Practical Reviews

Radiology - December 30, 2014 - Vol. 42 - No. 7

Non-Contrast Phase of Dual-Phase CTA Protocol Very Important

Author(s): Lemos AA, Pezzullo JC, et al

Author Email: alemos@sirm.org

This article counts as 0.25 credits in Cardiovascular Imaging.

For patients with suspected acute aortic syndrome, the addition of the noncontrast phase to a CT angiography protocol significantly improves the study's diagnostic accuracy to evaluate for aortic intramural hematoma.

Objective: To evaluate the effect of eliminating the noncontrast phase of a dual-phase chest pain CT angiography (CTA) protocol on the accuracy of detecting aortic intramural hematoma.

Design: Retrospective.

Participants: 306 patients with suspected acute aortic syndrome who underwent CTA.

Methods: A 64-MDCT scanner was used. Noncontrast images of the chest were performed using low-dose technique. The radiation dose of this phase was 3.82 ± 0.4 mSv. This was subsequently followed by contrast-enhanced images of the chest, abdomen, and pelvis. An arterial phase was acquired. If a dissection was seen, an additional portal venous phase was acquired. ECG gating was not employed. The radiation dose of the contrast-enhanced phase was 21.7 ± 2.9 mSv. The single contrast-enhanced phase and both the noncontrast and contrast-enhanced phases were independently presented for interpretation to 2 cardiovascular radiologists. To minimize recall bias, the different phase acquisitions obtained in each study were read >1 month apart. When evaluating just the contrast-enhanced phase without access to the noncontrast phase, an intramural hematoma was defined as a crescentic or circumferential aortic wall thickening, absence of contrast enhancement in the wall, a smooth lumen-wall interface, an intact intima with no false lumen, and an intimal defect with associated penetrating atherosclerotic ulcer or aortic dissection. When given access to both the noncontrast and contrast-enhanced phases, an intramural hematoma was defined similarly with the additional criteria of crescentic or circumferential aortic wall thickening showing higher attenuation than that of the aortic lumen on the contrast-enhanced images as well as displaced intimal calcifications. The reference standard was surgical and pathologic diagnoses as well as subsequent imaging and clinical follow-up.

Results: 36 patients (12%) were suspected of having intramural hematoma. Sixteen patients had both surgery and transesophageal echocardiography (TEE), and 20 had no surgery but did have TEE. The sensitivity, specificity, and accuracy of CTA when both the noncontrast and contrast-enhanced images were available for review for intramural hematoma was 94.4%, 99.3%, and 98.7%, respectively. The sensitivity, specificity, and accuracy of CTA when only the contrast-enhanced images were available for review was 68.4%, 96.3%, and 92.8%, respectively. These differences between the 2 methods were all statistically significant. There were more false-positive and false-negative diagnoses when only the contrast-enhanced phase was available for review.

Conclusions: In patients with suspected acute aortic syndrome, the addition of the noncontrast phase to a CTA protocol significantly improves the diagnostic accuracy of the study to evaluate for aortic intramural hematoma.

Reviewer's Comments: The results of this study show that the noncontrast phase is a very important component of any CTA protocol to evaluate for acute aortic syndrome.(Reviewer–Vineet R. Jain, MD).

Article Reviewed: Can the Unenhanced Phase Be Eliminated From Dual-Phase CT Angiography for Chest Pain? Implications for Diagnostic Accuracy in Acute Aortic Intramural Hematoma. Lemos AA, Pezzullo JC, et al: AJR Am J Roentgenol; 2014;203 (December): 1171-1180.


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Stephen R. Baker, MD
Coordinating Editor

Program Director, Professor, and Chairman of Radiology
Associate Dean for Graduate Medical Education
New Jersey Medical School
Scotch Plains, NJ
Rutgers University – New Jersey Medical School
Department of Radiology
Newark, NJ
Reports no commercial interest

Humaira Chaudhry, MD
Assistant Professor
Rutgers – New Jersey Medical School
Department of Radiology
Newark, NJ
Reports no commercial interest

Basil Hubbi, MD
Assistant Professor of Radiology and Director of Breast Imaging
Rutgers University – New Jersey Medical School
Newark, NJ
Reports no commercial interest

Vineet R. Jain, MD
Associate Professor of Radiology
Department of Radiology
Montefiore Medical Center
Bronx, NY
Reports no commercial interest

Abhishek Kumar, MD
Department of Radiology
Rutgers University – New Jersey Medical School
Newark, NJ
Reports no commercial interest


Otha W. Linton, MSJ
Executive Director
International Society of Radiology
Potomac, MD
Reports no commercial interest

John C. Sabatino, MD
Assistant Professor
Rutgers University – New Jersey Medical School
Department of Radiology
Newark, NJ
Reports no commercial interest

Sebastian Sadowski, MD
Radiology Imaging Specialists
Evergreen Park, IL
Reports no commercial interest

Uma Thakur, MD, MSK
Attending Radiologist
Radiology Imaging Associates
Waldorf, MD
Reports no commercial interest

Guest
David Bushnell, MD

Professor of Radiology
University of Iowa
Chief, Diagnostic Imaging Service
Veteran’s Association Medical Center
Iowa City, IA
Reports no commercial interest

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