Ventilation/Perfusion Scan, Pulmonary Scintigraphy
Nuclear scanning of the lungs includes two imaging procedures—ventilation scans and perfusion scans—that may be performed either separately or together. For the ventilation scan, you must inhale a radioactive gas; the perfusion scan is done by injecting a radioactive tracer into your bloodstream. A special camera then records the movement and uptake of the radioactive material in your breathing passages, air sacs, and pulmonary blood vessels. The resulting images indicate which portions of your lungs are receiving air and blood.
Purpose of the Lung Nuclear Scan
- To help diagnose pulmonary embolism (a blood clot in an artery in the lung) and pulmonary effusion (build-up of fluid around the lungs)
- To identify areas of the lung that are capable of ventilation (taking in air)
- To evaluate the function of different parts of the lung prior to lung surgery
- To assess growths in the lungs before and after therapy
- To evaluate pneumonia, bronchitis, or other infections/inflammation
- To diagnose atelectasis - collapsed area(s) within a lung
- To evaluate emphysema or chronic obstructive pulmonary disease (COPD)
- To diagnose tumors or other obstructions in the lungs
Who Performs It
- A physician or a technician who specializes in nuclear medicine.
- If you have had other recent nuclear imaging tests, such as a thyroid or bone scan, the results of this test may not be accurate.
- This test should not be performed in pregnant women because of possible risks to the fetus.
- The presence of conditions such as pneumonia, emphysema, pleural effusion (excess fluid in the space that surrounds the lungs), or tumors may interfere with interpretation of the results.
Before the Lung Nuclear Scan
- Your physician will explain the procedure. Ask any questions you have.
- You may be asked to sign a consent form.
- Generally, no prior preparation is necessary.
- Notify the radiologist or technologist if you have any allergies or sensitivities, such as to drugs, dyes, shelfish or latex.
- If you have not yet told your doctor that you are or could be pregnant, do so before the scan.
- You will be asked to wear a hospital gown or comfortable clothing and to remove all jewelry.
- A chest x-ray may be performed within 12 hours prior to this test or immediately afterward to detect any abnormalities that might affect the results of the scan.
- Immediately before the test, you will be asked to disrobe above the waist. (Women may wear a loose-fitting hospital gown that opens in the front.)
What You Experience
- You are seated and the examiner places a breathing mask over your nose and mouth.
- The examiner asks you to follow specific instructions about inhaling and exhaling as you breathe in a mixture of air and radioactive gas.
- A large scanning camera takes pictures of your chest, recording the gamma rays emitted by the radiotracer.
- The examiner injects a small amount of radioactive material into a vein in your hand or arm. Other than this injection, the procedure is painless.
- A large scanning camera takes pictures of your chest from various angles as you are sitting or lying down and breathing freely.
- The combined ventilation/perfusion scan takes approximately 30 to 60 minutes.
Risks and Complications
- The trace amount of radioactive material used in this test is not associated with significant risks or complications.
- In extremely rare cases, patients may be hypersensitive to the radiotracer and may experience an adverse reaction.
- You may feel uncomfortable from lying still on the scanning table until the scan is over.
- Certain factors, allergies (see above) or conditions may interfere with the results of the test. These can include, among other things, remaining radionuclide in your system (from a recent nuclear medicine procedure), pneumonia or obstructive lung disease, structural abnormality of the chest and a poorly-fitting mask used in a ventilation scan.
After the Lung Nuclear Scan
- Drink extra fluids to aid in the excretion of the radioactive material.
- You may leave the testing facility and resume your normal activities.
- After a perfusion scan, blood may collect and clot under the skin (hematoma) at the injection site; this is harmless and will resolve on its own. For a large hematoma that causes swelling and discomfort, apply ice initially; after 24 hours, use warm, moist compresses to help dissolve the clotted blood.
- A physician analyzes the results of the ventilation and perfusion scans for evidence of a specific disorder, such as pulmonary embolism or pneumonia.
- If a definitive diagnosis can be made, appropriate therapy will be started, depending on the specific problem.
- In some cases, additional diagnostic tests, such as pulmonary angiography or arteriography, may be needed to clarify the results.
The Johns Hopkins Consumer Guide to Medical Tests
Simeon Margolis, M.D., Ph.D., Medical Editor
Updated by Remedy Health Media