title: Radiofrequency coil for the creation of large ablations: ex vivo and in vivo testing.
abstract: OBJECTIVE
  Various radiofrequency (RF) ablation electrode designs have been developed to increase ablation volume. Multiple heating cycles and electrode positions are often required, thereby increasing treatment time. The objective of this study was to evaluate the performance of a high-frequency monopolar induction coil designed to produce large thermal lesions (>3 cm) with a single electrode insertion in a treatment time of less than 10 minutes.
  
  
  METHODS
  A monopolar nitinol interstitial coil operated at 27.12 MHz and 200 W was evaluated. Ex vivo performance was tested in excised bovine liver (n = 22). In vivo testing (n = 10) was conducted in livers of seven Yorkshire pigs. Visual inspection, contrast-enhanced computed tomography (CT), and pathologic evaluation of ablation zones were performed.
  
  
  RESULTS
  Average ablation volumes in ex vivo and in vivo tests were 60.5 cm(3) ± 14.1 (5.9 × 4.4 × 4.4 cm) and 57.1cm(3) ± 13.8 (6.1 × 4.5 × 4.1cm), with average treatment times of 9.0 minutes ± 3.0 and 8.4 minutes ± 2.7, respectively. Contrast-enhanced CT ablation volume measurements corresponded with findings of gross inspection. Pathologic analysis showed morphologic and enzymatic changes suggestive of tissue death within the ablation zones.
  
  
  CONCLUSIONS
  The RF ablation coil device successfully produced large, uniform ablation volumes in ex vivo and in vivo settings in treatment times of less than 10 minutes. Ex vivo and in vivo lesion sizes were not significantly different (P = .53), suggesting that the heating efficiency of this higher-frequency coil device may help to minimize the heat-sink effect of perfusion.
authors.affiliation: Division of Biophysics and Bioimaging, Ontario Cancer Institute, Princess Margaret Hospital, University Health Network, Toronto, Ontario, Canada. afurse@uhnresearch.ca
authors.forename: Alex
authors.initials: A
authors.lastname: Furse
authors.forename: Brock J
authors.initials: BJ
authors.lastname: Miller
authors.forename: Claire
authors.initials: C
authors.lastname: McCann
authors.forename: John R
authors.initials: JR
authors.lastname: Kachura
authors.forename: Michael A
authors.initials: MA
authors.lastname: Jewett
authors.forename: Michael D
authors.initials: MD
authors.lastname: Sherar
mesh_terms: D000497:Alloys; D000818:Animals; D017115:Catheter Ablation / Q000295:instrumentation*; D002417:Cattle; D016923:Cell Death; D004566:Electrodes; D004867:Equipment Design; D008099:Liver / Q000000981:diagnostic imaging / Q000473:pathology / Q000601:surgery*; D008422:Materials Testing; D013552:Swine; D013997:Time Factors; D014057:Tomography, X-Ray Computed
chemical_list: D000497:Alloys; C013616:nitinol