A.A. Bobrov, V.N. Makarov, S.M. Makarova, M.A. Makhov, M.Yu. Proshkin, G.V. Yushchenko

The paper presents features of universal system for radiofrequency ablation of tumors «Metatom-2» in different operation modes (monopolar, bipolar and resection). The research was conducted to determine operation modes which provide maximum warming up area size under heating up to necessary temperatures (50 - 60С). The experiments have shown that in monopolar mode maximum coagulation zones diameters under radiofrequency heating with use of perfusion or water-cooled electrodes under the same conditions (diameter and work surface length of electrodes, HF generator power, process time) differ slightly and amount 37 mm and 40 mm. In the bipolar mode coagulation zone is asymmetrical: its size along the axis connecting electrodes is always more than in perpendicular direction. The coagulation zone size grows with the increase of needle electrode diameter and its work surface length both in monopolar and bipolar operation modes. The maximum coagulation zone size in the bipolar mode is observed when distance between electrodes is 20 mm and amounts 50 mm. The experiments indicate that under radio-frequency heating with use of the same (diameter of 1.6 mm, work surface length of 30 mm) perfusion and water-cooled electrodes and at optimum distance between them coagulation volume (V = D1D2D3 / 6, D1,D2,D3 - the sizes of coagulation area in three mutually perpendicular directions) in the bipolar mode is 1.4-1.8 times more than in the monopolar mode. In the resection mode width of tissue strip heating up to coagulation condition amounts 5 - 7 mm at depth of 35 and 45 mm for electrodes with work surface length of 30 and 37 mm. The heating area length for one application amounts 13 - 15 mm.