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What is a V/Q scan?
A Nuclear Medicine V/Q scan is a scan using a small amount of radiation to test if there are any blood clots in your lungs. A blood clot in the lungs is known as a pulmonary embolism; this can be very serious and potentially life-threatening.
There are 2 parts to the examination which may be done on the same day, or on separate days.
- The first part of the V/Q scan involves breathing in a small amount of radioactive gas through a breathing tube showing the air flow to the lungs, and then pictures will be taken of your chest.
- The second part of the scan involves the injection of a small amount of radioactive tracer into a vein in your arm through an IV cannula. This part of the V/Q scan shows the blood flow pattern in your lungs, and then pictures will be taken of your chest.
A specialist doctor called a Nuclear Medicine Physician compares the air flow scan and blood flow scan to identify areas of the blood vessels in the lungs where the blood flow pattern is changed or unusual because of ‘a blood clot. Sometimes, the doctor may decide that you don’t need the second part based on viewing the images from the first part.
What is radioactivity?
Radioactivity is a form of radiation. This kind of radiation is invisible. Nuclear Medicine scans use radioactivity in the form of gamma rays to make images organs in your body. The patient is slightly radioactive for a short time afterwards; this will be discussed with you by the Nuclear Medicine Technologist.
Is it safe to be exposed to radioactivity (have a nuclear medicine scan) while I’m pregnant?
If your referring doctor finds you need a V/Q scan to diagnose a blood clot in your lungs, they will weigh up the benefit to you versus the risk to you and your baby.
Taking into account that you are pregnant, we aim to reduce the radiation dose to around half of that of a regular V/Q scan. Any Nuclear Medicine scan involving exposure to radiation comes with the potential of a slightly increased risk of cancer over the course of a lifetime. This risk increases with the radiation dose; however, this needs to be compared with the natural risk of cancer. According to the Royal Australian and New Zealand College of Radiologists (RANZCR, 2017), the average natural risk of childhood cancer is approximately 1 in 500 (0.2%) so the risk of childhood cancer from each part of a V/Q scan is much lower (0.001% to 0.0001% for the ‘air flow part and 0.01% to 0.001% for the ‘blood flow’ part).
Could I have another test instead of V/Q scan?
Your referring doctor may suggest a CT Pulmonary Angiogram (CTPA) which also uses radiation and the risk from radiation exposure is comparable to the air flow part of a V/Q scan.
Ultrasound and MRI are not suitable examinations to investigate for pulmonary embolism.
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 scan takes about 25 to 30 minutes.
Is there any special preparation required?
There is no preparation required for a V/Q scan unless your doctor requests that you have a Chest X-ray before the scan, this is not a requirement for all patients. You will not feel any different after the V/Q scan, and you can continue to eat and drink as normal and take any medications necessary.
If you are breastfeeding, please tell the Nuclear Medicine Technologist who will discuss this with you and provide you with advice.
What do I need to do on the day of the scan?
On the day of your appointment, please ensure you bring:
- Your request form (if you have it)
- All previous relevant scans or X-rays
- Medicare and healthcare cards
Please tell the Nuclear Medicine Technologist before either part of the V/Q scan if you have any of the following conditions:
- Severe pulmonary hypertension
- Right-to-left heart shunts
- Acute cor pulmonale
- Any other severe impairment of pulmonary blood flow
What happens during the scan?
The Nuclear Medicine Technologist looking after you will explain the scan, check all your preparation is correct and notify you which part will be done first, Air Flow or Blood Flow. The order of the test is decided by the Nuclear Medicine Physician in charge at each Lumus Imaging centre.
Before the examination begins a thin plastic tube called an intravenous (IV) cannula is inserted into a vein in your arm, if you don’t already have one in place from the ward/Emergency Department.
For the Air Flow scan, a dose of the radio tracer will be breathed in through a tube or mask. The images will be taken using a nuclear medicine camera with you lying still on the nuclear medicine table; this takes 15-30 minutes.
For the Blood Flow scan, a dose of the radio tracer will be injected using the IV cannula, whilst lying still on the nuclear medicine table. The images will betaken using a nuclear medicine camera; this takes 15-30 minutes.
The IV cannula will be removed once both parts are complete and before you go home or back to the ward/Emergency Department.
Are there any after effects from the treatment?
A V/Q scan is a painless procedure, without any known after effects. The radioactive material used in a V/Q scan is not known to interfere with any food or medications you might be taking.
What happens after the procedure?
Our staff will provide you with instructions on ways to look after yourself following a V/Q scan, including arranging a follow up appointment with your referring doctor.
After your scan, although small amounts of radioactivity are released from your body, the Australian Radiation and Nuclear Safety Agency (ARPANSA) recommend that there is no requirement that you should avoid close prolonged contact with others.
If you are breastfeeding, you will need to stop breastfeeding for 13 hours after the scan.
What are the benefits?
Th eV/Q scan is a simple, low-risk examination that assesses the breath and blood supply to the lungs and provides your doctor with information on how your lungs are working. The results of the scan help your doctor to assess the risk that you may have a blood clot in your lungs and treat this appropriately.
Are there any risks?
In referring you for this scan, your doctor is of the opinion that the benefits of this scan for you, and your baby, in order to manage your condition should you have a blood clot are greater than the risks.
The main risks of the V/Q scan relate to the Blood Flow component. Although adverse reactions specifically attributed to the radio tracer injection have not been noted, the literature contains reports of deaths occurring in patients with pre-existing severe pulmonary hypertension. These risks are minimised by closely monitoring you. If serious complications occur, you may require an admission to hospital.
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. Nuclear Medicine scans have been associated with a very small increased risk of cancer for an unborn baby, but the risk is very small. The risks of the radiation exposure from this scan needs to be compared to the risks of a blood clot in the lungs not being diagnosed and treated, which may result in death.
Prior to the scan, our clinical staff will discuss the scan with you in detail including any risks specific to you. You will be provided with the opportunity to ask questions.
When do I get the results?
Following the examination, a comprehensive report outlining the scan will be sent to your referring doctor and regular GP. Please ensure that you make an urgent follow-up appointment with your referring doctor 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 online information and are still unsure if this is the correct scan for you, 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 scan and other options for treatment.
If you have questions before your appointment about what is involved on the day, our staff would be happy to assist. Please contact the imaging centre where you have made your appointment.
