Lung Scan: About This Test

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The lungs

What is it?

A lung scan is a type of nuclear scanning test. It uses a special camera to take pictures of the lungs after a radioactive tracer is put into the body. It is most often used to find a pulmonary embolism. This is a blood clot that prevents normal blood flow in the lung.

Two types of lung scans are usually done together:

  • Ventilation scan. You inhale a radioactive tracer gas or mist. Pictures from this scan can show areas of the lungs that aren't getting enough air or that hold too much air.
  • Perfusion scan. A radioactive tracer is injected into a vein in your arm. It travels through your blood and into the lungs. Pictures from this scan can show areas of the lungs that aren't getting enough blood.

If both scans are done, the test is called a V/Q scan. The ventilation scan usually is done first.

In most cases, if the lungs are working as they should, both scans will show that the parts of the lungs that are getting air are also getting blood. If the two scan results don't match, the differences can help your doctor diagnose a problem with your lungs.

Lung scan results can help your doctor find out how likely it is that you have a blood clot in your lung. If there is a chance that you have a blood clot, your doctor may order more tests. If the chance is high, your doctor may give you medicine to treat the clot.

Why is this test done?

A lung scan is done to:

  • Find a blood clot that is preventing normal blood flow to part of a lung.
  • Look at the flow of blood or air through the lungs.
  • See which parts of the lungs are working and which are damaged. This is often done before surgery to remove parts of the lung.

How can you prepare for the test?

Before your lung scan, tell your doctor if:

  • You are or might be pregnant.
  • You are breastfeeding. The radioactive tracer used in this test can get into your breast milk. Do not breastfeed your baby for 1 or 2 days after this test. During this time, you can give your baby breast milk you stored before the test, or you can give formula. Don't use the breast milk you pump for the 1 or 2 days after the test. Throw it out.

What happens before the test?

  • A chest X-ray is usually done the same day, either before or after the lung scan.
  • You will need to remove any jewellery that might get in the way of the scan.
  • You may need to take off all or most of your clothes. You will be given a cloth or paper covering to use during the test.
  • You might lie on your back with the scanning camera over or under your chest. Or you might sit with the camera next to your chest.

What happens during the test?

Ventilation scan:

  • A mask will be placed over your mouth and nose. Or you may have a nose clip on your nose and a tube in your mouth that you use for breathing. You will take a deep breath and hold it.
  • The camera will take pictures as the tracer moves into your lungs.
  • You may be asked to breathe the gas in and out through your mouth for several minutes and then to hold your breath for short periods (about 10 seconds). You may have to change positions so your lungs can be viewed from other angles. The camera may move to take pictures from different angles.
  • Afterward, the gas or mist will clear from your lungs as you breathe.

Perfusion scan:

  • A small amount of the tracer will be injected into your arm.
  • The camera will take pictures as the tracer moves through the blood vessels in your lungs. The camera may be moved around your chest to get different views.

What are the risks of this test?

  • There is always a slight risk of damage to cells or tissue from being exposed to any radiation, even the low level of radiation released by the radioactive tracer used for this test. But the chance of damage is usually very low compared with the benefits of the test.
  • Allergic reactions to the radioactive tracer are very rare.

How long does the test take?

  • The test will take about an hour.

What happens after the test?

  • Most of the tracer will leave your body through your urine or stool within a day. So be sure to promptly flush the toilet and thoroughly wash your hands with soap and water. The amount of radiation is so small that it's safe for people to come in contact with you after the test.

Follow-up care is a key part of your treatment and safety. Be sure to make and go to all appointments, and call your doctor or nurse call line if you are having problems. It's also a good idea to keep a list of the medicines you take. Ask your doctor when you can expect to have your test results.

Where can you learn more?

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