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Lung Disease & Respiratory Health Center

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Lung Scan

Risks

Allergic reactions to the radioactive tracer are very rare. Most of the tracer will be eliminated from 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 is not a risk for people to come in contact with you following the test.

Occasionally, some soreness or swelling may develop at the injection site. These symptoms can usually be relieved by applying moist, warm compresses to your arm.

There is always a slight risk of damage to cells or tissue from being exposed to any radiation, including the low level of radiation released by the radioactive tracer used for this test.

Results

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
Normal:

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

Abnormal:

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:

  • Pregnancy. A lung scan is not usually done during pregnancy, because the radiation could damage the developing baby (fetus).
  • The inability to remain still during the test.
  • The inability to breathe through the mask or tube.
  • Medical conditions, such as pulmonary edema or chronic obstructive pulmonary disease (COPD), that involve the lungs or heart.

WebMD Medical Reference from Healthwise

Last Updated: October 01, 2012
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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