Jožef Stefan Institute, Complex matter, Ljubljana, Slovenia.
Faculty of Mathematics and Physics, Medical Physics, University of Ljubljana, Ljubljana, Slovenia.
Lasers Surg Med. 2024 Jan;56(1):107-118. doi: 10.1002/lsm.23739. Epub 2023 Nov 16.
Erbium lasers have become an accepted tool for performing both ablative and non-ablative medical procedures, especially when minimal invasiveness is desired. Hard-tissue desiccation during Er:YAG laser procedures is a well-known phenomenon in dentistry, the effect of which is to a certain degree being addressed by the accompanying cooling water spray. The desiccation of soft tissue has attracted much less attention due to the soft tissue's high-water content, resulting in a smaller effect on the ablation process.
In this study, the characteristics of skin temperature decay following irradiations with Er:YAG laser pulses were measured using a fast thermal camera.
The measurements revealed a substantial increase in temperature decay times and resulting thermal exposure times following irradiations with Er:YAG pulses with fluences below the laser ablation threshold. Based on an analytical model where the skin surface cooling time is calculated from the estimated thickness of the heated superficial layer of the stratum corneum (SC), the observed phenomena is attributed to the accelerated evaporation of water from the SC's surface. By using an Arrhenius damage integral-based variable heat shock model to describe the dependence of the critical temperature on the duration of thermal exposure, it is shown that contrary to what an inexperienced practitioner might expect, the low-to-medium level fluences may result in a larger thermal damage in comparison to treatments where higher fluences are used. This effect may be alleviated by hydrating the skin before Er:YAG treatments.
Our study indicates that tissue desiccation may play a more important role than expected for soft-tissue procedures. It is proposed that its effect may be alleviated by hydrating the skin before Er:YAG treatments.
铒激光已成为执行烧蚀和非烧蚀医疗程序的一种公认工具，尤其是在需要微创性时。在牙科中，Er:YAG 激光程序中的硬组织干燥是众所周知的现象，其影响在一定程度上可以通过伴随的冷却水喷雾来解决。由于软组织的高含水量，软组织的干燥受到的关注要少得多，这对烧蚀过程的影响较小。
在这项研究中，使用快速热像仪测量了 Er:YAG 激光脉冲照射后皮肤温度衰减的特性。
测量结果表明，在低于激光烧蚀阈值的 Er:YAG 脉冲照射下，温度衰减时间和由此产生的热暴露时间会显著增加。基于一种分析模型，该模型通过计算从角质层（SC）的受热浅层估计的皮肤表面冷却时间来计算，观察到的现象归因于 SC 表面的水加速蒸发。通过使用基于 Arrhenius 损伤积分的可变热冲击模型来描述临界温度对热暴露时间的依赖性，结果表明，与经验不足的从业者可能预期的相反，低至中等水平的辐照度可能会导致比使用更高辐照度的治疗更大的热损伤。在 Er:YAG 治疗前给皮肤补水可以缓解这种影响。
我们的研究表明，组织干燥在软组织手术中可能比预期的更重要。建议在 Er:YAG 治疗前给皮肤补水以缓解其影响。
