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.