Optical Parameters at 632.8 nm in Animal Tissue

Abstract

Dose in photodynamic therapy depends on the energy transport in the tissue as well as on the concentration of photosensitive substances. Knowledge about the most important optical properties in tissues (i.e., absorption and attenuation coefficient, scattering phase function, and scattering coefficient) is necessary to calculate the spatial distribution of light in tissue in vivo experiences. Several soft tissues have anisotropic scattering on the irradiation incidence axis for lasers with a short free mean path.

Using a directed method we measured the total attenuation coefficient and the scattering phase function in animal soft tissues irradiated with a 632.8 nm laser beam. The results reveal that scattering is sharply forward shaped for the tissues studied and has a medium cosine between 0.95 to 0.99. The attenuation coefficient takes values in the 10 to 100 mm⁻¹ interval.