A pulmonary ventilation/perfusion scan is a pair of nuclear scan tests. These tests use inhaled and injected radioactive material (radioisotopes) to measure breathing (ventilation) and circulation (perfusion) in all areas of the lungs.

The ventilation scan is used to see how well air reaches all parts of the lungs. The perfusion scan measures the blood supply through the lungs.

A ventilation and perfusion scan is most often done to detect a pulmonary embolus. It is also used to:

• Detect abnormal circulation (shunts) in the blood vessels of the lungs (pulmonary vessels)
• Test lung function in people with advanced pulmonary disease, such as COPD

A pulmonary ventilation/perfusion scan is actually two tests. These tests may be performed separately or together.

During the perfusion scan, a health care provider injects radioactive albumin into your vein. You are placed on a movable table that is under the arm of a scanner. The machine scans your lungs as blood flows through them to find the location of the radioactive particles.

During the ventilation scan, you breathe in radioactive gas through a mask while you are sitting or lying on a table under the scanner arm.

You do not need to stop eating (fast), eat a special diet, or take any medications before the test.

A chest x-ray is usually done before or after a ventilation and perfusion scan.

You will sign a consent form and wear a hospital gown or comfortable clothing that does not have metal fasteners.

The table may feel hard or cold. You may feel a sharp prick while the material is injected into the vein for the perfusion part of the scan.

The mask used during the ventilation scan may make you feel nervous about being in a small space (claustrophobia). You must lie still during the scan.

The radioisotope injection usually does not cause discomfort.