低温冷冻皮肤组织仿真实验结果分析

Analysis of Low Temperature Freezing Skin Tissue Simulation

目的:低温液氮冷冻是治疗色斑、疱疹、鸡眼、疣、血管瘤等各种皮肤疾病的有效手段,然而,液氮冷冻的临床应用大多凭经验进行,无法根据不同的病灶特点实现对冷冻区域、冷冻面积、冷冻时间、冷冻复温循环次数等的精确控制,为此,对液氮冷冻皮肤组织进行仿真分析。方法:根据皮肤组织的解剖模型,建立皮肤组织分层的三维模型,采用Pennes生物传热方程,借助于Fluent有限元软件,模拟皮肤组织在液氮冷冻条件下的温度变化,对液氮冷冻皮肤组织的温度变化特性进行研究。结果:给出了稳态条件下的温度分布云图及温度分布曲线。由于有效冷冻温度为-40℃,稳态时,在水平方向有效冷冻半径约为0.75 mm,竖直方向上有效冷冻半径为1.25 mm;在记录一定时间内不同点不同时刻的温度时,对比了不同位置处温度的变化趋势,即在离冷源相同距离的情况下,由于表面皮肤与空气换热的影响,竖直方向的温度普遍低于水平方向的温度。结论:模拟了皮肤组织在液氮冷冻条件下的温度变化情况,并找出最佳冷冻区域,对临床治疗和液氮冷冻装置的研发提供了理论依据。

Objective： Cryogenic liquid nitrogen refrigeration （CLNR） is an effective means of curing skin diseases such as mottling, herpes, corn, wart, hemangioma et al. At present, clinical application of the CLNR method is mostly implemented based on experience, this brings great difficulties for precisely controlling the key curing elements, for instance, frozen area, frozen time and freezing thawing cycles et al. To solve this problem, simulated analysis on skin tissue is proceeded. Methods： according to anatomical model of skin tissue, 3D heat transfer model of skin tissue is set up to describe its freezing process. Pennes bioheat equation is adopted in the model. With the help of fluent software, temperature variation is simulated under the condition of the skin tissue in liquid nitrogen freezing. Temperatures variation characteristics are discussed. Results： temperatures distribution cloud and curve on the steady and transient states is given. According to the effective temperature, which is -40℃, effective radius of frozen in the horizontal direction is 0.75 mm,while in the vertical direction is 1.25 mm. These dat are got in the stable state. Temperatures at different points as well as different time period are recorded. Temperatures variation trend in different positions is compared. The distances of the measuring points are the same. The temperatures in the vertical direction are lower than that in the horizontal direction. This is due to the effect of the heat exchanger between facial skin and the air. Conclusions： The temperature variation of skin tissue under cryogenic liquid nitrogen refrigeration is simulated. The best frozen area is given. This can provide a theoretical guideline for clinical treatment and also to the development of liquid cryosurgery device.