title: Predictive value of pattern classification 24 hours after radiofrequency ablation of liver metastases on CT and positron emission tomography/CT.
abstract: OBJECTIVE
  To assess a classification scheme for predicting local tumor progression (LTP) after radiofrequency (RF) ablation of liver metastases, using predefined patterns on contrast-enhanced computed tomography (CT) and positron emission tomography (PET) combined with CT (PET/CT) acquired 24 hours after RF ablation.
  
  
  METHODS
  There were 45 metastases in 20 patients treated. After 24 hours, imaging of the ablation zones was performed with contrast-enhanced PET/CT. Three independent radiologists prospectively assessed contrast-enhanced CT and combined PET/CT images to identify three patterns: pattern I, no tissue enhancement or fluorodeoxyglucose uptake between the ablation zone and the liver parenchyma; pattern II, a rimlike pattern; and pattern III, a peripheral nodule. PET/CT images obtained after 8-10 weeks were evaluated for LTP. The patterns were analyzed for their sensitivity, specificity, positive predictive value, and negative predictive value for predicting LTP.
  
  
  RESULTS
  Pattern I was most frequently observed (81% for contrast-enhanced CT and 61% for PET/CT) as well as for ablation zones that showed LTP (52% and 37%, respectively). Conversely, pattern II was observed for tumors that were completely ablated (6% and 29%, respectively). Patterns II and III together had the highest sensitivity for predicting LTP (48% and 63%, respectively); pattern III had the highest specificity (94% and 95%, respectively). For nodular patterns, test characteristics were better for PET/CT compared with contrast-enhanced CT, but the difference was not significant. Nodular patterns > 1 cm achieved high positive predictive value (both 100%).
  
  
  CONCLUSIONS
  Inflammation and hyperemia can hinder interpretation on imaging 24 hours after RF ablation, especially on PET/CT. Nodular patterns around the ablation zone on early contrast-enhanced CT and PET/CT have a high predictive value for LTP and should be taken into account for disease management.
authors: Department of Radiology, UZ Brussel, Laarbeeklaan 101, 1090 Brussels, Belgium. Electronic address: spovef@uzbrussel.be.
authors: Frederik
authors: F
authors: Vandenbroucke
authors: Department of Electronics and Informatics, Vrije Universiteit Brussel, Brussels, Belgium; Department of Future Media and Imaging, iMinds, Brussels, Belgium.
authors: Jef
authors: J
authors: Vandemeulebroucke
authors: Department of Radiology, UZ Brussel, Laarbeeklaan 101, 1090 Brussels, Belgium.
authors: Bart
authors: B
authors: Ilsen
authors: Department of Radiology, UZ Brussel, Laarbeeklaan 101, 1090 Brussels, Belgium.
authors: Douwe
authors: D
authors: Verdries
authors: Department of Radiology, UZ Brussel, Laarbeeklaan 101, 1090 Brussels, Belgium.
authors: Dries
authors: D
authors: Belsack
authors: Department of Nuclear Medicine, UZ Brussel, Laarbeeklaan 101, 1090 Brussels, Belgium.
authors: Hendrik
authors: H
authors: Everaert
authors: Department of Radiology, UZ Brussel, Laarbeeklaan 101, 1090 Brussels, Belgium.
authors: Nico
authors: N
authors: Buls
authors: Department of Radiology, University Hospitals Case Medical Center/Case Western Reserve University, Cleveland, Ohio.
authors: Pablo R
authors: PR
authors: Ros
authors: Department of Radiology, UZ Brussel, Laarbeeklaan 101, 1090 Brussels, Belgium.
authors: Johan
authors: J
authors: de Mey
mesh_terms: D017115:Catheter Ablation; D003287:Contrast Media; D018450:Disease Progression; D019788:Fluorodeoxyglucose F18; D006801:Humans; D007472:Iohexol / Q000031:analogs & derivatives; D008113:Liver Neoplasms / Q000000981:diagnostic imaging / Q000556:secondary* / Q000601:surgery*; D059146:Metastasectomy / Q000379:methods*; D064847:Multimodal Imaging; D018365:Neoplasm, Residual; D049268:Positron-Emission Tomography; D011237:Predictive Value of Tests; D011446:Prospective Studies; D019275:Radiopharmaceuticals; D012307:Risk Factors; D013997:Time Factors; D014057:Tomography, X-Ray Computed; D016896:Treatment Outcome
chemical_list: D003287:Contrast Media; D019275:Radiopharmaceuticals; D019788:Fluorodeoxyglucose F18; D007472:Iohexol; C038192:iopromide