A VQ scan is a short form for Lung or Pulmonary Ventilation (V) and Perfusion (Q) Scans, which is an imaging test that determines air and blood flow into the lungs. It comprises two imaging tests that look out for any lung issues. A ventilation scan measures how much air moves in and out of your lungs. A perfusion scan measures blood circulation in the lungs.

Read this article to get an overview of what is it and what to expect from this imaging test.
VQ Scan

How Does a VQ Scan Work?

A ventilation-perfusion (VQ) scan is a nuclear medicine imaging test that uses a small amount of radioactive material to determine airflow (ventilation) and blood flow(perfusion) in the lungs. The main aim of the scan is to find out for any evidence of blood clots in the lungs (pulmonary embolism). The V and Q is a math equation that assists doctors to calculate the air and blood flow.

Also Read: Pulmonary Embolism: Know The Causes, Symptoms And Treatment Of Blood Clot In The Lungs

The imaging test uses a special X-ray scanner outside the body and is carried out in two steps. In the first part, radioactive material is breathed in, and images are captured to look at the airflow in the lungs. In the second part, a different radioactive substance is injected into the vein in the arm and several pictures are captured to see the blood flow in the lungs.

What Is The Purpose Of The Scan?

This scan is mostly recommended by the physician to evaluate for pulmonary embolism (PE) and it is also used to:

Who Needs A V/Q Scan?

A person may require a VQ scan if they have symptoms of a pulmonary embolism (PE), which include:

  • Breathing difficulty
  • Chest pain
  • Coughing or bloody cough
  • Leg pain or swelling
  • Pain in your back
  • Profuse sweating
  • Rapid heartbeat
  • Light-headedness, dizziness,
  • Blue lips or nails

However, most of the people with a PE don’t show any symptoms. But the healthcare provider may suggest a VQ scan based on the physical examination and if a person have any of the below risk factors:

  • Family history of blood clots or PE
  • Extended periods of physical inactivity due to prolonged sitting
  • Recent surgery
  • Obesity
  • Aged
  • Smoking
  • Blood clotting disorder
  • Cancer
  • Heart disease

Also Read: Pulmonary Function Tests: What Is It And What To Expect

What To Expect During V/Q scan?

VQ scans are generally done in a hospital or radiology centre. A person may be required to get a ventilation scan or perfusion scan or may get both scans, which can be done one after the other.

For Both Types Of Scans:

The person is made to lie on a special table while the scanner captures the images of the lungs. Before the scan, the patient will be given a substance called a radioactive tracer. The tracer guides out a form of energy called gamma rays. The rays are collected by the scanner to create an image of the lungs

During A Ventilation Scan:

The patient will wear a face mask and breathe in a gas that contains the radioactive tracer. The doctor will capture the images of your lungs while you are holding your breath with the use of a scanner. This process will continue for a few more minutes and the healthcare provider will continue to take images. Once the tracer gas has collected in the lungs, the healthcare provider will remove the face mask. As you breathe normally, the tracer will get rid of your lungs.

During A Perfusion Scan:

The healthcare provider will inject the radioactive tracer into the vein via an intravenous (IV) line. The tracer will get accumulated in the blood vessels of your lungs. Then with help of a scanner healthcare provider will capture images of your lungs. The lungs will be moved into several positions during the test so the scanner can take images from different angles.

How To Prepare For The Test?

There is no specific preparation for the scan, however, the person is usually asked to get a chest X-ray before a VQ scan.


There is only very minimal exposure to radiation in a VQ scan, as only a little amount of radioactive substance is used, and all of the radiation element leaves the body within a few days.

Though radiation exposure is safe for most people, it can be quite dangerous to an unborn baby. So, ensure to inform your healthcare provider if you are pregnant or think you may be pregnant. Also, inform if you are breastfeeding, as the tracer may contaminate breast milk.

Additionally, you may have mild discomfort when the tracer is injected during a perfusion scan.

What Do The Results Mean?

Normal Result: If both the lungs are working well and air and blow flow are proper, you will get a normal result.

Abnormal Results: If the scan reveals that your lungs are not getting an adequate amount of air or blood pumping via them, then it will come back abnormal. And this could reveal that person may be suffering from the following problems:

  • Pneumonitis
  • Pulmonary embolism
  • Pneumonia
  • Chronic smoking or COPD lung damage
The doctor will evaluate the results and diagnose any underlying conditions that are affecting the lung VQ scan.

Frequently Asked Questions

What Is A VQ Scan Used For?

Healthcare providers mainly suggest a VQ scan to diagnose a blood clot in the lungs (pulmonary embolism).  It’s also used to diagnose chronic thromboembolic pulmonary hypertension (CTEPH) which is a cause of high blood pressure in the blood vessels in the lungs. Further, physicians can also use a VQ scan to monitor lung function:

  • After a lung transplant
  • Before lung surgery
  • To evaluate the lung function in people with chronic obstructive pulmonary disease (COPD) and other lung disorders
  • Find out issues with blood flow in the lungs

Why Do I Need A VQ Scan?

A person may need a VQ scan if they exhibit symptoms of pulmonary embolism (PE), which include:

  • Breathing difficulty
  • Chest pain
  • Coughing or coughing up blood
  • Rapid heartbeat

How Does CT Scan And VQ Scan Differ?

Both these scans take images of the lungs to help the doctor diagnose problems like blood clots. A CT scan uses a camera to get images of a contrast dye in your system and doctors look at the images to diagnose the problems.

A VQ scan is a two-step process where a camera takes images of radioactive particles in the body. The physician can look at one set of images or compare the two to have a clear idea of how your lungs are functioning.