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    Lung Scan

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    The results of a lung scan are usually ready 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. It may be a sign of chronic obstructive pulmonary disease (COPD) or asthma.

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

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

    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.

    What Affects the Test

    You may not be able to have the test, or the results may not be helpful, if:

    • You are pregnant. The radiation from a lung scan could harm the baby.
    • You're not able to stay still during the test.
    • You're not able to breathe through the mask or tube.
    • You have a medical condition that involves the lungs or heart, such as pulmonary edema or chronic obstructive pulmonary disease (COPD).

    What To Think About

    • Checking for a blood clot in your leg (deep venous thrombosis) can help your doctor decide if you are at high risk for having one in your lung. The doctor will ask about your medical history and do a physical exam to learn your risk level for deep leg vein thrombosis. Then an ultrasound is usually done. Your pretest probability and ultrasound results will help your doctor decide which follow-up tests you need. To learn more, see the topic Doppler Ultrasound.
    • If your perfusion scan results are unclear, your doctor may want to do more tests. Pulmonary angiography is an X-ray test that uses contrast material injected into the bloodstream to check the blood flow leading to the lungs. Many medical centers and doctors now use a newer CT scanning technique called CT pulmonary angiography, or CTPA.

    WebMD Medical Reference from Healthwise

    Last Updated: August 21, 2015
    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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