title: Helical CT of the liver with computer-assisted bolus-tracking technology: scan delay of arterial phase scanning and effect of flow rates.
abstract: OBJECTIVE
  The purpose of this work was to assess the scan delay and the effect of flow rates on arterial phase scanning of hepatic CT.
  
  
  METHODS
  One hundred twenty patients suspected of having hepatocellular carcinoma were examined by three-phase helical CT using computer-assisted bolus-tracking technology. We set the region of interest (ROI) in the abdominal aorta at the level of the celiac artery as a baseline. The triggering threshold was set at 100 HU. A volume of 100 ml of iomeprol (350 mg of I/ml) was administered at 2, 2.5, or 3 ml/s i.v.
  
  
  RESULTS
  In all cases, helical CT scanning began after reaching the ROI threshold. Then, portal venous phase scanning was initiated 50 s after arterial phase initiation. The mean delay time from the initiation of contrast agent administration to the beginning of arterial phase scanning was 29.2 +/- 3.8 s (mean +/- SD, range 22-39 s). A faster injection rate significantly shortened the scan delay (p < 0.01). In portal venous phase scanning, calculated areas under the hepatic enhancement curves were almost equal among different injection rates.
  
  
  CONCLUSIONS
  The computer-assisted bolus-tracking technology is a useful method for determining an individual scan delay of arterial phase CT.
authors.affiliation: Department of Radiology, Osaka Medical College, Japan. rad005@poh.osaka-med.ac.jp
authors.forename: T
authors.initials: T
authors.lastname: Shimizu
authors.forename: T
authors.initials: T
authors.lastname: Misaki
authors.forename: K
authors.initials: K
authors.lastname: Yamamoto
authors.forename: K
authors.initials: K
authors.lastname: Sueyoshi
authors.forename: I
authors.initials: I
authors.lastname: Narabayashi
mesh_terms: D000368:Aged; D001012:Aorta, Abdominal / Q000000981:diagnostic imaging; D019540:Area Under Curve; D006528:Carcinoma, Hepatocellular / Q000175:diagnosis / Q000000981:diagnostic imaging*; D003287:Contrast Media / Q000008:administration & dosage / Q000493:pharmacokinetics; D005069:Evaluation Studies as Topic; D005260:Female; D006801:Humans; D007275:Injections, Intravenous; D007479:Iopamidol / Q000008:administration & dosage / Q000031:analogs & derivatives / Q000493:pharmacokinetics; D008099:Liver / Q000000981:diagnostic imaging* / Q000378:metabolism; D008113:Liver Neoplasms / Q000175:diagnosis / Q000000981:diagnostic imaging*; D008297:Male; D008875:Middle Aged; D011856:Radiographic Image Enhancement / Q000379:methods*; D012680:Sensitivity and Specificity; D014057:Tomography, X-Ray Computed / Q000379:methods*
chemical_list: D003287:Contrast Media; C057937:iomeprol; D007479:Iopamidol