研究目的
To develop a simple and accurate empirical equation for diffuse reflectance from turbid media to facilitate the diagnosis of epithelial dysplasia by reducing computational complexity and time consumption in clinical setups.
研究成果
The proposed empirical equation, derived from Monte Carlo simulations and validated with tissue phantoms, provides a highly accurate and simple method for estimating diffuse reflectance from turbid media. It outperforms the diffusion approximation method by a factor of ten in accuracy and is reliable across a wide range of optical properties, including extremities. This approach reduces computational complexity and time, making it suitable for clinical applications in diagnosing epithelial dysplasia and other conditions through non-invasive spectroscopy.
研究不足
The Monte Carlo simulations assume a semi-infinite single-layer tissue model, which may not fully represent real tissues with layered structures. Approximations include an infinitely narrow light beam and circular detector geometry, which are not realistic. The empirical equation is less accurate for detector diameters below 3 mm, particularly in low absorption regions. The model is specific to the assumed optical properties and may require adjustments for different source-detector geometries or tissue types.
1：Experimental Design and Method Selection:
The study involved generating a diffuse reflectance lookup table using Monte Carlo simulations for a semi-infinite homogeneous turbid medium with typical biological tissue optical properties. An empirical equation was derived by surface fitting this lookup table using a polynomial function of the ratio of reduced scattering to absorption coefficients.
2：Sample Selection and Data Sources:
Monte Carlo simulations were performed for absorption coefficients (μa) and reduced scattering coefficients (μs') ranging from 2 to 50 cm?1. Tissue phantoms were prepared using monodisperse polystyrene spheres (
3：5, 75, 1 μm diameters) as scatterers and human hemoglobin as an absorber, with concentrations varied to achieve specific optical properties. List of Experimental Equipment and Materials:
Equipment included an in-house built Monte Carlo simulation program under MATLAB, Perkin Elmer spectrometer Lambda 35 with an integrating sphere setup for diffuse reflectance measurements, monodisperse polystyrene spheres from Polyscience Inc., human hemoglobin from Sigma-Aldrich, phosphate buffer saline solution, and a diffuse reflectance standard SRS-99 from Labsphere, Inc. Materials also included MATLAB software for data analysis.
4：Experimental Procedures and Operational Workflow:
The Monte Carlo simulation assumed a semi-infinite medium with refractive index
5：4, anisotropy coefficient 9, and Henyey-Greenstein phase function. The lookup table was generated, and surface fitting was done using MATLAB's fmin subroutine with Quasi Newton's algorithm. Tissue phantoms were prepared with varying concentrations, and diffuse reflectance was measured using the integrating sphere setup after baseline correction. Data Analysis Methods:
Data analysis involved calculating the sum of square error and root mean square error between empirical model predictions and Monte Carlo simulations or experimental measurements. Parameters of the empirical equation were optimized for minimum error.
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