title: High-powered microwave ablation with a small-gauge, gas-cooled antenna: initial ex vivo and in vivo results.
abstract: OBJECTIVE
  To evaluate the performance of a gas-cooled, high-powered microwave system.
  
  
  METHODS
  Investigators 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.
  
  
  RESULTS
  Single 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).
  
  
  CONCLUSIONS
  Gas-cooled, high-powered MW ablation allows the generation of large ablation zones in short times.
authors.affiliation: Department of Radiology, University of Wisconsin School of Medicine and Public Health, Madison, WI 53792-3252, USA. mlubner@uwhealth.org
authors.forename: Meghan G
authors.initials: MG
authors.lastname: Lubner
authors.forename: J Louis
authors.initials: JL
authors.lastname: Hinshaw
authors.forename: Anita
authors.initials: A
authors.lastname: Andreano
authors.forename: Lisa
authors.initials: L
authors.lastname: Sampson
authors.forename: Fred T
authors.initials: FT
authors.lastname: Lee
authors.forename: Christopher L
authors.initials: CL
authors.lastname: Brace
mesh_terms: D000818:Animals; D002245:Carbon Dioxide; D017115:Catheter Ablation / Q000009:adverse effects / Q000295:instrumentation* / Q000379:methods*; D002417:Cattle; D003080:Cold Temperature; D004566:Electrodes / Q000009:adverse effects; D004867:Equipment Design; D005260:Female; D005740:Gases; D006358:Hot Temperature; D008099:Liver / Q000473:pathology / Q000601:surgery*; D008422:Materials Testing; D008872:Microwaves / Q000009:adverse effects / Q000627:therapeutic use*; D023421:Models, Animal; D034421:Sus scrofa; D013997:Time Factors
chemical_list: D005740:Gases; D002245:Carbon Dioxide