Retrospective study for validation and improvement of numerical treatment planning of irreversible electroporation ablation for treatment of liver tumors.

Objective To determine the electric field threshold in our numerical model that best fits the local response to irreversible electroporation (IRE) ablation of hepatic tumors as seen in 6 week follow-up MRI. To numerically evaluate the heat generating effect of IRE and demonstrate the potential of treatment planning to avoid thermal damage and shorten procedures in the future. Methods In a retrospective study 18 cases of hepatic tumors treated with IRE ablation were numerically reconstructed and treatment outcome was computed with a numerical treatment planning framework. Simulated ablation volumes were compared to ablation volumes segmented from follow-up MRI. Two cases with a high thermal damage component were selected for numerical optimization. Results The best fit between segmented and simulated ablation zones was obtained at 900 V/cm threshold with the average absolute error of 5.6 1.5 mm. Considerable heating was observed in the dataset. In 7/18 cases >50 % of tumor volume experienced heating likely to cause thermal damage. In the selected two cases thermal damage was eliminated with adjustment of applied voltages. Conclusion Our results indicate that lesions visible on MRI 6 weeks post IRE represent areas that experienced an electric field of 900 V/cm or higher. Significance We developed a sophisticated method for validation of the numerical treatment planning framework. A future prospective study can be effectively designed based on the findings of this study.