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摘要: 提出一種基于參考模型的視網膜特征量化方法,結合醫生診斷過程中關注的視網膜形態變化特征,提出一系列適用于計算機判斷分析視網膜狀態的可量化特征.在完成正常光學相干斷層成像(OCT)中視網膜內界膜(ILM)、光感受器內外節交界處(ISOS)、布魯赫膜(BM)分割提取的基礎上,利用統計方法構建正常視網膜參考模型.結合參考模型和醫生所關注的視網膜厚度、邊界平滑度以及邊界連續性,實現視網膜不同區域厚度特征、厚度比值特征、梯度特征、曲率、標準差、相關系數特征的計算.基于正常OCT圖像所構建的參考模型,獲取了正常視網膜的厚度及形態特征量化數值.通過分析比較異常OCT圖像與參考模型特征數值之間的差異,可以對應表征出異常圖像中病變導致的異常形態所在位置及嚴重程度.實驗結果表明,通過參考模型獲得的正常視網膜特征信息可以為醫生提供數值參考,同時對異常OCT圖像量化得到的特征數值可以表現出圖像中的異常形態,為后續的異常判斷提供基礎.Abstract: Optical coherence tomography (OCT) plays an important role in the diagnosis of ocular fundus diseases. Retinal OCT images contain a large amount of useful information for the diagnosis of ocular fundus diseases and are often used to detect small lesions of the fundus. At present, many medical researchers have used OCT to determine the statistical characteristics of the retina to analyze various fundus diseases. When interpreting the OCT images, ophthalmologists will focus on the location of the lesions in the images and the characteristic morphology conducive to abnormal judgment and compare the histological structure of specific objects in the images with the known normal morphology. In the comparison process, the ophthalmologist will conduct a variety of quantitative analyses of OCT retinal images and determine the severity of the abnormalities and the location of the lesions. Finally, on the basis of the differences between the morphologies and types of diseases, the diagnostic decision is obtained. However, at present, OCT instruments generally only provide the thickness, area, and other commonly used characteristic data, and these data are often inadequate to determine the disease. Computer graphics processing technology has been applied to the auxiliary analysis of OCT images. However, this kind of research often confines the object of study to several specific fundus diseases and makes targeted selection of quantitative features. In the actual diagnosis process, it is difficult to confine the retinal images to some known abnormal cases because of the complexity of the situation. In this study, a retinal feature quantization method based on a reference model was proposed, and a series of quantifiable features suitable for computer judgment and analysis of retinal state were proposed. On the basis of the segmentation and extraction of the internal limiting membrane (ILM), junctions of the inner and outer segments of photoreceptors (ISOS) and Bruch's membrane (BM) in normal OCT images, a reference model of normal retina was constructed by the statistical method. Combining the reference model with the retinal thickness, smoothness, and continuity, the thickness characteristics, thickness ratio characteristics, gradient characteristics, curvature, standard deviation, and correlation coefficient characteristics of different regions of the retina were calculated. On the basis of the reference model of normal OCT images, the quantitative values of retinal thickness and morphological characteristics were obtained. By analyzing and comparing the characteristic value differences between abnormal OCT images and reference model, the location and severity of abnormal morphology caused by lesions could be characterized in the abnormal OCT images. The experimental results show that the normal retinal feature information obtained by the reference model can provide a numerical reference for ophthalmologists. At the same time, the characteristic values obtained by quantizing the abnormal OCT images can show the abnormal morphology, which provides a basis for subsequent abnormal judgment.
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表 1 正常黃斑測量厚度與參考模型量化數值比較
Table 1. Comparison between normal macular thickness and reference model ?
μm 測量途徑 中心凹最小值 中心 內環 外環 Stratus OCT 150.3±18.1 176.4 ±17.5 255.3±14.9 237.7 ±12.4 Spectralis SD-OCT 215.4±13.6 257.9±19.2 339.2±14.6 299.1±14.3 Ref Model 202.6±12.5 233.6±15.0 313.7±15.5 286.5±21.9 表 2 視網膜厚度特征數據表
Table 2. Retinal thickness characteristic data ?
