What is a Lung Scan?
A Ventilation-Perfusion (“V/Q”) lung scan is a medical imaging test used by your doctor to look at the circulation of air (ventilation) and blood (perfusion) of the lungs. It is usually done in the nuclear radiology department of a hospital.
Why do this test?
The most common reason for your doctor to order this test is to look for blood clots in the lungs. Other indications are to look at the blood or airflow of the lungs or to examine lung performance before or after lung surgery.
How is it done?
During the Ventilation phase, you will breath in a radioactive tracer gas mixed with oxygen. A special camera detects where the gas went in the lungs and provides an image for the doctor. The Perfusion phase involves injecting a
radioactive tracer liquid into a vein in your arm. This liquid travels through your blood and goes to the lungs, where the camera takes images.
Often your doctor will perform a chest x-ray to help with interpreting the V/Q scan result.
What does a V/Q scan show?
Normally, the blood and air should flow to all parts of your lungs and areas should not abnormally retain the air (“air trapping”). If there is a large area of decreased blood flow, especially in a wedge or pie shape, and the air flow appears normal (so-called “ventilation-perfusion mismatch”), you may have a pulmonary embolism. A scan showing low blood flow in spots may reflect other lung problems, such as lung damage from COPD. Areas of excess retained tracer gas may indicate air trapping, commonly seen in asthma or COPD.
What are the risks?
Lung ventilation/perfusion scans involve little risk for most people. The test does not hurt, except for a slight prick when inserting the IV catheter in your arm. The radioisotopes used for both tests expose you to a low level of radiation- altogether about the same amount a person is naturally exposed to in one year. Although very rare, the radioisotopes may cause an allergic reaction, such as hives or a rash. There is a risk of radiation to your fetus if you are pregnant and a risk of radiation to your infant if you are breastfeeding. Your doctor may need to take special precautions or use alternative testing.
How should I prepare for this test?
Usually, no preparation is necessary and most people can return to their normal routines right after a VQ scan. You will need to lie still for about one hour to complete the test. If you are pregnant (or might be pregnant), tell your doctor. If you are breastfeeding, use formula and discard your breast milk. Ask your doctor how long you should wait after the test before you resume breastfeeding.
Where can I find out more?