Lung Perfusion (VQ) scan

What is a V/Q scan?

A Nuclear Medicine V/Q scan is a scan using a small amount of radiation to evaluate the circulation of air and blood within your lungs and helps in the diagnosis of lung conditions. It is commonly used to detect the presence of a blood clot in the lungs, known as a pulmonary embolism; this can be very serious and potentially life-threatening.

There are two parts to the examination which may be done on the same day, or on separate days.

  • The first part (ventilation) of the V/Q scan involves breathing in a small amount of radioactive gas through a breathing tube to show the air supply to the lungs, and images will be taken of your lungs.
  • The second part (perfusion) of the scan involves the injection of a small amount of radioactive tracer into a vein in your arm. The tracer travels in your blood stream to the blood vessels in your lungs. This part of the V/Q scan shows the blood supply to your lungs, and images will be taken of your lungs.

A specialist doctor, called a Nuclear Medicine Specialist, compares the ventilation scan and perfusion scan to identify areas the ventilation pattern and blood flow pattern have changed.

How long will the procedure take?

The V/Q scan is a two-part test, comparing the air and the blood supply to the lungs.

The whole procedure takes approximately 25 to 45 minutes.

Is there any special preparation required?

There is no preparation required for a V/Q scan. You will not feel any different after the scan, and you can continue to eat and drink as normal and take any medications necessary.

What do I need to do on the day of the scan?

On the day of your appointment, please ensure you bring:

  • Your Request (if you have it)
  • All previous relevant scans (e.g. CT Chest, Chest X-ray) or reports
  • Medicare and healthcare cards

Please tell the nuclear medicine technologist before the start of your procedure if you have any of the following conditions:

  • Pulmonary hypertension
  • Right-to-left shunt
  • Acute cor pulmonale
  • Any other severe impairment of pulmonary blood flow
  • Hypersensitive reactions or contraindications to human serum albumin

What happens during the scan?

The nuclear medicine technologist looking after you will explain the procedure.

For the ventilation scan, a dose of the radiotracer will be breathed in using a breathing tube or mask. Once enough of the radioactive gas is present in your lungs a nuclear medicine camera will take the images, this takes 10 to 15 minutes.

For the perfusion scan, a dose of the radiotracer will be injected into a vein, whilst you are lying on the nuclear medicine table. The images will be taken using a nuclear medicine camera, this takes 10 to 15 minutes.

If the scan was to assess for the presence of a blood clot a Nuclear Medicine Specialist will assess the images

  • Outpatients – if the scan is negative, you will be able to go home. If the scan is positive, your referring Doctor may be contacted, or you may be referred to the nearest emergency department for treatment.
  • Inpatients – the results of your scan will be conveyed to the ward or Emergency Department as soon as possible.

Are there any after effects from the treatment?

The risk of having an adverse reaction to the nuclear medicine tracer is rare (1 in 10,000). The likelihood of a serious allergic reaction is very rare.

What happens after the procedure?

After your scan small amounts of radioactivity are released from your body and you should avoid close prolonged contact with pregnant women or young children for 4 hours after the scan.

If you are breastfeeding, you will need to stop breastfeeding for 13 hours after the scan. Please refer to ‘Patient Information Breast Feeding Mothers’.

What are the benefits?

A V/Q scan is simple, low-risk examination that assesses the airflow and blood flow to your lungs. It can help diagnose a blood clot (pulmonary embolism), if these are left undiagnosed it could be fatal.

Are there any risks?

In referring you for this scan, your doctor is of the opinion that the benefits of this procedure for you are greater than the risks.

Nuclear medicine scans use ionising radiation to produce the images. The radiation dose associated with this examination is very low and the associated radiation risks, such as an increased lifetime risk of developing cancer caused by the exposure to radiation, are small. The risks of the radiation exposure from this scan needs to be compared to the risks of a pulmonary embolism not being treated.

When do I get the results?

Following the examination, a comprehensive report outlining the scan will be sent to your referring doctor. Please ensure that you make a follow-up appointment with your referring doctor within one week of your scan to discuss the results so they can explain what the results mean for you.

I still have questions; who can I ask?

Medical information can be complex, and you may receive information that you do not fully understand. It is important for you to consider the risks and outcomes of the procedure as well as your personal needs before making a decision to undergo the procedure.

If you have read this information and are still unsure if this is the correct procedure for you; before making a booking, you should discuss your questions or concerns with your referring doctor in the first instance. Your regular GP and/or your family may also be a useful resource. Your referring doctor can answer questions about the risks and benefits of not having the procedure and other options for treatment.

If you have questions before your appointment about what is involved on the day, our staff would be happyto assist. Please contact the imaging centre where you have made your appointment.

Feb 2024