Combination of diffuse reflectance and transmittance spectroscopy to obtain optical properties of liquid phantoms

Abstract

We present a simple fiber-optics probe system that could be used in any lab for convenient determination of optical properties of liquid phantoms based on diffuse reflectance and transmittance measurements in the visible/near-infrared region. We employed Monte Carlo simulations to determine the optimal system setup and to test the inverse algorithm employed to extract the optical properties from measured reflectance and transmittance. The inverse algorithm involved obtaining the fit merit function for values within the optical property range and determining the minimum. The performance of the method was tested by predictive error and validated using similar matrix of milk–ink phantoms on reflectance and transmittance. In the range of optical properties of phantoms with optical properties of 0 to 0.5 cm−1 for μa and 20 to 140 cm−1 for μs, the median prediction error for the test phantoms at 630 nm was 1.51% for μs and 8.82% for μa. The median difference in predicted values versus expected values was 1.15 cm−1 for μs and 0.01 cm−1 for μa. In comparison with other techniques, our method was a simple, fast, and convenient way to determine optical properties of liquid phantoms.