- 學位論文
利用光學同調斷層掃描血管造影術於小動物模型之量化微血管成像分析
Quantitative Microvascular Imaging Analysis of the Small Animal Model with Optical Coherence Tomography Angiography Technology
摘要
光學同調斷層掃描血管造影術可以提供快速、立體和非侵入式的組織微血管系統之成像。本論文將介紹多種光學同調斷層掃描血管造影術演算法並應用在小動物模型之中。這些演算法使用光學同調斷層掃描術信號的訊息，包括相位、強度或複數值。另外，為了研究ㄧ維掃描速率和掃描間隔時間如何影響光學同調斷層掃描血管造影術的對比度和動態範圍，我們開發了中心波長位於 1.06 微米之掃頻光源式光學同調斷層掃描術系統，使用兩個光源實現100 kHz 或 200 kHz ㄧ維縱向深度掃描速率。光學同調斷層掃描血管造影術可以識別更複雜的小鼠耳朵微血管網絡，當掃描間隔時間相對較長時（例如 12.5 ms比上6.25 ms）。另一方面，由相同掃描間隔時間（例如 12.5 ms）與不同ㄧ維掃描速率產生的光學同調斷層掃描血管造影術影像集也被加以比較。以 100 kHzㄧ維掃描速率獲取的光學同調斷層掃描血管造影術影像顯示出比其他成像方式更精細的微血管系統。我們也針對以不同ㄧ維掃描速率和掃描間隔時間重建的光學同調斷層掃描血管造影術影像的對比度進行了定量分析，這些量化包括血管面積、總血管長度和連接點密度等。 此外，傳統的光學同調斷層掃描術之儀器設置不適合對行為自由的動物進行成像，因為該系統龐大而笨重。這些缺點限制了光學同調斷層掃描術在神經科學中更廣泛的應用，因為研究人員對動物進行大腦成像時，只能是在麻醉下或是將大腦保持在固定位置。因此，在本論文中，亦提出了 1.3 µm 微型頭戴式光學同調斷層掃描術成像裝置，其具有400 kHzㄧ維掃描速率並允許在自由移動狀態下對小鼠大腦進行連續成像。該裝置利用微機電系統掃描技術和高速波長掃描光源，以實現鼠腦的高速光學同調斷層掃描術成像。另外，為了觀察大腦活動與相關生理條件之間的關係，我們使用光學同調斷層掃描血管造影術來獲取不同生理條件下小鼠大腦的微血管訊息。這些生理條件包括麻醉、清醒中和活動狀態以及電刺激狀態。因此，本裝置的發明將能延伸光學同調斷層掃描術在行為神經科學中的血流動力學或血管生成研究領域的應用。
並列摘要
Optical coherence tomography angiography (OCTA) can provide rapid, volumetric, and noninvasive imaging of tissue microvasculature. In this dissertation, various OCTA algorithms will be introduced and implemented to provide microvascular imaging of the small animal models. These algorithms leverage the variation of the OCT signal, including phase, intensity, or complex value, due to the moving red blood cells in the microvascular network. Also, to investigate how A-scan rate and interscan time affected the contrast and dynamic range of OCTA imaging, we developed a 1.06-µm swept-source OCT system enabling 100-kHz or 200-kHz A-scan rate using two light sources. OCTA can identify more intricate microvascular networks of mice ear skin with a relatively long interscan time (e.g., 12.5 ms vs. 6.25 ms for 200-kHz OCT). Moreover, OCTA image sets with the same interscan time (e.g., 12.5 ms) but different A-scan rate were also compared. OCTA images acquired with a 100-kHz A-scan rate showed finer microvasculature than did other imaging modalities. We also performed quantitative analysis on the contrast of OCTA images reconstructed with different A-scan rates and interscan time intervals in terms of vessel area, total vessel length, and junction density. Besides, the conventional optical coherence tomography (OCT) instrument setup is unsuitable for imaging in freely-behaving animals because the system is enormous and heavy. These disadvantages limit the broader implementations of OCT in neuroscience owning that researchers can only perform brain imaging of the animal, either under anesthesia or keeping the brain in a fixed position. Therefore, in this dissertation, the 1.3-µm miniature head-mounted OCT (MH-OCT) imaging device having a 400-kHz A-scan rate and allowing continuous imaging of the mouse brain in a freely-moving state has been developed and demonstrated. This device utilizes the micro-electro-mechanical system (MEMS) scanning technologies and a high-speed wavelength-swept light source to enable fast mouse brain OCT imaging. Furthermore, to observe the relationship between brain activity and associated physiological conditions, we used OCT angiography (OCTA) to obtain the microvasculature information of the mouse brain under different physiological conditions. These physiological conditions include anesthetized, waking, and active as well as electrical stimulation states. Therefore, the invention of this device will extend the application of optical coherence tomography in the field of hemodynamics or angiogenesis in behavioral neuroscience.