title: [Computed tomography appearance of high-dose-irradiated hepatic parenchyma surrounding small tumors after stereotactic radiotherapy].
abstract: BACKGROUND
  The purpose of this study was to demonstrate the computed tomography (CT) appearance of high-dose-irradiated hepatic parenchyma surrounding small tumors after stereotactic radiotherapy (SRT).
  
  
  METHODS
  Thirteen patients were enrolled between September 1999 and August 2001. We treated 15 lesions [six hepatocellular carcinomas (HCC) and nine liver metastases] with SRT using a linear accelerator. We used two SRT protocols of 45 Gy/3 fractions or 60 Gy/8 fractions. Hepatic CT examinations were performed at 3- to 4-month intervals after SRT.
  
  
  RESULTS
  We classified the appearance of high-dose-irradiated hepatic parenchyma on CT into three types: Type 1: eight lesions (53.3%) showed low attenuation areas on non-contrast CT and high attenuation areas on contrast CT; Type 2: five lesions (33.3%) showed low attenuation areas on non-contrast and contrast CT; Type 3: two lesions (13.3%) showed no change. The CT appearance of Type 1 after SRT was similar to that of pre-irradiated HCC, but the other types were easily differentiated from the primary tumors. These changes were observed and continued for 6 to 22 months after treatment. In two cases of Type 1, we performed histological examinations of the regions of high attenuation on contrast CT. These specimens revealed only radiation-induced hepatic injury.
  
  
  CONCLUSIONS
  This study showed three types of CT appearance in high-dose-irradiated hepatic parenchyma. We suggest that other examinations be considered to distinguish between radiation hepatitis and local recurrences for HCC after SRT.
authors.affiliation: Department of Radiology, Takeda General Hospital.
authors.forename: Hitoshi
authors.initials: H
authors.lastname: Wada
authors.forename: Kenji
authors.initials: K
authors.lastname: Nemoto
authors.forename: Kazuhiro
authors.initials: K
authors.lastname: Majima
authors.forename: Shin
authors.initials: S
authors.lastname: Hitachi
authors.forename: Akihiro
authors.initials: A
authors.lastname: Sato
authors.forename: Kunihiko
authors.initials: K
authors.lastname: Tominaga
authors.forename: Shogo
authors.initials: S
authors.lastname: Yamada
mesh_terms: D000328:Adult; D000368:Aged; D006528:Carcinoma, Hepatocellular / Q000000981:diagnostic imaging* / Q000532:radiotherapy; D003937:Diagnosis, Differential; D005260:Female; D006505:Hepatitis / Q000000981:diagnostic imaging* / Q000209:etiology; D006801:Humans; D008099:Liver / Q000000981:diagnostic imaging*; D008113:Liver Neoplasms / Q000000981:diagnostic imaging* / Q000532:radiotherapy; D008297:Male; D008875:Middle Aged; D011832:Radiation Injuries / Q000000981:diagnostic imaging* / Q000209:etiology; D011882:Radiotherapy, High-Energy / Q000009:adverse effects*; D013238:Stereotaxic Techniques; D014057:Tomography, X-Ray Computed