A helical CT scan can detect a blockage in a pulmonary artery, caused by a pulmonary embolism. Helical CT offers the advantage of being less invasive than other diagnostic tests for pulmonary embolism.

During CT pulmonary angiography, an x-ray dye is injected into the bloodstream before the CT scan is performed. The dye outlines the blood flow through the arteries. The addition of dye slightly increases the risk, but can dramatically increase the accuracy in detecting pulmonary embolism.