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Medical Imaging

Nuclear Medicine > Exams & Procedures > Lung Scan (VQ Scan)

This scan assesses the air supply and blood supply to your lungs and looks for differences between them. This test may have been ordered by your doctor to investigate several different possible disease processes:

  • Rule out blood clots to the lungs (pulmonary embolism).
  • Evaluate air supply changes in lung disorders (e.g. COPD, lung cancer, and obstructive conditions).
  • Evaluate blood supply changes in lung disorders (e.g. emphysema, chronic bronchitis, asthma, and inflammation conditions).
  • Staging for lung cancer.
  • Evaluate blood shunting from the right to the left side of the heart.
  • Preoperative lung assessment.

The test involves you breathing in radioactive aerosol through a mask that lets us see the air supply to your lungs. After breathing this aerosol, pictures will be taken from different angles around your lungs. Following these pictures, you will be given an injection of a radioactive tracer that allows us to see the blood supply to your lungs. Again, pictures will be taken from different angles around your lungs.


  • Chest X-ray performed within 24 hours of the lung scan.
  • Bring a list of all medications and supplements you take. This includes vitamins, herbal remedies, and holistic medications.
  • Do not bring children or pregnant women with you to the department. We do not want to expose them to unnecessary radiation.
  • Any of these procedures is subject to change according to the nuclear medicine physician. The duration of the tests is a rough estimate. Please be aware that the time may be lengthened if a scan has to be repeated, if emergency cases are brought to the department or due to unforeseen circumstances.

About the Procedure

  • The procedure takes about 45 to 60 minutes.
  • A technologist will briefly explain the test to you and try to answer any questions you may have about the procedure.
  • A technologist will ask you a few questions about your medical history and medications.
    Air Supply (Ventillation) Scan
  • A mask will be placed over your face and you will inhale a mixture of oxygen and radioactive mist for about 10 minutes.
  • The technologist will ask you to lie down on the bed and the camera will be positioned above your chest.
  • Pictures will be taken from different angles around your lungs.
    Blood Supply (Perfusion) Scan
  • You will receive an injection of another radioactive tracer into a vein.
  • Pictures are taken as the tracer is injected to determine the blood flow to the lungs.
  • Again, pictures will be taken from different angles around your lungs.
    Procedure Modifications

Some patient conditions dictate modification of this test to better ensure the safety of the procedure. The main patient conditions that indicate procedure modification include:

  • Severe high blood pressure in the lungs (pulmonary hypertension).
  • Right to left blood leak in the heart (right to left cardiac shunt).
  • Pregnancy and breastfeeding. Sometimes your doctor deems it necessary to have the test even when you are pregnant. The nuclear medicine doctor will discuss with you the risks to your baby and the benefits of having the test.