It is generally believed that radiofrequency energy delivered to the tissue determines the RFA lesion size. The purpose of this study was to re-evaluate this relationship and propose a potentially parameter of temperature-time integration as a better indicator of RFA lesion size. Using an Ex Vivo lesioning model, fixed 300 J RFA lesions were created under target temperature settings of 65, 75, and 85°C. The lesion sizes were recorded and compared. Under the target temperature of 65 and 75°C, the RFA procedures were sustained for a period of time after reaching the target temperature. The correlation between the lesion size and the sustained time (Ts) after reaching the target temperature was calculated. Under the same amount of energy output (300 J), the lesion size created under the three different target temperatures (65, 75, and 85°C) differs significantly. When the target temperature was set to 75°C, the correlation coefficient between the Ts and the lesion area and the maximal effective radius (Mer) were 0.913 and 0.971, respectively. When the target temperature was set to 65°C, the correlation coefficient between the Ts and the lesion area and the Mer were 0.962 and 0.923, respectively. The RFA lesion size is not proportional to the total delivered energy. The Temperature-time integration appears to be a much better indicator that critically influences the lesion size.
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