title: MR appearances of radiofrequency thermal ablation region: histopathologic correlation with dog liver models and an autopsy case.
abstract: OBJECTIVE
  The purpose of this study was to evaluate the utility of magnetic resonance (MR) imaging for indicating the extent of true tissue necrosis of the liver after radiofrequency (RF) ablation in comparison with histopathologic findings in dog models and an autopsy case.
  
  
  METHODS
  RF ablation of the liver parenchyma was performed on three dogs under general anesthesia. MR appearances of the RF-ablated regions on T1-weighted fast-low angle shot (FLASH; repetition time/echo time [TR/TE]/flip angle: 120/3.8/70),T2-weighted turbo spin echo (3000/80/echo train = 25) and contrast-enhanced T1-weighted images were compared with histopathologic findings. An autopsy case with hepatocellular carcinoma was also enrolled in this study.
  
  
  RESULTS
  All ablated regions showed three zones on T1-weighted FLASH images: a central zone with low intensity, a broad hyperintense middle zone, and a surrounding hypointense band. The central and middle zones corresponded to the degrees of coagulation necrosis observed during histopathologic examination, whereas no viable cells were seen in these zones during the microscopic examination using nicotinamide adenine dinucleotide diaphorase stain. The surrounding hypointense band corresponded to sinusoidal congestion in the acute phase and to fibrotic change in the subacute phase.
  
  
  CONCLUSIONS
  MR imaging using the FLASH sequence can accurately determine the extent of the necrotic area after RF ablation.
authors.affiliation: Department of Radiology, Osaka University Graduate School of Medicine, 2-2, Yamadaoka, Suita, Osaka 565-0871, Japan.
authors.forename: Hiromitsu
authors.initials: H
authors.lastname: Onishi
authors.forename: Masaki
authors.initials: M
authors.lastname: Matsushita
authors.forename: Takamichi
authors.initials: T
authors.lastname: Murakami
authors.forename: Takeshi
authors.initials: T
authors.lastname: Tono
authors.forename: Shigeru
authors.initials: S
authors.lastname: Okamoto
authors.forename: Yoshiko
authors.initials: Y
authors.lastname: Aoki
authors.forename: Riccardo
authors.initials: R
authors.lastname: Iannaccone
authors.forename: Masatoshi
authors.initials: M
authors.lastname: Hori
authors.forename: Tonsok
authors.initials: T
authors.lastname: Kim
authors.forename: Keigo
authors.initials: K
authors.lastname: Osuga
authors.forename: Kaname
authors.initials: K
authors.lastname: Tomoda
authors.forename: Roberto
authors.initials: R
authors.lastname: Passariello
authors.forename: Hironobu
authors.initials: H
authors.lastname: Nakamura
mesh_terms: D000368:Aged; D000818:Animals; D001344:Autopsy; D006528:Carcinoma, Hepatocellular / Q000473:pathology* / Q000601:surgery*; D017115:Catheter Ablation; D004285:Dogs; D006801:Humans; D008099:Liver / Q000473:pathology* / Q000601:surgery*; D008113:Liver Neoplasms / Q000473:pathology* / Q000601:surgery*; D008279:Magnetic Resonance Imaging; D008297:Male