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Two types of lung scans are usually done together:
If the lungs are working normally, blood flow on a perfusion scan matches air flow on a ventilation scan. A mismatch between the ventilation and perfusion scans may mean a pulmonary embolism.
Ventilation and perfusion scans can be done separately or together to diagnose certain lung diseases. If both scans are done, the test is called a V/Q scan. The ventilation scan usually is done first.
A lung scan is done to:
Before your lung scan, tell your doctor if:
A chest X-ray is usually done the same day either before or after the lung scan.
You may be asked to sign a consent form.
Talk to your doctor about any concerns you have regarding the need for the test, its risks, how it will be done, or what the results will mean. To help you understand the importance of this test, fill out the medical test information form(What is a PDF document?).
You will need to remove any jewelry that might interfere with the scan. You may need to take off all or most of your clothes, depending on which area is being examined (you may be allowed to keep on your underwear if it does not interfere with the test). You will be given a cloth or paper covering to use during the test.
During the scan, you will either lie on your back with the scanning camera positioned over or under your chest, or you will sit with the camera positioned next to your chest. The camera does not produce any radiation, so you are not exposed to any more radiation while the scan is being done.
For the ventilation scan, a mask will be placed over your mouth and nose. Or you may have a nose clip on your nose and a tube in your mouth that you use for breathing. You will inhale the tracer gas or mist through the mask or tube by taking a deep breath and then holding it. The camera will scan for radiation released by the tracer and produce pictures as the tracer moves through your lungs. You may be asked to breathe the gas in and out through your mouth for several minutes. You may then be asked to hold your breath for short periods (about 10 seconds) and to change positions so your lungs can be viewed from other angles. The camera may move to take pictures from different angles. You need to remain very still during the scans to avoid blurring the pictures.
Afterward, the radioactive gas or mist will clear from your lungs as you breathe.
The ventilation scan takes about 15 to 30 minutes.
For the perfusion scan, the technologist cleans the site on your arm where the radioactive tracer will be injected. A small amount of the radioactive tracer is then injected.
After the radioactive tracer is injected, the camera will scan for radiation released by the tracer and produce pictures as the tracer moves through your lungs. The camera may be repositioned around your chest to get different views. You need to remain very still during the scans to avoid blurring the pictures.
The perfusion scan takes about 5 to 10 minutes.
You may find that breathing through the mask during the ventilation scan is uncomfortable, especially if you feel very short of breath. But you will be given plenty of oxygen through the mask.
You may feel nothing at all from the needle puncture when the tracer is injected, or you may feel a brief sting or pinch as the needle goes through the skin. Otherwise, a lung scan is usually painless. You may find it hard to remain still during the scan. Ask for a pillow or blanket to make yourself as comfortable as possible before the scan begins.
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.
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:
Reasons you may not be able to have the test or why the results may not be helpful include:
Other Works Consulted
- Fischbach FT, Dunning MB III, eds. (2009). Manual of Laboratory and Diagnostic Tests, 8th ed. Philadelphia: Lippincott Williams and Wilkins.
- Pagana KD, Pagana TJ (2010). Mosby’s Manual of Diagnostic and Laboratory Tests, 4th ed. St. Louis: Mosby Elsevier.
|Primary Medical Reviewer||Anne C. Poinier, MD - Internal Medicine|
|Specialist Medical Reviewer||Myo Min Han, MD - Nuclear Medicine|
|Last Revised||October 1, 2012|
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