Copyrighted Material - Taylor & Francis

Light interactions with biological tissues and fluids can be categorized into two large classes of biological media: (1) strongly scattering (opaque) with skin, brain, vessel walls, eye sclera, blood, and lymph, and (2) weakly scattering (transparent) with cornea, crystalline lens, vitreous humor, and aqueous humor of the front chamber of the eye.1–7 Light interactions with tissues of the first class can be described as a model of multiple scattering of scalar or vector waves in a randomly nonuniform medium with absorption. Interactions with tissues of the second class can be described as a model of single (or low-step) scattering of an ordered isotropic or anisotropic medium with closely packed scatterers made from material with absorptive properties. The surrounding medium could also be considered to have refractive and absorptive properties. The transparency of tissues reaches its maximum in the near infrared (NIR), which is associated with the fact that living tissues do not contain strong intrinsic chromophores that can absorb radiation within this spectral range.1–7 Light penetrates into a tissue over several centimeters, which is important for the transillumination of thick human organs (brain, breast, etc.). However, in spite of scattering decay with the increase in wavelength, tissues are still characterized by rather strong scattering of NIR radiation. This prevents one from obtaining clear images of localized inhomogeneities arising in tissues 3