V/Q Scan: MedlinePlus Medical Test (2024)

What is a V/Q scan?

A V/Q scan consists of two imaging tests that look for certain lung problems. The tests are:

  • A ventilation scan, which measures how air moves in and out of your lungs
  • A perfusion scan, which measures circulation (how blood flows in the lungs)

The two scans may be done separately or together.

A V/Q scan uses a small amount of a radioactive substance called a tracer that helps look for disease in the body. The scans help diagnose different lung conditions, including a pulmonary embolism (PE). A PE is a life-threatening blockage in an artery in the lungs. It usually happens when a blood clot in another part of the body breaks loose and travels to the lungs.

Other names: ventilation/perfusion scan, pulmonary ventilation/perfusion scan, lung scan, lung V/Q scan

What is it used for?

A V/Q scan is most often used to check for a pulmonary embolism (PE). It may also be used to:

  • Find problems with blood flow in the lungs
  • Check lung function before lung surgery
  • Test lung function in people with certain lung diseases, such as COPD (chronic obstructive pulmonary disease), a disease that causes coughing, wheezing, and shortness of breath.

Why do I need a V/Q scan?

You may need a V/Q scan if you have symptoms of a pulmonary embolism (PE). These include:

  • Trouble breathing
  • Chest pain
  • Coughing or coughing up blood
  • Rapid heartbeat

Many people with a PE don't have symptoms. But your provider may order a V/Q scan based on a physical exam and/or if you have certain risk factors. These include:

  • Family history of blood clots or PE
  • Long periods of inactivity that may be due to prolonged sitting (such as from long car trips or flights), bed rest or other reasons
  • Recent surgery
  • Obesity
  • Older age
  • Smoking

You may also be at higher risk if you have:

  • A clotting disorder
  • Cancer
  • Heart disease
  • Another lung disease, such as COPD

What happens during a V/Q scan?

V/Q scans are usually performed in a radiology clinic or a hospital. You may be getting a ventilation scan or a perfusion scan, or you may get both scans. If you are getting both, one scan will be done right after the other.

For both types of scans:

  • You will lie very still on a special table while the scanner takes pictures of your lungs.
  • Before the scan, you will be given a substance called a radioactive tracer. The tracer sends out a form of energy called gamma rays. The rays are picked up by the scanner to create images of your lungs.

During a ventilation scan:

  • You will wear a face mask and breathe in a gas that contains the radioactive tracer
  • A health care provider will use the scanner to take pictures of your lungs while you are holding your breath.
  • Your provider will continue to take pictures while you breathe in the tracer gas for a few more minutes.
  • After the tracer gas has collected in your lungs, your provider will remove your face mask. As you breathe normally, the tracer will leave your lungs.

During a perfusion scan:

  • A health care provider will inject the radioactive tracer into your vein through an intravenous (IV) line.
  • The tracer will collect in the blood vessels of your lungs.
  • Your provider will use the scanner to take pictures of your lungs.
  • You will be moved into several positions during the test so the scanner can capture images of the lungs from different angles.

Will I need to do anything to prepare for the test?

A chest x-ray is usually done before a V/Q scan.

Are there any risks to the test?

There is very little exposure to radiation in a V/Q scan. Only a small amount of radioactive substance is used, and all of the radiation leaves the body within a few days.

While radiation exposure in a V/Q scan is safe for most adults, it can be harmful to an unborn baby. So be sure to tell your provider if you are pregnant or think you may be pregnant Also, tell your provider if you are breastfeeding, because the tracer may contaminate your breast milk.

You may have a little discomfort when the tracer is injected during a perfusion scan.

Allergic reactions to the tracer are rare and usually mild.

What do the results mean?

If your ventilation and/or perfusion scan results were not normal, it may mean you have a pulmonary embolism (PE) and will need medical treatment right away.

The scans may also show that you have a different condition affecting your lungs. These include:

  • COPD
  • Pneumonia
  • Heart failure

If you have questions about your results, talk to your health care provider.

Is there anything else I need to know about a V/Q scan?

If you are diagnosed with a pulmonary embolism (PE), your treatment may include medicines such as blood thinners, which help prevent clots from forming, or clot busters, which help dissolve clots quickly.

