What is the primary use of CT angiography in acute chest pain when pulmonary embolism is suspected?

• A. To visualize the pulmonary arteries for filling defects consistent with acute PE using IV iodinated contrast.
• B. To evaluate for aortic dissection.
• C. To assess myocardial perfusion.
• D. To visualize brain structures.

Answer: (A)

In acute chest pain with a suspicion of pulmonary embolism, the main goal of CT angiography is to directly visualize the pulmonary arteries after injecting IV iodinated contrast. The contrast opacifies the arterial lumen, allowing any clot to appear as a filling defect where the contrast fails to fill the vessel. Seeing such a defect within the pulmonary arteries confirms the presence of an embolus and PE, guiding urgent management like anticoagulation or thrombolysis.

This study is chosen because it provides rapid, high-resolution images of the pulmonary vasculature and can exclude PE if no filling defects are seen. While CT angiography can also assess other conditions (for example, it can evaluate the aorta for dissection or give broad chest information), the primary use in this scenario—suspected PE—is to detect or exclude emboli in the pulmonary arteries. Other options like assessing myocardial perfusion or visualizing brain structures are not the main goal when the question centers on PE in the chest.