Introduction: Heat distribution and 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, we simulated the heat distribution and thermal damage patterns of CO2 fractional lasers for different spot sizes, pulse durations, and powers to optimize the laser procedure.

Methods: COMSOL software was used for the simulations. The skin was modeled as three homogenous layers of epidermis/dermis/hypodermis. Opto-thermal coefficients of the components and the radiant parameters of the laser (CO2, 10600 nm- Deka) were defined.

Results: Our results show that power of 10w with different time pulses creates a better microtunnel in the tissue while preventing unwanted injuries. At a power higher than 15 watts and 5 pulses, the tissue will be damaged inconsiderably. Fractional laser creates heat only at the desired point of the treatment, and this heat is absorbed through the tissue, and microtunnels in it form the tissue. Also, 10w power with a low time width does not have a good effect on the tissue, but with an increase in the pulse width, it causes less damage to the surroundings. With a power higher than 15w, fractional laser irradiation creates wider microtunnels which might damage the tissue due to the adjacent microtunnels.

Conclusions: Due to the absorbed laser light in tissue and the creation of the heat, skin damage as microtunnels is caused. The greater the distance between the laser irradiation, the better the microtunnels will be created. Also, COMSOL seems to be promising software for preclinical investigations and optimizing laser treatment plans.