title: Signal intensity of small hepatocellular carcinoma on apparent diffusion coefficient mapping and outcome after radiofrequency ablation.
abstract: OBJECTIVE
  It has been reported that the apparent diffusion coefficient (ADC) value of hepatocellular carcinomas (HCC) on diffusion-weighted magnetic resonance imaging (MRI) is associated with their histological grade. The present study aimed to evaluate whether the signal intensity of small hypervascular HCC on the ADC map is related to the treatment outcome of radiofrequency ablation (RFA).
  
  
  METHODS
  Between February 2008 and August 2012, 136 consecutive patients with initial small hypervascular HCC (≤3 tumors and ≤3 cm in diameter) were examined by diffusion-weighted MRI before RFA. The signal intensities of HCC on the ADC map were visually compared with the surrounding liver and categorized as hypointense and non-hypointense. Critical recurrence was defined as more than three intrahepatic recurrences, recurrence with vascular invasion, seeding, dissemination and/or extrahepatic metastasis.
  
  
  RESULTS
  The median follow up was 619 days. The cumulative 2-year recurrence rates of the hypointense and non-hypointense on the ADC map groups were 79% and 50% (P < 0.001), respectively, with cumulative 2-year local recurrence rates of 18% and 7% (P = 0.014) and cumulative 2-year critical recurrence rates of 38% and 13% (P = 0.005), respectively. The cumulative 3-year survival rates were 60% and 82% (P = 0.007), respectively. On multivariate analysis, hypointensity on the ADC map was the strongest independent factor related to recurrence and survival after RFA.
  
  
  CONCLUSIONS
  The signal intensity of HCC on the ADC map was strongly associated with outcome after RFA. These results suggest that treatment strategy should be determined carefully even for small HCC when they appear hypointense on the ADC map.
authors.affiliation: Second Department of Internal Medicine, Wakayama Medical University, Wakayama, Japan.
authors.forename: Yoshiyuki
authors.initials: Y
authors.lastname: Mori
authors.forename: Hideyuki
authors.initials: H
authors.lastname: Tamai
authors.forename: Naoki
authors.initials: N
authors.lastname: Shingaki
authors.forename: Kosaku
authors.initials: K
authors.lastname: Moribata
authors.forename: Hisanobu
authors.initials: H
authors.lastname: Deguchi
authors.forename: Kazuki
authors.initials: K
authors.lastname: Ueda
authors.forename: Izumi
authors.initials: I
authors.lastname: Inoue
authors.forename: Takao
authors.initials: T
authors.lastname: Maekita
authors.forename: Mikitaka
authors.initials: M
authors.lastname: Iguchi
authors.forename: Jun
authors.initials: J
authors.lastname: Kato
authors.forename: Masaki
authors.initials: M
authors.lastname: Terada
authors.forename: Masao
authors.initials: M
authors.lastname: Ichinose
keywords: apparent diffusion coefficient map; diffusion-weighted imaging; hepatocellular carcinoma; magnetic resonance imaging; radiofrequency ablation