Department of Mechanical Engineering, The Hong Kong Polytechnic University (PolyU), KLN, Hong Kong.
Department of Mechanical Engineering, Faculty of Engineering and Physical Sciences, University of Southampton, Southampton, UK; Department of Human Biology, Faculty of Health Sciences, University of Cape Town, Observatory 7935, South Africa.
Comput Methods Programs Biomed. 2022 Apr;216:106653. doi: 10.1016/j.cmpb.2022.106653. Epub 2022 Jan 22.
This paper presents the development of a 3D physics-based numerical model of skin capable of representing the laser-skin photo-thermal interactions occurring in skin photorejuvenation treatment procedures. The aim of this model was to provide a rational and quantitative basis to control and predict temperature distribution within the layered structure of skin. Ultimately, this mathematical and numerical modelling platform will guide the design of an automatic robotic controller to precisely regulate skin temperature at desired depths and for specific durations.
The Pennes bioheat equation was used to account for heat transfer in a 3D multi-layer model of skin. The effects of blood perfusion, skin pigmentation and various convection conditions are also incorporated in the proposed model. The photo-thermal effect due to pulsed laser light on skin is computed using light diffusion theory. The physics-based constitutive model was numerically implemented using a combination of finite volume and finite difference techniques. Direct sensitivity routines were also implemented to assess the influence of constitutive parameters on temperature. A stability analysis of the numerical model was conducted.
Finally, the numerical model was exploited to assess its ability to predict temperature distribution and thermal damage via a multi-parametric study which accounted for a wide array of biophysical parameters such as light coefficients of absorption for individual skin layers and melanin levels (correlated with ethnicity). It was shown how critical is the link between melanin content, laser light characteristics and potential thermal damage to skin.
The developed photo-thermal model of skin-laser interactions paves the way for the design of an automated simulation-driven photorejuvenation robot, thus alleviating the need for inconsistent and error-prone human operators.
本文提出了一种基于 3D 物理的皮肤数值模型，该模型能够描述皮肤光热相互作用，应用于皮肤光老化治疗过程中。该模型旨在为控制和预测皮肤分层结构内的温度分布提供合理的定量基础。最终，该数学和数值建模平台将指导自动机器人控制器的设计，精确调节皮肤的期望深度和特定时长的温度。
彭内斯生物传热方程用于描述皮肤 3D 多层模型中的热传递。还纳入了血液灌注、皮肤色素沉着和各种对流条件的影响。皮肤对脉冲激光光的光热效应是通过光扩散理论计算的。基于物理的本构模型使用有限体积和有限差分技术的组合进行数值实现。还实施了直接灵敏度例程来评估本构参数对温度的影响。对数值模型进行了稳定性分析。
最后，通过多参数研究评估了数值模型预测温度分布和热损伤的能力，该研究考虑了广泛的生物物理参数，如各个皮肤层的光吸收系数和黑色素水平（与种族有关）。结果表明，黑色素含量、激光特性与皮肤潜在热损伤之间的联系至关重要。
开发的皮肤-激光相互作用光热模型为设计自动模拟驱动的光老化机器人铺平了道路，从而减轻了对不一致和容易出错的人工操作员的需求。
