利用光学相干断层扫描减轻脉络膜高透射和低透射缺陷对脉络膜血管指数评估的影响。
Mitigating the effects of choroidal hyper- and hypo-transmission defects on choroidal vascularity index assessments using optical coherence tomography.
作者信息
Zhou Hao, Lu Jie, Chen Kelly, Shi Yingying, Gregori Giovanni, Rosenfeld Philip J, Wang Ruikang K
机构信息
Department of Bioengineering, University of Washington, Seattle, WA, USA.
Department of Ophthalmology, Bascom Palmer Eye Institute, University of Miami Miller School of Medicine, Miami, FL, USA.
出版信息
Quant Imaging Med Surg. 2022 May;12(5):2932-2946. doi: 10.21037/qims-21-1093.
BACKGROUND
Changes in choroidal vascularity index (CVI) are associated with multiple choroid-related ocular diseases. CVI is calculated as the area/volume ratio of vessels in the choroid, which could be affected by alterations in regional signal intensities due to hypo-transmission defects (hypoTDs) caused by drusen and retinal pigment epithelium (RPE) detachments, and hyper-transmission defects (hyperTDs) caused by the absence of RPE. To develop a simulation model to verify the CVI assessments in eyes with hyper/hypoTDs and demonstrate that accurate CVIs can be achieved after attenuation correction on swept-source optical coherence tomography (SS-OCT).
METHODS
A simulation model was developed on 6×6 mm macular scans from normal subjects. Signal intensity in a cylindrical region below RPE was altered to mimic hyper/hypoTDs. CVIs were compared inside and outside the simulated regions before and after attenuation correction. CVI assessments of OCT scans from patients with hyperTDs due to geographic atrophy (GA) and from patients with hypoTDs due to drusen that subsequently resolved with the disappearance of the hypoTDs were compared with and without attenuation correction.
RESULTS
Ten normal eyes were recruited to generate the hyper/hypoTD simulation model. In eyes with hypoTDs, CVIs were overestimated, and in eyes with hyperTDs, the CVIs were underestimated (P<0.001). After attenuation correction, the uneven distribution of signal intensity was eliminated and the resulting CVI showed no significant difference compared with the 'ground truth', which is measured from the original scans. Attenuation correction successfully eliminated the influence of hyperTDs caused by GA on CVI measurements (n=38). Quantitatively, no significant difference was found in the CVIs of eyes before and after drusen collapse with attenuation correction (n=8).
CONCLUSIONS
The simulation model could reveal the impact of hypo/hyperTDs on CVI quantification in eyes with choroid-involved ocular diseases. The importance of attenuation correction to ensure accuracy in choroidal vessel segmentation was demonstrated by analyzing eyes with GA or drusen.
背景
脉络膜血管指数（CVI）的变化与多种脉络膜相关眼病有关。CVI通过脉络膜血管的面积/体积比来计算，其可能会受到由玻璃膜疣和视网膜色素上皮（RPE）脱离引起的低透射缺陷（hypoTDs）以及由RPE缺失引起的高透射缺陷（hyperTDs）导致的区域信号强度改变的影响。为了开发一个模拟模型来验证在存在高/低透射缺陷的眼中的CVI评估，并证明在扫频源光学相干断层扫描（SS-OCT）上进行衰减校正后可以获得准确的CVI。
方法
基于正常受试者的6×6 mm黄斑扫描开发了一个模拟模型。改变RPE下方圆柱形区域的信号强度以模拟高/低透射缺陷。在衰减校正前后比较模拟区域内外的CVI。对因地图样萎缩（GA）导致高透射缺陷的患者以及因玻璃膜疣导致低透射缺陷且随后随着低透射缺陷消失而消退的患者的OCT扫描进行CVI评估，并在有无衰减校正的情况下进行比较。
结果
招募了10只正常眼以生成高/低透射缺陷模拟模型。在存在低透射缺陷的眼中，CVI被高估，而在存在高透射缺陷的眼中，CVI被低估（P<0.001）。经过衰减校正后，信号强度的不均匀分布被消除，得到的CVI与从原始扫描测量的“真实值”相比无显著差异。衰减校正成功消除了GA引起的高透射缺陷对CVI测量的影响（n=38）。定量分析显示，在进行衰减校正后，玻璃膜疣消退前后眼睛的CVI无显著差异（n=8）。
结论
该模拟模型可以揭示低/高透射缺陷对患有累及脉络膜眼病的眼睛中CVI定量的影响。通过分析患有GA或玻璃膜疣的眼睛，证明了衰减校正对于确保脉络膜血管分割准确性的重要性。
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