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Caudocranial Scan Direction and Patient-Specific Injection Protocols Optimize ECG–Gated and Non–Gated Thoracic CTA

Saade, Charbel Mast App Sc; Bourne, Roger PhD; Wilkinson, Mark RANZCR; Evanoff, Michael PhD; Brennan, Patrick C. PhD

Journal of Computer Assisted Tomography: September/October 2013 - Volume 37 - Issue 5 - p 725–731
doi: 10.1097/RCT.0b013e31829e02b9
Thoracic and Cardiovascular Imaging

Objectives 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.

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.

Received for publication April 25, 2013; accepted May 28, 2013.

Reprints: Charbel Saade, Mast App Sc, Department of Radiology, Royal Prince Alfred Hospital, Sydney, Missenden Rd LPO, PO Box M199 Camperdown, 2050 Sydney, Australia (e-mail:

All authors have no grants, contracts, and other forms of financial support. Therefore, there are no conflicts of interest.

Copyright © 2013 Wolters Kluwer Health, Inc. All rights reserved.