Optical properties of tissues after laser treatments in the wavelength range of 350 - 1000 nm

Abstract

In laser medicine, the accurate knowledge about the optical properties of target tissue is important for the understanding prediction of propagation and distribution of light in tissues. Light propagations, absorption and scattering, changes by the kinetic changes of optical properties in laser irradiations. This problem is clinically very important for the realization of safe laser treatments because the understandings of optical properties by several laser parameters can realize the pre-estimated treatment effects. The objective of this study is determination of the optical properties of treated tissues for the safe laser treatments. In this paper, we examined to determine the optical properties changes of a coagulated tissue after the Er:YAG laser irradiations by using double integrating sphere system and inverse adding-doubling method in the wavelength range of 350 - 1000 nm. After laser irradiations with a variety of irradiation parameters, the absorption coefficient of a treated tissue decreased and the reduced scattering coefficient of a treated tissue increase. In carbonization, observed in 30 sec-300 mJ irradiation, the absorption coefficient of a treated tissue re-increased and the reduced scattering coefficient of a treated tissue re-decrease. The changes of optical properties should be accounted for while planning the therapeutic procedure for the realization of safe laser treatments.