Vergleich eines neuen bipolaren Applikationssystems zur Hochfrequenzinduzierten Thermotherapie (HFITT) mit dem Diffuser-Tip-Applikator zur Laserinduzierten Thermotherapie (LITT) in der Therapie von Lebertumoren in vivo

Abstract

Introduction: Thermal in situ ablation techniques are of increasing importance in the palliative therapy of liver tumors. Only monopolar application systems have thus far been available for high-frequency thermotherapy (HFITT); their applicability is limited due to incalculable energy flows, reduced electrical tissue conductivity and limited lesion size. Accordingly, we developed a novel bipolar cooled HFITT application system, which was tested in vivo for the first time under experimental conditions. The aims of the study were to test the effectiveness of the procedure and evaluate the impact of interrupted hepatic perfusion on inducible lesion size. An established clinical application system for laserinduced thermotherapy (LITT) was used for comparison. Material and Methods: Thirty pigs (25 – 30 kg); laparotomy under i.v. anesthesia; six groups (n = 5). HFITT application (cooled bipolar applicator, Ø3 mm, electrode length 16 mm) was used in the groups HF and LITT (Nd:YAG laser, diffuser tip applicator) in groups LITT. Each animal underwent two to four applications using the highest possible energy/power for the application system. The applications were performed with maintained hepatic perfusion (group_mono), after i.a. application of degradable starch microspheres (DSM) via the hepatic artery (group_DSM) and after temporary occlusion of the hepatoduodenal ligament (group_Pringle ). The liver was removed after the intervention. The lesion was then measured longitudinally (1) and transversally (t) to the applicator axes and the volume (V) calculated. Results: HFITT and LITT applications were free of complications. A volume increase was achieved in both procedures by interrupting hepatic perfusion (_DSM/Pringle) ( p < 0.05 ). Less energy was applied in group HF_Pringle (34.2 ± 1.7 kJ) than in group HF_mono (41.9 ± 1.3 kJ) (p < 0.01). The volumes in groupLITT _Pringle with 60.2 ± 2.2 cm₃ were larger than in group HF _Pringle with 48.6 ± 4.3 cm₃ (p < 0.005). The data are given in the table below (* =p < 0.05, Kruskal- Wallis test). Conclusions: (1) The bipolar HFITT applicator enabled reproducible induction of clinically relevant lesions comparable to the LITT applicator system. (2) Interrupting hepatic perfusion leads to a volume increase with both application systems. (3) Interrupted perfusion reduces the maximal applicable energy after HFITT but yields comparatively lower volumes than after LITT, which may limit the use of interrupted perfusion.