MW and RF ablation zones are similar in pathologic appearance and imaging characteristics. Increased length with MW ablation is likely caused by the length of the radiating segment of the antenna. MW ablation may be less affected by the heat-sink effect that is thought to contribute to local recurrence after RF ablation.

Purpose:To compare the performance of equivalently sized radiofrequency and microwave ablation applicators in a normal porcine lung model. Materials and Methods:All experiments were approved by an institutional animal care and use committee. A total of 18 ablations were performed in vivo in normal porcine lungs. By using computed tomographic (CT) fluoroscopic guidance, a 17-gauge cooled triaxial microwave antenna (n ϭ 9) and a 17-gauge cooled radiofrequency (RF) electrode (n ϭ 9) were placed percutaneously. Ablations were performed for 10 minutes by using either 125 W of microwave power or 200 W of RF power delivered with an impedance-based pulsing algorithm. CT images were acquired every minute during ablation to monitor growth. Animals were sacrificed after the procedure. Ablation zones were then excised and sectioned transverse to the applicator in 5-mm increments. Minimum and maximum diameter, cross-sectional area, length, and circularity were measured from gross specimens and CT images. Comparisons of each measurement were performed by using a mixed-effects model; P Ͻ .05 was considered to indicate a significant difference. Results:Mean diameter (3.32 cm Ϯ 0.19 [standard deviation] vs 2.70 cm Ϯ 0.23, P Ͻ .001) was 25% larger with microwave ablation and mean cross-sectional area (8.25 cm 2 Ϯ 0.92 vs 5.45 cm 2 Ϯ 1.14, P Ͻ .001) was 50% larger with microwave ablation, compared with RF ablation. With microwave ablation, the zones of ablation were also significantly more circular in cross section (mean circularity, 0.90 Ϯ 0.06 vs 0.82 Ϯ 0.09; P Ͻ .05). One small pneumothorax was noted during RF ablation but stabilized without intervention. Conclusion:Microwave ablation with a 17-gauge high-power triaxial antenna creates larger and more circular zones of ablation than does a similarly sized RF applicator in a preclinical animal model. Microwave ablation may be a more effective treatment of lung tumors.

A single generator may effectively deliver microwave power to multiple antennas. Large volumes of tissue may be ablated and large vessels coagulated with multiple-antenna ablation in the same time as single-antenna ablation.

Loop microwave antennas allow precise control and effective ablation of targeted tissue, particularly in the orthogonal configuration.

Instillation of D5 into the peritoneal cavity before hepatic radiofrequency ablation decreases the risk and severity of diaphragm and lung injuries compared with no pretreatment or pretreatment with 0.9% saline in this animal model. Pretreatment with D5 may increase both the safety of and the number of patients eligible for treatment with thermal therapies.