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Absorption effects in optical coherence tomography modeling

Estimation of the tissue optical characteristics using optical coherence tomography (OCT) requires good modeling. Present modeling of the system includes effects such as scattering of light in tissues. However, absorption effects were often neglected in the model. They may be significant depending on the tissue type and the wavelength of the light source. We present a study where the effects of absorption in light propagation in biological tissue were examined in the theoretical modeling of OCT based on the single-scattering model. OCT M-scans were performed on liquid tissue phantoms at 1% concentration. In order to mimic the effects of absorption, India ink was added to the solution. Different concentrations of Indian ink were used to vary the absorption coefficient in the tissue phantoms. Estimation of the absorption, scattering coefficients from the OCT signal were obtained. Substantial reduction in the slope of the logarithmic OCT signal was observed when India ink was introduced to the liquid tissue phantoms. The results suggest that the effects of the absorption clearly affected the estimation of the overall extinction coefficient. In order to improve the accuracy of estimation of these characteristics, absorption effects should be taken into account.