Aortic dissection CT

Aortic dissection Microchapters
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Case #1

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor-In-Chief: Cafer Zorkun, M.D., Ph.D. [2]

Computed tomography angiography

Computed tomography angiography is a fast non-invasive test that will give an accurate three-dimensional view of the aorta. These images are produced by taking rapid thin cut slices of the chest and abdomen, and combining them in the computer to create cross-sectional slices. In order to delineate the aorta to the accuracy necessary to make the proper diagnosis, an iodinated contrast material is injected into a peripheral vein. Contrast is injected and the scan performed using a Bolus Tracking method. This is a type of scan timed to an injection, in order to capture the contrast as it enters the aorta. The scan will then follow the contrast as it flows though the vessel.

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  Aortic dissection Type Stanford A
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  Aortic dissection Type Stanford A - '1 Aorta ascendens, true Lumen - 2 false Lumen - 3 Pulmonary artery - 4 Aorta descendens - 5 thoracic vertebra

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  Another example of Stanford A type dissection

It has a sensitivity of 96 - 100% and a specificity of 96 to 100%. Disadvantages include the need for iodinated contrast material and the inability to diagnose the site of the intimal tear.

CT scanning with contrast has a reported sensitivity of 94% and a specificity of 87%. Unfortunately, the intimal flap is seen in < 75% of cases. Additionally, one can not assess the coronary arteries or for the presence of AI. Over the past few years, spiral CT and ultrafast CT (electron beam CT) have substantially improved the accuracy in the diagnosis of aortic dissection.

Differentiating a true lumen from the false lumen

• Beak sign: In the false lumen, there will be an acute angle between the dissection flap and the arterial wall.
• Aortic cobwebs: In the false lumen, there may be fibroelastic bands.
• Size: False lumen is usually larger than the true lumen.
• Diplaced intimal calcification: Usually faces the true lumen.

Labeled CT images shown below are courtesy of Radswiki and copylefted:

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