If the medicines don't work, or you have a very large clot, you may need a surgical procedure to prevent and/or remove the clots.

References

  1. Bajc M, Jonson B. Ventilation/Perfusion SPECT for Diagnosis of Pulmonary Embolism and Other Diseases. Int J Mol Imaging [Internet]. 2010 Dec 19 [cited 2021 Jan 5]; 2011: 682949. Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3065883
  2. Mayo Clinic [Internet]. Mayo Foundation for Medical Education and Research; c1998–2021. Pulmonary embolism: Diagnosis and treatment; 2020 Jun 13 [cited 2021 Jan 5]; [about 4 screens]. Available from: https://www.mayoclinic.org/diseases-conditions/pulmonary-embolism/diagnosis-treatment/drc-20354653
  3. Mayo Clinic [Internet]. Mayo Foundation for Medical Education and Research; c1998–2021. Pulmonary embolism: Symptoms and causes; 2020 Jun 13 [cited 2021 Jan 5]; [about 3 screens]. Available from: https://www.mayoclinic.org/diseases-conditions/pulmonary-embolism/symptoms-causes/syc-20354647
  4. National Blood Clot Alliance: Stop the Clot [Internet]. Philadelphia: National Blood Clot Alliance; How is PE Diagnosed?; [cited 2021 Jan 5]; [about 3 screens]. Available from: https://www.stoptheclot.org/learn_more/signs-and-symptoms-of-blood-clots/how_is_pe_diagnosed
  5. National Heart, Lung, and Blood Institute [Internet]. Bethesda (MD): U.S. Department of Health and Human Services; COPD; [cited 2021 Jan 5]; [about 3 screens]. Available from: https://www.nhlbi.nih.gov/health-topics/copd
  6. National Heart, Lung, and Blood Institute [Internet]. Bethesda (MD): U.S. Department of Health and Human Services; Lung VQ Scan; [cited 2021 Jan 5]; [about 3 screens]. Available from: https://www.nhlbi.nih.gov/health-topics/lung-vq-scan
  7. RadiologyInfo.org [Internet]. Radiological Society of North America, Inc.; c2021. General Nuclear Medicine; [cited 2021 Jan 5]; [about 3 screens]. Available from: https://www.radiologyinfo.org/en/info.cfm?pg=gennuclear
  8. RadiologyInfo.org [Internet]. Radiological Society of North America, Inc.; c2021. Pulmonary Embolism; [cited 2021 Jan 5]; [about 3 screens]. Available from: https://www.radiologyinfo.org/en/info.cfm?pg=pulmonary-embolism
  9. UF Health: University of Florida Health [Internet]. Gainesville (FL): University of Florida Health; c2021. Pulmonary ventilation/perfusion scan: Overview; [updated 2021 Jan 5; cited 2021 Jan 5]; [about 2 screens]. Available from: https://ufhealth.org/pulmonary-ventilationperfusion-scan
  10. University of Rochester Medical Center [Internet]. Rochester (NY): University of Rochester Medical Center; c2021. Health Encyclopedia: Lung Scan; [cited 2021 Jan 5]; [about 2 screens]. Available from: https://www.urmc.rochester.edu/encyclopedia/content.aspx?contenttypeid=92&contentid=P07751
  11. University of Rochester Medical Center [Internet]. Rochester (NY): University of Rochester Medical Center; c2021. Health Encyclopedia: Pulmonary Embolism; [cited 2021 Jan 5]; [about 2 screens]. Available from: https://www.urmc.rochester.edu/encyclopedia/content.aspx?contenttypeid=85&contentid=p01308
V/Q Scan: MedlinePlus Medical Test (2024)

FAQs

What can be diagnosed on a VQ scan? ›

A VQ scan can help to diagnose a blood clot in the lungs. If left untreated, blood clots can be fatal. If you have symptoms of a blood clot, such as shortness of breath and a sharp pain when you breathe in, your doctor might recommend a VQ scan. A blood clot is also known as a pulmonary embolism or PE.

How long does it take to get results from a VQ scan? ›

You'll usually know the results of a VQ scan within 24 hours.

