Therapie-Planungssystem zur Berechnung des thermischen Destruktionsvolumens der Radiofrequenzablation von Lebertumoren – ex-situ Evaluation unter Einbeziehung des Kühleffektes von Lebergefäßen

Abstract

Objective: The oncologically safe application of radiofrequency ablation (RFA) is limited by the cooling effect of liver vessels. The aim of the current study was to validate a planning system for RFA of liver tumors with regard to the calculation of thermal lesions including the cooling effect of liver vessels ex-vivo. Methods: A bipolar RFA applicator (diameter: 1.8 mm, electrode length: 30 mm, internal cooling) was inserted parallel at a distance of 5 mm to a perfused glass tube (diameter: 5 mm; flow: 0–500 ml/min) in porcine liver ex-vivo. RFA was performed with 30 W/15 kJ. The liver was cut perpendicular to the applicator after RFA and the thermal lesion was digitally measured. RFA was simulated with the planning system using the aforementioned parameters. A morphometric analysis was carried out in order to assess the correlation between the thermal lesion and the result of the planning system. Results: 40 RFA were carried out. Sensitivity (correct prediction of the destruction volume) was 0.96 ± 0.05. Specificity (correct prediction of non-destructed tissue) was 0.75 ± 0.10. No significant differences for sensitivity and specificity were found for flows of 0 ml/min (glass tube without perfusion) and flows of 1, 5, 10, 100, 250 and 500 ml/min. Conclusions: (1) A computer planning system was developed for predicting thermal lesions resulting from RFA. (2) The calculation of the cooling effect of intrahepatic vessels is possible for the first time with this system. (3) Ex-situ validation showed a high sensitivity of the planning system, but specificity has to be improved (DFG, Ref-No. RI1131/3-2).