CC BY
3The 30th International Conference on Advanced Laser Technologies B-I-27
ALT'23
Analytical and numerical models for advancement of diffuse
spectroscopic techniques
M. Kirillin1, D. Kurakina1, V. Perekatova1, V. Shishkova1, A. Kostyuk1, A. Khilov1, I.Turchin1,
and E. Sergeeva1
1-A.V. Gaponov-Grekhov Institute of Applied Physics RAS, 46 Uljanov St., Nizhny Novgorod, 603950, Russia
mkirillin @yandex. ru
Optical diffuse spectroscopy (ODS) is an efficient tool for non-invasive evaluation of biotissue chromophore content. Being based of reflectometry principles, it consists in wideband or wavelength-by-wavelength biotissue probing and calculation of basic chromophores concentrations from the reconstructed biotissue absorption and/or scattering spectra. For reconstruction of absorption and scattering spectra from the registered reflectance spectra one requires to employ a model of light propagation in tissue. Traditionally, for fast reconstruction, an analytical solution of the diffuse approximation of the radiative transfer equation in infinite medium is employed [1,2]. However, this approach suffers from it marginal applicability, especially for relatively small source-detector separation. Account for semi-infinite medium allows one to significantly increase the accuracy of the diffuse approximation model [3], however, such approach may provide some deviation at relatively small distances. Moreover, one should account that due to strong dispersion of the biotissue optical properties in the visible and NIR ranges, wideband measurements may result in different probing depth for different probing wavelength adding additional uncertainty to the measurement results. Moreover, generally one should account for different transfer functions of the different channels in the measurement setup, however, this problem could be overcome using so-called dual-slope method, that uses ratiometric approach to diminish the effect of channel transfer functions [2].
This paper considers application or the analytical and numerical models in order to enhance the reconstruction in ODS. A refined analytical model is proposed based on diffuse approximation solution in a semi-infinite medium, which provides higher accuracy as compared to currently employed model [3]. The model was verified by the comparison with the results of extensive Monte Carlo simulations for source-detector separations corresponding to a real existing system [4,5] and biotissue optical properties typical for human skin. The effect of the superficial layer with different optical properties, mimicking stratum corneum and skin, is discussed, since it may affect the results obtained using model for a uniform medium. The Monte Carlo simulations for multi-layer geometry were also employed for estimation of typical probing depth spectra for different source detector separations, which also affects the accuracy of the chromophore content reconstruction [6].
The good agreement of the developed analytical model with the results of Monte Carlo simulations provides an ultimate opportunity for creating large datasets of synthetic data the could be successively employed for machine-learning based algorithms for chromophores concentrations reconstruction.
The authors acknowledge the support by Center of Excellence «Center of Photonics» funded by the Ministry of Science and Higher Education of the Russian Federation, Contract No. 075-15-2022-316.
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