Heat diffusion and ablation front dynamics in Er:YAG laser skin resurfacing

Deep coagulation of dermal collagen with repetitive Er:YAG laser irradiation

“…At the lower pulse fluence of 1.1 J/cm 2 , coagulation was observed to extend deeper than at 1.4 J/cm 2 . This finding has been predicted theoretically for the ablation regime [7,8,21] and can be explained by the reduced ablation efficiency at lower fluences, which results in a larger deposition of heat in tissue underneath the ablation crater. This effect is most likely exaggerated by thermal buildup during the high-repetition-rate irradiation sequence, which desiccates the tissue between subsequent laser pulses and deprives it of the main chromophore for Er:YAG laser radiation [11].…”

“…Therefore, one approach to achieve deep collagen coagulation is to use long laser pulses [7,8]. However, given the limitations of existing laser technology, coagulation depths beyond 30-50 m are not possible with single-pulse Er:YAG exposure.…”

Laser Skin Resurfacing: Perspectives at the Millennium

“…Systematic investigation of depth-specific ablative and thermal wounds should help elucidate this issue. 28,29 Nonablative lasers are being explored for the treatment of photodamage. Laser instrumentation and treatment techniques can be manipulated to provide varying degrees of ablation and coagulation.…”

“…8 The thermal coagulative ability of erbium:YAG lasers can be increased by reducing the fluences below the ablation threshold, or by increasing the pulse duration or repetition rate. 28,29 Nonablative lasers are being explored for the treatment of photodamage. 30,31 These systems combine topical skin cooling with deeper penetrating wavelengths to provide selective dermal heating without creating an open wound.…”