肝肿瘤温控射频消融温度分布的有限元建模

    Finite Element Modeling of Temperature Distribution During Temperature-controlled Radiofrequency Ablation of Liver Tumor

    • 摘要: 为了提高肝肿瘤射频温控消融温度分布的预测精度,建立了具有比例积分(proportional integral,PI)反馈控制器的射频消融温度分布仿真模型,并且研究了有限元模型中不同传热方程(Pennes和Hyperbolic生物传热方程)对温度分布的影响.首先,利用单电极热消融仪对离体猪肝进行温控射频消融实验,电极针尖稳态温度设定为90℃,消融时间为600 s,并利用测温针获得各测温点的热消融数据.然后,建立具有PI控制器的肝肿瘤温控射频消融有限元模型,其中PI控制器通过反馈调节电压源来使针尖温度与实测数据保持一致,传热方程分别采用基于非傅里叶传热规律的Hyperbolic方程和基于傅里叶传热规律的Pennes方程,生物组织电导率和导热率选用温度依赖性函数.最后,通过仿真温度和实测温度进行对比验证.结果表明,相比于Hyperbolic方程,采用Pennes方程的仿真模型具有较高的精度,各测温点的仿真温度与实验结果之间的标准偏差、平均误差和最大误差的均值分别为0.78、1.46、2.90℃.因此,基于PI控制器和Pennes生物传热方程的肝肿瘤温控射频消融有限元模型能够有效地预测热消融温度.

       

      Abstract: To improve the temperature prediction accuracy of liver tumor radiofrequency ablation (RFA), a temperature distribution model with a proportional integral (PI) feedback controller was established. Furthermore, the influences of different heat transfer equations (Pennes and Hyperbolic equations) on temperature distribution in simulation models were studied. First, a single-electrode RFA ablator was used to perform RFA experiments on ex vivo pig livers. The steady-state temperature of the electrode tip was set to 90℃, the ablation time was 600 s, and the ablation data of the temperature measurement points was obtained by using thermometers. Second, a finite element model was constructed in combination with a PI controller. The PI controller dynamically adjusted the voltage source to maintain the tip temperature consistent with the experimental data. Hyperbolic equation based on the non-Fourier heat transfer law and Pennes equation based on the Fourier heat transfer law were investigated. Temperature-dependent functions for the electrical conductivity and thermal conductivity of the biological tissue were employed. Finally, the simulation data was verified by comparison with the measured temperatures. Results show that compared with Hyperbolic equation, the simulation model using Pennes equation achieves higher prediction accuracy. The mean values of the standard deviation, the average error and the maximum error between the simulations and the measurements are 0.78, 1.46 and 2.90℃, respectively. Therefore, the finite element model based on PI controller and Pennes bio-heat transfer equation can effectively predict RFA temperatures.

       

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