Combined Radiofrequency Ablation and Hot Saline Injection in Rabbit Liver

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Abstract
Rationale and Objectives: To determine whether combining hot saline injection (HSI) and radiofrequency ablation (RFA) can increase the extent of thermally mediated coagulation in in vivo rabbit liver tissue. Methods: In 66 rabbits, RF energy and/or hot saline-induced coagulations were produced using a 17-gauge cooled electrode or 21-gauge needle under ultrasound guidance. Rabbits were allocated into 1 of 5 groups: group A, RFA alone (n = 15); group B, HSI (1 mL hot saline infused, n = 10); group C, combined therapy for HSI followed by RFA (n = 21); group D, combined therapy for RFA immediately followed by HSI (n = 10); and group E, 1 mL room temperature saline infusion before RFA (n = 10). RF energy (30 W) was applied for 3 minutes. The changes in tissue impedance, current, power output, and temperature of the electrode tip were automatically measured. Before RFA, precontrast computed tomography was performed, and after RFA, pre- and postcontrast spiral computed tomographic scans were acquired. The maximum diameters of the thermal lesions on the gross specimens and complications of each group were compared. Results: All procedures were technically successful. There were 9 of 61 procedure-related complications (14.8%) including 6 localized hematomas and 3 thermal injuries to the diaphragm and the stomach. In rabbits in groups C and E, a marked decrease of tissue impedance (43.4 Ω, 44.1Ω) and an increase of current (709 mA, 722 mA) occurred with instillation of saline infusion compared with RFA only. Combined therapy for HSI followed by RFA produced a greater short-axis mean diameter of coagulation (14.6 ± 4.3 mm) than that in rabbits of other groups, for RFA only (10.4 ± 2.4 mm), HSI only (8.7 ± 3.3 mm), and combined therapy for RFA immediately followed by HIS (12.0 ± 1.4 mm; P < 0.05). Conclusion: Combined therapy for HSI followed by RFA can increase the volume of RFA-induced coagulation in the liver with a single application, and therefore may improve the results of RFA for the treatment of larger tumors.