title: Visualizing ex vivo radiofrequency and microwave ablation zones using electrode vibration elastography.
abstract: OBJECTIVE
  Electrode vibration elastography is a new shear wave imaging technique that can be used to visualize thermal ablation zones. Prior work has shown the ability of electrode vibration elastography to delineate radiofrequency ablations; however, there has been no previous study of delineation of microwave ablations or radiological-pathological correlations using multiple observers.
  
  
  METHODS
  Radiofrequency and microwave ablations were formed in ex vivo bovine liver tissue. Their visualization was compared on shear wave velocity and maximum displacement images. Ablation dimensions were compared to gross pathology. Elastographic imaging and gross pathology overlap and interobserver variability were quantified using similarity measures.
  
  
  RESULTS
  Elastographic imaging correlated with gross pathology. Correlation of area estimates was better in radiofrequency than in microwave ablations, with Pearson coefficients of 0.79 and 0.54 on shear wave velocity images and 0.90 and 0.70 on maximum displacement images for radiofrequency and microwave ablations, respectively. The absolute relative difference in area between elastographic imaging and gross pathology was 18.9% and 22.9% on shear wave velocity images and 16.0% and 23.1% on maximum displacement images for radiofrequency and microwave ablations, respectively.
  
  
  CONCLUSIONS
  Statistically significant radiological-pathological correlation was observed in this study, but correlation coefficients were lower than other modulus imaging techniques, most notably in microwave ablations. Observers provided similar delineations for most thermal ablations. These results suggest that electrode vibration elastography is capable of imaging thermal ablations, but refinement of the technique may be necessary before it can be used to monitor thermal ablation procedures clinically.
authors.affiliation: Department of Medical Physics, University of Wisconsin-Madison, Madison, WI 53705, USA. dewall@wisc.edu
authors.forename: Ryan J
authors.initials: RJ
authors.lastname: Dewall
authors.forename: Tomy
authors.initials: T
authors.lastname: Varghese
authors.forename: Chris L
authors.initials: CL
authors.lastname: Brace
mesh_terms: D055011:Ablation Techniques / Q000379:methods*; D000818:Animals; D002417:Cattle; D054459:Elasticity Imaging Techniques / Q000295:instrumentation / Q000379:methods*; D004566:Electrodes; D008099:Liver / Q000000981:diagnostic imaging / Q000528:radiation effects; D008872:Microwaves / Q000627:therapeutic use*; D015588:Observer Variation; D014732:Vibration