Histological Study of Skin Damage by 2.0 μm Laser Irradiation

摘要

The aim of this study was to determine the histopathologic effect on the skin of 2.0 μm wavelength laser with various exposure conditions 48 hours after irradiation. Histological sections of lesions were created at, below and beyond the threshold for grossly apparent thermal lesions. These lesions were studied to 1)identify and define the microscopically apparent threshold lesions, 2)determine the mechanisms producing the gross and microscopic threshold lesions in the skin, and 3)map the extent and severity of the lesions. Grossly apparent threshold lesion were defined as persistent surface redness at 48 hours. Histologically, these lesions showed relatively severe thermal damage in both the epidermis and the dermis. Damage included death and necrosis of the epidermal cells and endothelial necrosis, intravascular thrombosis as well as perivascular edema and inflammation in dermal blood vessels. The collagen bundles below the epidermis were slightly swollen but there was no change in birefringence image intensity. For each threshold lesion, three quantitative parameters were measured to map the extent of thermal damage: 1) the width of necrotic epidermis, 2) the depth measured from the epidermal/dermal junction to the deepest extent of thrombosis, and 3) the depth measured from the epidermal/dermal junction to the deepest extent of perivascular inflammation and edema. Birefringence change of dermal collagen which occurred at powers above threshold was another measurable damage marker which indicated coagulation of collagen bundles.These quantitative histopathologic data for skin damage associated with the transient temperature profiles and irradiation parameters provided important information to mathematically derive rate process coefficients for thermal damage and formulate mathematical tissue damage models for each cutaneous damage effect.