Laser-tattoo removal - A study optimal treatment strategy via of the mechanism and the computer simulations
Laser-tattoo removal - A study optimal treatment strategy via of the mechanism and the computer simulations
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DOI：
10.1002/lsm.10065
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发表时间：
2002-01-01
影响因子：
2.4
通讯作者：
Young, DA
中科院分区：
文献类型：
--
作者：
Ho, DDM;London, R;Young, DA
背景和目的：激光-纹身相互作用的物理机制和纹身颗粒破碎过程还没有很好的理解。这项研究调查是否可以通过计算机模拟来识别破碎过程的机制，并提出了一种治疗策略，可以最大限度地减少对周围组织的附带损害。注意，“去除”纹身颗粒在这里被定义为分裂成更小的颗粒，其尺寸接近或小于可见光波长，使得它们变得不那么可见。研究设计/材料和方法：辐射流体动力学代码LATIS用于建模。我们首先确定石墨纹身颗粒内部产生的拉伸应力的大小作为激光脉冲长度和颗粒尺寸的函数。然后，我们计算的表面激光能量密度（定义为时间积分的能量通量）和纹身颗粒的拉伸强度之间的关系，在一个给定的depth.Results：如果激光脉冲长度是足够短的，强的声波与拉伸强度超过石墨的断裂阈值产生。波的强度随着颗粒尺寸减小而减小，并且随着激光脉冲长度减小而增大。模拟结果与临床研究基本一致。虽然纹身颗粒的温度从未达到熔点，但可以在颗粒周围形成空化气泡。产生的水蒸气可以进入裂解颗粒并引起水蒸气-碳反应。激光能量密度随着趋肤深度的增加而迅速减小。因此，最小的表面激光能量密度，对于一个给定的脉冲长度，需要打破纹身颗粒在一个给定的皮肤深度，增加与粒子depth.Conclusions：计算机模拟证实，纹身颗粒的分裂是光声的。对于相同量的激光能量，较短的脉冲更有效。最佳脉冲长度约为10-100皮秒，以使激光能量密度和附带损伤最小化。粉碎直径小于10 nm的最小纹身颗粒更困难;然而，较小的颗粒不太重要，因为它们不太可见。纹身颗粒周围的组织可能会被空化气泡损坏。这些气泡可能是治疗后在整个真皮中观察到的灰白色病变中空泡的原因。可以诱导蒸汽-碳反应。由于这种反应，颗粒然后变得非常透明。对于不同深度的色素应使用不同的激光强度，以尽量减少对真皮的附带损伤。(C)2002 Wiley-Liss，Inc.
Background and Objective: The physical mechanisms for laser-tattoo interactions and the tattoo particle breakup process are not well understood. This study investigates whether the mechanism of the breakup process can be identified via computer simulations and proposes a treatment strategy that can potentially minimize the collateral damage to the surrounding tissues. Note that the "removal" of tattoo particles is defined here as breakup of particles into smaller ones with sizes approaching or smaller than the visible wavelength of light so that they become less visible.Study Design/Materials and Methods: The radiation-hydrodynamics code LATIS is used for the modeling. We first identify the magnitude of the tensile stress generated inside graphite tattoo particles as functions of laser pulse length and particle size. We then calculate the relationship between the surface laser fluence (defined as the time integrated energy flux) and the tensile strength of the tattoo particle at a given depth.Results: If the laser pulse length is sufficiently short, strong acoustic waves with tensile strengths exceeding the fracture thresholds for graphite are generated. The strength of the wave decreases with particle size and increases as the laser pulse length decreases. Simulation results are in general agreement with clinical studies. Although temperatures of the tattoo particles never reach the melting point, a cavitation bubble around the particle can be formed. The steam generated can get into the cracked particles and induce steam-carbon reactions. Laser energy density decreases rapidly with the skin depth. Therefore, the minimum surface laser fluence, for a given pulse length, required for breaking up tattoo particles at a given skin depth, increases with particle depth.Conclusions: Computer simulations confirm that the breakup of tattoo particles is photoacoustic. For the same amount of laser energy, a shorter pulse is more efficient. The optimal pulse length is approximately 10-100 pico-second to minimize the laser fluence and the collateral damage. It is more difficult to break up the smallest tattoo particles that have diameters smaller than 10 nm; however, smaller particles are less important because they are less visible. Tissue surrounding the tattoo particles can be damaged by cavitation bubbles. These bubbles could be the cause of the empty vacuoles in the ash-white lesions throughout the dermis seen after treatment. Steam-carbon reactions can be induced. Particles then become grossly transparent because of this reaction. Different laser intensity should be used for pigments at different depths in order to minimize the collateral damage to the dermis. (C) 2002 Wiley-Liss, Inc.