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