title: Assessment of ablative margin by unenhanced magnetic resonance imaging after radiofrequency ablation for hepatocellular carcinoma.
abstract: OBJECTIVE
  The aim of this study was to evaluate the feasibility of magnetic resonance imaging (MRI) without a contrast agent to visualize the ablative margin after radiofrequency ablation (RFA) for hepatocellular carcinoma (HCC), compared with enhanced CT.
  
  
  METHODS
  Twenty-five HCCs in 19 patients were treated by RFA. T1-weighted MRI was performed before and after RFA, and the signal intensities of the tumors and surrounding liver tissues were measured. Treatment efficacy was assessed based on three grades: margin (+), a continuous high-intensity rim around the index tumor; margin zero, a partially discontinuous high-intensity rim; margin (-), the tumor extends beyond the high-intensity rim.
  
  
  RESULTS
  Twelve (86%) of fourteen low-intensity tumors on the pre-MRI were visualized as low-intensity tumors on post-MRI, and the ablative margins were visualized as high-intensity rims. Two (67%) of three high-intensity tumors on pre-MRI were visualized as higher-intensity tumors in the high-intensity ablative margin. Because the signal intensities of tumors and surrounding tissues in 14 tumors that were low- or high-intensity tumors on pre-MRI increased to the same extent, the tumors and ablative margin could be distinguished on post images. In 6 (75%) of the 8 iso-intensity tumors on pre-MRI, the ablative margin and tumor could also not be discriminated on post-MRI. The overall agreement between MRI and CT for the ablative margin was good (κ coefficient=0.716, p=0.00002).
  
  
  CONCLUSIONS
  In 82% of low- or high-intensity tumors on pre-MRI, post-MRI without a contrast agent enabled visualization of the ablative margin as a high-intensity rim, and it was possible to evaluate the ablative margin earlier and easier than with enhanced CT.
authors.affiliation: Division of Medicine and Clinical Science, Department of Multidisciplinary Internal Medicine, Tottori University School of Medicine, Yonago 683-8504, Japan. masakoda@grape.med.tottori-u.ac.jp
authors.forename: Masahiko
authors.initials: M
authors.lastname: Koda
authors.forename: Shiho
authors.initials: S
authors.lastname: Tokunaga
authors.forename: Kennichi
authors.initials: K
authors.lastname: Miyoshi
authors.forename: Manabu
authors.initials: M
authors.lastname: Kishina
authors.forename: Yuki
authors.initials: Y
authors.lastname: Fujise
authors.forename: Jun
authors.initials: J
authors.lastname: Kato
authors.forename: Tomomitsu
authors.initials: T
authors.lastname: Matono
authors.forename: Kinya
authors.initials: K
authors.lastname: Okamoto
authors.forename: Yoshikazu
authors.initials: Y
authors.lastname: Murawaki
authors.forename: Suguru
authors.initials: S
authors.lastname: Kakite
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D006528:Carcinoma, Hepatocellular / Q000473:pathology* / Q000601:surgery*; D003287:Contrast Media; D005240:Feasibility Studies; D005260:Female; D006498:Hepatectomy / Q000379:methods; D006801:Humans; D007089:Image Enhancement; D008099:Liver / Q000473:pathology* / Q000601:surgery*; D008113:Liver Neoplasms / Q000473:pathology* / Q000601:surgery*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D025321:Surgery, Computer-Assisted / Q000379:methods; D016896:Treatment Outcome
chemical_list: D003287:Contrast Media