title: Creation of short microwave ablation zones: in vivo characterization of single and paired modified triaxial antennas.
abstract: OBJECTIVE
  To characterize modified triaxial microwave antennas configured to produce short ablation zones.
  
  
  METHODS
  Fifty single-antenna and 27 paired-antenna hepatic ablations were performed in domestic swine (N = 11) with 17-gauge gas-cooled modified triaxial antennas powered at 65 W from a 2.45-GHz generator. Single-antenna ablations were performed at 2 (n = 16), 5 (n = 21), and 10 (n = 13) minutes. Paired-antenna ablations were performed at 1-cm and 2-cm spacing for 5 (n = 7 and n = 8, respectively) and 10 minutes (n = 7 and n = 5, respectively). Mean transverse width, length, and aspect ratio of sectioned ablation zones were measured and compared.
  
  
  RESULTS
  For single antennas, mean ablation zone lengths were 2.9 cm ± 0.45, 3.5 cm ± 0.55, and 4.2 cm ± 0.40 at 2, 5, and 10 minutes, respectively. Mean widths were 1.8 cm ± 0.3, 2.0 cm ± 0.32, and 2.5 cm ± 0.25 at 2, 5, and 10 minutes, respectively. For paired antennas, mean length at 5 minutes with 1-cm and 2-cm spacing and 10 minutes with 1-cm and 2-cm spacing was 4.2 cm ± 0.9, 4.9 cm ± 1.0, 4.8 cm ± 0.5, and 4.8 cm ± 1.3, respectively. Mean width was 3.1 cm ± 1.0, 4.4 cm ± 0.7, 3.8 cm ± 0.4, and 4.5 cm ± 0.7, respectively. Paired-antenna ablations were more spherical (aspect ratios, 0.72-0.79 for 5-10 min) than single-antenna ablations (aspect ratios, 0.57-0.59). For paired-antenna ablations, 1-cm spacing appeared optimal, with improved circularity and decreased clefting compared with 2-cm spacing (circularity, 0.85 at 1 cm, 0.78 at 2 cm).
  
  
  CONCLUSIONS
  Modified triaxial antennas can generate relatively short, spherical ablation zones. Paired-antenna ablations were rounder and larger in transverse dimension than single antenna ablations, with 1-cm spacing optimal for confluence of the ablation zone.
authors.affiliation: Department of Radiology, University of Wisconsin School of Medicine and Public Health, E3/311 Clinical Sciences Center, 600 Highland Ave., Madison, WI 53792. Electronic address: mlubner@uwhealth.org.
authors.forename: Meghan G
authors.initials: MG
authors.lastname: Lubner
authors.affiliation: Department of Radiology, University of Wisconsin School of Medicine and Public Health, E3/311 Clinical Sciences Center, 600 Highland Ave., Madison, WI 53792.
authors.forename: Tim J
authors.initials: TJ
authors.lastname: Ziemlewicz
authors.affiliation: Department of Radiology, University of Wisconsin School of Medicine and Public Health, E3/311 Clinical Sciences Center, 600 Highland Ave., Madison, WI 53792.
authors.forename: J Louis
authors.initials: JL
authors.lastname: Hinshaw
authors.affiliation: Department of Radiology, University of Wisconsin School of Medicine and Public Health, E3/311 Clinical Sciences Center, 600 Highland Ave., Madison, WI 53792.
authors.forename: Fred T
authors.initials: FT
authors.lastname: Lee
authors.affiliation: Department of Radiology, University of Wisconsin School of Medicine and Public Health, E3/311 Clinical Sciences Center, 600 Highland Ave., Madison, WI 53792.
authors.forename: Lisa A
authors.initials: LA
authors.lastname: Sampson
authors.affiliation: Department of Radiology, University of Wisconsin School of Medicine and Public Health, E3/311 Clinical Sciences Center, 600 Highland Ave., Madison, WI 53792; Department of Biomedical Engineering, University of Wisconsin School of Medicine and Public Health, E3/311 Clinical Sciences Center, 600 Highland Ave., Madison, WI 53792; Department of Medical Physics, University of Wisconsin School of Medicine and Public Health, E3/311 Clinical Sciences Center, 600 Highland Ave., Madison, WI 53792.
authors.forename: Christopher L
authors.initials: CL
authors.lastname: Brace
mesh_terms: D000818:Animals; D006528:Carcinoma, Hepatocellular / Q000473:pathology / Q000601:surgery; D017115:Catheter Ablation / Q000295:instrumentation* / Q000379:methods*; D015179:Colorectal Neoplasms / Q000473:pathology; D004566:Electrodes; D004867:Equipment Design; D006801:Humans; D008099:Liver / Q000000981:diagnostic imaging / Q000473:pathology / Q000601:surgery*; D008113:Liver Neoplasms / Q000473:pathology / Q000556:secondary / Q000601:surgery; D008872:Microwaves / Q000627:therapeutic use*; D023421:Models, Animal; D034421:Sus scrofa; D013997:Time Factors; D014057:Tomography, X-Ray Computed