Preinjected Fluids do not Benefit Microwave Ablation as Those in Radiofrequency Ablation

Rationale and Objectives: To detect whether the efficacy of microwave ablation (MWA) could be improved by preinjected fluids in an ex vivo porcine liver model. Materials and Methods: Ablations were performed for 12 minutes using energy output of impedance-based (power output gradually rose to 200W, maintained until increases in tissue impedance of 20 Omega, reduced to 10W, and switched on again 15 seconds later) in radiofrequency ablation (RFA) or 80 W in MWA. Before ablation, 5 mL of ethanol, distilled water, 0.9% NaCl solution, or 10% NaCl solution (n = 6 each) was injected into the targeted liver tissue. Ablations without fluid injection served as control. The ablation diameter, volume, shape index, and temperature were recorded and compared. Results: Preinjection of 0.9% or 10% NaCl solution resulted in larger coagulation volumes than that of the control group in RFA experiments (28.1 +/- 2.9 cm(3), 45.3 +/- 6.3 cm(3), 20.0 +/- 2.5 cm(3), respectively; P < .05). Ethanol and distilled water had no impact on coagulation volumes in RFA. Preinjection of ethanol or 10% NaCl solution created smaller coagulation volumes than that of the control group in MWA experiments (34.3 = 2.0 cm(3), 33.9 +/- 4.1 cm(3), 58.0 +/- 6.6 cm(3), respectively; P < .001). 0.9% NaCl solution and distilled water had no impact on coagulation volumes in MWA. Conclusion: In an ex vivo porcine liver, preinjected fluids do not benefit microwave ablation as those in radiofrequency ablation.