Definition A pulmonary perfusion scan is used most often to diagnose a blood clot in the lung, known as a pulmonary embolism. The scan shows the blood flow to all the areas of the lungs.
Who is a candidate for the test? A pulmonary perfusion scan is usually recommended for a person with chest pain, shortness of breath, or abnormal pulmonary function studies. A woman who is on oral contraceptives and who is having these symptoms is often given this test. Other candidates include a person with a blood clot, or deep venous thrombosis, in the legs as well as someone who has problems breathing after surgery.
How is the test performed? Before the pulmonary perfusion scan, a chest x-ray is taken. For the perfusion lung scan, a person is often asked to sit upright. If a person is unable to sit, he or she can lie flat on a table. A radioactive substance known as Tc-99m macroaggregated albumin will be injected into a vein in the arm. The substance gives off gamma rays from within the body. These rays are detected by a "gamma camera" that is positioned over the chest. A computer then generates pictures that can be interpreted by a doctor. The lungs will be scanned in multiple positions (usually six). The examination takes approximately 45 minutes. Usually, a second test called a pulmonary ventilation scan will follow the perfusion study.
What is involved in preparation for the test? The person undergoing the scan will undress from the waist up and will put on an examination gown. All jewellery and metal objects will be removed because these may interfere with the examination.
What do the test results mean? A normal test proves that the blood flow to the lung is normal. An abnormal test result often indicates a problem with blood flow to the lungs caused by a pulmonary embolism.
Author: James Compton, MD Reviewer: eknowhow Medical Review Panel Editor: Dr John Hearne Last Updated: 6/06/2005 Contributors Potential conflict of interest information for reviewers available on request
