Basic Research on Real-time Evaluating of Thermal Damage of Tissues by Visible-Near Infrared Spectra

The feasibility of evaluation thermal damage in real time by Visible-Near Infrared (V-NIR) spectroscopy is investigated. Thermal damage are produced in fresh porcine livers in vitro by laser (808nm, 5W). The V-NIR spectra (330-1100 nm) at distances of 4, 8 and 12 mm from the center of the damage are acquired respectively, and diffused light intensities at 720 nm (Rd720) are chosen as the evaluation factors. The results show that Rd720 increases quickly with tissue's temperature going up at the beginning of heating. After an effective damage is attained, temperature continues going up while Rd720 reaches a stable state if keeping heating. After the laser is turned off, temperature gradually returns to room temperature, meanwhile, Rd720 decreases slightly and remains almost a constant which is far higher than its value at the beginning. In conclusion, the intensity of diffused V-NIR light intensity can be used as an important parameter to real-time assess the thermal damage of biological tissues.