The laser treatment is an ideal option to conduct a surgical resection since it enables to provide higher accuracy and to
cause less damage when targeting invariant tissue areas. Compared to traditional mechanical or chemical treatment
modalities, it can shrink or destroy cancer cells using a narrow, focused light beam without harming normal tissue nearby.
Laser speckle contrast image (LSCI) is a powerful technology that is able to capture dynamic changes of backscattered
light, and then, convert it to relative flow using speckle contrast analysis. When the coherent light illuminates biological
tissue, random interference patterns will be received at the detector. If the particles are moving, patterns will result in
fluctuation as known as speckle patterns. By setting the exposure time equal to or longer than the speckle fluctuation
duration, such intensity fluctuation can be recorded, forming the speckle image. Since red blood cell is the primary
moving particles in vessels, the blurring can be related to flow information. Previous reports have also indicated that the
autocorrelation time is inversely related to the blood flow velocity. As a result, microvasculature and blood flow data can
be represented by analyzing the speckle variance of biological tissue spatially and temporarily. In this study, we propose
to use LSCI to in vivo investigate the induced thermal effect by laser illumination, and the difference in the thermal effect
caused by the CW and pulsed lasers will be compared. Finally, the treatment outcomes on brain tumor will be also
compared.
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.
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.
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.
KEYWORDS: Optical coherence tomography, Angiography, Cancer, Imaging systems, In vivo imaging, Reflectivity, 3D image processing, Tissues, Visualization, 3D printing
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.
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