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(s)-in-Chief: Cafer Zorkun, M.D., Ph.D. [2], Aarti Narayan, M.B.B.S [3]

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

Advantages of CT

• Readily available at most hospitals, even on an emergency basis.
• Easy identification of intraluminal thrombus and pericardial effusions.
• CT scanning with contrast has a reported sensitivity of 94% and a specificity of 87%. The accuracy of CT can be further improved with spiral CT and ultrafast CT (Electron beam CT).

Disadvantages of CT

• The need for iodinated contrast material.
• Inability to see the intimal flap in more than 75 % of patients.
• Inability to diagnose the site of the intimal tear.
• Assessment of coronary arteries and aortic incompetence is difficult with a CT.

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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