Lung Scan

Overview

A lung scan is a nuclear scanning test that is most commonly used to detect a blood clot that is preventing normal blood flow to part of a lung (pulmonary embolism ).

Two types of lung scans are usually done:

• Ventilation scan: During a ventilation scan, a radioactive tracer gas is inhaled into the lungs. Pictures from this scan can show areas of the lungs that are not receiving enough air or that retain too much air. Areas of the lung that retain too much air show up as bright or “hot” spots on the pictures. Areas that are not receiving enough air show up as dark or “cold” spots.
• Perfusion scan: During a perfusion scan, a radioactive tracer substance is injected into a vein in the arm. It travels through the bloodstream and into the lungs. Pictures from this scan can show areas of the lungs that are not receiving enough blood. The tracer is absorbed evenly in areas of the lung where the blood flow is normal. These areas show up with the tracer distributed evenly. Areas that are not receiving enough blood show up as cold spots.

If the lungs are working normally, blood flow on a perfusion scan matches air flow on a ventilation scan. A mismatch between the ventilation and perfusion scans may indicate a pulmonary embolism.

Ventilation and perfusion scans can be done separately or together to diagnose certain lung diseases. If both scans are done, the test is called a V/Q scan. In this case, the ventilation scan is usually done first.

Patient Prep

There is no preparation for this test.

Test Procedure

A lung scan is usually done by a nuclear medicine technologist. The scan pictures are usually interpreted by a radiologist or nuclear medicine specialist.

You will need to remove any jewelry that might interfere with the scan. You may need to take off all or most of your clothes; depending on which area is being examined (you may be allowed to keep on your underwear if it does not interfere with the test). You will be given a cloth or paper covering to use during the test.

During the scan, you will either lie on your back with the scanning camera positioned over your chest or you will sit with the camera positioned next to your chest. The camera does not produce any radiation, so you are not exposed to any additional radiation while the scan is being done.

Ventilation scan

For the ventilation scan, a mask will be placed over your mouth and nose. You will inhale the tracer gas through the mask by taking a deep breath and then holding it. The camera will scan for radiation released by the tracer and produce pictures as the tracer moves through your lungs. You may be asked to breathe the gas in and out through your mouth into a bag for several minutes. You may then be asked to hold your breath for short periods (about 10 seconds) and to change positions so your lungs can be viewed from other angles. The camera may move to take pictures from different angles. You need to remain very still during the scans to avoid blurring the pictures.

Afterward, the radioactive gas will clear from your lungs as you breathe.

The ventilation scan takes about 15 to 30 minutes.

Perfusion scan

For the perfusion scan, the technologist cleans the site on your arm where the radioactive tracer will be injected. A small amount of the radioactive tracer is then injected.

After the radioactive tracer is injected, the camera will scan for radiation released by the tracer and produce pictures as the tracer moves through your lungs. You may be asked to move into different positions (onto your side and stomach) so your lungs can be viewed from other angles, or the camera may be repositioned around your chest to obtain other views. You need to remain very still during the scans to avoid blurring the pictures.

The perfusion scan takes about 15 to 30 minutes

Test Results

It can take time for the test results and how long will depend on the reasons for the scan. Usually, a specialist in radiology examines the scan and a report will be sent to your physician, who reviews the results with you.