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Significance of an additional unenhanced scan in computed tomography angiography of patients with suspected acute aortic syndrome - PubMed

  • ️Mon Jan 01 2018

Significance of an additional unenhanced scan in computed tomography angiography of patients with suspected acute aortic syndrome

Nikolaos Panagiotopoulos et al. World J Radiol. 2018.

Abstract

Aim: To assess potential benefits of an additional unenhanced acquisition in computed tomography angiography (CTA) in patients with suspected acute aortic syndrome (AAS).

Methods: A total of 103 aortic CTA (non-electrocardiography-gated, 128 slices) performed due to suspected AAS were retrospectively evaluated for acute aortic dissection (AAD), intramural hematoma (IMH), or penetrating aortic ulcer (PAU). Spiral CTA protocol consisted of an unenhanced acquisition and an arterial phase. If AAS was detected, a venous phase (delay, 90 s) was added. Images were evaluated for the presence and extent of AAD, IMH, PAU, and related complications. The diagnostic benefit of the unenhanced acquisition was evaluated concerning detection of IMH.

Results: Fifty-six (30% women; mean age, 67 years; median, 68 years) of the screened individuals had AAD or IMH. A triphasic CT scan was conducted in 76.8% (n = 43). 56% of the detected AAD were classified as Stanford type A, 44% as Stanford type B. 53.8% of the detected IMH were classified as Stanford type A, 46.2% as Stanford type B. There was no significant difference in the involvement of the ascending aorta between AAD and IMH (P = 1.0) or in the average age between AAD and IMH (P = 0.548), between Stanford type A and Stanford type B in general (P = 0.650) and between Stanford type A and Stanford type B within the entities of AAD and IMH (AAD: P = 0.785; IMH: P = 0.146). Only the unenhanced acquisitions showed a significant density difference between the adjacent lumen and the IMH (P = 0.035). Subadventitial hematoma involving the pulmonary trunk was present in 5 patients (16%) with Stanford A AAD. The difference between the median radiation exposure of a triphasic (2737 mGy*cm) compared to a biphasic CT scan (2135 mGy*cm) was not significant (P = 0.135).

Conclusion: IMH is a common and difficult to detect entity of AAS. An additional unenhanced acquisition within an aortic CTA protocol facilitates the detection of IMH.

Keywords: Acute aortic syndrome; Aortic dissection; Computed tomography angiography; Intramural hematoma; Pulmonary trunk subadventitial hematoma.

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Conflict of interest statement

Conflict-of-interest statement: None of the authors states a conflict of interest concerning firms and products reported in this study.

Figures

Figure 1
Figure 1

Selection process of the study cohort. After the exclusion of chronic dissections and patients with a history of aortic surgery, 56 cases made up the study cohort of individuals with a newly diagnosed acute aortic syndrome. AAS: Acute aortic syndrome.

Figure 2
Figure 2

Extent of dissection and intramural hematoma. Nearly one third of acute aortic syndrome was limited to the thoracic aorta. There was no case in which the intramural hematoma extended into the iliac arteries. AAD: Acute aortic dissection; IMH: Intramural hematoma.

Figure 3
Figure 3

Boundaries of acute aortic dissection and intramural hematoma. Anatomic features detain a distal progression of acute aortic dissection and intramural hematoma. AAD: Acute aortic dissection; IMH: Intramural hematoma.

Figure 4
Figure 4

Density measurements, absolute values. Absolute values of the density measurements in true and false lumen/intramural hematoma in arterial, venous and unenhanced phase of (A) thoracic and (B) abdominal aorta. IMH: Intramural hematoma.

Figure 5
Figure 5

Density measurements, differences. Density differences between true and false lumen/intramural hematoma (IMH) in arterial, venous and unenhanced phase of (A) thoracic and (B) abdominal aorta. Differences in radiodensity between true lumen and IMH as well as true lumen and thrombosed false lumen, respectively, were only significant in the unenhanced acquisition (P = 0.035). IMH: Intramural hematoma.

Figure 6
Figure 6

Acute intramural hematoma. Triphasic computed tomography angiography with an acute intramural hematoma (IMH) type Stanford A in the ascending and descending aorta. The unenhanced scan (U) shows a hyperdense wall thickening compared to the lumen (arrows). In the arterial (A) and venous (V) phase of the enhanced scans, the IMH con not be differentiated from a thrombotic layer.

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