Definition A pulmonary ventilation/perfusion scan is a pair of nuclear scan tests that use inhaled and injected material to measure breathing (ventilation) and circulation (perfusion) in all areas of the lungs
Why is the Test Performed? - The ventilation scan is used to evaluate the ability of air to reach all portions of the lungs.
- The perfusion scan measures the supply of blood through the lungs.
- A ventilation and perfusion scan is most often performed to detect a pulmonary embolus. It is also used to evaluate lung function in people with advanced pulmonary disease such as COPD, and to detect the presence of shunts (abnormal circulation) in the pulmonary blood vessels.
How is the Test Performed? - A Pulmonary ventilation/perfusion scan is actually two tests that may be performed separately or together.
- The perfusion scan is performed by injecting albumin into a vein. The patient is immediately placed on a movable table that is positioned under the arm of a scanner. The lungs are scanned to detect the location of the radioactive particles as blood flows through the lungs.
- The ventilation scan is performed by scanning the lungs while having the person inhale gas. A mask is placed over the nose and mouth, and the patient is asked to breathe the gas while sitting or lying on the table beneath the arm of the scanner.
How to Prepare for the Test? - No special diet, medications, or fasting are necessary before the test.
- A chest x-ray is usually performed prior to or following a ventilation and perfusion scan.
- The patient usually signs a consent form and is asked to wear a hospital gown or comfortable clothing without metal fasteners.
How Will the Test Feel? The table may feel hard and/or cold. There may be a sharp prick during injection of material into the vein for the perfusion portion of the scan. The mask used during the ventilation scan may give you a claustrophobic feeling. You must lie still during scanning. The injection usually does not cause discomfort.
Risks - Risks are essentially the same as for x-rays (radiation) and needle pricks.
- There is a small exposure to radiation from the radioisotope. The radioisotopes used during scans are short lived, with almost all radiation gone in a few days. However, as with any radiation exposure, caution is advised during pregnancy or if a woman is breastfeeding. No radiation is emitted from the scanner; it detects radiation and converts it to a visible image.
- There is a slight risk for infection or bleeding at the site of the needle insertion. The risk with perfusion scan is no different than for placement of an intravenous needle for any other purpose.
- It is extremely rare, but a person may develop an allergy to the radioisotope, which may include serious anaphylactic reaction.
