Association of Liver Tissue Optical Properties and Thermal Damage

Complete thermocoagulation of tumors is vital to minimize the risk of local tumor recurrence after a thermal ablation. Histological assessments are not real-time and require experienced pathologists to grade the thermal damage (histopathology) [Correction added on 21 January, 2020 after first online publication: After thermal damage in the preceding sentence, (histopathology) was added]. Real-time assessment of thermal tissue damage during an ablation is necessary to achieve optimal tumor ablation. In our previous studies, we found that continuous monitoring of the wavelength-averaged (435-630 nm) tissue absorption coefficient (µ_a ) and the reduced scattering coefficient ( $$ ) during heating of a porcine liver at 100°C follows a sigmoidal growth curve. Therefore, we concluded that increases in the tissue µ_a and $$ during thermocoagulation were correlated with true thermal damage. The goal of this study was to determine if increases in the tissue µ_a and $$ during thermocoagulation are correlated with true thermal damage.

In this paper, continuously measured values of µ_a and $$ during heating of the porcine liver tissue were compared with the histology-assessed thermal damage scores at four different temperature points (37°C, 55°C, 65°C, and 75°C).

The damage scores for the tissues in Group 3 (65°C) and Group 4 (75°C) were significantly different from each other and from the other groups. The damage scores were not significantly different between Group 1 (37°C) and Group 2 (55°C).

The results indicate that relative changes in µ_a and $$ can be used to classify thermal damage (histopathology) scores with an overall accuracy of 72.5% up to 75°C. [Correction added on 21 January, 2020 after first online publication: After thermal damage in the preceding sentence, (histopathology) was added]. Lasers Surg. Med. © 2019 Wiley Periodicals, Inc.