A new mathematical approach to the diffusion approximation theory for selective photothermolysis modeling and its implication in laser treatment of port-wine stains
A new mathematical approach to the diffusion approximation theory for selective photothermolysis modeling and its implication in laser treatment of port-wine stains
复制标题
DOI：
10.1002/lsm.20028
复制
发表时间：
2004-01-01
影响因子：
2.4
通讯作者：
Waner, M
中科院分区：
文献类型：
--
作者：
Shafirstein, G;Bäumler, W;Waner, M
背景和目标：光-组织相互作用的蒙特卡罗（MC）模拟和扩散近似理论的解析解已被用于确定最佳激光波长和辐射曝光来治疗葡萄酒色斑（PWS）。这两种方法都表明，最佳参数是585或595 nm的波长，脉冲时间为0.45-20毫秒。然而，哪些参数是最佳的仍然不清楚。由于血管尺寸和血管内温度分布的差异似乎是对相同激光治疗的不同反应的主要原因，我们试图开发一种扩散近似的解决方案，以计算特定血管内的温度分布和由此产生的凝固模式。研究设计/材料和方法：采用有限元法同时求解光、热扩散方程。蒸发潜热包括在热分析中。计算了585和595 nm激光波长下，在异质介质中特定血管的温度和凝血模式，并结合临床参数。在1.2 mm深处，计算预测直径为50 - 100 μ m的血管将从上到下凝固，小血管（10 μ m）将被保留，并且大于150 μ m的血管将被部分凝固。与585 nm波长相比，595 nm波长的血管凝固更均匀。最高温度不超过100degreesC，因为列入潜热在thermal calculation.Conclusions：研究激光治疗PWS的扩散近似，有限元法是一种有效的方法来计算特定血管内的凝血模式。为了提高585和595 nm波长下的凝血功效，应在不增加辐照度的情况下增加辐射暴露。(C)2004 Wiley-Liss，Inc.
Background and Objectives: Monte Carlo (MC) simulations of light-tissue interactions and analytical solutions for the diffusion approximation theory have been used to determine the optimal laser wavelength and radiant exposure to treat port-wine stains (PWS). Both approaches suggest that optimal parameters are a wavelength of 585 or 595-nm with pulse times of 0.45-20 milliseconds. However, which parameters are optimal is still unclear. As differences in vessel size and in temperature distribution within vessels appeared to be the main reasons for the varied responses to the same laser treatments, we sought to develop a solution to the diffusion approximation in order to calculate temperature distribution and the resulting coagulation pattern within specific blood vessels.Study Design/Materials and Methods: The light and heat diffusion equations were simultaneously solved with the finite element method (FEM). The latent heat of evaporation was included in the thermal analysis. The temperature and coagulation patterns across specific blood vessels, within a heterogeneous medium, were calculated for laser wavelengths of 585 and 595-nm with clinical parameters.Results: At 1.2 mm deep, the calculations predicted that vessels ranging from 50 to 100 pm in diameter would be coagulated from top to bottom, small vessels (10 pm) would be spared, and vessels larger than 150 mum would be partially coagulated. Coagulation across vessels was more uniform for the 595-nm than for the 585-nm wavelength. Maximal temperatures did not exceed 100degreesC because of the inclusion of latent heat in the thermal calculations.Conclusions: To study laser treatments of PWS with the diffusion approximation, FEM is an effective method to calculate the coagulation patterns within specific blood vessels. To improve coagulation efficacy at 585 and 595-nm wavelengths, the radiant exposure should be increased without increasing the irradiance. (C) 2004 Wiley-Liss, Inc.