In Silico Evaluation of Nanosecond Laser Treatment of Pigmented Lesions Based on Skin Optical Properties Using a Model of Melanosome Disruption Threshold Fluence.

Objectives: This study aimed to evaluate the efficacy and safety of nanosecond laser treatment of pigmented lesions in silico using a model of melanosome disruption threshold fluence (MDTF) based on skin optical properties.

Methods: Particle size analysis and scanning electron microscopy were performed to determine the threshold fluence for melanosome disruption using a nanosecond laser. By inputting the obtained threshold fluence into the MDTF model and considering the variability in skin optical properties, irradiation parameters were calculated and compared with the results from clinical studies.

Results: The threshold fluences for 532 and 755 nm nanosecond laser irradiation were determined to be 3.0 and 15.0 J/cm², respectively. In silico analysis showed that the incident fluence for moderately pigmented skin should be 1.2 times that for lightly pigmented skin, whereas it should be 50% lower than that for lightly pigmented skin to achieve the same level of energy deposition. Clinically applied fluences for moderately pigmented skin are at the low end of the calculated range of values, suggesting that the clinical fluence is chosen to minimize energy deposition in normal tissues.

Conclusions: Our results showed that the MDTF model can be used to evaluate nanosecond laser treatments and provide clinical guidance on fluence settings based on laser-tissue interactions in moderately pigmented skin. The in silico method can, therefore, provide a robust and quantitative retrospective evaluation of the treatment effects that accounts for variation in irradiation parameters among patients by combining the MDTF model with the in vivo optical properties of individual skin types.