The ventilation-perfusion scan gets its name because it studies air flow (ventilation) and blood flow (perfusion) in the lungs. The initials "V-Q" are often used to name this test because these are the initials used in mathematical equations that calculate air flow and blood flow. This test is used to see if a blood clot has blocked blood flow through a oxygen level and shortness of breath.
How do I Prepare for the Test?
Around one hour before the test, you will need to have an intravenous line (IV) placed. A slightly radioactive version of the mineral technetium mixed with some liquid protein will be injected through the IV. (This substance will help your blood vessels show up on pictures later.)
What Happens When the Test is Performed?
The test is performed in a special part of the radiology (x-ray) department called nuclear medicine. You will wear a hospital gown for the test. Multiple pictures of your chest will be taken from different angles – for half of these pictures you will be asked to breathe from a tube that has a mixture of air, oxygen and a slightly radioactive version of the gas "xenon" that can be detected by the camera. While the other pictures are being taken, the camera will detect the medicine that flowed through your IV and into the blood vessels of your lung. Except for the minor discomfort of having the IV placed, the test is painless and usually takes less than an hour.
What Risks are There from the Test?
Many people worry when they first hear that the liquid and gas used un this test are slightly radioactive. In truth, the amount of radioactivity is too small to cause any side effect or complication to occur.
How Long is it Before the Result of the Test is Known?
The results of the test are usually available within a few hours. The pictures themselves who the shape of your lungs with many small dots inside the lungs where there is air flow or blood flow. The test only provides indirect evidence of a blood clot; it cannot provide an exact answer. Instead, doctors will say the test shows you have a "high probability", "low probability", or "intermediate probability" of having a true blood blot in your lungs. Usually your doctor will be convinced enough about your diagnosis after this test that treatment decision can be made safely. A minority of patients will have an additional test recommended to know for sure whether a blood clot is the problem. This test is call a "pulmonary angiogram".
Disclaimer
Reviewed by Alberta clinical experts. Brought to you by HealthLink Alberta. Copyright.
This material is designed for information purposes only. It should not be used in place of medical advice, instruction and/or treatment. For more health advice call Capital Health Link at 780-408-LINK (5465) 24 hours a day, seven days a week. In Alberta, call Toll-free: 1-866-408-LINK (5465)
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