Diffuse reflectance spectroscopy utilizing optical fiber probes is a useful and simple method for non-invasive determination of biological tissue optical properties. In order to extract the optical properties from the acquired diffuse reflectance spectra, an accurate light propagation model, such as Monte Carlo, is required. The results obtained by the model can significantly depend on the description of the tissue and optical fiber probe geometry. Optical fiber probes commonly comprise fibers arranged into a desired source-detector layout enclosed in a stainless steel ferrule. By using Monte Carlo simulations, we investigate the impact of the stainless steel optical fiber probe-tissue interface on the diffuse reflectance spectra. For this purpose, a commonly used simple laterally uniform optical probe-tissue interface with mismatched refractive indices was compared to the improved optical probe-tissue interface taking into account the fiber layout and the specular reflections from the stainless steel probe tip. The results show that the error introduced into the simulated diffuse reflectance by the simplified probe-tissue interface can easily exceed 5%.
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