Tissue Optics and Photonics: Light-Tissue Interaction

Abstract

Abstract. This is the second section of the review-tutorial paper describing fundamentals of tissue optics and photonics. As the first section of the paper was mostly devoted to description of biological tissue structures and their specificity related to interactions with light [1], this section 3 describes light-tissue interactions themselves that are caused by tissue dispersion, scattering, and absorption properties, including light reflection and refraction, absorption, elastic, and quasi-elastic scattering. The major tissue absorbers and modes of elastic scattering, including Rayleigh and Mie scattering, will be presented. © 2015 Samara State Aerospace University (SSAU).

Tissue Optics and Photonics: Light-Tissue Interaction II

“…In clinical studies the effectiveness of ischemic stroke treatment in humans was shown when initiated within 24 hours of stroke onset at the application of a hand-held 808-nm laser probe to twenty predetermined locations on the shaved scalp for 2 min in each location with the predicted power density of ∼10-15 mW/cm 2 on the dura mater. The light-induced regeneration of the crushed rat facial nerves was found to be the best for 633-nm laser with the dosage of 162.4 J/cm 2 comparing with the other wavelengths tested, such as 361, 457, 514, 720, and 1064 nm. Phototherapy can progressively improve nerve function, and can be used in patients with longterm peripheral nerve injury at 780-nm laser treatment.…”

“…where χ (2) is the second order nonlinear susceptibility, E(ω) and τ p are the laser pulse energy and width, respectively. As in two-photon fluorescence (see Eq.…”

“…The macroscopic value χ (2) can be expressed in terms of the first molecular hyperpolarizability β M as …”

“…The first part of the paper was mostly devoted to description of tissue structures and their specificity related to interactions with light [1]. The second part presented light-tissue interactions originated from tissue dispersion, scattering, and absorption properties, including light reflection and refraction, absorption, elastic, and quasi-elastic scattering [2]. This last part of the paper, underlines mostly photothermal and nonlinear interactions such as temperature rise and tissue damage, photoacoustic and acoustooptical, nonlinear sonoluminescence, Raman scattering, multiphoton autofluorescence, second harmonic generation (SHG), terahertz (THz) radiation interactions, and finally photochemical interactions with description of two widely spread therapeutic applications: photodynamic therapy (PDT) and low level light therapy (LLLT).…”

OCT study of skin optical clearing with preliminary laser ablation of epidermis

“…Skin has a complex inhomogeneous structure causing a strong light scattering, which limits the optical methods applicability to the diagnostics and treatment of various diseases [1,2]. The development of methods enhancing the optical clearing of skin is an urgent problem that has been a subject of multiple studies [3,4].…”