Can a VQ scan be wrong? ›

Abstract. Ventilation/perfusion (V/Q) scans are highly sensitive in detecting clinically significant pulmonary embolisms; however, V/Q mismatches are not specific to pulmonary embolism alone, and other etiologies can cause false-positive results.

What is a normal lung perfusion scan result? ›

A normal pulmonary perfusion scan has no perfusion defects or perfusion exactly outlines the shape of the lungs seen on the chest radiograph. It should be noted that a normal perfusion scan may demonstrate hilar and aortic impressions and the chest radiograph and/or ventilation study may be abnormal.

What do the results of a VQ scan mean? ›

Interpretation of scans is based on determining whether the perfusion scan defects correspond to the anatomic segments or sub- segments of the lung. The size and number of segmental defects are used to estimate the likelihood that the defects are due to PE.

What is the difference between VQ scan and lung perfusion scan? ›

A ventilation-perfusion (VQ) scan is a diagnostic test using radioisotopes to evaluate lung perfusion and ventilation. Ventilation-perfusion scan consists of two portions, a ventilation (V) scintigraphy and a perfusion (Q) scintigraphy.

Can a VQ scan detect COPD? ›

Rule of V/Q scan in chronic obstructive pulmonary disease (COPD)- It is used to assess both early ventilation and perfusion defect in COPD in addition to the extent of the disease. [21] Preoperative lung scintigraphy- it provides more anatomical information.

How long before a pulmonary embolism kills you? ›

The most severe form of PE is acute massive. Approximately one-quarter of people with acute massive PE may die suddenly within the first few hours of symptoms appearing.

What should I do before a VQ scan? ›

There is no special preparation for this scan. You can eat, drink and take any medicines as normal. You should be prepared to be at the hospital for up to 1 hour. If you are breastfeeding, contact the department before your appointment so we can give you more information before you come for your scan.

What is the alternative to VQ scan? ›

CTPA is a better alternative to a VQ scan in critically ill patients, in the obese and in those with abnormal chest X-rays or significant underlying pulmonary conditions.

What are the side effects of VQ scan? ›

There are minimal risks involved in the VQ scan. Allergic reactions to the radiopharmaceuticals are rare and will be treated as needed. The test involves exposure to ionising radiation (see Radiation Risk of Medical Imaging in Adults and Children).

What diseases have high vq mismatch? ›

Anything that affects your body's ability to deliver enough oxygen to your blood can cause a V/Q mismatch.
  • Chronic obstructive pulmonary disease (COPD) ...
  • Asthma. ...
  • Pneumonia. ...
  • Chronic bronchitis. ...
  • Pulmonary edema. ...
  • Airway obstruction. ...
  • Pulmonary embolism. ...
  • Obstructive sleep apnea.
Oct 26, 2018

What is poor lung perfusion? ›

Ventilation-perfusion (V/Q) mismatch occurs when either the ventilation (airflow) or perfusion (blood flow) in the lungs is impaired, preventing the lungs from optimally delivering oxygen to the blood.

What is the perfusion ratio for a patient who has healthy lungs? ›

At rest, ventilation is about 4.2 L/min and pulmonary blood flow is about 5.5 L/min, so that the overall ventilation–perfusion ratio ( ratio) is approximately 0.8. However, this ratio is not uniform throughout the lungs, ranging between the approximate limits 0.5 and 3.0.

What is a bad pulmonary function test score? ›

American Thoracic Society Grades for Severity of a Pulmonary Function Test Abnormality
SeverityFEV1 percentage of predicted
Mild> 70
Moderate60 to 69
Moderately severe50 to 59
Severe35 to 49
1 more row
Mar 1, 2014

What conditions are detected by ventilation perfusion lung scan? ›

A ventilation and perfusion scan is most often done to detect an acute pulmonary embolus (blood clot in the lungs). It is also used to: Detect abnormal circulation (shunts) in the blood vessels of the lungs (pulmonary vessels) Detect abnormal circulation from multiple old blood clots (chronic thromboembolic disease)

Does a VQ scan show pulmonary hypertension? ›

In patients with unexplained pulmonary hypertension, a ventilation-perfusion (VQ) scan should be considered the initial diagnostic test of choice. VQ scans are widely available with excellent sensitivity, specificity, and diagnostic accuracy.

References

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