It uses special x ray scanners outside of your body to create pictures of air and blood flow patterns in your lungs. This test can help diagnose or rule out a pulmonary embolism, or a blood clot in your lung. A VQ scan also can detect regional differences in lung blood flow and air distribution. Doctors may use VQ scans to examine the lungs before some surgeries.
Lung VQ scans are performed in radiology clinics or hospitals. There is no preparation for a VQ scan other than having had a recent chest x ray. The test will take about an hour. For each scan, you will need to lie very still on a table as the table moves under the scanner and pictures are taken of your lungs. Before each scan, you will need to hold your breath for a few seconds. If you think you may have trouble staying still for the test, ask your doctor to suggest ways to avoid moving during the test. Before the ventilation scan, you will wear a breathing mask over your nose and mouth and will breathe in a small amount of a radioisotope gas mixed with oxygen. Before the perfusion scan, the technician will inject a small amount of radioisotope into a vein in your arm. You may feel discomfort from the injection. The scanner detects the energy that the radioisotopes release inside your body and uses the energy to make pictures of your lungs.
Lung VQ scans involve little pain or risk for most people. You may bruise at the injection site. In rare instances, some people have a treatable allergic reaction to the radioisotope. This test uses small amounts of radiation from the radioisotope that you breathe in and that is injected into your vein. Talk to your doctor and the technicians performing the test about whether you are or could be pregnant. If the test is not urgent, they may have you wait to do the test until after your pregnancy. If it is urgent, the technicians will take extra steps to protect your baby during this test. Let your doctor know if you are breastfeeding because radiation can pass into your breast milk. You may want to pump and save enough breast milk for one to two days after your test, or you may bottle-feed your baby for that time.
Visit Pulmonary ventilation/perfusion scan for more information about this topic.
The National Heart, Lung, and Blood Institute (NHLBI) leads or sponsors many studies aimed at preventing, diagnosing, and treating heart, lung, blood, and sleep disorders.