<title>Heat-induced changes of the optical properties of liver tissue</title>

Abstract

For prediction of the effectiveness of laser-induced thermotherapy of liver metastases and for the understanding and optimal use of laser applications in medicine, especially for dosimetrical questions, the knowledge of the specific optical properties and their thermo-induced changes is important. In our study we were able to evaluate the optical properties of human liver tissue and metastatic tissue. Furthermore, we investigated the dynamic temperature behavior between 45 degree(s)C and 80 degree(s)C at three different exposure times using a double-integrating sphere system. We found significant differences between normal and metastatic tissue resulting in a higher optical penetration depth in the tumorous tissue. During the coagulation the absorption coefficient, anisotropy and optical penetration depth decreased significantly in the temperature range from 45 degree(s)C to 65 degree(s)C, whereas the scattering coefficient increased. Above and below this temperature range the changes of the optical properties were not significant. The coagulation rate differed between the exposure times.