![]() Simple mathematical models of polarization rotation by rods were used to qualitatively describe observed intensity profiles. 9 In an earlier study, 10 it was shown both theoretically and experimentally that the anisotropy of scattered light is sensitive to fiber (rod) orientation, fiber thickness, and the spatial periodicity of the sample structure. ![]() The influence of relative orientations of collagen film samples and polarization analyzers on the angular distribution of linearly polarized light, transmitted through this film, has been analyzed previously. 7 8 Such cameras with increased dynamic range (12 bits and more) may be particularly useful in the measurement of 2-D intensity distributions, which result from a light beam being diffusively transmitted through or reflected from a turbid media. 2 3 4 The development of digital cameras has created new possibilities for video reflectometry, 5 polarimetry, 6 and polarized photography to map the structural characteristics of tissue. Different physical modalities based on absorption and/or scattering of electromagnetic, acoustic, or thermal waves have been used to analyze tissue structure noninvasively. ![]() 1 These structure modifications are related to the transition from normal to pathologic tissue. Fibrosis is caused by a change in the collagen or other fiber structure as a result of the skin being exposed to x-ray irradiation. Diseases such as graft versus host disease (GVHD) and systemic sclerosis and treatment procedures such as ionizing radiation for cancer treatment can initiate keloid formation and skin fibrosis, characterized histologically by a drastic modification of the collagen bundles. There is a significant interest in medicine and biology to define tissue layer thicknesses and to observe changes in tissue fiber orientation in vivo. The polarized videoreflectometry of the skin may be a useful tool to assess skin fibrosis resulting from radiation treatment. For the anisotropic media (demineralized bone and human and mouse skin), a qualitative difference between intensity distributions for cross- and co-polarized orientations of the polarization analyzer is observed up to a distance of 1.5 to 2.5 mm from the entry point. Variation of equi-intensity profiles with distance from the incident beam is analyzed for different initial polarization states of the light and the relative orientation of polarization filters for incident and backscattered light. The ratio of the ellipse semiaxes is well correlated with the ratio of reduced scattering coefficients obtained from radial intensity distributions. Equi-intensity profiles of light, backscattered from the sample, are fitted with ellipses that appear to follow the orientation of the collagen fibers. Two types of tissuelike media are used as controls to verify the technique: isotropic delrin and highly anisotropic demineralized bone with a priori knowledge of preferential orientation of collagen fibers. An incident beam (linearly polarized, wavelength 650 nm) is focused at the sample surface. Anisotropy of mouse and human skin is investigated in vivo using polarized videoreflectometry.
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