In CT angiography of the chest, what finding would indicate a pulmonary embolism?

• A. Free air under the diaphragm
• B. Calcified plaque in a pulmonary artery
• C. Enlarged pulmonary arteries without filling defects
• D. Filling defect within a contrast-filled pulmonary artery

Answer: (D)

CT angiography relies on IV contrast to fill the pulmonary arteries. A pulmonary embolism appears as a filling defect within that contrast-filled lumen, meaning the thrombus occludes part of the vessel so you see a dark slot where the bright contrast should be. This intraluminal defect is the classic sign of a PE on CTA. Other options don’t fit as well: free air under the diaphragm points to GI perforation, calcified plaque suggests chronic disease, and enlarged pulmonary arteries without filling defects imply dilation or hypertension without an acute occlusion. So the finding of a filling defect within a contrast-filled pulmonary artery best indicates a pulmonary embolism.