康）进行OCTA检查。每位受试者间隔1 - 2分钟进行三次扫描；前两次扫描在标准条件下进行，第三次扫描时，通过应用局部药膏降低图像质量指数。使用视网膜浅层和深层（SRL、DRL）的默认分割方法生成视网膜血管的OCTA正面图像。组内相关系数（ICC）用作重复性的度量指标。还比较了三次扫描中分割误差、运动伪影、条带伪影和投影伪影的频率。
高图像质量和低图像质量扫描之间，分割误差和运动伪影的频率在统计学上相似（P分别为0.707和1）。然而，投影和条带伪影的频率在图像质量较低时更高。SRL中的血管密度在高图像质量扫描中具有高度重复性（ICC = 0.8），但是，比较高图像质量和低图像质量测量时，重复性较低（ICC = 0.3）。在DRL中，血管密度测量的重复性在高质量扫描中尚可（有和无自动伪影去除时，ICC分别为0.6和0.5），而比较高图像质量和低图像质量扫描时较差（有和无自动伪影去除时，ICC分别为0.3和0.06）。
图像质量较低时，伪影频率更高，测量的重复性更低。在基于OCTA的定量测量中应始终考虑图像质量指数的影响。
