Enhanced diagnostic of skin conditions by polarized laser speckles:Phantom studies and computer modeling

The incidence of the skin melanoma, the most commonly fatal form of skin cancer, is increasing faster than any other potentially preventable cancer. Clinical practice is currently hampered by the lack of the ability to rapidly screen the functional and morphological properties of tissues. In our previous study we show that the quantification of scattered laser light polarization provides a useful metrics for diagnostics of the malignant melanoma. In this study we exploit whether the image speckle could improve skin cancer diagnostic in comparison with the previously used free-space speckle. The study includes skin phantom measurements and computer modeling. To characterize the depolarization of light we measure the spatial distribution of speckle patterns and analyse their depolarization ratio taken into account radial symmetry. We examine the dependences of depolarization ratio vs. roughness for phantoms which optical properties are of the order of skin lesions. We demonstrate that the variation in bulk optical properties initiates the assessable changes in the depolarization ratio. We show that image speckle differentiates phantoms significantly better than free-space speckle. The results of experimental measurements are compared with the results of Monte Carlo simulation

Skin Roughness Assessment

Non

Real-Time Raman Spectroscopy for Noninvasive in vivo Skin Analysis and Diagnosis

Non

Human skin optical properties and autofluorescence decay dynamics

Human skin is an optical organ which constantly interacts with light. Its optical properties are fundamental to understanding various effects of light-tissue interaction inhuman skin and to laser applications in medicine and biology. The aim of this thesis was to test two hypotheses: (1) that skin optical properties can be quantitatively modeled, and (2)that in vivo spectroscopic measurements can be used to derive information about skin structures. Both theoretical and experimental procedures were used to test these hypotheses. Experimental studies were completed in terms of macroscopic, in vivo diffuse reflectance spectroscopy, autofluorescence spectroscopy, and temporal behavior of the autofluorescence signal during continuous laser exposure, as well as microscopic in vitro fluorophore distribution and spectral differences. Several interesting physical phenomena were discovered. Three new methods were developed for deriving information of different skin layers from in vivo and in vitro measurements. The most interesting finding was that, under continuous laser exposure, skin autofluorescence decays following a double exponential function and that the autofluorescence recovery takes about six days. A seven layer skin optical model was developed based on(1) the structural anatomy of skin, (2) published optical properties of different skin layers and blood, and (3) measured skin fluorophore micro-distribution. Monte Carlo simulation was used to solve the Boltzmann equation of radiative transfer for the new skin model. The solutions provided a detailed knowledge of light propagation in skin tissue. The theoretical modeling unified the microscopic properties with the macroscopic in vivo skin measurements. The physical meaning of the auto fluorescence double exponential decay dynamics was also elucidated. It was shown that the coefficients of the double decay can be used to estimate the fractional contributions of different skin layers to the observed in vivo auto fluorescence signal. Using this approach, it was determined that the fractional contribution of the stratum corneum was - 14%, while the calculated value for the Monte Carlo skin model was - 15%, providing a close agreement between experimental and theoretical values. The dermis contributed the remaining 85% of the observed in vivo signal. We therefore, believe that the thesis hypotheses have been substantially proven. Although the skin has complicated inhomogeneous structures, its optical properties can now be quantitatively modeled and various modalities of in vivo skin spectroscopy can be used to derive information on skin structures.Science, Faculty ofPhysics and Astronomy, Department ofGraduat

Diagnostic endoscopy

xiii, 256 p.; il.; 24 c

Collision Enhanced Raman Scattering (CERS): An Ultra-High Efficient Raman Enhancement Technique for Hollow Core Photonic Crystal Fiber Based Raman Spectroscopy Gas Analyzer

Raman enhancement techniques are essential for gas analysis to increase the detection sensitivity of a Raman spectroscopy system. We have developed an efficient Raman enhancement technique called the collision-enhanced Raman scattering (CERS), where the active Raman gas as the analyte is mixed with a buffer gas inside the hollow-core photonic-crystal fiber (HCPCF) of a fiber-enhanced Raman spectroscopy (FERS) system. This results in an enhanced Raman signal from the analyte gas. In this study, we first showed that the intensity of the 587 cm−1 stimulated Raman scattering (SRS) peak of H2 confined in an HCPCF is enhanced by as much as five orders of magnitude by mixing with a buffer gas such as helium or N2. Secondly, we showed that the magnitudes of Raman enhancement depend on the type of buffer gas, with helium being more efficient compared to N2. This makes helium a favorable buffer gas for CERS. Thirdly, we applied CERS for Raman measurements of propene, a metabolically interesting volatile organic compound (VOC) with an association to lung cancer. CERS resulted in a substantial enhancement of propene Raman peaks. In conclusion, the CERS we developed is a simple and efficient Raman-enhancing mechanism for improving gas analysis. It has great potential for application in breath analysis for lung cancer detection

Enhanced Circular Dichroism by F-Type Chiral Metal Nanostructures

Circular dichroism (CD) effects have broad applications in fields including biophysical analysis, analytical chemistry, nanoscale imaging, and nanosensor design. Herein, a novel design of a tilted F-type chiral metal nanostructure composed of circular nanoholes with varying radii has been proposed to achieve remarkable CD effects, and the results demonstrate the generation of a significant current oscillation at the sharp edges where the nanoholes overlap under circularly polarized light, resulting in a strong CD effect. The CD effect can reach up to 7.5%. Furthermore, spectral modulation of the resonant wavelength can be achieved by adjusting the structural parameters, which enhances the tunability of the structure. Overall, these results provide theoretical or practical guidance for enhancing the circular dichroism signal strength of chiral metal nanostructures and designing new types of two-dimensional chiral structures