光學同調斷層影像應用於小動物生理發展評估之研究

Abstract

光學同調斷層掃描是一項非常新興的醫學影像技術，研究主軸是以光學同調斷層掃描系統當主要研究工具，主要針對動物模型的發展來做研究。動物模型有很多種，在此針對斑馬魚與渦蟲兩種動物模型來做研究。第一部分則是主要研究成年斑馬魚腦部發展的情況。斑馬魚近年來已經成為研究脊椎動物發育以及人類遺傳疾病的新興模式動物，所以，目前的研究是利用光學同調斷層掃描來研究成年斑馬魚腦部的發展情況，藉此了解斑馬魚腦發展的情況。並且延伸更多的研究，利用光學斷層掃描來即時追蹤及記錄斑馬魚器官發展的情況。第二部分則是研究渦蟲的再生，渦蟲本身具有特殊的再生能力，將渦蟲一切為二可再生回完整的渦蟲。所以，可以利用光學同調斷層掃描技術來觀察渦蟲於整個的再生過程的情況。 本研究所採用的分析方法主要有兩種，第一種是訊號衰減率，主要是利用光在組織穿透過程中，所訊號經過組織造成的衰減而產生的趨勢。第二種則是紋理分析方法，主要是計算出影像紋理在相對位置下像素對的灰階值關係，其中紋理特性會計算出五種參數，分別為：對比度、相關性、均質性、能量、熵。而這兩種方法主要是利用光學同調斷層掃描所得之B-mode影像並且圈選有興趣之區域(ROIs)來分析。結果的顯示中，訊號衰減率的分析方法顯示可以有效的辨別出成年斑馬魚腦部發展的趨勢，也可以辨別渦蟲的再生過程之表現。但是在紋理特性於五個參數的表現中，於成年斑馬魚腦部發展過程中，並沒有計算出可以了解斑馬魚腦部發展之趨勢，而在觀察渦蟲的再生情況的過程中，在對比度、相關性、均質性這三個紋理特性，則有比較顯著的趨勢存在。所以，光學同調斷層掃描是一項很有潛力的工具，使用來觀察小動物模型的發展。

The zebrafish is a well-established model system used to study and understand various human biological processes. The present study used optical coherence tomography (OCT) to investigate growth of the adult zebrafish brain. Twenty zebrafish were studied, using their standard lengths as indicators of their age. Zebrafish brain aging was evaluated by analyzing signal attenuation rates and texture features in regions of interest (ROIs). Optical scattering originates from light interaction with biological structures. During development, the zebrafish brain gains cells. Signal attenuation rate, therefore, increases with increasing zebrafish brain age. This study’s analyses of texture features could not identify aging in zebrafish brain. These results, therefore, indicated that the OCT signal attenuation rate can indicate zebrafish brain aging, and its analysis provides a more effective means of observing zebrafish brain aging than texture features analysis. Using OCT system could further increase the technique’s potential for recognition and monitoring of zebrafish brain development The planarian is widely used as a model for studying tissue regeneration. In this study, we used optical coherence tomography (OCT) for the real-time, high-resolution imaging of planarian tissue regeneration. Five planaria were sliced transversely to produce 5 head and 5 tail fragments. During a 2-week regeneration period, OCT images of the planaria were acquired to analyze the signal attenuation rates, intensity ratios, and image texture features (including contrast, correlation, homogeneity, energy, and entropy) to compare the primitive and regenerated tissues. In the head and tail fragments, the signal attenuation rates of the regenerated fragments decreased from -0.2 dB/μm to -0.05 dB/μm, between Day 1 and Day 6, and then increased to -0.2 dB/μm on Day 14. The intensity ratios decreased to approximately 0.8 on Day 6, and increased to between 0.8 and 0.9 on Day 14. The texture parameters of contrast, correlation, and homogeneity exhibited trends similar to the signal attenuation rates and intensity ratios during the planarian regeneration. The proposed OCT parameters might provide biological information regarding cell apoptosis and the formation of a mass of new cells during planarian regeneration. Therefore, OCT imaging is a potentially effective method for planarian studies.