VQ Scan

A VQ scan examines how well air and blood flow in your lungs.

What is a VQ scan?
Why do I need a VQ scan?
What are the risks of having a VQ scan?
How do I prepare for a VQ scan?
What happens during a VQ scan?
What happens after a VQ scan?

What is a VQ scan?

A VQ scan, also called a Ventilation (V) Perfusion (Q) scan, is made up of two scans that examine air flow and blood flow in your lungs. The first scan measures how well air flows through your lungs. The second scan looks at where the blood flows in your lungs.

If the lungs are working properly, the air flow seen on the ventilation scan will match the blood flow seen on the perfusion scan. A mismatch between the ventilation and perfusion scans (V better than Q) could indicate a blockage or PE.

In both scans, you will be given a low-risk radioactive substance called a “tracer”. This substance sends out rays which show up any areas where there is abnormal blood flow or air flow.

Why do I need a VQ scan?

A VQ scan can help to diagnose a blood clot in the lungs. If left untreated, blood clots can be fatal. If you have symptoms of a blood clot, such as shortness of breath and a sharp pain when you breathe in, your doctor might recommend a VQ scan. A blood clot is also known as a pulmonary embolism or PE.

Your doctor might also ask you to have a VQ scan to test how well your lungs work before or after surgery.

Below, you can watch a short video from one of our doctors explaining more about VQ scans.

 

Below, you can watch an animation explaining what happens during a VQ scan.

What are the risks of having a VQ scan?

There is a low risk with having a VQ scan. You may get a small bruise on the area of your skin where the injection went in. In rare cases, you may have an allergic reaction to the tracer. Allergic reactions are treatable.

If you are pregnant, or think you could be, talk to your doctor. If the VQ scan isn’t urgent, you may be able to have it after your baby is born. If your VQ scan is urgent, your doctor and medical team will take extra steps to protect your baby. If you are breastfeeding, tell your doctor. Radiation can pass into your breast milk. Your doctor may suggest you pump before your test so you have enough breast milk for a few days after your test. Or, you could bottle-feed your baby instead.

If you have any questions or concerns about the risks of having a VQ scan, speak to your doctor.

How do I prepare for a VQ scan?

You don’t need to do anything special to prepare for a VQ scan, though you will need to have had a recent chest x ray.

What happens during a VQ scan?

VQ scans involve two separate scans. In the first scan:

  • You will lie on a table and must be careful not to move around
  • You will be asked to wear a breathing mask over your nose and mouth
  • You will be asked to breathe in a small amount of low-risk radioactive gas through a tube, for around five minutes The gas won’t make you feel any different
  • The table will move under a scanner, and you must lie very still
  • The scanner will take photos of your chest and the airflow in your lungs

In the second scan:

  • You will lie on a table and must be careful not to move around
  • Your doctor will inject a low-risk radioactive dye into your arm
  • The dye will travel through your blood and into your lungs
  • The table will move under a scanner, and you must lie very still
  • The scanner will take images of the blood flow in your lungs

Each scan takes around 15 minutes. The entire VQ scan takes around 45-60 minutes to complete.

What happens after a VQ scan?

After the VQ scan is finished, you can eat and drink as normal and resume your normal activities. You can drive yourself home from the hospital.

You shouldn’t feel any different after the scan. But, if you’re still not feeling quite right after a few days, call your doctor.