基于方差分析的2450MHz微波消融温度场仿真模型参数研究

为了提供2 450 MHz微波消融温度场模型在不同时间和不同位置的显著性影响因素,基于电磁方程和生物传热方程建立微波有限元模型,利用方差分析技术获得密度(ρ)、比热容(c)、对流交换系数(h)、电导率(σ)、导热率(K)和相对介电常数(ε)等模型参数对于温度变化的方差贡献率(SS)和主效应.研究表明,微波天线冷却水对于中心点温度具有一定影响,方差贡献率约为0.09,但对于近场点和远场点温度的影响几乎为零.在水冷侧近场区域中,消融前期c和σ对温度场的影响显著,K几乎无影响,消融后期K和σ的影响越来越高;在无水冷侧近场区域中,电特性参数对温度的影响随时间而增加,而c的影响逐步降低,K的影响一直较小;在远场区域中,消融区温度为各模型参数共同作用的结果,各参数敏感性差异不大;根据主效应分析,仿真温度与参数σ成正相关,与c、ρ、h呈负相关,而仿真温度与k和ε的相关性随时间和位置而有所不同.因此,基于方差分析的参数研究可为仿真模型的特异性分析提供科学可靠的参考依据,尤其是在近场区域,模型参数对于不同时间的仿真温度具有特异性影响.根据水冷侧近场区域中的分析结果对参数进行反馈调节,可获得与实测数据具有良好一致性的温度场仿真结果.

Parameter Study of 2 450 MHz Microwave Ablation Temperature Field Model Based on Variance Analysis

To provide the significance factors of 2 450 MHz microwave ablation temperature field model at different times and different positions,a microwave finite element model was established according to the electromagnetic equation and the biological heat transfer equation. The variances of the model parameters such as density (ρ), specific heat capacity (c), convective exchange coefficient (h), conductivity (σ),thermal conductivity (K) and relative dielectric constant (ε) were then calculated to obtain the contribution rate (SS) and main effect. Results show that the water cooling effect of microwave antenna has certain influence on the temperature of the center point,SS was about 0.09,but has no effect on the near field and the far field temperature. In the near field region on water-cooled side, c and σ have significant effects on the temperature field during the early stage of ablation,and the influences of K and σ are higher in the later session. In the near field region with no cooled water, the influences of the electrical parameters on the temperature increases with the simulation time,and the effect of c decreases gradually,and the effect of K is always small. In the far field region,the temperature changes are caused by the interaction of the model parameters, and the sensitivity of the parameters is very similar. According to the main effect analysis, the temperature is positively correlated with σ, and is negatively correlated with c,ρ,h. Moreover,the correlation between the temperature and K,ε varies with time and position. Therefore,the parameter research based on variance analysis can provide scientific and reliable reference for the specificity analysis of the ablation models, and model parameters have the special sensitivity especially for the near field temperature at different time. According to the analysis results in the near region on water-cooled side, the model parameters can be adjusted by feedback, and the temperature field simulation results with a high precision can be obtained.