Optical Spectra of Some Pathological Conditions of Stomach Tissues

Abstract

Diffuse reflection spectra, diffuse and collimated transmittance spectra of the mucous tissue of stomach anthrus in norm and at a low-differential form of stomach cancer are measured in 300–800 nm spectrum range. The optical coefficients of absorption (μa), scattering (μs) and anisotropy factor (g) for tissues with pathological changes have been calculated by the three-flux model and diffusion approximation methods. It has been determined that the magnitude of optical parameters grows with the development of malignant processes in stomach tissues which indicates the prevalence of forward light scattering and the increase in Mi scatter contribution to the total scattering coefficient of malignant tissues. It has also been shown that the application of two independent theories as methods of tissues' optical parameters determination (μa,μs,g) gives satisfactorily similar results.

Optical absorption and scattering spectra of pathological stomach tissues

“…It has been shown [7,8] that the values of μ a , μ s , and g obtained with the 3-flux model are in good agreement with the optical indices calculated by the addition-doubling method [12,13] and the diffusion approximation [6,15], and are preferable to data from the last model. The method for determining the optical indices of biotissues with the aid of the 3-flux model is described in more detail in [7,8].…”

“…The first involves measuring the diffuse reflection coefficient with spatial resolution and analyzing the data in the approximation of a semi-infinite medium with a diffusion or P 3 -approximation for the radiative transfer equations [3,6]. The second approach involves measuring the optical transmission and reflection coefficients assuming media with finite thicknesses and solving the inverse problem for the radiative transfer equations in various numerical or analytical model approximations [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15]. Although the experimental and theoretical approaches are well developed, these methods have a number of well-known and mutually exclusive shortcomings that reduce their information content and practical value [3].…”

“…Otherwise, the T t (λ), R t (λ), and T c (λ) signals were analyzed spectrally and detected similarly to the methods used for measuring the diffuse reflection R d (λ) spectra. The techniques for measuring the spectrophotometric coefficients are discussed in more detail elsewhere [7,8].…”

“…In the first stage, based on the measured spectrophotometric coefficients T t (λ), R t (λ), and T c (λ), and the solution of the inverse problem for a 3-flux radiative transfer model, we calculated the spectra of the optical indices for the blood-free in vitro samples. This method was first described in [9] and has been developed in [7][8][9][10][11]. It involves solving a system of three differential equations coupling three luminous fluxes, one collimated and propagating in the forward direction (F c + ) and two diffuse fluxes propagating in the forward (F d + ) and reverse (F d − ) directions.…”

“…The method for determining the optical indices of biotissues with the aid of the 3-flux model is described in more detail in [7,8].…”