Light-Tissue Interactions BT - Biophotonics: Concepts to Applications

Abstract

A fundamental challenge in biophotonics is to understand the interaction of light with multilayered, multicomponent, and optically inhomogeneous biological tissues. The effects of light-tissue interactions include reflection and refraction when light encounters different tissue types, absorption of photon energy, and multiple scattering of photons. Light absorption determines how far light can penetrate into a specific tissue. It depends strongly on wavelength and is important in the diagnosis and therapy of abnormal tissue conditions. Scattering of photons in tissue is another significant factor in light-tissue interactions. Together, absorption and multiple scattering of photons cause light beams to broaden and decay as photons travel through tissue. Light can interact with biological tissue through many different mechanisms, including photobiomodulation, photochemical interactions, thermal interactions (e.g., coagulation and vaporization), photoablation, plasma-induced ablation, and photodisruption. Two key phenomena used in tissue analyses are random interference patterns or speckle fields and the principles of fluorescence.