- 學位論文
整合光學同調斷層掃描及眼底攝影影像於青光眼診斷之特徵分析
Feature Analysis for Glaucoma diagnosis in Integrating Optical Coherence Tomography and Fundus Image
摘要
摘 要 青光眼為眼科疾病中常見之致盲疾病之一，所有治療方式僅能暫緩視野惡化程度，因此青光眼疾病早期發現、早期治療是相當重要的。光學同調斷層掃描(Optical Coherence Tomography, OCT)為對於青光眼疾病早期診斷為最重要之方式。但僅依賴OCT可能產生導致視神經盤定位錯誤而降低診斷之正確性。本研究整合眼底攝影(Fundus)與光學同調斷層掃描，進行視神經盤影像定位正確性評估分析。 本研究主要使用眼底攝影及光學同調斷層掃描之視神經盤影像進行量化分析。在眼底攝影之視神經盤輪廓圈選上，採用影像處理時可調控之JSEG演算法，以方便對於擷取參數作微調之用，並增加使用者語意辨別，減少JSEG演算法在影像過度分割。在掃描中心點定位上，以光學同調斷層掃描視神經盤眼底影像之掃描中心點，比對以JSEG分割後之視神經盤位置，取得正確之掃描中心。計算具有描述視神經盤形狀、邊界情形與嚴重程度之影像參數並進行參數分析，影像參數包含有各角度視神經盤、視杯、環狀結構(Rim)之水平及垂直直徑、面積、比例以及Rim volume等形態特徵。本研究使用經證實之病案，共14例(正常4例、青光眼10例)，首先對於正常人案例進行量化分析，確認無誤後進而以青光眼病例探討。最後以系統與醫師所擷取參數之相關係數作為評估之依據。 本研究發現掃描中心定位及視杯邊界圈選之準確性會影響Rim volume正確性，並進一步影響及相關係數，故以統計計算中心點平均偏移量為15 pixel修正光學同調斷層掃描之中心點，並依視神經盤及視杯之距離校正眼睛顳側壓縮偏移比例，得到正確之定位座標點。研究結果顯示於正常人之相關係數平均為0.85，其中視杯/視神經盤比相關係數平均為0.86，與Rim volume相關係數為0.59；青光眼病患相關係數平均為0.86，視杯/視神經盤比相關係數平均為0.88，與Rim volume相關係數為0.59。 本研究提供一套完善之電腦輔助診斷系統介面，讓醫師或使用者操作便利之用。也藉由眼底攝影輔助光學同調斷層掃描，解決了眼科OCT輔助診斷系統中視神經盤及視杯定位缺失；而本系統對於眼底攝影影像中，視杯輪廓界線模糊不明以及視神經盤血管周圍滲血現象，無法達到預期功效。此外在青光眼判定之有利參數上，Rim volume為主要之評估依據，而其他相關參數也不可或缺。若能增加光學同調斷層掃描之視神經纖維厚度影像，加以評估各角度相關參數，必可以提升準確性。
並列摘要
Abstract Glaucoma is one of familiar blind diseases in the ophthalmology. Treatments only can temporarily decelerate worse degree, it’s important to discover and treat in early stages. Optical coherence tomography (OCT) is the major method for the early detection of Glaucoma. However, only depending on OCT may induce optical disc positioning error and reduce the accuracy of diagnosis. The purpose of this study is focused on disc position detection and feature analysis for glaucoma diagnosis in integrating OCT and Fundus image. In the study, Fundus image and OCT disc photo, disc scans in six directional angles were used for Quantitative analysis. First, disc and cup in color Fundus images are segmented by semi-automatic method, following matching disc and cupping with OCT disc photo, getting correct scan center, further against OCT disc scans of the six directional angles. Image parameters which include diameter and area of disc, cup and rim, cup/disc (C/D) ratio, and rim volume were then calculated and analyzed. The shape, boundary, and serious degree of disc and cup were found during this procedure. Totally, 4 Normal cases and 10 glaucoma cases were used for test. First of all, normal cases are evaluated in Quantitative analysis and then evaluated the Glaucoma cases. Finally, the Correlation analysis between computer generated segmentation and ophthalmologist’s manual segmentation was used to evaluate this system. This study finds that the position of scan center and the accuracy of cup boundary segmentation will affect the calculation of Rim volume and correlation coefficient. In order to get correct scan center, we revise OCT scan center 15 pixels by statistics. Based on temporal distance compression ratio of eye, the distances from center to disc and cup was correct. Result showed that average correlation coefficient in normal cases is 0.85, average C/D ratio is 0.86, and Rim volume is 0.59. For glaucoma cases, average correlation coefficient is 0.86, average C/D ratio is 0.88, and Rim volume is 0.59, respectively. In conclusion, this study provide an OCT computer-aided diagnosis interface, let ophthalmologist or user operate conveniently. This system also solve optical disc and cup positioning error in Ophthalmology OCT computer-aided diagnosis. However, system limited to that disc or cup boundary is fuzzy, and disc blood vessel surroundings are bleeding. In addition, Rim volume is not only major parameter in diagnosis of glaucoma. If OCT retinal fiber layer (RNFL) image can be used to evaluate parameter in each angles, the accuracy can be raised.