What is a VQ scan?

A ventilation-perfusion (VQ) scan uses radioactive material (low-risk) to examine the air flow (ventilation) and blood flow (perfusion) in your lungs.

Why is a VQ scan needed?

This test can show blood vessel blockages in your lungs. It is usually done to look for a pulmonary embolism (blood clot) in your lungs. A pulmonary embolism may be caused by a blood clot in your leg that traveled to your lungs.

How is the test done?

Preparation: Remove anything with metal, such as hooks or clips because it can block the scanner’s view. You will be required to lie very still. Your health care provider may prescribe medication to help relax you for the scan.

A VQ scan is done in two stages.

  1. Stage One: The first stage checks the air flow (ventilation) through your lungs. A breathing mask is placed over your nose and mouth. You will breathe in a small amount of radioactive gas as the scanner takes pictures. You may be asked to hold your breath for a few seconds at a time.
  2. Stage Two: This stage checks blood flow (perfusion) through your lungs. A small amount of radioactive liquid will be injected into your IV. The scanner will then take photos of the dye traveling through your blood vessels in your lungs.

What happens after a VQ scan?

Drink plenty of fluids to help flush the radioactive material out of your body.

This scan will not confirm if you have a pulmonary embolism, but it will determine your probability from low to high. Your doctor will discuss the results with you.

Download the VQ scan brochure.