title: Multi-detector row CT: effect of iodine dose reduction on hepatic and vascular enhancement.
abstract: OBJECTIVE
  To evaluate the impact of different iodine concentrations of intravenous contrast agent on hepatic and vascular enhancement during arterial and porto-venous phase imaging using a 4-channel multi-detector row CT (MDCT).
  
  
  METHODS
  One hundred consecutive patients referred for triphasic abdominal MDCT were randomly assigned into four groups receiving different iodine concentration (200, 250, 300 or 350 mg/ml). Non-contrast, arterial, and porto-venous phase 4-channel MDCT imaging was performed (VolumeZoom, Siemens, Germany). A fixed volume of 150 ml intravenous contrast agent at a rate of 3 ml/s was injected using an automatic bolus-tracking system (Care Bolus, Siemens, Erlangen). Hepatic and vascular enhancement values were measured over time and non-contrast values were subtracted in order to compute arterial and porto-venous mean hepatic (MHE) and mean aortic (MAE) enhancement for each group. Mean change of enhancement > 80 HU for the aorta and > 40 HU for the liver during porto-venous phase imaging was considered as sufficient enhancement.
  
  
  RESULTS
  All groups achieved sufficient vascular enhancement during arterial phase imaging; MAE with 350 mg/ml (222 HU) and 300 mg/ml (213HU) was significantly better than with 250 mg (196HU) and 200 mg/ml (169 HU), whereas MHE showed no statistically significant difference between the groups (range 16 - 25 HU). Porto-venous MHE showed increased enhancement with larger concentrations, with significant differences among the groups. Only the higher concentration groups (350 mg/ml und 300 mg/ml) fulfilled in every individual the guidelines for sufficient porto-venous MHE. In the lower concentration groups, 8 patients with 200 mg/ml and 3 patients with 250 mg/ml showed enhancement values below the required minimum.
  
  
  CONCLUSIONS
  A decrease in iodine contrast agent down to 200 mg/ml concentration is only tenable for propose of vascular aortic and hepatic arterial enhancement, whereas hepatic porto-venous phase imaging still requires concentrations at or above the level of 300 mg/ml.
authors.affiliation: Institute of Diagnostic Radiology, University Hospital Zurich, Switzerland. justus.roos@usz.ch
authors.forename: J E
authors.initials: JE
authors.lastname: Roos
authors.forename: L M
authors.initials: LM
authors.lastname: Desbiolles
authors.forename: D
authors.initials: D
authors.lastname: Weishaupt
authors.forename: S
authors.initials: S
authors.lastname: Wildermuth
authors.forename: P R
authors.initials: PR
authors.lastname: Hilfiker
authors.forename: B
authors.initials: B
authors.lastname: Marincek
authors.forename: T
authors.initials: T
authors.lastname: Boehm
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000704:Analysis of Variance; D001027:Aortography / Q000379:methods; D003287:Contrast Media / Q000008:administration & dosage*; D003627:Data Interpretation, Statistical; D005260:Female; D006801:Humans; D007275:Injections, Intravenous; D007455:Iodine / Q000008:administration & dosage*; D008099:Liver / Q000000981:diagnostic imaging*; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D011860:Radiography, Abdominal / Q000379:methods; D013997:Time Factors; D014057:Tomography, X-Ray Computed / Q000379:methods*; D014283:Triiodobenzoic Acids / Q000008:administration & dosage*
chemical_list: D003287:Contrast Media; D014283:Triiodobenzoic Acids; C053571:iopentol; D007455:Iodine