title: How influential is the duration of contrast material bolus injection in perfusion CT? evaluation in a swine model.
abstract: OBJECTIVE
  To analyze the effect of the duration of contrast material bolus injection on perfusion values in a swine model by using the maximum slope method.
  
  
  METHODS
  This study was approved by the institutional animal care committee. Twenty pigs (weight range, 63-77 kg) underwent dynamic volume computed tomography (CT) of the kidneys during suspended respiration. Before the CT examination, a miniature cuff-shaped ultrasonographic flow probe encircling the right renal artery was surgically implanted in each pig to obtain true perfusion values. Two sequential perfusion CT series were performed in 30 seconds, each comprising 30 volumes with identical parameters (100 kV, 200 mAs, 0.5 sec rotation time). The duration of contrast material bolus (0.5 mL/kg of body weight) was 3.8 seconds in the first series (short bolus series) and 11.5 seconds in the second series (long bolus series), and the injection flow rate was adapted accordingly. In each pig, cortical kidney volume was determined by using the volume with the highest cortical enhancement. CT perfusion values were calculated for both series by using the maximum slope method and were statistically compared and correlated with the true perfusion values from the flow probe by using linear regression analysis.
  
  
  RESULTS
  Mean true perfusion and CT perfusion values (in minutes(-1)) for the short bolus series were 1.95 and 2.03, respectively (P = .22), and for the long bolus series, they were 2.02 and 1.92, respectively (P = .12). CT perfusion showed very good correlation with true perfusion in both the short (slope, 1.01; 95% confidence interval: 0.91, 1.11) and long (slope, 0.92; 95% confidence interval: 0.78, 1.04) series. On the basis of the regression analysis, CT perfusion values in the short bolus series were overestimated by 1% and those in the long bolus series were underestimated by 8%.
  
  
  CONCLUSIONS
  Duration of contrast material bolus injection does not influence CT perfusion values substantially. The longer, clinically preferred intravenous injection scheme is sufficiently accurate for CT perfusion.
authors.affiliation: From the Department of Medical Imaging, Toronto General Hospital, University of Toronto, 585 University Ave, NCSB 1C560, Toronto, ON, Canada M5G 2N2.
authors.forename: Sonja M
authors.initials: SM
authors.lastname: Kandel
authors.forename: Henning
authors.initials: H
authors.lastname: Meyer
authors.forename: Markus
authors.initials: M
authors.lastname: Boehnert
authors.forename: Bernice
authors.initials: B
authors.lastname: Hoppel
authors.forename: Narinder Singh
authors.initials: NS
authors.lastname: Paul
authors.forename: Patrik
authors.initials: P
authors.lastname: Rogalla
mesh_terms: D000818:Animals; D001783:Blood Flow Velocity; D003287:Contrast Media / Q000493:pharmacokinetics*; D007091:Image Processing, Computer-Assisted; D007275:Injections, Intravenous; D007668:Kidney / Q000098:blood supply / Q000000981:diagnostic imaging* / Q000378:metabolism*; D013552:Swine; D013997:Time Factors; D014057:Tomography, X-Ray Computed / Q000379:methods*; D014283:Triiodobenzoic Acids / Q000493:pharmacokinetics*; D014463:Ultrasonography
chemical_list: D003287:Contrast Media; D014283:Triiodobenzoic Acids; C044834:iodixanol