title: Influence of Respiratory Position on Contrast Attenuation in Pulmonary CT Angiography: A Prospective Randomized Clinical Trial.
abstract: OBJECTIVE
  The purpose of this study was to prospectively compare the effect of inspiration and resting expiratory position on contrast enhancement in pulmonary CT angiography (CTA) in a randomized clinical trial.
  
  
  METHODS
  In accordance with a power analysis performed before the study, we included 28 consecutive patients referred for evaluation of suspected pulmonary embolism in this prospective study. Patients were randomly assigned to perform either inspiration (n = 14; six men, eight women; mean age [SD], 38.1 ± 9.8 years) or resting expiratory position (n = 14; six men, eight women; mean age: 42.1 ± 9.2 years). All patients were scanned in a standardized supine position and scanning parameters were kept constant. Contrast medium was injected automatically with bolus tracking. Objective pulmonary vessel attenuation was quantified with digital measurement. Results were analyzed by using the unpaired t test and chi-square test.
  
  
  RESULTS
  Patients in the resting expiratory position showed significantly higher contrast attenuation than those who performed inspiration (302.9 ± 11.9 HU vs 221.5 ± 20.9 HU; p < 0.01). There were no significant differences in applied total volume of contrast agent (76.8 ± 1.9 mL vs 75.7 ± 1.6 mL; p = 0.6765), total volume including normal saline bolus (116.8 mL ± 2.8 mL vs 121.8 mL ± 2.3 mL; p = 0.1724) or flow rate (3.1 mL/s ± 0.1 mL/s vs 3.2 mL/s ± 0.1 mL/s).
  
  
  CONCLUSIONS
  Pulmonary CTA should be performed in the resting expiratory position, and patients should be instructed to avoid inspiration to achieve the highest possible attenuation in the pulmonary arteries.
authors.affiliation: 1 Department of Diagnostic and Interventional Radiology, Saarland University Medical Center, Kirrberger Str 1, 66421 Homburg/Saar, Germany.
authors.forename: Paul
authors.initials: P
authors.lastname: Raczeck
authors.affiliation: 1 Department of Diagnostic and Interventional Radiology, Saarland University Medical Center, Kirrberger Str 1, 66421 Homburg/Saar, Germany.
authors.forename: Peter
authors.initials: P
authors.lastname: Minko
authors.affiliation: 2 Institute of Medical Biometry, Epidemiology and Medical Informatics, Saarland University Medical Center, Homburg/Saar, Germany.
authors.forename: Stefan
authors.initials: S
authors.lastname: Graeber
authors.affiliation: 1 Department of Diagnostic and Interventional Radiology, Saarland University Medical Center, Kirrberger Str 1, 66421 Homburg/Saar, Germany.
authors.forename: Peter
authors.initials: P
authors.lastname: Fries
authors.affiliation: 1 Department of Diagnostic and Interventional Radiology, Saarland University Medical Center, Kirrberger Str 1, 66421 Homburg/Saar, Germany.
authors.forename: Roland
authors.initials: R
authors.lastname: Seidel
authors.affiliation: 1 Department of Diagnostic and Interventional Radiology, Saarland University Medical Center, Kirrberger Str 1, 66421 Homburg/Saar, Germany.
authors.forename: Arno
authors.initials: A
authors.lastname: Buecker
authors.affiliation: 1 Department of Diagnostic and Interventional Radiology, Saarland University Medical Center, Kirrberger Str 1, 66421 Homburg/Saar, Germany.
authors.forename: Jonas
authors.initials: J
authors.lastname: Stroeder
mesh_terms: D000328:Adult; D000792:Angiography; D003287:Contrast Media; D045853:Exhalation; D005260:Female; D006801:Humans; D001239:Inhalation; D008168:Lung / Q000000981:diagnostic imaging* / Q000503:physiopathology; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D011651:Pulmonary Artery / Q000000981:diagnostic imaging* / Q000503:physiopathology; D011655:Pulmonary Embolism / Q000000981:diagnostic imaging* / Q000503:physiopathology; D014057:Tomography, X-Ray Computed
chemical_list: D003287:Contrast Media
keywords: contrast medium; pulmonary CT angiography; pulmonary artery; pulmonary embolism; respiration