Association of Liver Tissue Optical Properties and Thermal Damage

Abstract

Background and Objectives 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 (µa) and the reduced scattering coefficient ( μ s ′) during heating of a porcine liver at 100°C follows a sigmoidal growth curve. Therefore, we concluded that increases in the tissue µa and μ s ′ during thermocoagulation were correlated with true thermal damage. The goal of this study was to determine if increases in the tissue µa and μ s ′ during thermocoagulation are correlated with true thermal damage. Study Design/Materials and Methods In this paper, continuously measured values of µa and μ s ′ 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). Results 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). Conclusion The results indicate that relative changes in µa and μ s ′ 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.

Temperature induced changes in the optical properties of skin in vivo

“…Therapeutic and surgical applications of light often cause an increase in temperature 1 – 13 , which may alter the optical properties of target and adjacent organs. Such changes have been reported in several tissues, including adipose 14 , brain 15 , 16 , skin 17 – 19 , prostate 20 , and liver 21 – 23 . Thus, there is a great need to examine dependence of the optical properties on tissue temperature.…”

“…Thus, there is a great need to examine dependence of the optical properties on tissue temperature. Several groups investigated the impact of freezing or heating on the ex vivo optical properties 14 , 17 , 19 – 23 . In vivo studies are rare and often restricted to narrow wavelength ranges 24 – 27 .…”

Hyperspectral image-based analysis of thermal damage in living liver undergoing laser ablation

“…Indeed, H2O experiences a decrease during the whole procedure reaching a minimum value of around 50% at 110° C. After switching off the laser, a plateau is achieved for the three tissue elements corresponding to an advanced stage for thermal damage. Previous works showed the possibility to detect chemical and structural changes in tissue undergoing thermal ablation with spectroscopy [18] [19] [20] [21]. In the investigations, they used a probe inserted into the tissue in order to collect optical tissue response.…”

Photoacoustic Spectral Sensing Technique for Diagnosis of Biological Tissue Coagulation: In-Vitro Study

“…Since tissues undergo drastic changes in cellular conformation during thermal coagulation, the mechanobiological property also alters significantly [2,23,24]. For laser-induced thermal coagulation of tissues, we used the optical fluence of 100 mJ/cm 2 for 1 min (i.e., 600 laser pulses).…”