激光照射下生物组织中非傅里叶传热现象的研究

发布时间：2018-07-21 22:10

【摘要】：激光具有高单色性、高方向性、高亮度性和良好的相干性等特点。激光问世以来，已被广泛应用于临床治疗。其中大部分的应用都涉及热效应，如激光高热疗法、凝结以及激光外科。为了确保治疗安全和提高效率，开展针对生物组织的光热效应与热损伤的研究就显得十分必要。本文首先基于双相位滞后模型，根据激光在生物组织内部热传导的实际情况，对激光照射下生物组织中非傅里叶传热现象进行了数值模拟。其次对连续He-Ne激光照射下大鼠皮肤组织温度随时间变化的规律进行了实验研究。实验采用将热电偶从激光照射面的对面插入，通过改变激光照射时间、功率等相关参数，按照一定的采样速度采集每一次信号，记录下该位置处组织温度随时间变化的温度数据。本文采用数值模拟中的有限差分法，，对双相位滞后模型进行数值模拟。通过改变τ_T和τ_q的取值，将双相位滞后模型、傅里叶模型和双曲热波模型的数值模拟结果进行比较和分析。模拟结果表明：当τ_T和τ_q的取值相等并且都非常小时，双相位滞后模型的数值模拟结果和傅里叶模型的数值模拟结果相同。否则，即使τ_T=τq，DPL模型描述的热传导也不同于传统傅里叶热模型。在激光照射生物组织前期，τ_q对温度的影响更大些，激光停止照射后，τ_T对温度的影响更大些。当τ_q固定在16s，τ_T变化时，在取消激光照射后，生物组织温度变化会随着τ_T取值增大而增大；当τ_T固定在0.05s，τ_q变化时，τ_q的取值越大，组织的温度越高。对连续He-Ne激光照射下大鼠皮肤组织的温度随时间变化的规律进行了实验研究，实验采用He-Ne激光器照射大鼠组织表面和皮下组织1mm处，通过红外辐射测温仪和热电偶探针来探测被照组织的温度，通过改变激光照射时间和功率，研究被照组织温度随时间的变化情况。实验结果表明：当激光开始照射时，大鼠组织表面和皮下组织1mm处的温度在照射期间会随着照射时间的增加而迅速增加，当激光照射停止后，大鼠组织表面温度快速下降，而大鼠皮下组织1mm处温度缓慢下降。当用相同激光能量照射大鼠组织表面时，随着功率的增加，组织表面温度也相应增加，组织表面温度出现波动现象，并在25s后组织表面温度趋于平稳。组织表面温升随着激光照射中心的径向距离的增加而减小。
[Abstract]:Laser has the characteristics of high monochromatic, high directivity, high brightness and good coherence. Since the advent of laser, it has been widely used in clinical treatment. Most of these applications involve thermal effects, such as laser hyperthermia, coagulation, and laser surgery. In order to ensure the safety of treatment and improve efficiency, it is necessary to study the photothermal effects and thermal damage of biological tissues. In this paper, based on the two-phase hysteresis model, the non-Fourier heat transfer phenomenon of biological tissue under laser irradiation is numerically simulated according to the actual condition of laser heat conduction in biological tissue. Secondly, the changes of skin temperature with time under continuous He-Ne laser irradiation in rats were studied experimentally. In the experiment, the thermocouple is inserted from the opposite side of the laser irradiation surface. By changing the laser irradiation time, power and other related parameters, each signal is collected at a certain sampling rate. Record the temperature data of tissue temperature over time at this position. In this paper, the finite difference method in numerical simulation is used to simulate the double phase lag model. By changing the values of 蟿 T and 蟿 Q, the numerical simulation results of biphase lag model, Fourier model and hyperbolic heat wave model are compared and analyzed. The simulation results show that when the values of 蟿 T and 蟿 Q are equal and very small, the numerical simulation results of the two-phase delay model are the same as those of the Fourier model. Otherwise, the heat conduction described by the 蟿 T = 蟿 QO DPL model is different from that of the traditional Fourier model. In the early stage of laser irradiation to biological tissue, 蟿 _ Q has a greater effect on temperature, and 蟿 _ T has more effect on temperature after laser irradiation is stopped. When T _ Q is fixed at 16 s and 蟿 _ T is changed, when laser irradiation is cancelled, the temperature change of biological tissue will increase with the increase of 蟿 _ T value; when 蟿 _ T is fixed at 0.05s and 蟿 _ S _ Q changes, the higher the 蟿 _ Q value is, the higher the tissue temperature will be. The effect of continuous He-Ne laser irradiation on the temperature of rat skin tissue was studied. The He-Ne laser was used to irradiate the surface of the rat tissue and the 1mm of the subcutaneous tissue. Infrared radiation thermometer and thermocouple probe are used to detect the temperature of irradiated tissue. By changing the time and power of laser irradiation, the variation of the temperature of irradiated tissue with time is studied. The results showed that the temperature of 1mm in tissue and subcutaneous tissue of rats increased rapidly with the increase of irradiation time when laser irradiation was started, and the temperature of tissue surface decreased rapidly after laser irradiation stopped. However, the temperature of 1mm in rat subcutaneous tissue decreased slowly. When the tissue surface was irradiated with the same laser energy, the tissue surface temperature increased with the increase of power, and the temperature of the tissue surface fluctuated, and the temperature of the tissue surface tended to be stable after 25 seconds. The temperature rise of the tissue surface decreases with the increase of the radial distance of the laser irradiation center.
【学位授予单位】：河南科技大学
【学位级别】：硕士
【学位授予年份】：2012
【分类号】：R318.51

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