Different heating modes of Cool-tip on coagulation zone and thremal distribution: in vitro and in vivo experiment

Objective To compare the features of different heating modes(cauterization mode and standard ablation mode) of Cool-tip on coagulation zone and thermal field distribution in order to provide references for focused and accurate vascular occlusion, and explore the primary efficacy of Cool-tip applied to intrahepatic vascular occlusion in living dogs. Methods Ex-vivo porcine livers were ablated for 2, 4, 6, 8 minites with cauterization mode and standard ablation mode respectively, and the long- and short-axis diameters in the greatest dimension were compared. The tissue temperature around the tip, midpoint and end of the exposed part of radiofrequency electrode were measured under the circumstance of 4 min ablation by the two modes respectively. Animal experiment: the intrahepatic vessels of 2 Beagles were ablated with cauterization mode, one procedure for each animal, and contrast-enhanced ultrasound was used to evaluate the perfusion change of liver tissue. Gross anatomy and pathological examination of the liver was performed after 1 week. Results In the 2 min, 4 min, 6 min and 8 min ablation, the coagulation volume of cauterization mode and standard ablation mode were (1.01±0.41)cm3 vs (2.95±0.74)cm3, (1.47±0.33)cm3 vs (5.03±1.06)cm3, (2.29±0.49)cm3 vs (9.23±2.53)cm3, (2.70±0.24)cm3 vs (15.89±0.77)cm3. The coagulation volume was significant smaller in cauterization mode than in standard ablation mode (P<0.05 for all) .The peak temperature of cauterization mode presented on the tip of electrode, which averaged 94.4 ℃ in maximum and maintain around 70 ℃ in the equilibrium phase. The peak temperature of standard mode presented on the midpoint of the electrode, which periodically variated between 70 ℃-100 ℃. The result of the animal experiment showed that cauterization mode could be used to occlude the intrahepatic vessel in vivo, which induced the ischemia and necrosis in the corresponding area. Conclusions Cauterization mode and standard alation mode of Cool-tip have different characteristic in terms of coagulation zone and thermal distribution, and carterization mode may have a promising application in intrahepatic vascular occlusion. Key words: Radiofrequency ablation; Coagulation zone; Cauterization mode; Thermal field; Vascular occlusion.