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Intensity Profiles of Linearly Polarized Light Backscattered From Skin and Tissue-Like Phantoms
Anisotropy of mouse and human skin is investigated in vivo using polarized videoreflectometry. An incident beam (linearly polarized, wavelength 650 nm) is focused at the sample surface. 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. Equi-intensity profiles of light, backscattered from the sample, are fitted with ellipses that appear to follow the orientation of the collagen fibers. The ratio of the ellipe semiaxes is well correlated with the ratio of reduced scattering coefficients obtained from radial intensity distributions. 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. 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. The polarized videoreflectometry of the skin may be a useful tool to assess skin fibrosis resulting from radiation treatment.
 
(left) Depolarization of initially linearly polarized light with distance from the entry point (light is diffusively reflected by mouse skin). (right) The dependence ln[r2/(r)] for (a) demineralized bone and (b) human forearm skin, measured along the main axes of the external ellipse. Mean slopes of linear fits are shown for both vertical and horizontal axes.
Equi-intensity profiles of the pencillike probe beam diffusively reflected from the sample of demineralized bone and their elliptical fits. The collagen fibers of the sample were assembled vertically for (a) Hv and (b) Hh configurations of analyzer-polarizer, respectively.
Enhancement of hidden structures of early skin fibrosis using polarization degree patterns and Pearson correlation analysis
The skin of athymic nude mice was irradiated with a single dose of X-ray irradiation that initiated fibrosis. Digital photographs of the irradiated mice were taken by illuminating the mouse skin with linearly polarized probe light of 650 nm. The specific pattern of the surface distribution of the degree of polarization allowed for the detection of initial skin fibrosis structures that were not visually apparent. Data processing of the raw spatial distributions of the degree of polarization based on Fourier filtering of the high frequency noise improved subjective perception of the revealed structure in the images. In addition, Pearson correlation analysis provided information about skin structural size and directionality.
 
(left) A typical image of untreated area of a mouse. (right) The Fourier transformed image of degree of polarization data.
Sviridov, A.P., Z. Ulissi, V. Chernomordik, M. Hassan, and A.H. Gandjbakhche. Visualization of biological texture using correlation coefficient images. Journal of Biomedical Optics 11(6) (2006).
Sviridov, A., V. Chernomordik, M. Hassan, A. Russo, A. Eidsath, P. Smith, and A. Gandjbakhche. Intensity profiles of linearly polarized light backscattered from skin and tissue-like phantoms. J. Biomedical Optics 10(1), (Jan/Feb 2005).
Sviridov, A., V. Chernomordik, M. Hassan, A. Russo, P. Smith, and A. Gandjbakhche. Enhancement of hidden structures of early skin fibrosis using polarization degree patterns and Pearce correlation analysis. J. Biomed. Opt., 10(5):051706 (Sep-Oct 2005).
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