title: Value or waste: Perfusion imaging following radiofrequency ablation - early experience.
abstract: BACKGROUND
  Radiofrequency ablation (RFA) is an evolving technique in treatment of hepatic malignant tumors. By heating local tissue it leads to coagulative necrotic areas around the ablation probe. Temperature falls with increasing distance to the probe, risking incomplete necrosis at the margins of the RFA-induced lesion. Therefore, immediate non-invasive and precise detection of incomplete ablation is necessary for early enlargement of the ablation if needed.
  
  
  OBJECTIVE
  This in vivo pig study compares early experiences of immediate post-interventional computed tomography (CT) perfusion volume analysis to macroscopic and CT image evaluation in healthy pig liver.
  
  
  METHODS
  RFA was performed in vivo in healthy pig livers. Different CT perfusion algorithms (Maximum slope analysis and Patlak plot) were used to quantify three different perfusion parameters. Data points were acquired from rectangular grids. These grids were semiautomatically overlayed to macroscopic images documented after liver explantation. Each data point was visually assigned to zones defined as "inner" and "outer necrotic zone", "margin" or "vital tissue".
  
  
  RESULTS
  Significant differences between necrotic zones and vital tissue are shown for equivalent blood volume (p <  0.0001), arterial flow (p <  0.01) and flow extraction product (p <  0.001). Looking at equivalent blood volume and flow extraction product, there were also significant differences (EquivBV: p <  0.0001, FE: p <  0.001) between margins, necrotic and vital areas.
  
  
  CONCLUSIONS
  In a porcine model these early results could show that all of the used CT perfusion parameters allowed discrimination of necrosis from vital tissue after RFA at high levels of significance. In addition, the parameters EquivBV and FE that give an estimate of the tissue blood volume and the permeability, were able to precisely discern different zones also seen macroscopically. From this data CT perfusion analysis could be precise tool for measurement and visualization of ablated liver lesions and for immediate detection of incomplete ablation areas.
authors.affiliation: Department of Radiology, Charité-University Medicine Berlin, Berlin, Germany.
authors.forename: Stefan F
authors.initials: SF
authors.lastname: Thieme
authors.affiliation: Department of Radiology, Charité-University Medicine Berlin, Berlin, Germany.
authors.forename: Janis L
authors.initials: JL
authors.lastname: Vahldiek
authors.affiliation: Theoretische Biophysik, Humboldt-Universität zu Berlin, Berlin, Germany.
authors.forename: Katja
authors.initials: K
authors.lastname: Tummler
authors.affiliation: Department of Surgery, Charité-University Medicine Berlin, Berlin, Germany.
authors.forename: Franz
authors.initials: F
authors.lastname: Poch
authors.affiliation: Department of Surgery, Charité-University Medicine Berlin, Berlin, Germany.
authors.forename: Ole
authors.initials: O
authors.lastname: Gemeinhardt
authors.affiliation: Center for Medical Basic Research, Martin-Luther-University Halle-Wittenberg, Halle (Saale), Germany.
authors.forename: Bernhard
authors.initials: B
authors.lastname: Hiebl
authors.affiliation: Department of Surgery, Charité-University Medicine Berlin, Berlin, Germany.
authors.forename: Kai S
authors.initials: KS
authors.lastname: Lehmann
authors.affiliation: Department of Radiology, Charité-University Medicine Berlin, Berlin, Germany.
authors.forename: B
authors.initials: B
authors.lastname: Hamm
authors.affiliation: Department of Radiology, Charité-University Medicine Berlin, Berlin, Germany.
authors.forename: Stefan M
authors.initials: SM
authors.lastname: Niehues
mesh_terms: D000818:Animals; D017115:Catheter Ablation; D008099:Liver / Q000000981:diagnostic imaging / Q000473:pathology*; D008113:Liver Neoplasms / Q000000981:diagnostic imaging / Q000473:pathology / Q000601:surgery*; D023421:Models, Animal; D009336:Necrosis / Q000000981:diagnostic imaging; D055420:Perfusion Imaging; D013552:Swine; D014057:Tomography, X-Ray Computed
keywords: Liver; animal model; interventional radiology; multidetector computed tomography (CT); perfusion CT; radiofrequency ablation (RFA)