title: Caudocranial scan direction and patient-specific injection protocols optimize ECG-gated and non-gated thoracic CTA.
abstract: OBJECTIVE
  Caudocranial scan direction and contrast injection timing based on measured patient vessel dynamics can significantly improve artery opacification and reduce contrast dose in the assessment of acute aortic syndrome using gated and non-gated thoracic CTA. This study aimed to investigate enhancement of the thoracic aorta using caudocranial scan direction and a patient-specific contrast regimen.
  
  
  METHODS
  Electrocardiogram-gated (n = 120) and non-gated (n = 200) thoracic computed tomography angiography was performed on patients with nontraumatic acute aortic syndrome. Patients were assigned to one of 2 acquisition/contrast regimens, namely, regimen A, craniocaudal scan direction with 120 mL contrast, and regimen B, caudocranial scan direction using a patient-specific contrast formula. Opacity of 9 arterial and venous segments was measured, arteriovenous contrast ratio calculated, and values compared using Mann-Whitney U statistics. Receiver operating characteristic analyses and visual grading characteristic assessed diagnostic efficacy and clinical image quality. Interobserver variations were investigated using κ methods.
  
  
  RESULTS
  Regimen B when compared to A, for both scanning/contrast techniques, demonstrated higher opacification in the aorta (P < 0.01) and lower opacification in the venous system (P < 0.0001). For protocol B, arteriovenous contrast ratio was significantly increased (P < 0.0001) and mean contrast volume reduced (P < 0.05) during gated [94 (10 mL)] and non-gated [78 (5 mL)] thoracic computed tomography angiography compared to A. Receiver operating characteristic analysis Az scores and interobserver agreement were significantly higher with regimen B than A (P < 0.05).
  
  
  CONCLUSIONS
  Caudocranial scan direction and injection timing based on patient-specific vessel dynamics can optimize artery opacification and diagnostic efficacy while reducing contrast volumes.
authors.affiliation: From the *Department of Radiology, Royal Prince Alfred Hospital, Sydney; †Discipline of Medical Radiation Sciences, The University of Sydney; ‡American Board of Radiology, The University of Sydney, Lidcombe, NSW, Australia; and §American University of Beirut, Lebanon.
authors.forename: Charbel
authors.initials: C
authors.lastname: Saade
authors.forename: Roger
authors.initials: R
authors.lastname: Bourne
authors.forename: Mark
authors.initials: M
authors.lastname: Wilkinson
authors.forename: Michael
authors.initials: M
authors.lastname: Evanoff
authors.forename: Patrick C
authors.initials: PC
authors.lastname: Brennan
mesh_terms: D000208:Acute Disease; D000293:Adolescent; D000328:Adult; D000368:Aged; D000792:Angiography / Q000379:methods*; D001018:Aortic Diseases / Q000000981:diagnostic imaging*; D055424:Cardiac-Gated Imaging Techniques / Q000379:methods*; D003287:Contrast Media / Q000008:administration & dosage*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D056888:Patient Positioning / Q000379:methods*; D011856:Radiographic Image Enhancement / Q000379:methods; D013902:Radiography, Thoracic / Q000379:methods*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013577:Syndrome; D014057:Tomography, X-Ray Computed / Q000379:methods*; D055815:Young Adult
chemical_list: D003287:Contrast Media