Parametric sensitivity analysis of critical factors affecting the thermal damage during RFA of breast tumor

A sensitivity analysis has been conducted to quantify the relative influence of several critical parameters on the size of ablation volume generated during temperature-controlled radiofrequency ablation (RFA) of breast tumor. In order to minimize the number of experiments, Taguchi's L16 orthogonal array has been utilized to determine the effect of four parameters with 4-levels each. The parameters considered are breast density composition, target tip temperature, tumor blood perfusion rate and location of tumor from body core. A three-dimensional heterogeneous numerical model of breast with a spherical tumor of 2.2 cm has been developed for this purpose. Temperature-controlled RFA has been performed by incorporating the closed-loop feedback proportional-integral-derivative (PID) controller in the numerical model using monopolar multi-tine electrode. The size of the tumor ablation volume has been taken as the response variable that has been obtained from finite element analysis by incorporating the coupled electric field distribution, the Pennes bioheat equation and the first-order Arrhenius rate equation. A non-linear piecewise model of blood perfusion has been considered to achieve better correlation with the clinical RFA. Also, the effects of temperature-dependent changes in electrical and thermal conductivity have been incorporated. Further, analysis of variance (ANOVA) has been performed to quantify the ranking and contribution of each parameter on the size of ablation volume produced during RFA. The results obtained from the numerical study revealed that the target tip temperature and tumor blood perfusion, followed by breast density composition, have a maximum influence on the ablation volume generated during temperature-controlled RFA.