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Ventilation/Perfusion (V/Q) Scan

Overview

A Ventilation-Perfusion (V/Q) scan is a nuclear medicine diagnostic test used to evaluate blood flow (perfusion) and airflow (ventilation) in the lungs. It helps doctors detect lung conditions or diseases affecting breathing and circulation.

Your doctor may recommend a V/Q scan to: 

  • Detect or rule out a pulmonary embolism (blood clot in the lung)
  • Evaluate lung function in conditions such as chronic obstructive pulmonary disease (COPD) or emphysema
  • Assess lung health before or after surgery

The V/Q scan has two main steps:

Ventilation Scan:

  • You will inhale a small amount of radioactive gas through a mask or mouthpiece to help visualise airflow into the lungs.
  • A gamma camera will take images of your lungs as you breathe.
  • This step usually takes 20–40 minutes depending on your lung capacity and is painless.

Perfusion Scan:

  • You will receive an injection of a small amount of radiopharmaceutical into a vein in your arm to visualise blood flow in the lungs.
  • The gamma camera will take more images of your lungs while you lie down on a table. The camera will move around your chest but will not touch you.
  • This step usually takes 15–40 minutes.
  • The procedure is generally painless, though you may feel a slight pinch from the injection.painless, though you may feel a slight pinch from the injection.

The ventilation scan takes around 20–40 minutes, and the perfusion scan takes 15–40 minutes. The total imaging procedure usually takes 1–1.5 hours, depending on your lung capacity. 

  • Medications: Inform your doctor about all medications you are taking, including blood thinners or inhalers. You may be asked to stop certain medications before the scan.
  • Allergies: Notify your doctor of any allergies, especially to iodine, contrast agents, or medications.
  • Pregnancy and breastfeeding: If you are pregnant or breastfeeding, inform your doctor. Ventilation (V) scans are generally avoided during pregnancy unless absolutely necessary. Perfusion (Q) scans may be performed with a much smaller dose.

  • The test is safe and well-tolerated.
  • Exposure to radiation is minimal and the tracer leaves the body naturally within 24 hours.
  • Allergic reactions are extremely rare, but you should discuss any concerns or allergies with your healthcare provider before the scan.

  • You can resume normal activities immediately after the scan.
  • Drink plenty of fluids after the scan to help flush out the radioactive tracer from your body.
  • The radioactive material will naturally leave your body within 24 hours.

Disclaimer:

The information in this Health Library is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always consult a qualified healthcare professional with any questions about a medical condition or before starting any treatment. Use of this site and its content does not establish a doctor–patient relationship. In case of a medical emergency, call your local emergency number or visit the nearest emergency facility immediately.