μm 計算機量化特征名稱 參考模型數值 黃斑小凹平均厚度,TFov 206.8±13.2 左側中心凹平均厚度,TFV_L 266.6±30.3 右側中心凹平均厚度,TFV_R 269.7±31.2 左側旁中心凹平均厚度,TPA_L 320.2±15.9 右側旁中心凹平均厚度,TPA_R 319.3±15.6 左側中心凹周圍區平均厚度,TPE_L 296.1±20.8 右側中心凹周圍區平均厚度,TPE_R 295.5±20.1 表 3 視網膜厚度比值特征數據表
Table 3. Retinal thickness ratio characteristics
計算機量化特征名稱 定義 參考模型數值 左側中心凹厚度比,RFV_L TFV_L/TFov 1.29±0.15 右側中心凹厚度比,RFV_R TFV_R/TFov 1.30±0.15 左側旁中心凹厚度比,RPA_L TPA_L/TFov 1.55±0.10 右側旁中心凹厚度比,RPA_R TPA_R/TFov 1.54±0.10 左側中心凹周圍區厚度比,RPE_L TPE_L/TFov 1.43±0.13 右側中心凹周圍區厚度比,RPE_R TPE_R/TFov 1.43±0.13 表 4 厚度特征數值比較
Table 4. Comparison of the thickness characteristics
圖 4 TFov TPA_L RPA_L (a) 205.6 304.9 1.48 (b) 304.8 341.0 1.12 (c) 325.0 391.3 1.20 (d) 181.8 343.2 1.88 Ref 206.8 320.2 1.55 表 5 形態特征數值比較
Table 5. Comparison of the morphological characteristics
邊界 圖 4 標準差 相關系數 正梯度 負梯度 曲率 (a) 1.29 0.99 0 -6.45 0.519 (b) 25.81 -0.55 2.80 -1.38 1.91 ILM (c) 22.47 -0.98 0.69 0 0.46 (d) 5.47 0.98 0 -5.37 0.37 Ref 0 1 0 -6.93 0.50 (a) 2.52 0.99 0 -4.56 0.79 (b) 2.68 0.99 0 -3.31 0.18 ISOS (c) 39.67 0.98 8.63 0 0.69 (d) 16.63 0.96 3.54 -9.78 6.55 Ref 0 1 0 -4.18 0.26 (a) 1.67 0.99 0 -5.16 0.45 (b) 1.96 0.99 0 -4.85 0.57 BM (c) 3.97 0.98 0 -3.06 1.15 (d) 3.49 0.96 0.51 -3.33 2.92 Ref 0 1 0 -4.46 0.30 www.77susu.com -
參考文獻
[1] Huang D, Swanson E A, Lin C P, et al. Optical coherence tomography. Science, 1991, 254(5035): 1178 doi: 10.1126/science.1957169 [2] Virgili G, Menchini F, Casazza G, et al. Optical coherence tomography (OCT) for detection of macular oedema in patients with diabetic retinopathy. Cochrane Database Syst Rev, 2015(1): CD008081 http://www.ncbi.nlm.nih.gov/pubmed/25564068 [3] Ouyang Y, Heussen F M, Hariri A, et al. Optical coherence tomography-based observation of the natural history of drusenoid lesion in eyes with dry age-related macular degeneration. Ophthalmology, 2013, 120(12): 2656 doi: 10.1016/j.ophtha.2013.05.029 [4] Andreoli M T, Lim J I. Optical coherence tomography retinal thickness and volume measurements in X-linked retinoschisis. Am J Ophthalmol, 2014, 158(3): 567 doi: 10.1016/j.ajo.2014.05.028 [5] Roh Y R, Park K H, Woo S J. Foveal thickness between stratus and spectralis optical coherence tomography in retinal diseases. Korean J Ophthalmol, 2013, 27(4): 268 doi: 10.3341/kjo.2013.27.4.268 [6] Liu Y Y, Chen M, Ishikawa H, et al. Automated macular pathology diagnosis in retinal OCT images using multi-scale spatial pyramid and local binary patterns in texture and shape encoding. Med Image Anal, 2011, 15(5): 748 doi: 10.1016/j.media.2011.06.005 [7] Liu Y Y, Ishikawa H, Chen M, et al. Computerized macular pathology diagnosis in spectral domain optical coherence tomography scans based on multiscale texture and shape features. Invest Ophthalmol Vis Sci, 2011, 52(11): 8316 doi: 10.1167/iovs.10-7012 [8] Koprowski R, Teper S, Wrobel Z, et al. Automatic analysis of selected choroidal diseases in OCT images of the eye fundus. BioMed Eng OnLine, 2013, 12: 117 doi: 10.1186/1475-925X-12-117 [9] Xu J, Ishikawa H, Wollstein G, et al. Three-dimensional spectral-domain optical coherence tomography data analysis for glaucoma detection. PLoS One, 2013, 8(2): e55476 doi: 10.1371/journal.pone.0055476 [10] Koprowski R, Rzendkowski M, Wrobel Z. Automatic method of analysis of OCT images in assessing the severity degree of glaucoma and the visual field loss. BioMed Eng OnLine, 2014, 13: 16 doi: 10.1186/1475-925X-13-16 [11] Chen H Y, Chen X J, Qiu Z Q, et al. Quantitative analysis of retinal layers' optical intensities on 3D optical coherence tomography for central retinal artery occlusion. Sci Rep, 2015, 5(10): 9269 http://pubmedcentralcanada.ca/pmcc/articles/PMC4363859/ [12] Hu Z H, Shi Y, Nandanan K, et al. Semiautomated segmentation and analysis of retinal layers in three-dimensional spectral-domain optical coherence tomography images of patients with atrophic age-related macular degeneration. Neurophotonics, 2017, 4(1): 011012 doi: 10.1117/1.NPh.4.1.011012 [13] Rashno A, Koozekanani D D, Drayna P M, et al. Fully automated segmentation of fluid/cyst regions in optical coherence tomography images with diabetic macular edema using neutrosophic sets and graph algorithms. IEEE Trans Biomed Eng, 2018, 65(5): 989 http://europepmc.org/abstract/MED/28783619 [14] Chiu S J, Allingham M J, Mettu P S, et al. Kernel regression based segmentation of optical coherence tomography images with diabetic macular edema. Biomed Opt Exp, 2015, 6(4): 1172 doi: 10.1364/BOE.6.001172 [15] Duan X R, Liang Y B, Friedman D S, et al. Normal macular thickness measurements using optical coherence tomography in healthy eyes of adult Chinese persons: the Handan Eye Study. Ophthalmology, 2010, 117(8): 1585 doi: 10.1016/j.ophtha.2009.12.036 [16] Shen L, Gao F, Xu X L, et al. Macular thickness in Chinese. Acta Ophthalmol, 2013, 91(1): e77 doi: 10.1111/j.1755-3768.2012.02428.x -