电磁加热条件下皮肤组织的生物热力学行为

研究目的是开发一种数学方法来计算传热过程、热引起的力学响应以及相应的疼痛等级,从而对临床上应用的各种加热疗法之间的差别进行定量评估.采用基于有限差分法的数值模拟方法,基于无限大和均匀化假设,分析了各种热疗法中皮肤组织的温度、烧伤和热应力分布.研究发现:充血对热损伤的影响很小,但对皮肤的温度分布影响很大,而这又反过来显著影响由此产生的热应力场;对于激光加热,光波越短则峰值温度越高,但峰值更接近皮肤表面温度;激光和微波加热所产生的热应力集中于表皮顶层,因为发热量沿皮肤深度方向呈指数衰减;薄角质层(常常被忽略)对皮肤组织的热力学响应起主导作用.

THE BIOTHERMOMECHANICAL BEHAVIOUR OF SKIN TISSUE UNDER ELECTROMAGNETIC HEATING

Electromagnetic heating is widely used in medical treatments, such as microwave, radiofrequency, laser, etc. Recent advances in these technologies resulted in remarkable developments of thermal treatments for a multitude of diseases and injuries involving skin tissue. The comprehension of heat transfer and related thermomechanics in skin tissue during these treatments is thus of great importance, and can contribute to the further developments of these medical applications. Biothermomechanics of skin is highly interdisciplinary, involving bioheat transfer, burn damage, biomechanics and physiology. The aim of this study is to develop a computational approach to examine the heat transfer process, heat-induced mechanical response as well as the associated pain level, so that the differences among the clinically applied heating modalities can be quantified. In this paper, numerical simulations with the finite difference method (FDM) was used to analyze the temperature, burn damage and thermal stress distributions in the skin tissue subjected to various thermal treatments. The results showed that the thermo-mechanical behavior of skin tissue is very complex: blood perfusion has little effect on thermal damage but large influence on skin temperature distribution, which, in turn, influences significantly the resulting thermal stress field; for laser heating, the peak temperature is higher for laser with shorter wavelength, but the peak is closer to the skin surface; the thermal stress due to laser and microwave heating is mainly limited to the top epidermis layer due to the exponential decrease of heat generation along skin depth; the thin (and commonly overlooked) stratum corneum layer dominates the thermomechanical response of skin tissue.