A simulation-based optical safety framework for dermatologic laser wavelength selection across Fitzpatrick skin...

Area of Science:

• Dermatology and Biomedical Optics
• Computational Modeling and Simulation
• Photomedicine

Background:

• Laser wavelength selection in dermatology is complex, with risks of epidermal injury, especially in darker skin phototypes.
• Inappropriate wavelength choices can lead to adverse events due to varying light absorption and energy deposition in skin layers.
• Quantifying optical safety across different skin types is essential for guiding clinical laser use.

Purpose of the Study:

• To develop and validate a simulation-based optical safety framework for dermatologic laser wavelength selection.
• To quantify phototype-dependent epidermal energy deposition and dermal-to-epidermal energy balance.
• To identify optimal laser wavelengths for enhanced safety and efficacy across Fitzpatrick skin types I-VI.

Main Methods:

• Utilized a Monte Carlo light-transport model to simulate photon propagation in a three-layer skin model.
• Evaluated four common dermatologic laser wavelengths (532, 755, 808, and 1064 nm) across Fitzpatrick skin types I-VI.
• Quantified epidermal thermal risk using the Epidermal Thermal Risk Index (ETRI) and dermal-to-epidermal energy balance using the Benefit-Risk Ratio (BRR).

Main Results:

• Shorter wavelengths (e.g., 532 nm) showed significantly higher epidermal energy deposition, increasing with melanin content in higher phototypes.
• The 1064 nm wavelength consistently exhibited the lowest ETRI values across all skin phototypes.
• A robust composite score, integrating safety and energy balance, favored 1064 nm across all phototypes, confirmed by sensitivity analysis.

Conclusions:

• The developed simulation framework provides interpretable guidance for selecting dermatologic laser wavelengths based on optical safety.
• Longer wavelengths, particularly 1064 nm, demonstrate the most favorable epidermal safety profile and energy balance for diverse skin phototypes.
• This framework serves as relative optical safety guidance, requiring integration with clinical factors like treatment indication and device settings.