High-powered Microwave Ablation with a Small-gauge, Gas-cooled Antenna: Initial Ex Vivo and In Vivo Results

Abstract

PurposeTo evaluate the performance of a gas-cooled, high-powered microwave system. Materials and MethodsInvestigators performed 54 ablations in ex vivo bovine livers using three devices—a single 17-gauge cooled radiofrequency(RF) electrode; a cluster RF electrode; and a single 17-gauge, gas-cooled microwave (MW) antenna—at three time points (n = 6 at 4 minutes, 12 minutes, and 16 minutes). RF power was applied using impedance-based pulsing with maximum 200 W generator output. MW power of 135 W at 2.45 GHz was delivered continuously. An approved in vivo study was performed using 13 domestic pigs. Hepatic ablations were performed using single applicators and the above-mentioned MW and RF generator systems at treatment times of 2 minutes (n = 7 MW, n = 6 RF), 5 minutes (n = 23 MW, n = 8 RF), 7 minutes (n = 11 MW, n = 6 RF), and 10 minutes (n = 7 MW, n = 9 RF). Mean transverse diameter and length of the ablation zones were compared using analysis of variance (ANOVA) with post-hoc t tests and Wilcoxon rank-sum tests. ResultsSingle ex vivo MW ablations were larger than single RF ablations at all time points (MW mean diameter range 3.5–4.8 cm 4–16 minutes; RF mean diameter range 2.6–3.1 cm 4–16 minutes) (P < .05). There was no difference in mean diameter between cluster RF and MW ablations (RF 3.3–4.4 cm 4–16 minutes; P = .4–.9). In vivo lesion diameters for MW (and RF) were as follows: 2.6 cm ± 0.72 (RF 1.5 cm ± 0.14), 3.6 cm ± 0.89 (RF 2.0 cm ± 0.4), 3.4 cm ± 0.87 (RF 1.8 cm ± 0.23), and 3.8 cm ± 0.74 (RF 2.1 cm ± 0.3) at 2 minutes, 5 minutes, 7 minutes, and 10 minutes (P < .05 all time points). ConclusionsGas-cooled, high-powered MW ablation allows the generation of large ablation zones in short times.