Abstract
With a Gaussian-like broadband light source from high brightness Ce(3+):YAG single-clad crystal fiber, a full-field optical coherence tomography using a home-designed Mirau objective realized high quality images of in vivo and excised skin tissues. With a 40 × silicone-oil-immersion Mirau objective, the achieved spatial resolutions in axial and lateral directions were 0.9 and 0.51 μm, respectively. Such a high spatial resolution enables the separation of lamellar structure of the full epidermis in both the cross-sectional and en face planes. The number of layers of stratum corneum and its thickness were quantitatively measured. This label free and non-invasive optical probe could be useful for evaluating the water barrier of skin tissue in clinics. As a preliminary in vivo experiment, the blood vessel in dermis was also observed, and the flowing of the red blood cells and location of the melanocyte were traced.
Highlights
In recent years, optical coherence tomography (OCT) has been widely applied on threedimensional (3-D) image reconstruction of skin tissue [1,2]
The broadband output power after coupling into multi-mode fiber (Thorlabs, 400-μm-diameter, numerical aperture (NA): 0.39, America) is 30 mW, and becomes 5 mW after passing through Mirau objective onto the sample. This light source is eminently suitable for Full-field OCT (FF-OCT) because it is unnecessary to use infrared-cut filter to prevent from thermal problem on sample [24]
FF-OCT takes the en face image from calculating the stack information via phasestepped technique with single-shot CCD at 0°, 90°, 180°, and 270° [27], of which the phase was shifted by triangularly oscillated motion of PZT
Summary
Optical coherence tomography (OCT) has been widely applied on threedimensional (3-D) image reconstruction of skin tissue [1,2]. To non-invasively probe the layer parameters (LPs), such as average total thickness (a-TT), average number of layers (a-NOLs), and average cellular layer thickness (a-CLT), for stratum corneum (SC) becomes important for evaluating the skin moisturization of epidermis [3] On this application, axial resolution better than 1.2 μm in tissue is the doorsill to measure LPs of the SC [4]. Compared with the single-point scanning via Ce3+:YAG double-clad crystal fiber light source [20,21], this platform provides high frame speed and low incident power for 3-D reconstruction of skin tissue. The broadband output power after coupling into multi-mode fiber (Thorlabs, 400-μm-diameter, NA: 0.39, America) is 30 mW, and becomes 5 mW after passing through Mirau objective onto the sample This light source is eminently suitable for FF-OCT because it is unnecessary to use infrared-cut filter to prevent from thermal problem on sample [24]. Polarized incident light was adopted because it can provide deeper penetration [25]; weak signal light can be strongly enhanced by the reference one
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