Oblique incidence reflectometry is a simple and accurate method for measuring the absorption and the reduced-scattering coefficients of turbid media. We used this technique to deduce absorption and reduced-scattering spectra from wavelength-resolved measurements of the relative diffuse reflectance profile of white light as a function of source-detector distance. In this study, we measured the absorption and the reduced-scattering coefficients of chicken breast tissue in the visible range ͑400 -800 nm͒ with the oblique incidence probe oriented at 0°and 90°relative to the muscle fibers. We found that the deduced optical properties varied with the probe orientation. Measurements on homogenized chicken breast tissue yielded an absorption spectrum comparable with the average of the absorption spectra for 0°and 90°probe orientations measured on the unhomogenized tissue. The reduced-scattering spectrum for homogeneous tissue was greater than that acquired for unhomogenized tissue taken at either probe orientation. This experiment demonstrated the application of oblique-incidence, fiber-optic reflectometry to measurements on biological tissues and the effect of tissue structural anisotropy on optical properties.

Fiber-optic-based oblique-incidence reflectometry is a simple and accurate method for measuring the absorption and reduced scattering coefficients a and Ј s of semi-infinite turbid media. Obliquely incident light produces a spatial distribution of diffuse reflectance that is not centered about the point of light entry. The amount of shift in the center of diffuse reflectance is directly related to the medium's diffusion length D. We developed a fiber-optic probe to deliver light obliquely and sample the relative profile of diffuse reflectance. Measurement in absolute units is not necessary. From the profile, it was possible to measure D, perform a curve fit for the effective attenuation coefficient eff , and then calculate a and Ј s . This method was verified with Monte Carlo simulations and tested on tissue phantoms. Our measurements of D and eff had an accuracy of approximately 5%, thus giving us 10% and 5% accuracy for a and Ј s , respectively.

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Oblique incidence reflectometry is a simple and accurate method for measuring the absorption and reduced scattering coefficients of turbid media. We used this technique to deduce absorption and reduced scattering spectra from wavelength resolved measurements of the relative diffuse reflectance profile of white light. In this study we measured the absorption and reduced scattering coefficients of chicken breast in the visible (400-800nm) with the oblique incidence probe oriented at 0, 30, 60, and 90 degrees relative to the muscle fibers. We found that the reconstructed optical properties varied with probe orientation. This experiment demonstrates 1) the application of oblique-incidence fiber-optic reflectometry to measurements on biological tissue and 2) the effect of structural anisotropy on optical properties.

A new, simple and quick approach, oblique-incidence reflectometry, was used to measure the absorption and reduced scattering coefficients of a semi-infinite turbid medium. An obliquely incident light beam causes the center of the far diffuse reflectance to shift from the point of incidence, where the far diffuse reflectance refers to the diffuse reflectance that is several transport mean free paths away from the incident point. The amount of shift yields the diffusion constant by a simple formula, and the slope of the diffuse reflectance yields the attenuation coefficient. Only the relative profile of the diffuse reflectance is needed to deduce both optical parameters, which makes this method attractive in clinical settings because it does not require a stringent calibration for absolute quantity measurements. This method was tested theoretically by Monte Carlo simulations and experimentally by a reflectometer. Because this method can be used to measure optical properties of biological tissues quickly and requires on inexpensive equipment, it has potential clinical application to the diagnosis of disease or monitoring of treatments.