Determination of optical property changes by laser treatments using inverse adding-doubling method

Abstract

It is widely recognized for the realization of the pre-estimated treatment effects that the knowledge about the optical properties of the target tissues used to understanding the prediction of propagation and distribution of light within tissues would suffer from the technical problem such as the kinetic changes of the optical properties in laser irradiation. In this study, the optical properties of normal and laser coagulated chicken breast tissues and porcine intervertebral disks, normal and laser ablation have been determined in vitro in the spectral range between 350 and 1000 nm. In addition, the optical properties of the normal and photodynamic therapy (PDT) treated tumor, Lewis lung carcinoma, tissues have been determined. Diffuse reflectance and total transmittance of the samples are measured using an integrating-sphere technique. From these experimental data, the absorption coefficients and the reduced scattering coefficients of the samples are determined employing an inverse adding-doubling method. Laser coagulations and ablations have clearly increased the reduced scattering coefficient and slightly reduced the absorption coefficient. PDT treatment has increased absorption and reduced scattering coefficient. It is our expectation that these data will provide fundamental understandings on laser irradiation interactions behavior with tissues. The changes of the optical properties should be accounted for while planning the therapeutic procedure for the realization of safe laser treatments.