What is a Ventilation-Perfusion Scan?
A ventilation-perfusion (VQ) scan is a diagnostic imaging test that helps identify conditions affecting blood flow and air movement in your lungs, particularly pulmonary embolism (blood clots in the lungs). The test has two parts:
- Perfusion Scan: Examines blood flow through your lungs
- Ventilation Scan: Shows how air fills your lungs
Why is this test performed?
This test helps your doctor:
- Detect blood clots in your lungs (pulmonary embolism)
- Evaluate lung function before surgery
- Assess damage from lung diseases
How does the test work?
When blood clots travel to the lungs, they block blood vessels and affect blood flow to sections of lung tissue. The VQ scan allows us to see these affected areas.
- Perfusion (Blood Flow) Component: We inject a small amount of radioactive protein particles (called MAA) into your bloodstream. These particles travel to your lungs and become trapped in tiny blood vessels (capillaries). In healthy lungs, the particles distribute evenly. If a blood clot is present, the particles cannot reach certain areas, creating “cold spots” on the scan image.
- Ventilation (Breathing) Component: You’ll inhale a small amount of radioactive gas or vapor. This shows how air fills your lungs. By comparing both scans, doctors can determine if reduced blood flow is caused by a clot or another condition.
What can I expect during the procedure?
- You’ll lie comfortably on an examination table.
- For the ventilation scan, your nose will be gently closed, and you’ll breathe in the radioactive gas or vapor through a mouthpiece.
- A special camera will take images of your lungs while you breathe normally.
- For the perfusion scan, a small amount of radioactive material will be injected into a vein in your arm.
- The camera will take additional images of your lungs.
- The entire procedure usually takes 30-60 minutes.
The amount of radiation used is very small and poses minimal risk. A nuclear medicine physician will analyze the images and send a report to your doctor.
Preparation
- No special preparation is needed
- You can eat and drink normally before the test
- Wear comfortable clothing
- Inform your doctor if you’re pregnant or breastfeeding
After the test
- You can resume normal activities immediately
- The radioactive material will naturally leave your body within 24 hours
- Your doctor will discuss the results with you during your follow-up appointment
