摻鈦藍寶石晶體光纖之平行式光學同調斷層掃描術研究

Abstract

光學同調斷層掃描術為目前最主要的非侵入式光學診斷技術之一。利用光源的低同調性，可達到微米等級的縱向解析度。此掃描技術是利用光子在組織內散射特性的變化，以提供組織內部的結構性資訊，此資訊會被顯現在重建的影像中。光學同調斷層掃描術能提供活體掃描的二維的斷層影像與三維立體資訊。因此，對於在一些在傳統上無法做生物切片或明顯危害到組織的觀察上，更為重要，例如眼睛的研究。 在此論文中，我們實驗室自製了單纖衣結構的摻鈦藍寶石晶體光纖，並以此建立了二套光學影像系統，包含非接觸式眼底鏡與平行式光學同調斷層掃描儀。當此光纖透過波長為532 nm的綠光連續固態雷射作為幫浦光時，可產生中心波長780 nm、頻寬180 nm之放大自發輻射，我們將其作為光學同調斷層掃描術的光源。透過其極寬與高斯狀分布的頻譜，我們可得到1.5 μm 的理論縱向解析度。 為了進行此系統對眼睛掃描的研究，我們以掃描活體大鼠眼睛的實驗來驗證我們的系統。利用設計的非接觸式眼底鏡，我們成功的將大鼠眼底的區域成像，其中包含了視神經血管與眼睛視盤。我們並利用全域式光學同調斷層掃描儀進行對大鼠角膜與網膜的掃瞄。藉由重建的二維斷層影像我們可以看出組織內結構層與層之間的差異與區隔。藉由與傳統生物切片的比較，可以得知，與我們的實驗結果吻合。此研究成果展現了此系統對於眼睛臨床上與醫學的研究上極具應用潛力。此外，我們以初期模型展現了平行式頻域同調斷層掃描術應用於手指皮膚的掃描。此系統的線照明方式可提供及時的二維斷層掃描影像，並具有提供三維立體資訊的潛力。

Optical coherence tomography (OCT) is one of the most rapidly advancing noninvasive medical imaging modalities that uses coherence gating to obtain tomographic images with micrometer-scale axial resolutions. By detecting the variation of scattering property of biological sample, structural information can be reconstructed. OCT is promising in providing cross-sectional images and 3-D volumetric images of biological tissues in vivo, especially in area where conventional excision examination is impossible or hazardous, such as ophthalmology. In this study, a non-contact ophthalmoscope and parallel-OCT scanning technique, i.e., full-field OCT (FF-OCT), based on the broadband amplified spontaneous emission of our home-made Ti:Al2O3 single-clad crystal fiber are built and analyzed. With the advantage of the wide bandwidth of the light source and its Gaussian-shape spectrum, a theoretical axial resolution of 1.5 μm is achieved. In order to demonstrate the feasibility of the developed system in ophthalmology applications, rodent eye scanning is performed in vivo. We have successfully obtained the fundus region imaging, including the optic nerve fibers and optic disk for non-contact ophthalmoscope. The scanning of rat cornea and retina using our FF-OCT system is also demonstrated. The revealed internal layers can be differentiated from the reconstructed cross-sectional images. By comparing our result to that of the histology biopsy, we concur the accordance in the OCT images, showing the potential of this imaging modality in clinical ophthalmology study and applications. We also demonstrate a parallel spectral-domain OCT scanning in its prototype in fingerpad scanning. The line-illumination technique used in this imaging modality provides real-time cross-sectional image that is promising for 3-D volume rendering.