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
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.
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
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
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
- Medical conditions, such as
pulmonary edema or chronic obstructive pulmonary
disease (COPD), that involve the lungs or heart.