Checking for a blood clot in your leg (deep venous thrombosis) can help your doctor decide if you are at high risk for having one in your lung. The doctor will ask about your medical history and do a physical exam to learn your risk level for deep leg vein thrombosis. Then an ultrasound is usually done. Your pretest probability and ultrasound results will help your doctor decide which follow-up tests you need. To learn more, see the topic Doppler Ultrasound.
If your perfusion scan results are unclear, your doctor may want to do more tests. Pulmonary angiography is an X-ray test that uses contrast material injected into the bloodstream to check the blood flow leading to the lungs. Many medical centers and doctors now use a newer CT scanning technique called CT pulmonary angiography, or CTPA.