title: Optimal scan delay in spiral CT for the diagnosis of acute pulmonary embolism.
abstract: OBJECTIVE
  The purpose of this work was to assess whether easily obtained clinical parameters can predict optimal scan delay for contrast-enhanced spiral CT of pulmonary arteries and to compare image quality between individualized contrast timing versus a fixed scan delay.
  
  
  METHODS
  We used an individualized delay in 85 patients by measuring the contrast transit time through the pulmonary circulation (Group A) and assessed the correlation between transit time and clinical parameters. In 56 patients (Group B), we used a 20 s fixed scan delay. The CT examinations of both groups were compared with regard to image quality.
  
  
  RESULTS
  Contrast transit times (mean 10.5 s, range 4-26 s) did not correlate significantly with heart rate, blood pressure, body length, weight, body surface area, or cardiac function. Although contrast transit times were significantly related to gender and age, only 14.8% of the variation could be explained by these clinical parameters. Data of 57 patients in Group A and 50 patients in Group B were available for analysis. Image quality was not significantly different between Groups A and B, which was good, moderate, and poor in 61, 32, and 7% in Group A and 60, 34, and 6% in Group B, respectively (p = 1.0).
  
  
  CONCLUSIONS
  One cannot predict individual scan delay from easily obtainable clinical parameters. Fortunately, a 20 s fixed scan delay provides equal image quality as individualized contrast timing.
authors.affiliation: Departments of Radiology, University Medical Center Utrecht, The Netherlands. I.J.C.Hartmann@azu.nl
authors.forename: Ieneke J C
authors.initials: IJ
authors.lastname: Hartmann
authors.forename: Rob T H
authors.initials: RT
authors.lastname: Lo
authors.forename: Jeannette
authors.initials: J
authors.lastname: Bakker
authors.forename: Wouter
authors.initials: W
authors.lastname: de Monyé
authors.forename: Paul F G M
authors.initials: PF
authors.lastname: van Waes
authors.forename: Peter M T
authors.initials: PM
authors.lastname: Pattynama
mesh_terms: D000208:Acute Disease; D016022:Case-Control Studies; D003287:Contrast Media; D005260:Female; D006801:Humans; D007472:Iohexol / Q000031:analogs & derivatives*; D008297:Male; D008875:Middle Aged; D011651:Pulmonary Artery / Q000000981:diagnostic imaging; D011655:Pulmonary Embolism / Q000000981:diagnostic imaging*; D013997:Time Factors; D014057:Tomography, X-Ray Computed / Q000379:methods*
chemical_list: D003287:Contrast Media; D007472:Iohexol; C038192:iopromide