Correct!
5. Unenhanced and enhanced thoracic CT angiogram (CTA)
The combination of initial unenhanced CT followed by enhanced CT angiography is the proper “aortic dissection” protocol. While enhanced CT alone is a reasonable test for suspected aortic pathology, the unenhanced portion of the “CT aorta” protocol optimizes detection of aortic intramural hematomas and assists in distinguishing eccentric atherosclerotic plaque within the aorta from both intramural hematomas and the thrombosed false lumen of a dissection. Both intramural hematomas and thrombosed false lumens in dissection patients can be recognized at enhanced CT, but, owing to the presence of intraluminal intravenous contrast, these pathologies will appear as low attenuation foci and may therefore resemble low attenuation atherosclerotic plaque. On unenhanced imaging, however, the acute blood products of intramural hematoma and acutely thrombosed dissection false lumens will show hyperattenuation, whereas atherosclerotic plaque will appear as low attenuation. Thoracic MRI with contrast-enhanced MRA is an excellent test for suspected aortic pathology and is the test of choice when thoracic CTA cannot be performed, such as for patients with iodinated contrast allergies. However, thoracic CTA remains the first-line examination for suspected acute aortic syndromes owing to its widespread availability and speed, as well as the fact CT is well-tolerated {i.e., no claustrophobia]. Repeat chest radiography is unlikely to be of benefit. 99mTc-MAA scintigraphy is primarily used for suspected pulmonary embolism, but pulmonary embolism is not the primary consideration for this patient’s presentation.
The patient underwent unenhanced and enhanced thoracic CTA (Figure 2).
Figure 2. Upper Left, A-I: Static axial images from the unenhanced and enhanced thoracic CTA (unenhanced phase not displayed). Upper Right: Axial video of enhanced thoracic CT. Lower Left: J-L: Static sagittal images from the enhanced thoracic CTA. Lowe Right: Sagittal video of enhanced thoracic CT scan.
Which of the following is correct regarding the description of the thoracic CT findings? (Click on the correct answer to proceed to the fourth of eight panels)