Majaron B, Verkruysse W, Kelly K M, Nelson J S
Beckman Laser Institute and Medical Clinic, University of California, Irvine, California 92612, USA.
Lasers Surg Med. 2001;28(2):131-7. doi: 10.1002/lsm.1027.
To analyze the effects of laser pulse duration and cryogen spray cooling (CSC) on epidermal damage and depth of collagen coagulation in skin resurfacing with repetitive Er:YAG laser irradiation.
STUDY DESIGN/MATERIALS AND METHODS: Evolution of temperature field in skin is calculated using a simple one-dimensional model of sub-ablative pulsed laser exposure and CSC. The model is solved numerically for laser pulse durations of 150 and 600 microsec, and 6 msec cryogen spurts delivered just prior to ("pre-cooling"), or during and after ("post-cooling") the 600 microsec laser pulse.
The model indicates a minimal influence of pulse duration on the extent of thermal effect in dermis, but less epidermal damage with 600 microsec pulses as compared to 150 microsec at the same pulse fluence. Application of pre- or post-cooling reduces the peak surface temperature after laser exposure and accelerates its relaxation toward the base temperature to a different degree. However, the temperature profile in skin after 50 msec is in either example very similar to that after a lower-energy laser pulse without CSC.
When applied in combination with repetitive Er:YAG laser exposure, CSC strongly affects the amount of heat available for dermal coagulation. As a result, CSC may not provide spatially selective epidermal protection in Er:YAG laser skin resurfacing.
分析激光脉冲持续时间和冷冻喷雾冷却（CSC）对重复铒激光皮肤磨削术中表皮损伤和胶原蛋白凝固深度的影响。
研究设计/材料与方法：使用亚消融脉冲激光照射和CSC的简单一维模型计算皮肤温度场的演变。针对150微秒和600微秒的激光脉冲持续时间以及在600微秒激光脉冲之前（“预冷却”）、期间和之后（“后冷却”）进行的6毫秒冷冻剂喷射，对该模型进行数值求解。
该模型表明脉冲持续时间对真皮热效应程度的影响最小，但在相同脉冲能量密度下，600微秒脉冲造成的表皮损伤比150微秒脉冲小。预冷却或后冷却的应用降低了激光照射后的表面峰值温度，并在不同程度上加速其向基础温度的恢复。然而，50毫秒后皮肤中的温度分布在任何一种情况下都与没有CSC的低能量激光脉冲后的温度分布非常相似。
当与重复铒激光照射联合应用时，CSC强烈影响可用于真皮凝固的热量。因此，在铒激光皮肤磨削术中，CSC可能无法提供空间选择性的表皮保护。
