Lung scan

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. They are:

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.

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.

During the scans, the camera may move to take pictures from different angles.

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.
• 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.

If you are breastfeeding, you may want to pump enough breast milk before the test to get through 1 to 2 days of feeding. The radioactive tracer used in this test can get into your breast milk and is not good for the baby.

The results of a lung scan are usually ready in 1 day.

Lung scan results can help your doctor find out how likely it is that you have a blood clot in your lung (pulmonary embolism). The results are most often reported in one the following ways:

• Normal. The results do not show any problem with your lungs.
• Low probability. The results show that the likelihood of a blood clot is low. Your doctor may feel that you need more tests.
• Indeterminate or intermediate probability. The lung scan results show it is possible that you have a blood clot. More tests may be needed.
• High probability. The results show a high likelihood of a blood clot. Your doctor will give you medicine to treat the clot.