Best initial imaging for suspected pulmonary embolism in a stable patient?

• A. Ventilation-perfusion scan
• B. Chest X-ray
• C. D-dimer level
• D. CT pulmonary angiography

Answer: (D)

In a patient who is stable with suspected pulmonary embolism, the best initial imaging test is CT pulmonary angiography. This test uses contrast-enhanced CT to directly visualize clots in the pulmonary arteries, offering high sensitivity and specificity and the quickest, most definitive answer. It also helps identify alternative causes of symptoms if PE is not present.

Chest X-ray isn’t reliable for diagnosing PE and mainly helps rule out other chest problems. D-dimer is a blood test, not imaging, and while it can help exclude PE in low-suspicion cases, its usefulness decreases with higher pretest probability. A ventilation-perfusion scan is a reasonable alternative if CT angiography cannot be performed (for example, due to contrast allergy or poor renal function), but when available, CT angiography is preferred for accuracy and speed.