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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.

The test has two parts:

  • Ventilation Scan: Assesses how well air is flowing into your lungs
  • Perfusion Scan: Evaluates how blood is flowing through the lungs

A V/Q scan is often recommended to:  

  • Detect or rule out a pulmonary embolism
  • Evaluate lung conditions such as chronic obstructive pulmonary disease (COPD) or emphysema

  • 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 V/Q scan has two main steps:

  1. Ventilation Scan:
    • You will inhale a small amount of radioactive gas through a mask or mouthpiece to help visualise airflow into the lungs. This process can take anywhere from 20 to 45 minutes, depending on your lung capacity.
    • A gamma camera will take images of your lungs as you breathe.
    • This part of the scan takes about 20 to 40 minutes and is painless.
  2. 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 part also takes about 15-40 minutes.
    • The procedure is generally painless, though you may feel a slight pinch from the injection.

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