Laser parameter optimization for nevus of Ota using a local non-equilibrium three-temperature heat transfer model

Laser thermal therapy based on the selective photothermolysis has been widely used for Nevus of Ota (NO) treatment, yet experience-dependent parameter selection often leads to suboptimal outcomes. With consideration of competitive absorption by hemoglobin and melanin, a local non-equilibrium three-temperature heat transfer model based on the porous medium theory was developed to investigate the interaction between normal and hyperplastic melanin, blood, and tissue under laser irradiation and optimize laser parameters for NO at varying depths. Results revealed that blood (0–20 % volume fraction) significantly reduce temperature of hyperplastic melanin due to competitive absorption, necessitating higher energy densities. The optimal energy ranges of 755 nm and 1064 nm lasers in shallow (0.06–0.5 mm), middle (1.0–2.5 mm) and deep (2.5–4 mm) NO layer ( ε m = 0.7 % and ε b = 10 %) are determined to be 0.7–3.4 J⋅cm −2 , 1.9–8.5 J⋅cm −2 and 10.2–28.1 J⋅cm −2 (755 nm), as well as 2.2–5.4 J⋅cm −2 , 3.8–9.2 J⋅cm −2 and 7.3–38.8 J⋅cm −2 (1064 nm), respectively. Based on evaluation of energy density and treatment window with varying contents of blood (0–20 %) and melanin (0.1–0.9 %), different lasers are recommended for different NO types. Validation against clinical data confirmed that energy densities falling within predicted ranges achieved higher cure rates. This result provides a theoretical foundation for personalized laser therapy and data source for clinical laser parameter selection.