title: Pulmonary embolism: prospective comparison of iso-osmolar and low-osmolarity nonionic contrast agents for contrast enhancement at CT angiography.
abstract: OBJECTIVE
  To prospectively evaluate contrast enhancement on pulmonary computed tomographic (CT) angiograms obtained by using an iso-osmolar versus a low-osmolarity contrast agent to exclude pulmonary embolism.
  
  
  METHODS
  Written patient consent was obtained on a form approved by the institutional review board, and the board approved the study. This prospective, randomized, double-blinded clinical trial included 47 patients referred for multi-detector row CT angiography to exclude pulmonary embolism over a 5-month period. Patients received either iohexol or iodixanol as an intravenous contrast agent. Three radiologists independently evaluated enhancement homogeneity and quality in designated pulmonary artery branches at four consecutive levels in the lower lobe of the left lung from lobar to subsegmental arteries. This evaluation was performed at a workstation separately for homogeneity and quality with two different three-level scales established with consensus. Percentages of each given score were compared with the chi2 test. The mean attenuation (expressed in Hounsfield units) for each contrast agent was compared with Student t test, and interobserver agreement (kappa value) was calculated.
  
  
  RESULTS
  The percentages of arteries graded as excellent or not diagnostic were not statistically different (P >.05), with comparison of the two contrast agents at all levels. The intensity of enhancement (quantitative evaluation of enhancement by using mean attenuation of vessel lumen) was similar (P >.05) in the two groups. The kappa values varied from 0.35 to 0.56 among readers.
  
  
  CONCLUSIONS
  Use of an iso-osmolar contrast agent at multi-detector row CT angiography to exclude pulmonary embolism did not significantly improve enhancement quality when this feature was compared with that of a low-osmolarity contrast agent.
authors.affiliation: Department of Radiology, Centre Hospitalier Universitaire de Sherbrooke, 3001 12 Ave Nord, Local 2525, Sherbrooke, Quebec, Canada J1H 5N4.
authors.forename: Justine P
authors.initials: JP
authors.lastname: Bédard
authors.forename: Christian
authors.initials: C
authors.lastname: Blais
authors.forename: Yves G
authors.initials: YG
authors.lastname: Patenaude
authors.forename: Ernest
authors.initials: E
authors.lastname: Monga
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000792:Angiography; D016009:Chi-Square Distribution; D003287:Contrast Media; D004311:Double-Blind Method; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted; D007472:Iohexol; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D011655:Pulmonary Embolism / Q000000981:diagnostic imaging*; D014057:Tomography, X-Ray Computed / Q000379:methods*; D014283:Triiodobenzoic Acids
chemical_list: D003287:Contrast Media; D014283:Triiodobenzoic Acids; D007472:Iohexol; C044834:iodixanol