title: Dynamic CT for detecting small hepatocellular carcinoma: usefulness of delayed phase imaging.
abstract: OBJECTIVE
  The purpose of this retrospective study was to determine the usefulness of delayed phase imaging for detecting small (< or = 2 cm) hepatocellular carcinomas (HCCs) in patients with liver cirrhosis.
  
  
  METHODS
  Triphasic (arterial, portal venous, and delayed phases) dynamic CT was performed in 33 patients with 48 HCCs proven histopathologically and in 65 control subjects. Arterial, portal venous, and delayed phase images were obtained 30 seconds, 68-70 seconds, and 5 minutes after the start of contrast material injection, respectively. Three blinded observers reviewed the images independently and evaluated tumor attenuation. Diagnostic performance for the combination of phases was assessed using receiver operating characteristic (ROC) curve analysis.
  
  
  RESULTS
  On arterial phase images, 28 of the 48 HCCs were hyperattenuating, nine were isoattenuating, and 11 were hypoattenuating. On portal venous phase images, three tumors were hyperattenuating, 17 were isoattenuating, and 28 were hypoattenuating. On delayed phase images, five tumors were isoattenuating, and 43 were hypoattenuating. The mean sensitivity for the combination of arterial and portal venous phase imaging was 86.8%, that for the combination of arterial and delayed phase imaging was 90.3%, and that for the combination of all three phase imaging was 93.8%. The area underneath composite ROC curve (A(Z)) for the combination of all three phase imaging (A(Z) = 0.940) was significantly higher than that for the combination of arterial and portal venous phase imaging (A(Z) = 0.917) and for the combination of arterial and delayed phase imaging (A(Z) = 0.922).
  
  
  CONCLUSIONS
  Delayed phase imaging is useful for detecting small HCCs and should be included in dynamic CT examinations of patients with liver cirrhosis.
authors.affiliation: Department of Radiology, Yamanashi Hospital, Kofu, Yamanashi, Japan.
authors.forename: Shuichi
authors.initials: S
authors.lastname: Monzawa
authors.forename: Tomoaki
authors.initials: T
authors.lastname: Ichikawa
authors.forename: Hiroto
authors.initials: H
authors.lastname: Nakajima
authors.forename: Yuki
authors.initials: Y
authors.lastname: Kitanaka
authors.forename: Kosaku
authors.initials: K
authors.lastname: Omata
authors.forename: Tsutomu
authors.initials: T
authors.lastname: Araki
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000465:Algorithms; D006528:Carcinoma, Hepatocellular / Q000000981:diagnostic imaging*; D005260:Female; D006801:Humans; D008113:Liver Neoplasms / Q000000981:diagnostic imaging*; D008297:Male; D008875:Middle Aged; D011856:Radiographic Image Enhancement / Q000379:methods*; D011857:Radiographic Image Interpretation, Computer-Assisted / Q000379:methods*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013997:Time Factors; D014057:Tomography, X-Ray Computed / Q000379:methods*