V/Q Scan

What is a V/Q scan?

A V/Q scan consists of two imaging tests that look for certain lung problems. The tests are:

• A ventilation scan, which measures how air moves in and out of your lungs
• A perfusion scan, which measures circulation (how blood flows in the lungs)

The two scans may be done separately or together.

A V/Q scan uses a small amount of a radioactive substance called a tracer that helps look for disease in the body. The scans help diagnose different lung conditions, including a pulmonary embolism (PE). A PE is a life-threatening blockage in an artery in the lungs. It usually happens when a blood clot in another part of the body breaks loose and travels to the lungs.

Other names: ventilation/perfusion scan, pulmonary ventilation/perfusion scan, lung scan, lung V/Q scan

What is it used for?

A V/Q scan is most often used to check for a pulmonary embolism (PE). It may also be used to:

• Find problems with blood flow in the lungs
• Check lung function before lung surgery
• Test lung function in people with certain lung diseases, such as COPD (chronic obstructive pulmonary disease), a disease that causes coughing, wheezing, and shortness of breath.

Why do I need a V/Q scan?

You may need a V/Q scan if you have symptoms of a pulmonary embolism (PE). These include:

• Trouble breathing
• Chest pain
• Coughing or coughing up blood
• Rapid heartbeat

Many people with a PE don't have symptoms. But your provider may order a V/Q scan based on a physical exam and/or if you have certain risk factors. These include:

• Family history of blood clots or PE
• Long periods of inactivity that may be due to prolonged sitting (such as from long car trips or flights), bed rest or other reasons
• Recent surgery
• Obesity
• Older age
• Smoking

You may also be at higher risk if you have:

• A clotting disorder
• Cancer
• Heart disease
• Another lung disease, such as COPD

What happens during a V/Q scan?

V/Q scans are usually performed in a radiology clinic or a hospital. You may be getting a ventilation scan or a perfusion scan, or you may get both scans. If you are getting both, one scan will be done right after the other.

For both types of scans:

• You will lie very still on a special table while the scanner takes pictures of your lungs.
• Before the scan, you will be given a substance called a radioactive tracer. The tracer sends out a form of energy called gamma rays. The rays are picked up by the scanner to create images of your lungs.

During a ventilation scan:

• You will wear a face mask and breathe in a gas that contains the radioactive tracer
• A health care provider will use the scanner to take pictures of your lungs while you are holding your breath.
• Your provider will continue to take pictures while you breathe in the tracer gas for a few more minutes.
• After the tracer gas has collected in your lungs, your provider will remove your face mask. As you breathe normally, the tracer will leave your lungs.

During a perfusion scan:

• A health care provider will inject the radioactive tracer into your vein through an intravenous (IV) line.
• The tracer will collect in the blood vessels of your lungs.
• Your provider will use the scanner to take pictures of your lungs.
• You will be moved into several positions during the test so the scanner can capture images of the lungs from different angles.

Will I need to do anything to prepare for the test?

A chest x-ray is usually done before a V/Q scan.

Are there any risks to the test?

There is very little exposure to radiation in a V/Q scan. Only a small amount of radioactive substance is used, and all of the radiation leaves the body within a few days.

While radiation exposure in a V/Q scan is safe for most adults, it can be harmful to an unborn baby. So be sure to tell your provider if you are pregnant or think you may be pregnant Also, tell your provider if you are breastfeeding, because the tracer may contaminate your breast milk.

You may have a little discomfort when the tracer is injected during a perfusion scan.

Allergic reactions to the tracer are rare and usually mild.

What do the results mean?

If your ventilation and/or perfusion scan results were not normal, it may mean you have a pulmonary embolism (PE) and will need medical treatment right away.

The scans may also show that you have a different condition affecting your lungs. These include:

• COPD
• Pneumonia
• Heart failure

If you have questions about your results, talk to your health care provider.

Is there anything else I need to know about a V/Q scan?

If you are diagnosed with a pulmonary embolism (PE), your treatment may include medicines such as blood thinners, which help prevent clots from forming, or clot busters, which help dissolve clots quickly.

If the medicines don't work, or you have a very large clot, you may need a surgical procedure to prevent and/or remove the clots.