Ventilation Perfusion Scan (VQ Scan)

A VQ scan is a specialized test that we use to diagnose chronic PE and CTEPH, advanced forms of pulmonary embolism. 

If you have a suspected acute, or sudden, pulmonary embolism (PE, a blood clot in the lungs), we’ll use a series of tests, including a combination CT scan of the chest and ultrasound of the legs, a chest X-ray and an electrocardiogram. However, if we suspect your pulmonary embolism has developed into a chronic PE or chronic thromboembolic pulmonary hypertension (CTEPH), progressive forms of pulmonary embolism, we will perform a different series of tests. 

This includes a noninvasive exam called a ventilation perfusion scan (VQ scan), which consists of two separate tests: 

• Ventilation scan: Measures airflow in and out of your lungs. 
• Perfusion scan: Measures blood flow in and out of your lungs. 

Collectively, these help identify chronic blockages in the pulmonary arteries in your lungs. These are often performed together, one right after the other. 

How does a VQ scan work? 

A ventilation perfusion scan is a type of nuclear medicine exam, which uses a very small amount of radioactive material (radiopharmaceuticals) that act as tracers. These are detected by image scanning to provide very precise images of your lungs:

• Before you have the ventilation perfusion scan, you’ll get a chest X-ray. This helps when interpreting your VQ scan results. 
• During the exam, you’ll be placed on a movable table that is near a CT scanner that provides the images. 
• For the ventilation portion of the VQ scan: You’ll breathe in a small amount of radioactive particles while you are positioned on the table, under the scanner arm. These tracers allow us to see how air flows in and out of your lungs. 
• For the perfusion portion of the VQ scan: We’ll inject a small amount of radioactive particles into your bloodstream. These tracers allow us to see how blood flows in and out of your lungs. 
• During each test, your care team may reposition your body as necessary to ensure we’re getting all of the images we need. 
• A full VQ scan may take between 30 and 60 minutes. 
• The amount of radioactive material you’ll be exposed to in these tests is very small. We are committed to performing patient examinations with the lowest possible radiation exposure that will allow us to make an accurate diagnosis.
• After the exam, your body will filter out these radioactive tracers as you breathe in fresh air and use the bathroom.