What is a lung scan?

A lung scan is an imaging test to look at your lungs and help diagnose certain lung problems. A lung scan may also be used to see how well treatment is working.

A lung scan is a type of nuclear imaging test. This means that a tiny amount of a radioactive matter is used during the scan. The radioactive matter called tracers sends out gamma rays. These rays are picked up by the scanner to make a picture of your lungs.

A lung scan can be a ventilation scan or a perfusion scan. A ventilation scan looks at how air moves in and out of your lungs. In particular, it looks at how air moves through the bronchi and bronchioles within your lungs. A perfusion scan looks at how blood is flowing within your lungs.

In a perfusion scan, the radioactive tracer is absorbed evenly where blood flow is normal. Areas that are not getting blood don't absorb the tracer. In a ventilation scan, the tracer will fill the lungs unless you have an area where the air can't move.

The areas of the lungs where the radioactive tracer collects in greater amounts are called “hot spots.” The areas that don't absorb the tracer and appear less bright on the scan image are referred to as “cold spots.”

Lung scans are most often used to diagnose and find blood clots in the arteries of the lungs. But your healthcare provider may also use the scan to help diagnose other lung conditions.

Why might I need a lung scan?

You may need a lung scan if you have symptoms of a blood clot in your lung. Symptoms include:

• Fast heart rate

• Trouble breathing

• Chest pain not caused by your heart

If your healthcare provider thinks you may have a blood clot, you will have a ventilation scan and a perfusion scan. They will be done one right after the other. If the ventilation scan is normal, but the perfusion scan is not, it's called a mismatch. A mismatch may mean that you have a blood clot.

You may also need a lung scan if your healthcare provider thinks it will help determine your lung function before having lung surgery

Your healthcare provider may have other reasons to recommend a lung scan. Talk with your healthcare provider about the reason for your scan.

What are the risks of a lung scan?

The risk from the radioactive tracer is very low. The amount used in the test is very small. You may feel some slight discomfort when the tracer is injected. Allergic reactions to the tracer are rare, but they may happen.

Lying on the scanning table during the procedure may cause some discomfort or pain for certain people.

Tell your healthcare provider if you:

• Are allergic to or sensitive to medicines, contrast dyes, or latex

• Are pregnant or think that you might be pregnant since the scan may not be safe for the unborn baby

• Are breastfeeding since the tracer may contaminate your breast milk

You may have other risks that are unique to you. Let your healthcare provider know about all your medical conditions.  

Make a list of questions you have about the procedure. Be sure to discuss these questions and any concerns with your healthcare provider before the procedure. Consider bringing a family member or trusted friend to the medical appointment to help you remember your questions and concerns.  

Certain things can make a lung scan less accurate. These include:

• Having radioactive tracer in your body from another recent nuclear medicine test

• Pneumonia or obstructive lung disease

• Structural problem in your chest

• Ventilation scan mask that is loose or does not fit well

How do I get ready for a lung scan?

• Your healthcare provider will explain the procedure to you. Ask them any questions you have about the procedure.

• You may be asked to sign a consent form that gives permission to do the scan. Read the form carefully and ask questions if anything is not clear.

• You usually don't need to stop eating or drinking before the test. You also usually will not need medicine to help you relax (sedation).

• Tell your healthcare provider if you are pregnant or think you may be pregnant.

• You may need a chest X-ray before the scan if you did not have one in the previous 24 to 48 hours.

• Your healthcare provider may give you other instructions to get ready. Be sure to follow them.

What happens during a lung scan?

You may have a lung scan as an outpatient or as part of your stay in a hospital. The way the test is done may vary depending on your condition and your healthcare provider’s practices.

You may have either a perfusion scan or a ventilation scan. Or you may have both scans. If you have both scans, one will be done right after the other.

Generally, a lung scan follows this process:

1. You will be asked to remove any clothing, jewelry, or other objects that may get in the way of the scan.

2. You may be asked to remove clothing. If so, you will be given a gown to wear.

3. For a perfusion lung scan, an IV line will be started in a hand or arm so that you can be given the radioactive tracer.

4. The nuclear medicine technologist will slowly inject the tracer into your vein while you are lying flat on the test table.

5. The tracer will collect in the blood vessels of your lungs. The technologist will use the scanner to take images of the lungs. You will be helped into several different positions during the test. This will let the radiologist take images of the lungs from different angles.

6. For a ventilation scan, you will breathe in a gas with the tracer in it through a face mask or a tracer may be injected.

7. You will then be asked to hold your breath for a short time. The radiologist will use the scanner to take images of your lungs while you are holding your breath. They will continue to take images while you breathe in the tracer for a few more minutes. Be careful not to swallow the tracer. Swallowing the tracer could affect the quality of the images.

8. After the tracer gas has collected in your lungs, the technologist will remove the face mask. As you breathe normally, the tracer will gradually leave your lungs.

9. Once the scan is done, the IV line will be removed.

The lung scan is not painful. But you may have some discomfort or pain from lying still during the test. This may be because of recent surgery or a joint injury. The technologist will use all possible comfort measures and do the scan as quickly as possible to reduce any discomfort or pain.

What happens after a lung scan?

You may be watched for a short time after the test for any signs that mean you are allergic to the tracer.

You should move slowly when getting up from the scanner table to prevent any dizziness or lightheadedness you may have from lying flat on the table.

You may be told to drink plenty of fluids and empty your bladder often for 1 to 2 days after the scan. This will help flush the radioactive tracer from your body.

The medical staff will check the IV site for any signs of redness or swelling. Tell your healthcare provider if you see any pain, redness, or swelling at the IV site after you go home. These may be signs of infection or another type of reaction.

You should not have any other nuclear medicine tests for the next 24 to 48 hours after your lung scan.

You may go back to your usual diet and activities as directed by your healthcare provider.

Your healthcare provider may give you other instructions, depending on your situation.

Next steps

Before you agree to the test or procedure make sure you know:

• The name of the test or procedure

• The reason you are having the test or procedure

• What results to expect and what they mean

• The risks and benefits of the test or procedure

• What the possible side effects or complications are

• When and where you are to have the test or procedure

• Who will do the test or procedure and what that person’s qualifications are

• What would happen if you did not have the test or procedure

• Any alternative tests or procedures to think about

• When and how you will get the results

• Who to call after the test or procedure if you have questions or problems

• How much you will have to pay for the test or procedure