Polarization sensitive optical coherence tomography (PS-OCT) is an extension of conventional optical coherence tomography (OCT) which enable the function to investigate birefringence characteristic of materials of biological tissue. In this research, we utilized PS-OCT for evaluation of photodamage on skin and several parameters were developed to investigate the photodamage including birefringence, diattenuation and depolarization properties of mouse skin. Additionally, the recovering progress of mouse skin was observed. The results indicate that the birefringence of skin is changed by laser irradiation.
Laser Speckle Contrast Imaging (LSCI), which used coherent light, has fully been used for observing blood flow due to its non-invasive, non-contact acquisition method. Generally, LSCI system uses just a single wavelength for measurement. In this research, first, considering the biological characteristics of different reflection rates and absorption, we use two lasers at 633nm and 855 nm and two CCD cameras to build a microscopic LSCI system. Second, by using Spatial, Temporal Speckle Contrast Analysis methods and analysis with Beer–Lambert law, the microcirculation can be in vivo visualized and oxygenation can be observed. Such developed system can be further used for in vivo animal studies.
In the past reports, excessive or long-term ultraviolet (UV) irradiation may cause DNA damage, resulting in genetic mutations and probably leading to skin cancer. However, it is difficult to noninvasively diagnose skin damage in the early stage due to excessive and long-term UV exposures. In this study, we propose to use optical coherence tomography (OCT) for noninvasively investigating the progress of skin damage due to excessive UV irradiation. The developed OCT system can provide the ability of label-free 3D microstructural and microvascular imaging with the axial and transverse resolution of 7 and 5 m, respectively. Mouse skin is used as the experimental model and exposed to different UV exposure powers of 5, 20 and 50W (corresponding to the power densities of 1.6, 6.4, and 16 W/cm2) for various time periods. The results show that the morphological and microcirculation changes can be identified when the skin is exposed to different exposure powers. With a lower exposure power of 5 W, no significant structural change can be found from the OCT results, but the vessel sizes are slightly increased and the vessel density is also increased. When the exposure power of UV light is increased to 20 W, the vessel density is increased significantly with the exposure time and the structural damage is also can be found. Then, when mouse skin is exposed to a higher UV power of 50 W for 8 mins, the skin structure and vessels are severely damaged. Finally, the skin after the exposures of various UV powers is also followed up with OCT to evaluate the skin recovery. The results show that the structural and microvascular changes due to UV irradiation can be identified with OCT and OCT can be an effective and noninvasive diagnostic tool for the early-stage sun damage.
In this study, a swept-source optical coherence tomography (OCT) system is developed for in vivo visualization of structural and vascular morphology oral mucosa. For simplification of optical probe fabrication, probe weight, and system setup, the body of the scanning probe is fabricated by a 3D printer to fix the optical components and the mechanical scanning device, and a partially reflective slide is attached at the output end of probe to achieve a common-path configuration. Aside from providing the ability of 3D structural imaging with the developed system, 3D vascular images of oral mucosa can be simultaneously obtained. Then, different locations of oral mucosa are scanned with common-path OCT. The results show that epithelium and lamina propria layers as well as fungiform papilla can be identified and microvascular images can be acquired. With the proposed probe, the system cost and volume can be greatly reduced. Experimental results indicate that such common-path OCT system could be further implemented for oral cancer diagnosis.