title: Real-time monitoring of radiofrequency ablation and postablation assessment: accuracy of contrast-enhanced US in experimental rat liver model.
abstract: OBJECTIVE
  To examine the accuracy of the unenhanced zone at contrast material-enhanced ultrasonography (US) in predicting coagulative necrosis during and 21 days after radiofrequency (RF) ablation by using radiologic-pathologic comparison.
  
  
  METHODS
  Animal studies were approved by the Institutional Animal Care and Use Committee. The livers of 28 rats underwent US-guided RF ablation. In four animals, contrast-enhanced US was performed during ablation and 2 hours and 2, 7, 14, and 21 days after ablation. The unenhanced zone area on US images was measured. DiI-labeled microbubbles were administered during ablation at 2, 4, and 6 minutes or at 2 hours and 2, 7, 14, and 21 days after ablation in the remaining 24 animals (n = 3 at each time point). One minute later, the animal was euthanized, and the ablated liver was harvested. Tissue samples were imaged to quantify total fluorescence, and NADH staining was performed on the same slice. Hematoxylin-eosin staining was also performed. The findings on fluorescence images, NADH-stained images, and hematoxylin-eosin-stained images were compared. The areas of DiI bubble-negative zones, NADH-negative zones, and lightly NADH-staining zones were measured. Data were analyzed by using one-way analysis of variance.
  
  
  RESULTS
  The area of the unenhanced zone on contrast-enhanced US images increased during RF ablation and reached a maximum within 2 days after ablation. At histopathologic examination, a transition zone manifested adjacent to the coagulation zone until 2 days after ablation. The DiI-bubble negative zone on fluorescence images and the damaged zone (transition zone plus coagulation zone) on NADH-stained images increased rapidly within 2 hours after ablation, then slowly reached the maximum on day 2. The ratios of the mean areas of these two zones at hour 2 to those at day 2 were 94.6% and 95.6%, respectively. High uniformity between the damaged zone on NADH-stained images and the DiI bubble-negative zone on fluorescence images was noted at all time points.
  
  
  CONCLUSIONS
  The temporary transition zone in NADH staining is partially damaged and should transition to nonviability 2 days after ablation. These results demonstrate that contrast-enhanced US can help delineate the maximum area of cell damage (to within 5% of the maximum) as early as 2 hours after ablation. Contrast-enhanced US may be a simple and accurate tool for monitoring the effects of RF ablation and quantifying the size of thermal damage after treatment.
authors.affiliation: From Departments of Radiology (H.W., J.R.H., A.A.E.) and Pathology (N.P.Z.), Case Western Reserve University, 11100 Euclid Ave, Bishop s610, Cleveland, OH 44106; and Department of Radiology, University of Virginia, Charlottesville, Va (L.R.W.).
authors.forename: Hanping
authors.initials: H
authors.lastname: Wu
authors.forename: Luke R
authors.initials: LR
authors.lastname: Wilkins
authors.forename: Nicholas P
authors.initials: NP
authors.lastname: Ziats
authors.forename: John R
authors.initials: JR
authors.lastname: Haaga
authors.forename: Agata A
authors.initials: AA
authors.lastname: Exner
mesh_terms: D000818:Animals; D017115:Catheter Ablation; D003287:Contrast Media / Q000138:chemical synthesis; D008099:Liver / Q000000981:diagnostic imaging / Q000473:pathology / Q000601:surgery*; D045423:Microbubbles; D009336:Necrosis; D011237:Predictive Value of Tests; D051381:Rats; D017207:Rats, Sprague-Dawley; D013194:Staining and Labeling; D018084:Ultrasonography, Interventional
chemical_list: D003287:Contrast Media
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