CO2 Fractional Laser Induced Skin Micro-Tunnel Thermal Damage Patterns: A Simulation Study.

Introduction: The heat distribution and the resulting thermal damage pattern following the light absorption in tissue can be used for treatment optimization. Besides rejuvenating effects, CO2 fractional-induced microtunnels have recently become a tool for drug delivery. To minimize the unwanted thermal damage in this latter use and to optimize the laser program, we simulated the heat distribution and thermal damage models of CO2 fractional lasers of different sizes, pulse durations, and powers. Methods: COMSOL software is used for simulation. The skin is modeled as three homogeneous layers of epidermis/dermis/hypodermis. The photothermal coefficient of the tissue model and the irradiation laser system (CO2, 10600 nm) are defined as 0.07 mm spot size, 10, 12 and 15 W power range, and 0.5, 10 and 15 ms pulse durations, respectively. Results: Our results show that the power of 10 W with different time pulses creates a better micro-tunnel in the tissue while preventing unwanted injuries. At a power higher than 15 W and 5 pulses, the tissue will be damaged inconsiderably. The fractional laser creates heat only at the desired point of the treatment, and this heat is absorbed through the tissue, and micro-tunnels in it form the tissue. Also, 10 W power with a shorter pulse duration did not have a good effect on the tissue. Instead, by increasing the pulse duration, less damage to the surroundings resulted. Conclusion: Due to the absorbed laser light in tissue and the creation of heat, skin damage as micro-tunnels are caused. The greater distance between the created micro-tunnels indicates better tissue preservation. Also, COMSOL seems to be promising software for preclinical investigations and optimizing laser treatment plans.