Skin Measurements and Analysis on Dynamic Properties Using Mirau-based Full-field Optical Coherence Tomography

本論文使用實驗室自行生長的摻鈦藍寶石晶體光纖之放大自發輻射(Amplified spontaneous emission; ASE)作為光源，搭配輕薄簡單的Mirau物鏡與收取二維大角度成像的CMOS相機，架設全域式光學同調斷層掃描系統，並展示量測人類活體皮膚的結果。系統於組織中的縱向解析度與橫向解析度分別為1.3 μm 與 1.25 μm。運用此系統可以在前臂、手掌、手指與手腕得到高解析度的皮膚影像，並可由影像觀察到真皮與表皮之交界、汗腺、毛孔與血管等。量測前臂端手腕、前臂、手掌與拇指腹的角質層平均厚度，按厚度排列，結果分別為4 μm、13 μm、141 μm、306 μm。除了角質層厚度，本論文也針對區域性的軸向散射強度特徵進行分析。 正交偏振光譜影像(Orthogonal polarization spectral imaging)有著高對比度特性，本論文使用其研究紅血球的動態變化，並與OCT三維影像進行疊合，深入探討皮膚內部動態特性。此外，紅血球在不同光源下的吸收程度不同，也會導致其與周圍組織的對比度差異。在560 nm的光源下，吸收顯著，該處較無光線返回，呈現黑色圓點；在780 nm的光源下，吸收較小，與周圍組織的散射情形沒有顯著差異，唯有血球外緣的反射光較難收取，可以觀察出血球邊緣輪廓。 最後，使用質點影像速度分析的技術，針對影像中的微血管與小血管進行紅血球的流速運算，並使用平均影像與追跡影像的差值之區域標準差，標定正交偏振光譜影像中的流動區域。流速計算之結果，微血管的流速大約在30 – 80 μm/s，小血管的流速則大約在70 – 100 μm/s。本論文展示之OCT結合OPSI的方法，可以得到皮膚的結構資訊與紅血球之動態變化，可能可以提供醫師一些疾病診療的參考。 In this thesis, Mirau-based full-field optical coherence tomography system using homemade Ti:sapphire crystal fiber amplified spontaneous emission (ASE) as light source was demonstrated. The lateral and axial resolution of the system are 1.25 μm and 1.3 μm in tissue, respectively. High-resolution in-vivo human skin images acquired from various locations such as dorsal forearm, palm, finger and wrist were demonstrated. Besides the morphology, dermal-epidermal junction, sweat gland, pore and vessel could be found out. The stratum corneum thickness was compared between above locations. It is about 300 μm, the thickest, at thumb and about 4 μm, the thinnest, at wrist. Complementary to the morphology extracted with OCT system, orthogonal polarization spectral imaging (OPSI) was used to study the dynamic properties of red blood cells (RBC). Due to the absorption difference, RBC under OPSI has different appearance. At 560 nm, higher absorption, RBC is a black dot. At 780 nm, lower absorption, the boundary of RBC can be seen, but not that obvious compare with the circumstances of 560 nm. Finally, RBC velocity calculation was demonstrated with particle image velocimetry (PIV) method using cross-correlation algorithm. Using regional standard deviation, RBC flowing region can be found out. The RBC velocity of capillary is about 30 - 80 μm/s, and that in small vessel is at the range of 70 – 100 μm/s. Skin morphology acquired from OCT system combined with dynamic properties studied by OPSI and PIV may provide assistance for skin diseases related with structural change and RBC velocity change