Optical properties of native and coagulated human liver tissue and liver metastases in the near infrared range.

Background and Objective: Knowledge about optical parameters and the resultant light distribution in laser-treated tissue is important for predicting the effects of laser-induced thermotherapy of liver metastases (LITT).
Materials and Methods: The absorption and scattering coefficients as well as the anisotropy factors and the optical penetration depths of human liver tissue and colorectal liver metastases were determined at 850, 980, and 1,064 nm under native and thermocoagulated conditions.
Results: Liver metastases had a lower anisotropy factor, absorption, and scattering coefficient than healthy liver (P < 0.01), resulting in a significantly higher optical penetration depth in metastatic tissue. Coagulation significantly changes the optical parameters by reducing the optical penetration depth in both tissue types (P < 0.01).
Conclusions: A greater optical penetration depth in metastatic tissue is advantageous for LITT, since larger tumor volumes can be coagulated. At the same time, an adjustment of the application parameters during LITT is necessary to achieve optimal therapeutic success.