Ventilation-Perfusion Scan or"V-Q Scan"

What is the evaluation?

The ventilation-perfusion scan is a nuclear scan so named as it studies both air-flow (ventilation) and blood flow (perfusion) from the lungs. The initials V-Q are used. The evaluation is used primarily to help diagnose a blood clot in the lungs, also called a pulmonary embolus.

Today scans are rarely performed as a chest CT scan is a more accurate evaluation for detecting a pulmonary embolus.

How do I prepare for this test?

About one hour before the evaluation, a tech places an IV in your arm. A radioactive version of the nutrient technetium mixed with liquid protein has been injected through the IV to identify areas of the lung which have reduced blood flow.

What goes on when the test is performed?

The test is performed in an outpatient facility or in the radiology department of a hospital. You`re requested to put on a clinic gown. Multiple pictures of your torso are obtained with a special camera which finds the radionuclide As soon as you`re ready. For 50% of all these pictures, you are requested to breathe out of a tube which includes a mixture of atmosphere, oxygen, and a slightly radioactive form of a gas referred to as xenon, which is discovered by the camera, also which measures airflow in various regions of the lung. For another 50% of the pictures, the camera tracks the injected radionuclide to determine blood flow. A blood clot is suspected in regions of the lung which have good airflow however blood flow. Aside from the discomfort of having the IV placed, the evaluation is painless. It usually takes less than one hour.

What risks are there from this evaluation?

Many people worry when they hear which gas and the liquid used in this evaluation are radioactive. The radioactivity you are exposed to is so small there are no side effects or complications, unless you are pregnant.

Must I do anything special after the exam is over?

No.

How long is it before the results of the evaluation is known?

The answers are often available within a few hours, because the evaluation has been done primarily when you are suspected of having a potentially life-threatening condition (pulmonary embolus).

Further info

Always ask with your physician to be sure the information displayed on these pages applies to your circumstances.