title: Impact of iodine delivery rate with varying flow rates on image quality in dual-energy CT of patients with suspected pulmonary embolism.
abstract: OBJECTIVE
  To prospectively compare four contrast material injection protocols for dual-energy computed tomography (CT) pulmonary angiography (DE-CTPA) in patients with suspected pulmonary embolism (PE).
  
  
  METHODS
  One hundred twenty consecutive patients were randomized to contrast material injection protocols defined by different iodine concentrations and iodine delivery rates (IDRs): (A) 80 mL iopromide 370/4 mL/sec = IDR 1.4 gI/sec; (B) 80 mL iopromide 370 at 3 mL/sec = IDR 1.1 gI/sec; (C) 98 mL iopromide 300 at 4.9 mL/sec = IDR 1.4 gI/sec; and (D) 98 mL iopromide 300 at 3.7 mL/sec = IDR 1.1 gI/sec. Attenuation values were measured in the inflow tract (subclavian vein-superior vena cava-right atrium), target tract (right ventricle-pulmonary trunk-pulmonary arteries), and outflow tract (left atrium-left ventricle-ascending aorta). Two readers assessed subjective image quality of CTPA images and iodine perfusion maps. The number of artifacts due to hyperdense contrast material on iodine perfusion maps was recorded.
  
  
  RESULTS
  Target tract attenuation was highest for protocol A with 374 ± 98 Hounsfield units (HU) (highly concentrated contrast material/high IDR). This was significant compared to protocols B and D (P = .0118, P = .0427) but not compared to protocol C (P = .3395). No significant difference in target tract attenuation was found between protocols B (309 ± 80 HU), protocol C (352 ± 119 HU), and D (325 ± 74 HU). CTPA and iodine perfusion map image quality for protocol A was rated significantly higher compared to all other protocols (median score = 5/4; P < .0001 for both) with moderate interreader agreement (κ = 0.58/0.47). Protocols A and B displayed increased artifacts on iodine perfusion maps compared to protocols C and D (3 versus 2).
  
  
  CONCLUSIONS
  Despite increased artifacts on iodine perfusion maps, highly concentrated iodinated contrast material combined with high flow rates provides improved diagnostic image quality and has the highest target-tract attenuation for DE-CTPA protocols.
authors.affiliation: Institute of Clinical Radiology and Nuclear Medicine, University Medical Center Mannheim, Medical Faculty Mannheim - Heidelberg University, Theodor-Kutzer-Ufer 1-3, D-68167 Mannheim, Germany.
authors.forename: Jan
authors.initials: J
authors.lastname: Hansmann
authors.forename: Christian
authors.initials: C
authors.lastname: Fink
authors.forename: Gregor
authors.initials: G
authors.lastname: Jost
authors.forename: Hubertus
authors.initials: H
authors.lastname: Pietsch
authors.forename: Mathias
authors.initials: M
authors.lastname: Meyer
authors.forename: John W
authors.initials: JW
authors.lastname: Nance
authors.forename: Uwe J
authors.initials: UJ
authors.lastname: Schoepf
authors.forename: Ulrike I
authors.initials: UI
authors.lastname: Attenberger
authors.forename: Stefan O
authors.initials: SO
authors.lastname: Schoenberg
authors.forename: Thomas
authors.initials: T
authors.lastname: Henzler
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D003287:Contrast Media / Q000008:administration & dosage; D005260:Female; D006801:Humans; D007472:Iohexol / Q000008:administration & dosage / Q000031:analogs & derivatives*; D008297:Male; D008875:Middle Aged; D011655:Pulmonary Embolism / Q000000981:diagnostic imaging*; D011856:Radiographic Image Enhancement / Q000379:methods*; D015900:Radiography, Dual-Energy Scanned Projection / Q000379:methods*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D014057:Tomography, X-Ray Computed / Q000379:methods*
chemical_list: D003287:Contrast Media; D007472:Iohexol; C038192:iopromide
keywords: Dual-energy CT; iodine delivery rate; pulmonary embolism; pulmonary perfusion