Jia Wangcun, Aguilar Guillermo, Verkruysse Wim, Franco Walfre, Nelson J Stuart
Beckman Laser Institute, University of California, Irvine, 92612, USA. 92612, USA.
Lasers Surg Med. 2006 Feb;38(2):155-62. doi: 10.1002/lsm.20255.
Although cryogen spray cooling (CSC) in conjunction with laser therapy has become the clinical standard for treatment of port wine stain (PWS) birthmarks, the current approach does not produce complete lesion blanching in the vast majority of patients. The objectives of this study are to: (1) experimentally determine the dynamic CSC heat flux when a skin phantom is preheated, and (2) numerically study the feasibility of using skin preheating prior to CSC to improve PWS laser therapeutic outcome.
STUDY DESIGN/MATERIALS AND METHODS: A fast-response thin-foil thermocouple was used to measure the surface temperature and thus heat flux of an epoxy skin phantom during CSC. Using the heat flux as a boundary condition, PWS laser therapy was simulated with finite element heat diffusion and Monte Carlo light distribution models. Epidermal and PWS blood vessel thermal damage were calculated with an Arrhenius-type kinetic model.
Experimental results show that the skin phantom surface can be cooled to a similar minimum temperature regardless of the initial temperature. Numerical simulation indicates that upon laser irradiation, the epidermal temperature increase is virtually unaffected by preheating, while higher PWS blood vessel temperatures can be achieved. Based on the damage criterion we assumed, the depth and maximum diameter of PWS vessels that can be destroyed irreversibly with skin preheating are greater than those without.
Skin preheating prior to CSC can maintain epidermal cooling while increasing PWS blood vessel temperature before laser irradiation. Numerical models have been developed to show that patients may benefit from the skin preheating approach, depending on PWS vessel diameter and depth.
尽管冷冻喷雾冷却（CSC）联合激光治疗已成为鲜红斑痣（PWS）胎记治疗的临床标准方法，但目前的治疗方式在绝大多数患者中并不能使皮损完全消退。本研究的目的是：（1）通过实验确定皮肤模型预热后动态CSC热通量，以及（2）通过数值研究在CSC之前使用皮肤预热来改善PWS激光治疗效果的可行性。
研究设计/材料与方法：使用快速响应薄箔热电偶测量CSC过程中环氧皮肤模型的表面温度及热通量。以热通量作为边界条件，采用有限元热扩散模型和蒙特卡洛光分布模型模拟PWS激光治疗。用阿累尼乌斯型动力学模型计算表皮和PWS血管的热损伤。
实验结果表明，无论初始温度如何，皮肤模型表面均可冷却至相似的最低温度。数值模拟表明，激光照射时，表皮温度升高几乎不受预热影响，而PWS血管温度可更高。基于我们假设的损伤标准，皮肤预热时可不可逆破坏的PWS血管深度和最大直径大于未预热时。
CSC之前进行皮肤预热可在激光照射前维持表皮冷却并提高PWS血管温度。已开发的数值模型表明，根据PWS血管直径和深度，患者可能从皮肤预热方法中获益。
