Thermal response of XXXX skin epidermis to 595-nm laser irradiation at high incident dosages and long pulse durations in conjunction with cryogen spray cooling: an ex-vivo study.

@entity75 @entity1 @entity130
BACKGROUND AND OBJECTIVES: Improved laser treatment of @entity75 is expected by utilizing higher incident dosages, longer pulse durations and longer wavelengths than those currently used in clinical settings. However, simply increasing the incident dosage will also increase the risk of nonspecific @entity130 to the epidermis due to light absorption by melanin. In this study, we investigated the thermal response of @entity1 skin epidermis to 595-nm wavelength laser irradiation at high incident dosages (up to 20 J/cm(2)) and long pulse durations (up to 40 milliseconds) in conjunction with cryogen spray cooling (CSC) using ex-vivo @entity1 skin samples. STUDY DESIGN/MATERIALS AND METHODS: The Candela V-beam trade mark laser (595-nm wavelength) was used in the experiments. Ex-vivo @entity1 skin samples (Fitzpatrick types I-VI) were irradiated at the incident dosages D(0) = 4, 6, 10, 15, and 20 J/cm(2), laser pulse durations tau(laser) = 1.5, 10, and 40 milliseconds, without and with CSC (refrigerant-134A, spurt duration tau(CSC) = 100 milliseconds). @entity130 to the epidermis was evaluated by histological observations. RESULTS: Under the same incident dosage, longer pulse durations led to reduced @entity130 to the epidermis. Without CSC, no demonstrable @entity130 to the epidermis was observed in skin types I-II irradiated at the incident dosage as high as 15 J/cm(2), and in skin types III-IV at 10 J/cm(2). When CSC was applied, no evidence of @entity130 to the epidermis was present in skin types I-II even when irradiated at the maximum available incident dosage of the laser system (20 J/cm(2)). In skin types III-IV, no demonstrable @entity130 to the epidermis was observed when using incident dosage as high as 15 J/cm(2) in conjunction with CSC. In skin type VI, @entity130 to the epidermis could not be avoided even at the setting D(0) = 4 J/cm(2), tau(laser) = 40 milliseconds in conjunction with CSC. CONCLUSIONS: For a given incident dosage, longer pulse durations help reduce @entity130 to the epidermis. When a 100-millisecond cryogen spurt is applied, @entity130 to the epidermis can be prevented in ex-vivo skin types I-IV when irradiated at higher incident dosages (15-20 J/cm(2)) than those currently used in clinical settings. Further studies on optimizing the CSC parameters in conjunction with the laser irradiation parameters are needed to protect skin types V-VI from @entity130 to the epidermis.
