Thermal damage induced changes in optical properties of the porcine dermis.

Significance: Understanding thermal effects on tissue optical properties is fundamental for optimizing laser-based medical interventions. We address the critical knowledge gap of temperature-dependent changes in porcine dermis optical properties.

Aim: We explore the thermal damage influence on the excised dermis optical properties at wavelengths from 400 to 1100 nm.

Approach: Using a double-integrating-sphere system and inverse adding-doubling, we determined absorption, ${\mu }_a$ , and reduced scattering, ${\mu }_s^{\text{'}}$ , coefficients before and after a 2.5-min thermal exposure.

Results: We observed non-linear changes in both ${\mu }_a$ and ${\mu }_s^{\text{'}}$ across temperature regimes. Minimal changes occurred at 37°C and 43°C. At 50°C, slight increases in both coefficients were observed. Significant alterations occurred at 60°C, with substantial increases in ${\mu }_s^{\text{'}}$ and variable changes in ${\mu }_a$ depending on wavelength region. At 70°C, ${\mu }_s^{\text{'}}$ values remained elevated, whereas ${\mu }_a$ showed mixed responses, with some wavelength regions decreasing, indicating progressive structural breakdown. The Arrhenius damage model showed an exponential increase with temperature.

Conclusions: We reveal complex thermal-induced changes in tissue optical properties, particularly at higher temperatures. Findings reinforce a critical threshold between 50°C and 60°C where significant changes occur. The non-linear, wavelength-dependent responses emphasize the need for comprehensive data in laser-tissue interaction modeling, with important implications for optimizing laser-based medical treatments.