title: Carbon dioxide-contrasted computed tomography angiography: high pitch protocols and adapted injection parameters improve imaging quality.
abstract: OBJECTIVE
  To systematically investigate the impact of image acquisition and contrast injection parameters for CO2-enhanced CT angiography (CTA) of the aorto-iliac and peripheral arteries in a pig model using commercially available equipment. The aim was to establish an imaging protocol that is ready for use in human subjects.
  
  
  METHODS
  Three domestic swine underwent CO2-CTA with varying injection parameters: pitch (1.0, 3.0), injection pressure (0.7 bar, 1.0 bar, 1.3 bar) and scan delay (2 s, 4 s, 6 s). Objective (vessel diameter) and subjective (image quality) parameters and applied radiation doses were systematically evaluated. To ensure clinical applicability of the setting, only approved catheters/injectors and standard injection parameters were evaluated.
  
  
  RESULTS
  The image quality scores were superior and the vessel diameter was larger with high pitch in comparison to standard pitch (diameters: 4.7 ± 2.0 mm vs. 3.6 ± 2.1 mm, p = 0.0040, scores: 2.6 ± 1.1 vs. 2.0 ± 1.1, p = 0.0038). High injection pressure (1.3 bar) improved the image quality as assessed by subjective and objective ratings (diameters: 3.6 ± 2.0 mm, 4.0 ± 2.1 mm and 4.6 ± 2.1 mm, for 0.7, 1.0 and 1.3 bar, p-values ≤ 0.0052, scores: 1.9 ± 1.1, 2.3 ± 1.1 and 2.7 ± 1.2, p-values ≤ 0.0017), the same was observed for a shorter injection delay (diameters: 3.5 ± 2.0 mm, 4.2 ± 2.1 mm and 4.8 ± 2.1 mm, for 6 s, 4 s, and 2 s, p ≤ 0.0022, scores: 1.9 ± 1.1, 2.3 ± 1.1 and 2.7 ± 1.1, p-values ≤ 0.0013). The dose length products were 239 ± 47 mGycm (high pitch) and 565 ± 63 mGycm (standard pitch, p-values < 0.0001).
  
  
  CONCLUSIONS
  A higher pitch, shorter delay and higher injection pressure improve image quality in CO2-enhanced CTA. Since commercially available, clinically approved equipment was used. The protocol is now ready for use in human subjects.
authors.affiliation: Department of Diagnostic and Interventional Radiology, RWTH Aachen University Hospital, Aachen, Germany.
authors.forename: T
authors.initials: T
authors.lastname: Penzkofer
authors.forename: K
authors.initials: K
authors.lastname: Slebocki
authors.forename: J
authors.initials: J
authors.lastname: Grommes
authors.forename: P
authors.initials: P
authors.lastname: Bruners
authors.forename: P P
authors.initials: PP
authors.lastname: Isfort
authors.forename: N
authors.initials: N
authors.lastname: Heussen
authors.forename: T
authors.initials: T
authors.lastname: Schmitz-Rode
authors.forename: C K
authors.initials: CK
authors.lastname: Kuhl
authors.forename: S
authors.initials: S
authors.lastname: Langer
authors.forename: A H
authors.initials: AH
authors.lastname: Mahnken
mesh_terms: D000792:Angiography / Q000379:methods*; D000818:Animals; D002245:Carbon Dioxide / Q000008:administration & dosage*; D003287:Contrast Media / Q000008:administration & dosage*; D004305:Dose-Response Relationship, Drug; D023421:Models, Animal; D011312:Pressure; D011856:Radiographic Image Enhancement / Q000379:methods*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013552:Swine; D014057:Tomography, X-Ray Computed / Q000379:methods*
chemical_list: D003287:Contrast Media; D002245:Carbon Dioxide