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Lung Disease & Respiratory Health Center

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Lung Scan


A lung scan is a nuclear scanning test that is most commonly used to detect a blood clot that is preventing normal blood flow to part of a lung (pulmonary embolism). The results of a lung scan are usually available in 1 day.

Lung scan

The radioactive tracer is evenly distributed throughout the lungs during ventilation and perfusion.


The ventilation scan is abnormal but the perfusion scan is normal. This may mean abnormal airways in all or parts of the lung. Chronic obstructive pulmonary disease (COPD) or asthma may be present.

The perfusion scan is abnormal but the ventilation scan is normal. Depending on the difference between the two scans, a pulmonary embolism may be present.

Both the ventilation and perfusion scans are abnormal. This can be caused by certain types of lung disease, such as pneumonia, COPD, or a pulmonary embolism.

Lung scan results can help your doctor determine the likelihood that a pulmonary embolism is present. The results are generally 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 pulmonary embolism is low. Your doctor may feel that further testing is needed.
  • Indeterminate or intermediate probability. The lung scan results show there is a possibility of a pulmonary embolism. More tests, such as angiogram or CT pulmonary angiogram, may be needed.
  • High probability. The results show that the likelihood of a pulmonary embolism is high. No further diagnostic testing is generally necessary. Your doctor will give you medicine to treat the pulmonary embolism.

What Affects the Test

Reasons you may not be able to have the test or why the results may not be helpful include:

WebMD Medical Reference from Healthwise

Last Updated: September 09, 2014
This information is not intended to replace the advice of a doctor. Healthwise disclaims any liability for the decisions you make based on this information.

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