Some ways to optimize optical imaging of tumor-like inclusions in biological tissues

摘要

We use the diffusion approximation to the radiative transfer equation and the respective analytical relations to theoretically treat the imaging of phantom biological tissue with an inclusion under external illumination. The horizontal inhomogeneity of the scattering and absorbing tissue medium owing to the inclusion is taken into account. Several measuring setups are computationally considered to investigate their advantages and drawbacks under the sounding of inclusions by reflected and transmitted light. We varied the absolute and respective values of the absorption coefficients of the inclusion and surrounding tissue to illustrate the imaging of "clear" and "dark" inclusions through the turbid medium. The comparison is made with the so-called base scheme when a narrow laser beam illuminates the medium and narrow-angle receiver records reflected radiation at some distance or base from the light source. A simple formula to calculate the image contrast of a small inclusion is proposed to relate optical and geometrical properties of the inclusion with the contrast observed. We illustrate the computations by experimental spectral absorption and extinction curves to enable one an opportunity to estimate some advantages while searching and changing the operational range of wavelengths utilized to sound a tumor inside normal tissue.