What is the most reliable method for diagnosing a pulmonary embolism?

CT pulmonary angiography is considered the most reliable method for diagnosing a pulmonary embolism due to its ability to provide a detailed visualization of blood vessels in the lungs. This imaging technique uses contrast material injected into a vein, followed by a CT scan, to directly visualize the pulmonary arteries. It allows for the detection of clots in the artery, which is critical in diagnosing pulmonary embolism.

Other imaging methods have their limitations. While chest X-rays are often the first imaging study performed, they do not provide sufficient detail to diagnose embolisms specifically, as many patients with a pulmonary embolism may have a normal X-ray. Ultrasound is primarily used in cases of deep vein thrombosis as it detects clots in the leg veins, but it is not as effective for diagnosing clots in the pulmonary arteries. Magnetic resonance imaging, while useful in certain scenarios, is less commonly used for pulmonary embolism due to longer scan times and the need for patient stability, making CT pulmonary angiography the preferred choice in most clinical settings.